| Ablation | The process by which ice and snow dissipate owing to melting and evaporation. | NOAA Glossary of Hydrologic Terms |
| Ablation | (1) combined processes (such as sublimation, fusion or melting, evaporation) which remove snow or ice from the surface of a glacier or from a snow-field; also used to express the quantity lost by these processes (2) reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches. | NSIDC accessed 2016 |
| Ablation | (1) All processes that reduce the mass of the glacier. (2) The mass lost by the operation of any of the processes of sense 1, expressed as a negative number. The main processes of ablation are melting and calving (or, when the glacier nourishes an ice shelf, ice discharge across the grounding line). On some glaciers sublimation, loss of windborne snow and avalanching are significant processes of ablation. 'Ablation', unqualified, is sometimes used as if it were a synonym of surface ablation, although internal ablation, basal ablation, and frontal ablation, especially calving, can all be significant in some contexts. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ablation | Ablation refers to all processes by which snow, ice, or water in any form are lost from a glacier. Ablation is the loss of snow or ice by evaporation and melting. The rate at which ablation occurs depends on the atmospheric conditions present, such as air moisture content, solar radiation, temperature, and the reflectivity (Albedo) of the snow or ice surface. Fresh snow has a high albedo (0.7 to 0.9), indicating that 70 to 90 percent of the radiation received is reflected; glacier ice has a lower albedo of 0.2 to 0.4. Therefore, more radiation may be absorbed by glacier ice than by snow. Glaciers around the mountain receive different amounts of sunlight, so each glacier has its own characteristic ablation pattern. | Molnia USGS 2004 |
| Ablation | The loss of ice and snow from a glacier system. This occurs through a variety of processes including melting and runoff, sublimation, evaporation, calving, and wind transportation of snow out of a glacier basin. | Molnia USGS 2004 |
| Ablation | All processes that remove snow, ice, or water from a snowfield, glacier, etc., that is typically melt, evaporation, sublimation as well as wind erosion, avalanches, calving, etc.; in this sense, the opposite of accumulation. In many publications before 1980, ablation did not include mechanical removal of either snow or ice, i.e., wind erosion, avalanches, calving, etc. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Ablation | Depletion of snow and ice by melting and evaporation. | NOAA National Weather Service Glossary 2009 |
| Ablation | (1) Combined processes (such as sublimation, melting, evaporation) which remove snow or ice from the surface of a glacier or from a snow-field. Also used to express the quantity lost by these processes. (2) Reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches. | WMO METEOTERM accessed 2016 |
| Ablation | Reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches. | Environment and Climate Change Canada 2014 |
| Ablation | (1) Combined processes (such as melting, sublimation, evaporation or calving) which remove snow or ice from a glacier or from a snowfield; also used to express the quantity lost by these processes. (2) Reduction of the water equivalent of snow cover by melting, evaporation, wind and avalanches. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ablation | The process of wastage of snow or ice by melting, sublimation and calving. | Swisseduc - Photo glossary of glaciological terms |
| Ablation | 1. All processes that remove snow, ice, or water from a glacier, snowfield, etc.; in this sense, the opposite of accumulation. These processes include melting, evaporation, calving, wind erosion, and an avalanche. Air temperature is the dominant factor in controlling ablation, precipitation amounts exercising only secondary control. During the ablation season (usually summer), an ablation rate of about 2 mm/h is typical of glaciers in a temperate climate. 2. The amount of snow or ice removed by the above-described processes; in this sense, the opposite of accumulation. | AMS - glossary of meteorology |
| Ablation | Surface removal of ice or snow from a glacier or snowfield by melting, sublimation, and/or calving. | PhysicalGeography.net |
| Ablation | All processes by which snow, ice, or water in any form are lost from a glacier, floating ice or snow cover. These include melting, evaporation, calving, wind erosion and avalanches. Also used to express the quantity lost by these processes. | Illustrated Glossary of Snow and Ice |
| Ablation area | The area of a glacier where more glacier mass is lost than gained. | NSIDC accessed 2016 |
| Ablation area | Ablation area is the lower region of a glacier where snow ablation exceeds snowfall. A line that marks the limit on a mountain above which snow persists from one winter to the next is called the annual snowline, and this line on a glacier is called the firnline. Above the firnline, snow that falls each year packs down and changes into glacier ice as air is slowly forced out of it. This part of the glacier is its accumulation area where more snow falls each year than is lost by melting. Below the firnline is the ablation area, where melting predominates. | Molnia USGS 2004 |
| Ablation area | A synonym of ablation zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ablation area | That portion of a glacier surface below the firn line where ablation exceeds accumulation; the opposite of accumulation area. | AMS - glossary of meteorology |
| Ablation area/zone | That part of a glacier's surface, usually at lower elevations, over which ablationexceeds accumulation. | Swisseduc - Photo glossary of glaciological terms |
| Ablation cone | See dirt cone: A thin veneer of debris draping a cone of ice up to several metres high, formed because the debris has retarded ablation under it. | Swisseduc - Photo glossary of glaciological terms |
| Ablation hollows | Depressions in the snow surface caused by the sun or warm, gusty wind. | NSIDC accessed 2016 |
| Ablation hollows | Depressions in the snow surface caused by either a warm, gusty wind or the sun. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Ablation moraine | Mound or layer of moraine in the ablation zone of a glacier the rock has been plucked from the mountainside by the moving glacier and is melting out on the ice surface. | NSIDC accessed 2016 |
| Ablation moraine | An irregular-shaped layer or pile of glacier sediment formed by the melting of a block of stagnant ice. Ultimately, ablationa moraine is deposited on the former bed of the glacier. Also called Ablation Till. | Molnia USGS 2004 |
| Ablation season | A time span extending from a seasonal maximum of glacier mass to a seasonal minimum. The ablation season is the same as the summer season on most glaciers, which are of winter-accumulation type. Special cases include glaciers of summer-accumulation type and year-round ablation type, and glaciers that have more than one ablation season during the year. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ablation zone | The part of the glacier where ablation exceeds accumulation in magnitude, that is, where the cumulative mass balance relative to the start of the mass-balance year is negative. Unless qualified, for example by giving a date within the year, references to the ablation zone refer to its extent at the end of the mass-balance year. The extent of the ablation zone can vary strongly from year to year. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ablation zone | Region in a glacier where there is a surface net removal of snow and/or ice by melting, sublimation, and/or calving. | PhysicalGeography.net |
| Ablatometer | A device installed at the glacier surface for the measurement, during the ablation season, of changes in elevation of the glacier surface relative to a fixed elevation, such as that of the top of a mass-balance stake embedded in the ice beneath the surface. A star ablatometer is an array of rigid metal arms that can be attached to a stake and levelled. A graduated rod is lowered through holes in the arms to measure changes in the surface elevation, yielding a considerably larger sample than that obtained from readings of the stake alone. Sometimes an ablatometer is actually a sonic ranger. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Abrasion | Process of wearing down by friction, or the resulting effects, with movement of debris, whether it be in a stream, sea, ice or wind. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Abrasion | Physical wearing and grinding of a surface through friction and impact by material carried in air, water, or ice. | PhysicalGeography.net |
| Accreted ice | Ice formed by the freezing of water at the base of an ice body. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Accretion | Growth of a cloud or precipitation particle by the collision and union of a frozen particle (ice crystal or snowflake) with a supercooled liquid droplet which freezes on impact. | WMO METEOTERM accessed 2016 |
| Accretion | (1) Growth of a cloud or precipitation particle by collision with supercooled liquid droplets that freeze wholly or partially on impact. (2) The process by which a layer of ice or snow builds on solid objects such as overhead lines that are exposed to precipitation icing events. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Accumulation | All processes by which snow or ice are added to a glacier, this is typically the accumulation of snow, which is slowly transformed into ice; other accumulation processes can include avalanches, wind-deposited snow, and the freezing of rain within the snow pack. | NSIDC accessed 2016 |
| Accumulation | The addition of ice and snow into a glacier system. This occurs through a variety of processes including precipitation, firnification, and wind transportation of snow into a glacier basin from an adjacent area. | Molnia USGS 2004 |
| Accumulation | All processes that add mass to the snow cover or to a glacier, i.e., typically solid and liquid precipitation, ice deposition from atmospheric water vapour, wind-deposited snow, but also avalanches, etc. (opposite of ablation). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Accumulation | 1. All processes that add to the mass of the glacier. 2. The mass gained by the operation of any of the processes of sense 1, expressed as a positive number. The main process of accumulation is snowfall. Accumulation also includes deposition of hoar, freezing rain, solid precipitation in forms other than snow, gain of windborne snow, avalanching and basal accumulation (often beneath floating ice). Unless the rain freezes, rainfall does not constitute accumulation, nor does the addition of debris by avalanching, ashfall or similar processes. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Accumulation | Quantity of snow or any other form of water in the solid state which is added to a glacier or snow-field by alimentation; the opposite of ablation. | WMO METEOTERM accessed 2016 |
| Accumulation | The process of building-up of a pack of snow, refrozen slush, meltwater and firn. Net accumulation for one year is the material left over at the end of the melt-season. | Swisseduc - Photo glossary of glaciological terms |
| Accumulation | In glaciology, the quantity of snow or other solid form of water added to a glacier or snowfield by alimentation; the opposite of ablation. | AMS - glossary of meteorology |
| Accumulation | Surface addition of snow to a glacier or snowfield. | PhysicalGeography.net |
| Accumulation | All processes by which snow, ice, or water in any form are added to a glacier, floating ice or snow cover. These include direct precipitation of snow, ice or rain, condensation of ice from vapour, and transport of snow and ice to the glacier. Also used to express the quantity added by these processes. | Illustrated Glossary of Snow and Ice |
| Accumulation (of snow and ice) | Quantity of snow, or any other form of water in the solid state, which is added to a glacier, floating ice or a snow cover. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Accumulation area | The part of a glacier that is perennially covered with snow. | Molnia USGS 2004 |
| Accumulation area | Accumulation area is the upper region of a glacier where snow accumulation exceeds melting. A line that marks the limit on a mountain above which snow persists from one winter to the next is called the annual snowline, and this line on a glacier is called the firnline. Above the firnline, snow that falls each year packs down and changes into glacier ice as air is slowly forced out of it. This part of the glacier is its accumulation area where more snow falls each year than is lost by melting. Below the firnline is the ablation area, where melting predominates. | Molnia USGS 2004 |
| Accumulation area | A synonym of accumulation zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Accumulation area | That part of a glacier's surface, usually at higher elevations, on which there is net accumulation of snow, which subsequently turns into firn and then glacier ice. | Swisseduc - Photo glossary of glaciological terms |
| Accumulation area | That portion of the glacier surface above the firn line where the accumulation exceeds ablation; the opposite of ablation area. | AMS - glossary of meteorology |
| Accumulation season | A time span extending from a seasonal minimum of glacier mass to a seasonal maximum. The accumulation season is the same as the winter season on most glaciers, which are of winter-accumulation type. Special cases include glaciers of summer-accumulation type and year-round ablation type, and glaciers that have more than one accumulation season during the year. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Accumulation zone | The part of the glacier where accumulation exceeds ablation in magnitude, that is, where the cumulative mass balance relative to the start of the mass-balance year is positive. Unless qualified, for example by giving a date within the year, references to the accumulation zone refer to its extent at the end of the mass-balance year. The extent of the accumulation zone can vary strongly from year to year. The accumulation zone is not the same as the firn area. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Accumulation zone | (1) Region in a glacier where there is a surface net addition of snow. (2) Part of a hillslope that has a net gain of material leading to a progressive raising of the slope's surface. | PhysicalGeography.net |
| Accumulation-area ratio AAR | The ratio, often expressed as a percentage, of the area of the accumulation zone to the area of the glacier. The AAR is bounded between 0 and 1. On many glaciers it correlates well with the climatic mass balance. The likelihood that the climatic mass balance will be positive increases as the AAR approaches 1. Unless qualified by a different adjective, references to the AAR refer to the Annual AAR. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Acicular ice | Freshwater ice consisting of numerous long crystals and hollow tubes having variable form, layered arrangement, and a content of air bubbles. This ice often forms at the bottom of an ice layer near its contact with water. | AMS - glossary of meteorology |
| Active air-cooled thermal pile | A foundation pile on which a cold air refrigeration system has been installed to remove heat from the ground | Van Everdingen International Permafrost Association 2005 |
| Active construction methods in permafrost | Special design and construction methods used for engineering works in permafrost areas where permafrost degradation cannot be prevented | Van Everdingen International Permafrost Association 2005 |
| Active ice wedge | An ice wedge that is growing as a result of repeated (but not necessarily annual) winter cracking. | NSIDC accessed 2016 |
| Active ice wedge | An ice wedge that is growing as a result of repeated (but not necessarily annual) winter cracking | Van Everdingen International Permafrost Association 2005 |
| Active ice wedge | An Ice Wedge is termed 'active' if it is growing as a result of repeated (but not necessarily annual) winter cracking in Ground Ice containing Permafrost. Active Ice Wedges developed in mineral soil occur primarily in areas of Continuous Permafrost. | Trombotto et al. 2014 |
| Active layer | The layer of ground that is subject to annual thawing and freezing in areas underlain by permafrost; also known as seasonal frost. | NSIDC accessed 2016 |
| Active layer | The layer of ground that is subject to annual thawing and freezing in areas underlain by permafrost. | IPCC WGI AR5 2013 |
| Active layer | The layer of ground that is subject to annual thawing and freezing in areas underlain by permafrost | Van Everdingen International Permafrost Association 2005 |
| Active layer | The Active Layer is a layer of ground that is subject to annual thawing and freezing in areas underlain by Permafrost. In the zone of Continuous Permafrost the Active Layer generally reaches the Permafrost Table; in the zone of Discontinuous Permafrost it often does not. The Active Layer includes the uppermost part of the Permafrost wherever either the salinity or clay content of the Permafrost allows it to thaw and refreeze annually, even though the material remains cryotic (T < 0C). The Active Layer depth may vary considerably from one year to another depending on a number of variables (cf. Active Layer Thickness). If the ground thermal regime is no longer in long-term climatic equilibrium, Active Layers tend to show trends of increasing thickness. | Trombotto et al. 2014 |
| Active layer | That part of the soil included with the suprapermafrost layer (i.e., existing above permafrost) that usually freezes in winter and thaws in summer. Its bottom surface is the frost table, beneath which may lie permafrost or talik. The depth of the active layer varies anywhere from a few inches to several feet. (Also called frost zone, mollisol.) | AMS - glossary of meteorology |
| Active layer | Upper zone of soil in higher latitude locations that experiences daily and seasonal freeze-thaw cycles. | PhysicalGeography.net |
| Active layer failure | A general term referring to several forms of slope failures or failure mechanisms commonly occuring in the Active Layer overlying Permafrost. Such failures are often triggered by loss of shear strength due to high pore water pressures which result because the underlying Permafrost is quasi-impermeable. | Trombotto et al. 2014 |
| Active layer thickness | The thickness of the layer of the ground that is subject to annual thawing and freezing in areas underlain by Permafrost. The thickness of the Active Layer depends on factors such as the ambient air temperature, vegetation, drainage, soil or rock type (thermal properties of soil or rock), total water content, Snow Cover, and degree and orientation of slope. The thickness of the Active Layer can vary from year to year, primarily due to variations in the mean annual air temperature, distribution of soil moisture, and Snow Cover. The thickness of the Active Layer includes the uppermost part of the Permafrost wherever either the salinity or clay content of the Permafrost allows it to thaw and refreeze annually, even though the material remains cryotic (T < 0C). | Trombotto et al. 2014 |
| Active liquid refrigerant pile | A foundation pile on which a liquid coolant refrigeration system has been installed to remove heat from the ground | Van Everdingen International Permafrost Association 2005 |
| Active permafrost | Permanently frozen ground (permafrost) which, after thawing by artificial or unusual natural means, reverts to permafrost under normal climatic conditions; opposed to passive permafrost. | AMS - glossary of meteorology |
| Active rock glacier | A mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of present movement. | NSIDC accessed 2016 |
| Active rock glacier | A mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of present movement | Van Everdingen International Permafrost Association 2005 |
| Active rock glacier | A mass of rock fragments and finer material, generally on a slope, that contains either an Ice core or interstitial Ice, and shows evidence of on-going movement. Active Rock Glaciers possess steep fronts with slope angles that approach or exceed the angle of repose. | Trombotto et al. 2014 |
| Active thermokarst | The process by which characteristic landforms are currently developing as a result of thawing of ice-rich permafrost or melting of massive ice. | NSIDC accessed 2016 |
| Active thermokarst | The process by which characteristic landforms are currently developing as a result of thawing of ice-rich permafrost or melting of massive ice | Van Everdingen International Permafrost Association 2005 |
| Active-layer failure | A general term referring to several forms of slope failures or failure mechanisms commonly occurring in the active layer overlying permafrost. | NSIDC accessed 2016 |
| Active-layer failure | A general term referring to several forms of slope failures or failure mechanisms commonly occurring in the active layer overlying permafrost | Van Everdingen International Permafrost Association 2005 |
| Active-layer thickness | The thickness of the layer of the ground that is subject to annual thawing and freeing in areas underlain by permafrost. | NSIDC accessed 2016 |
| Active-layer thickness | The thickness of the layer of the ground that is subject to annual thawing and freeing in areas underlain by permafrost | Van Everdingen International Permafrost Association 2005 |
| Active-microwave sensor | A sensor transmitting radiation and receiving reflections in the radio or microwave regions of the electromagnetic spectrum; in glaciological applications, either an imaging radar or a radar configured as a scatterometer or radar altimeter. Frequencies from about 12 mhz up to about 15 ghz have various applications in the study of mass balance with Active-microwave sensors. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Activity index | The mass-balance gradient at the Balanced-budget ELA. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Additional zones | Additional zones present separate layers on an ice chart. If it is necessary to show the actual boundaries of zones of discontinuities (leads and fractures), changing hummock and ridge concentration, level ice, zones of different stages of melting or other additional characteristics, they are identified only by one characteristic. | Bushuyev 2004 |
| Adfreeze strength | The tensile or shear strength which has to be overcome to separate two objects that are bonded together by ice | Van Everdingen International Permafrost Association 2005 |
| Adfreeze/adfreezing | The process by which two objects are bonded together by ice formed between them | Van Everdingen International Permafrost Association 2005 |
| Adfreezing | The process by which one object becomes adhered to another by the binding action of ice. | AMS - glossary of meteorology |
| Adret | The slope (usually equatorward, or southward in the Northern Hemisphere) of a mountain that faces into the sun. The term is originally and most often used in referring to mountains in the Alps. Tilted toward the sun, an adret is characterized by higher temperatures, a longer growing season, less snow cover and a shorter duration of snow cover, and a higher timber line and snow line than the shaded side (the ubac). | AMS - glossary of meteorology |
| Advance | Increase of the length of a flowline, measured from a fixed point. In practice, when the advance is of a land-terminating glacier terminus, the fixed point is usually downglacier from the glacier margin, that is, on the glacier forefield. The quantity reported is most often the amount of advance rather than the length itself. Retreat is the opposite of advance, that is, retreat of the terminus. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Advance | An increase in the length of a glacier compared to a previous point in time. As ice in a glacier is always moving forward, a glacier's terminus advances when less ice is lost due to melting and/or calving than the amount of yearly advance. | Molnia USGS 2004 |
| Advection frost | Frost due primarily to the transport of moist air over a surface having a temperature below freezing. | WMO METEOTERM accessed 2016 |
| Age structure of ice | The observed, or model calculated age categories of ice and their partial concentrations. The sum of the partial concentrations of ice of different age should be equal to the total ice concentration in the given zone. | Bushuyev 2004 |
| Aged ridge | Ridge that has undergone considerable weathering. These ridges are best described as undulations. | WMO Sea Ice Nomenclature 2017 |
| Aged ridge | Sea ice terminology that describes a ridge which has undergone considerable weathering. These ridges are best described as undulations or waves. | Environment and Climate Change Canada 2014 |
| Agglomerate | An ice cover of floe formed by the freezing together of various forms of ice. | NOAA Glossary of Hydrologic Terms |
| Agglomerated brash | Canadian sea ice terminology that is not part of the World Meteorological Organization's (WMO) terminology. An area of brash ices that is not compacted. | Environment and Climate Change Canada 2014 |
| Aggradation | Aggradation is the term used to describe the increase in land elevation due to the buildup and growth of Ground Ice or deposition of sediments. | Trombotto et al. 2014 |
| Aggradational ice | The additional ground ice formed as a direct result of permafrost aggradation. | NSIDC accessed 2016 |
| Aggradational ice | The additional ground ice formed as a direct result of permafrost aggradation | Van Everdingen International Permafrost Association 2005 |
| Aggradational ice | Ground Ice formed as a direct result of Permafrost Aggradation. Ice lenses form seasonally, especially in the lower part of the Active Layer, and can be incorporated into the Permafrost if they do not melt over a period of years. | Trombotto et al. 2014 |
| Aggregation | 1.The process of combining different surface characteristics from neighboring heterogeneous regions into an average value for the area. It is used in boundary layer studies for surface fluxes, drag, and roughness. This process is often necessary to define surface characteristics for numerical models that have coarse horizontal grid mesh and that cannot resolve the individual surface areas. 2.The process of clumping together of snow crystals following collision as they fall to form snowflakes. This process is especially important near the melting layer where snow particles stick to each other more easily because of the liquid water on the surface. It also occurs at lower temperatures especially between dendritic snow crystals and occasionally rosette crystals in cirrus. | AMS - glossary of meteorology |
| Air freezing index | The cumulative number of degree-days below 0° C for the air temperature during a given time period | Van Everdingen International Permafrost Association 2005 |
| Air freezing index | The cumulative number of degree-days below 0C for the air temperature during a given time period. The Air Freezing Index differs from the corresponding surface Freezing Index (see n-factor). SUM (T_1) < 0 | Trombotto et al. 2014 |
| Air thawing index | The cumulative number of degree-days above 0°C for the air temperature during a given period | Van Everdingen International Permafrost Association 2005 |
| Air thawing index | The cumulative number of degree-days above 0C for the air temperature during a given period. The Air Thawing Index differs from the corresponding surface Thawing Index (see n-factor). | Trombotto et al. 2014 |
| Airborne Snow Survey Program | Center (NOHRSC) program that makes airborne snow water equivalent and soil moisture measurements over large areas of the country that are subject to severe and chronic snow melt flooding. | NOAA Glossary of Hydrologic Terms |
| Airborne Snow Water Equivalent Measurement Theory | A theory based on the fact that natural terrestrial gamma radiation is emitted from the potassium, uranium, and thorium radioisotopes in the upper eight inches of the soil. The radiation is sensed from low flying aircraft 500 feet above the ground. Water mass in the snow cover attenuates the terrestrial radiation signal. The difference between airborne radiation measurements made over bare ground and snow-covered ground can be used to calculate a mean areal snow water equivalent value with a root mean square error of less than a half inch. | NOAA Glossary of Hydrologic Terms |
| Alas/alass | A large depression of the ground surface produced by thawing of a large area of very thick and exceedingly ice-rich permafrost. | NSIDC accessed 2016 |
| Alas/alass | A large depression of the ground surface produced by thawing of a large area of very thick and exceedingly ice-rich permafrost | Van Everdingen International Permafrost Association 2005 |
| Alas/alass | A large depression of the ground surface produced by thawing of a large area of very thick and exceedingly ice-rich Permafrost. In the early stages of formation, a shallow (appx. 2 m) circular 'alas lake' forms in a steep-sided depression. Enlargement and ultimate drainage of a number of such lakes may leave low inter-alas plateaus. | Trombotto et al. 2014 |
| Alaska current | The eastern semi of the North Pacific subpolar gyre. It is a shallow current carrying relatively warm water northward and thus has a climate influence similar to that exercised by the North Atlantic and Norwegian Currents on the climates of northwestern Europe, though on a smaller scale. It flows cyclonically around the Gulf of Alaska, feeding into the Alaskan Stream. Freshwater from the many rivers of Canada and Alaska reduces the water density near the coast; the result is a pressure gradient normal to the coast that constrains the current geostrophically to the coastal region and increases its speed to 0.3 m/s. | AMS - glossary of meteorology |
| Alaskan stream | The continuation of the Alaska Current along the southern side of the Aleutian Islands. The distinction between the Alaskan Stream and the Alaska Current is gradual, and the two currents are sometimes regarded as one. They are, however, of different character, the Alaska Current being shallow and variable but the Alaskan Stream reaching to the ocean floor. Despite its modest speed of 0.3 m/s, it is a western boundary current. Most of the water of the Alaskan Stream feeds directly into the Oyashio. Some of its flow enters the Bering Sea between the Aleutian Islands (most of it between 168 and 172W) and follows a cyclonic path before feeding into the Kamchatka Current, thus eventually also contributing to the Oyashio | AMS - glossary of meteorology |
| Albedo | The portion of incoming radiation which is reflected by a surface. | NOAA Glossary of Hydrologic Terms |
| Albedo | A non-dimensional, unit-less quantity that measures how well a surface reflects solar energy; ranges from 0 - 1; a value of 0 means the surface is a 'perfect absorber', where all incoming energy is absorbed, a value of 1 means the surface is a 'perfect reflector', where all incoming energy is reflected and none is absorbed. | NSIDC accessed 2016 |
| Albedo | Reflectivity; the fraction of radiation striking a surface that is reflected by that surface. | NOAA National Weather Service Glossary 2009 |
| Albedo | The ratio of the reflected flux density to the incident flux density, usually referring either to the entire spectrum of solar radiation (broadband albedo) or just to the visible part of the spectrum. The broadband albedos of glacier surfaces exceed 0.8 for freshly fallen snow, are less for aged snow and firn, and are significantly less for exposed glacier ice. Snow and ice that are sediment-laden or covered by debris can have albedos still lower. The difference between the albedos of snow and glacier ice is significant in the seasonal evolution of the energy balance and therefore of the rate of surface ablation. Spectral albedo is the albedo at a single wavelength or, more loosely, over a narrow range of wavelengths. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Albedo | Albedo is the percentage of the incoming radiation that is reflected off a surface. An albedo of one indicates that 100 percent of the radiation is reflected. Fresh snow has a high albedo (0.7 to 0.9), indicating that 70 to 90 percent of the radiation received is reflected; glacier ice has a lower albedo of 0.2 to 0.4. Therefore, more radiation may be absorbed by glacier ice than by snow. | Molnia USGS 2004 |
| Albedo | Ratio of the radiation (radiant or luminous energy) reflected by a surface to that incident on it. | WMO METEOTERM accessed 2016 |
| Albedo | The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. | EU Climate-ADAPT |
| Albedo | The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Snow-covered surfaces have a high albedo, the albedo of soils ranges from high to low, and vegetation-covered surfaces and oceans have a low albedo. The Earth's planetary albedo varies mainly through varying cloudiness, snow, ice, leaf area and and cover changes. | IPCC WGI AR5 2013 |
| Albedo | Ratio of reflected radiation to incoming radiation, usually given in per cent. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Albedo | Albedo is a measure of the reflecting power of a surface, expressed as the fraction of the incoming solar radiation reflected by the surface | Van Everdingen International Permafrost Association 2005 |
| Albedo | The ratio of reflected flux density to incident flux density, referenced to some surface. Albedos commonly tend to be broadband ratios, usually referring either to the entire spectrum of solar radiation, or just to the visible portion. More precise work requires the use of spectral albedos, referenced to specific wavelengths. Visible albedos of natural surfaces range from low values of 0.04 for calm, deep water and overhead sun, to > 0.8 for fresh snow or thick clouds. Many surfaces show an increase in albedo with increasing solar zenith angle. See also plane albedo, planetary albedo, spherical albedo, directional-hemispherical reflectance, bihemispherical reflectance. | AMS - glossary of meteorology |
| Albedo | Is the reflectivity of a surface. | PhysicalGeography.net |
| Albedometer | Instrument for measuring the reflecting power of a surface (e.g., clouds, grass, snow). A pyranometer is sometimes inverted and used as an albedometer to measure the radiation reflected from the Earth's surface. | WMO METEOTERM accessed 2016 |
| Albedometer | An instrument used for the measurement of the reflecting power (the albedo) of a surface. A pyranometer adapted for the measurement of radiation reflected from the earth's surface is sometimes employed as an albedometer. | AMS - glossary of meteorology |
| Aleutian current | The southern, eastward flowing current of the subpolar gyre in the North Pacific. It is fed by the outflow from the Oyashio and lies north of the North Pacific Current, with which it establishes the polar front in the west and experiences much water exchange as it proceeds eastward. As it approaches the coast of North America, it divides to form the northward flowing Alaska Current and the southward flowing California Current. (Also called the Subarctic Current.) | AMS - glossary of meteorology |
| Aleutian low | The low pressure center located near the Aleutian Islands on mean charts of sea level pressure. It represents one of the main centers of action in the atmospheric circulation of the Northern Hemisphere. The Aleutian low is most intense in the winter months; in summer it is displaced toward the North Pole and is almost nonexistent. On a daily basis, the area of the Aleutian low is marked by alternating high and low pressure centers, moving generally to the eastward; it is not the scene of an intense stationary low. Normally the depth of intensity of the low pressure areas exceeds the intensity of the high pressure areas, so that the region is one of low pressure on the average. The travelling cyclones of subpolar latitudes usually reach maximum intensity in the area of the Aleutian low. The Aleutian low and its counterpart in the Atlantic Ocean, the Icelandic low, compose the Northern Hemisphere's subpolar low pressure belt. | AMS - glossary of meteorology |
| Alimentation | Various processes which operate to increase the mass of a glacier or of a snow-field (deposition of snow, precipitation, sublimation, etc.) | WMO METEOTERM accessed 2016 |
| Almwind | Local name for a foehn that blows from the south (Hungary) across the Tatra Mountains south of Krakow, Poland, and descends the northern valleys; similar to the Alpine south foehn. It is sometimes stormy and may reach 20-25 m/s (40-50 mph) in gusts, especially in spring and fall. It raises temperatures to as much as 14C above the normal for the season, and in winter and spring it causes avalanches. At Zakopane (in southern Poland) it sometimes blows as a high foehn. This wind occurs in front of depressions moving eastward in the Baltic. | AMS - glossary of meteorology |
| Along-valley winds | The component of topographically generated winds that are parallel to the valley axis and can occur during conditions of light or calm synoptic-scale winds such as those near the center of anticyclones. At night, cold, dense air flowing down the river valley from the higher elevations is called a mountain wind or drainage wind with typical depths of 10 to 400 m and speeds of 1 to 8 m/s, while the weaker return circulation aloft is called an anti-mountain wind. During the day, the gentle up-valley flow of warm air along the valley floor is called a valley wind, and the return circulation aloft is called an anti-valley wind. | AMS - glossary of meteorology |
| Alpenglow | The occasional reappearance of sunset colors on a (snow-covered) mountaintop soon after sunset and a similar phenomenon before sunrise. Alpenglow has three phases. During evening twilight, the first stage is the mountain peak's usual coloration seen at low sun elevations h0 (h0 < 2). Second is the alpenglow proper that occurs a few minutes after the first color has faded (h0 slightly less than 0). The peaks are still in direct sunlight, and their colors are purer and often pinker than before. The alpenglow boundary may first occur hundreds of meters below the summit, then moves upward, and finally fades as the atmosphere's dark segment rises. Third is the afterglow, which occurs nearly simultaneously with the first purple light. The peaks are no longer in direct sunlight; the illumination is more diffuse and its boundary vaguer than in the earlier stages. The third stage lasts longer than the other two (-5 < h0 < -9), and its color varies from yellow to purple. A faint second afterglow has been reported and is associated with the rare occurrence of a second purple light. The alpenglow appears to be much less common at sunrise than at sunset. The morning colors are more pink and purple, while those of evening are more orange and red. | AMS - glossary of meteorology |
| Alpine glacier | A glacier that is confined by surrounding mountain terrain; also called a mountain glacier. | NSIDC accessed 2016 |
| Alpine glacier | Same as mountain glacier. | AMS - glossary of meteorology |
| Alpine glacier | Small glacier that occupies a U-shaped valley on a mountain. Also called a mountain glacier. | PhysicalGeography.net |
| Alpine permafrost | Form of permafrost that exists at high altitudes in mountainous environments. | PhysicalGeography.net |
| Alpine tundra | A form of tundra in which the absence of trees is due to high altitude instead of high latitude. It lies roughly between the summer isotherm of 10C and the snow line. (Also called mountain tundra.) | AMS - glossary of meteorology |
| Alpine tundra | High altitude biome dominated by a few species of dwarf shrubs, a few grasses, sedges, lichens, and mosses. Productivity is low in this biome because of the extremes of climate. Quite similar to tundra. | PhysicalGeography.net |
| Altimetry | A remote-sensing technique in which surface altitudes (elevations) are estimated as a function of the travel time of a pulse of electromagnetic radiation transmitted from and received by a precisely located altimeter. Altimeters are mounted on either satellite or aircraft. Satellite altimeters use on-board Global Positioning System (GPS instruments and star trackers to determine orbital position and altimeter pointing angles. Aircraft systems measure the altimeter trajectory using GPS and inertial navigation systems. Accurate altimetry measurements, especially those acquired from space, require corrections for variations in atmospheric and ionospheric conditions, and for variations in orbital position of the sensor. Altimeters are either laser altimeters or radar altimeters. Each of the two radiation bands has strengths and weaknesses with respect to footprint size and ability to sample through atmospheric obstructions such as clouds. Altimetry measurements are compared with surface elevations obtained at identical points in horizontal space at an earlier time to calculate elevation changes which can then be used to compute volume changes. The earlier elevation measurement is commonly obtained from a previous altimetry pass, but can also be derived from other sources such as topographic maps. A mass balance is obtained from knowledge of the ice-column density usually supplied by Sorge's law. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Altitude | The vertical distance of a point above a datum. The vertical datum is usually an estimate of mean sea level. Older measurements were often determined in a local coordinate system and were not tied to a global reference frame. Some were made not with surveying instruments but with barometers, in reliance on the decrease of atmospheric pressure with altitude. It is now usual to measure altitude or elevation using the Global Positioning System or an equivalent global navigation satellite system. Altitude and elevation are synonyms in common usage, although altitude is less ambiguous. The unqualified word 'elevation' can also refer, for example, to the act of elevating or to angular distance above a horizontal plane. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Altitude | Vertical distance of a level, a point or an object considered as a point, measured from mean sea level. (TR) | UNESCO-WMO International Glossary of Hydrology 2012 |
| Altitude | A measure (or condition) of height, especially of great height, as a mountain top or aircraft flight level. In meteorology, altitude is used almost exclusively with respect to the height of an airborne object above the earth's surface, above a constant-pressure surface, or above mean sea level. The measurement of altitude is accomplished by altimeters in aeronautics, and the entire study is called altimetry. | AMS - glossary of meteorology |
| Altitude | Vertical distance above sea-level. | PhysicalGeography.net |
| Altitudinal limit of permafrost | The lowest altitude at which mountain permafrost occurs in a given highland area outside the general permafrost region | Van Everdingen International Permafrost Association 2005 |
| Altitudinal limit of permafrost | The lowest altitude at which Mountain Permafrost occurs in a given area downslope of the general Permafrost region. The altitudinal limit of Mountain Permafrost rises progressively with decreasing latitude in both hemispheres. | Trombotto et al. 2014 |
| Altitudinal zonation of permafrost | The vertical subdivision of an area of mountain permafrost into permafrost zones, based on the proportion of the ground that is perennially cryotic | Van Everdingen International Permafrost Association 2005 |
| Altitudinal zonation of permafrost | The vertical subdivision of an area of Mountain Permafrost into Permafrost zones, based on the proportion of the ground that is perennially cryotic. As mean annual temperatures decrease with increasing elevation, Mountain Permafrost can be expected to be more extensive, thicker and colder at higher elevations, although aspect and the extent of vegetation and Snow Cover will moderate this effect. | Trombotto et al. 2014 |
| Amorphous frost | Hoarfrost that possesses no apparent simple crystalline structure; opposite of crystalline frost. The lack of distinct crystal structure in forms of amorphous frost, however, is only a matter of scale. Such frost is built up of a multitude of units each of which has its own crystal structure, although no unit fits compatibly with its neighboring unit. | AMS - glossary of meteorology |
| Anabatic wind | In mountain meteorology, an upslope wind driven by heating (usually daytime insolation) at the slope surface under fair-weather conditions. The mechanism of the anabatic wind can be described as follows. The warm surface heats a vertical column of the atmosphere starting at the slope surface and reaching up to a few hundred meters deep. This column is warmer than the column at the same levels over the valley or plain, resulting in hydrostatic low pressure over the slope relative to over the valley or plain. The horizontal pressure gradient, maximized at the slope surface, drives an acceleration directed toward the slope, or up the slope. Although the pressure-gradient forcing is at its maximum at the slope, surface friction causes the peak in the anabatic wind speeds to occur above the surface, often by several tens of meters; if the surface heating is strong, however, the momentum will tend to be vertically mixed. Speeds in the mountain-valley anabatic flow layer are often 3-5 m/s. Because heating at the surface promotes deeper mixing than cooling does, the heated layer, often occurring as a convective or mixed layer, is generally deeper than a cooled or katabatic layer. Slopes occur on many scales, and consequently anabatic flows also occur on many scales. At local scales anabatic winds are an along-slope component of mountain-valley wind systems. At scales ranging from the slopes of individual hills and mountains to the slopes of mountain ranges and massifs, anabatic flows represent the daytime component of mountain-plains wind systems. In general usage, this term does not suffer from the multiplicity of meanings that katabatic wind does. | AMS - glossary of meteorology |
| Anadyr current | A current through the Bering Strait that carries low-salinity water of Pacific origin into the Arctic Ocean. It is concentrated on the Siberian side with speeds near 0.3 m/s and varies little with season. During winter it is augmented by additional flow from the Sphanberg Strait. With a total transport of less than 0.5 Sv (0.5 ? 10^6 m^3/s), the Anadyr Current contributes little to the mass balance of the World Ocean but is essential to its freshwater budget since the salinity of the North Pacific is so much lower than that of the North Atlantic. In terms of freshwater transport the modest Anadyr Current is equivalent to several Amazon Rivers. | AMS - glossary of meteorology |
| Anchor ice | Submerged frazil ice attached or anchored to the river bottom, irrespective of its formation. | NOAA Glossary of Hydrologic Terms |
| Anchor ice | Submerged ice which is attached to the bottom. | NSIDC accessed 2016 |
| Anchor ice | Sea ice terminology that describes submerged ice that is attached or anchored to the bottom of the sea, irrespective of the nature of its formation. | Environment and Climate Change Canada 2014 |
| Anchor ice | Submerged ice attached or anchored to the bottom, irrespective of the nature of its formation. | WMO Sea Ice Nomenclature 2017 |
| Anchor ice | Submerged ice found attached to underwater objects such as the channel bed and aquatic vegetation. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Anchor ice | Ice attached to the beds of streams, lakes, and shallow seas, irrespective of its nature of formation. On clear, cold nights in relatively still water, anchor ice may form directly on submerged objects. It also develops in supercooled water if turbulence is sufficient to maintain uniform temperature at all depths, in which case a spongy mass of frazil accumulates on objects exposed to rapid flow, and later deposition fills in the pores and creates solid ice. When the water temperature increases to above 0C, the ice rises to the surface, often carrying with it the object on which it had accumulated. Sometimes anchor ice is erroneously called ground ice, a term which should be reserved for bodies of more or less clear ice in frozen ground. | AMS - glossary of meteorology |
| Anchor ice | Submerged ice which is attached to the bottom. | Illustrated Glossary of Snow and Ice |
| Anchor ice dam | An accumulation of anchor ice which acts as a dam and raises the water level. | NOAA Glossary of Hydrologic Terms |
| Annual AAR | The AAR at the end of the mass-balance year. Annual AARs can vary greatly from year to year, but an average over a number of years, when compared with the Balanced-budget AAR, gives a measure of the health of the glacier. If the difference is large and in the same direction over a considerable time, a prolonged period of non-zero mass balance can be expected as the glacier seeks equilibrium. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Annual ablation | Ablation integrated over the mass-balance year. Annual ablation is the sum of winter ablation and summer ablation where winter and summer are well-differentiated. Formerly it was referred to as 'total ablation' when working in the stratigraphic system. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Annual accumulation | Accumulation integrated over the mass-balance year. Annual accumulation is the sum of winter accumulation and summer accumulation where winter and summer are well-differentiated. Formerly it was referred to as 'total accumulation' when working in the stratigraphic system. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Annual ELA | The ELA at the end of the mass-balance year. The Annual ELA is not in general the same as the average altitude of the Annual snowline. The superimposed ice zone lies below the Annual snowline and above the Annual ELA. However, if there is no superimposed ice, the Annual snowline can be used as a proxy for the Annual ELA. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Annual equilibrium line | The equilibrium line at the end of the mass-balance year. At the Annual equilibrium line, Annual ablation balances Annual accumulation and the Annual mass balance is zero. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Annual exchange | Annual accumulation minus Annual ablation. Ablation is defined to be negative, so the Annual exchange may also be regarded as the sum of the absolute values of accumulation and ablation. It is a possible measure of the amplitude of mass exchange between the glacier and its environment, but the mass-balance amplitude is more often used for that purpose. Formerly Annual exchange was defined only in the fixed-date system and total exchange was defined as its equivalent in the stratigraphic system. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Annual mass balance | The sum of accumulation and ablation over the mass-balance year, equivalent to the sum of Annual accumulation and Annual ablation, and also to the sum of winter mass balance and summer mass balance where winter and summer are well-differentiated; that is, ba = ca + aa = bw + bs. For reasons explained more fully under Net mass balance, the term Annual mass balance replaces the formerly distinct terms 'Annual balance' and 'net balance', which were used in the fixed-date system and the stratigraphic system respectively. The adjective 'Annual' describes the time span of the mass-balance measurement more adequately than the adjective 'net', which does not refer to a time period but rather to the mass that is remaining after all deductions (here ablation) have been made. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Annual snowline | The snowline at the end of the ablation season, usually representing the highest position of the snowline during the mass-balance year; end-of-summer snowline is a synonym. The snowline of any given balance year is established at the end of that balance year. If this newly established snowline is lower than the previous year's firn line, it also becomes the new firn line. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Antarctic air | A cold, dry air mass developed over the continent of Antarctica. Antarctic air is generally colder at the surface in all seasons, and at all levels in austral (Southern Hemisphere) autumn and winter, than arctic air. | AMS - glossary of meteorology |
| Antarctic anticyclone | The glacial anticyclone that has been said to overlie the continent of Antarctica; analogous to the Greenland anticyclone. Until the International Geophysical Year there had been insufficient observational evidence to either support or contradict this theory. | AMS - glossary of meteorology |
| Antarctic bottom water | A water mass formed by deep winter convection at the coast of Antarctica, particularly in the Weddell and Ross Seas but also at other shelf locations. Being the densest water mass of the World Ocean, AABW is found to occupy the depth range below 4000 m of all ocean basins that have a connection to the Southern Ocean at that level. At the time of formation its temperature is close to the freezing point (-1.9C), but to enter the oceans, AABW has to pass through and mix with the water of the Antarctic Circumpolar Current, which gives it its typical salinity of 34.7 psu and temperature of +0.3C. Because of this it is also known as Antarctic Circumpolar Water, particularly in the Indian and Pacific Oceans. | AMS - glossary of meteorology |
| Antarctic circle | The line of latitude 66 deg 34 min S (often taken as 66S). Along this line the sun does not set on the day of the summer solstice, about 22 December, and does not rise on the day of the winter solstice, about 21 June. | AMS - glossary of meteorology |
| Antarctic circle | Latitude of 66.5 South. The northern limit of the area of the Earth that experiences 24 hours of darkness or 24 hours of day at least one day during the year. | PhysicalGeography.net |
| Antarctic circumpolar current | An eastward flowing current, also known as the West Wind Drift, that circles Antarctica and extends from the surface to the ocean floor. With a volume transport of 130 Sv (130 ? 10^6 m^3/s) it is the largest of all ocean currents. Current speed in the ACC is comparatively modest (0.1 m/s, but larger in fronts), the large transport being achieved by the current's great depth. Seventy-five percent of the transport occurs in the polar and subantarctic fronts that make up only 20% of the ACC area. Interannual variability is about 15% of the mean but can reach 40% on occasions. The ACC is influenced by bottom topography, which causes deflections from its general westward path and eddy formation, particularly at the Scotia Ridge, the Kerguelen Plateau, and the Macquarie Ridge. The eddies are instrumental for the poleward transport of heat across the current, which would otherwise block meridional heat transfer. | AMS - glossary of meteorology |
| Antarctic divergence | The region near 60S, south of the Antarctic Polar Front, where high-salinity North Atlantic Deep Water upwells from 2500 m to just below the surface and mixes with low- salinity Antarctic Surface Water. | AMS - glossary of meteorology |
| Antarctic front | The semipermanent, semicontinuous front between the antarctic air of Antarctica and the polar air of the southern oceans; generally comparable to the arctic front of the Northern Hemisphere. | AMS - glossary of meteorology |
| Antarctic high | A region of high pressure that occupies central Antarctic throughout the year. This pressure system is responsible for very cold temperatures and extremely low humidity. | PhysicalGeography.net |
| Antarctic ice sheet | The continuous ice mass covering most of Antarctica. | AMS - glossary of meteorology |
| Antarctic intermediate water | A water mass identified by a salinity minimum found at depths between 700 and 1000 m in the Southern Hemisphere. It is formed at various locations along the Antarctic Polar Front and through deep winter convection east of southern Chile and south of the Great Australian Bight. It enters all oceans with the Antarctic Circumpolar Current and spreads toward the equator between the central water and the deep water. | AMS - glossary of meteorology |
| Antarctic ozone hole | A phenomenon discovered in the mid-1980s that occurs in the winter-spring lower stratosphere over Antarctica. Through a sequence involving heterogeneous chemistry on polar stratospheric clouds and (intermittent) illumination by sunlight, much or all of the ozone in the lower stratosphere can be photochemically destroyed. Halogen species (chlorine and bromine) contained in fairly robust molecules are transformed via heterogeneous reactions into molecules that are easily photolyzed resulting in atomic or monoxide halogens that lead to chemical destruction of ozone. This phenomenon also occurs over the Arctic, although to a lesser extent because of a lower incidence of polar stratospheric clouds. | AMS - glossary of meteorology |
| Antarctic polar front | The southern front of the Antarctic Circumpolar Current, also known as the antarctic convergence, that separates the Antarctic Zone in the south from the polar frontal zone in the north. It is characterized by sea surface temperatures near 5-6C and a salinity minimum of 33.8-34.0 psu produced by high rainfall. | AMS - glossary of meteorology |
| Antarctic stratospheric vortex | The vortex in the lower stratosphere over the Antarctic in austral winter. | AMS - glossary of meteorology |
| Antarctic surface water | The water mass of the Antarctic Zone. It has a temperature of 0.0 to -1.9C and a salinity below 34 psu. | AMS - glossary of meteorology |
| Antarctic zone | 1.The region between the Antarctic Polar Front and the Continental Water Boundary. 2.Geographically, the region between the Antarctic Circle (66 deg 32 min S) and the South Pole. Climatically, the limit of the zone may be set at about 60S, poleward of which the prevailing westerly winds give place to easterly or variable winds. Over most of this region the average temperature does not rise above 0C (32F) even in summer. | AMS - glossary of meteorology |
| Anti-icing | The prevention of ice accumulation on aircraft, ships and other objects. The most common measures are heating or the application of a dressing by brush or spray to weaken adhesion and facilitate removal (cf. De-icing). | Illustrated Glossary of Snow and Ice |
| Anti-syngenetic ice wedge | An ice wedge that grows progressively downwards into a receding slope, in a direction normal(perpendicular) to the surface. | NSIDC accessed 2016 |
| Anti-syngenetic ice wedge | An ice wedge that grows progressively downwards into a receding slope, in a direction normal to the surface | Van Everdingen International Permafrost Association 2005 |
| Aperwind | A warm wind of the Alps that thaws the snow. (Also called aberwind, alpach.) | AMS - glossary of meteorology |
| Apparent head capacity | The amount of heat required to raise the temperature of a unit mass of frozen ground by one degree. | NSIDC accessed 2016 |
| Apparent head capacity | The amount of heat required to raise the temperature of a unit mass of Frozen Ground by one degree Celsius/Kelvin. Because the phase change in Frozen Ground often occurs gradually over a range of temperatures, the Apparent Heat Capacity (which is the sum of the Specific Heat Capacity and the Latent Heat released) may vary significantly with temperature. | Trombotto et al. 2014 |
| Apparent heat capacity | The amount of heat required to raise the temperature of a unit mass of frozen ground by one degree | Van Everdingen International Permafrost Association 2005 |
| Approximate freezing index | The cumulative number of degree-days below 0°C for a given time period, calculated from the mean monthly temperatures for a specific station without making corrections for positive degree-days in spring and fall | Van Everdingen International Permafrost Association 2005 |
| Approximate thawing index | The cumulative number of degree-days above 0°C for a given time period, calculated from the mean monthly temperatures for a specific station without making corrections for negative degree-days in spring and fall | Van Everdingen International Permafrost Association 2005 |
| Ar?te | (from the French) A sharp, narrow, often pinnacled ridge, formed as a result of glacial erosion from both sides. | Swisseduc - Photo glossary of glaciological terms |
| Arctic | The region within the Arctic Circle, or, loosely, northern regions in general, characterized by very low temperatures. | NOAA National Weather Service Glossary 2009 |
| Arctic air | A type of air mass with characteristics developed mostly in winter over arctic surfaces of ice and snow. Arctic air is cold aloft and extends to great heights, but the surface temperatures are often higher than those of polar air. For two or three months in summer arctic air masses are shallow and rapidly lose their characteristics as they move southward. | AMS - glossary of meteorology |
| Arctic bottom water | The water mass formed in the Arctic Ocean by a combination of freezing on the arctic shelf and deep winter convection in the Greenland and Norwegian Seas. Freezing increases the salinity under the ice; the dense water sinks to the ocean floor and leaves the arctic basins to enter the Greenland and Norwegian Seas, where it mixes with water that sinks under the influence of surface cooling. The resulting water mass has a salinity of 34.95 psu and a temperature of -0.8 to -0.9C. It fills the Arctic Ocean at all depths below 800 m, the sill depth to the Atlantic. It enters the Atlantic in bursts, when the passage of atmospheric depressions lifts the thermocline and allows Arctic Bottom Water to flow over the sill. Overflow events in the Denmark Strait and across the Iceland-Faeroe sill contribute some 5 Sv (5 ? 10^6 m3/s) to the formation of North Atlantic Deep Water. | AMS - glossary of meteorology |
| Arctic circle | The line of latitude 66 deg 34 min N (often taken as 66N). Along this line the sun does not set on the day of the summer solstice, about June 21, and does not rise on the day of the winter solstice, about December 22. From this line the number of twenty- four-hour periods of continuous day or of continuous night increases northward to about six months each at the North Pole. | AMS - glossary of meteorology |
| Arctic circle | Latitude of 66.5 North. The southern limit of the area of the Earth that experiences 24 hours of darkness or 24 hours of day at least one day during the year. | PhysicalGeography.net |
| Arctic desert | "Any area in the high latitudes dominated by bare rocks, ice, or snow, and having a sparse vegetation and a low annual precipitation." [from Glossary of Arctic and Subarctic Terms (1955)]. Thus stated, this includes portions of both ice cap and tundra regions of both hemispheres. The term barrens is sometimes used, but this has more general application. | AMS - glossary of meteorology |
| Arctic front | The semipermanent, semicontinuous front between the deep, cold arctic air and the shallower, basically less cold polar air of northern latitudes; generally comparable to the antarctic front of the Southern Hemisphere. | AMS - glossary of meteorology |
| Arctic haze | Haze in Arctic regions which reduces horizontal and oblique visibility and which may extend to a height of about 10 km. It appears blue-grey when viewed away from the Sun, and reddish-brown toward it. | WMO METEOTERM accessed 2016 |
| Arctic haze | A condition of reduced horizontal and slant visibility (but unimpeded vertical visibility) encountered by aircraft in flight over arctic regions. | AMS - glossary of meteorology |
| Arctic high | A weak high that appears on mean charts of sea level pressure over the Arctic basin during late spring, summer, and early autumn. (Also called arctic anticyclone, polar anticyclone, polar high.) | AMS - glossary of meteorology |
| Arctic intermediate water | A water mass identified by a salinity minimum found at a depth of about 800 m in the North Atlantic Ocean. It is formed in two varieties in the Labrador Sea and in the Iceland Sea, from where it spreads southward but is quickly absorbed by North Atlantic Deep Water. The equivalent water mass in the Pacific Ocean is known as Subarctic Intermediate Water. | AMS - glossary of meteorology |
| Arctic mist | A mist of ice crystals; a very light ice fog. | AMS - glossary of meteorology |
| Arctic pack | Pack ice of the Arctic Ocean. The arctic pack ice varies from about 9 ? 10^6 km^2 to 16 ? 10^6 km^2. | AMS - glossary of meteorology |
| Arctic polar front | The frontal zone between the subtropical and subpolar gyres of the Northern Hemisphere. In the Atlantic Ocean it is established by the meeting of the warm and saline Gulf Stream and the cold and fresh Labrador Current and extends as a temperature and salinity front, sometimes also known as the cold wall, from south of Newfoundland and the Grand Banks northeastward to the central North Atlantic. In the Pacific Ocean it consists of two parts, separated by the Japanese islands. The larger fresh is formed by the confluence of the warm and saline Kuroshio and the cold and fresh Oyashio and seen as a temperature and salinity front extending eastward from Japan near 35N. The smaller fresh extends across the Sea of Japan in the west, where it separates the warm and saline Tsushima Current from the cold and fresh Mid-Japan Sea Cold Current. | AMS - glossary of meteorology |
| Arctic sea smoke | Steam fog, but often specifically applied to steam fog rising from small open water within sea ice. | NOAA National Weather Service Glossary 2009 |
| Arctic sea smoke (also called Steam fog) | A type of fog that forms when an outbreak of cold Arctic air settles over an expanse of open, relatively warmer water. | Environment and Climate Change Canada 2014 |
| Arctic stratospheric vortex | The vortex in the lower stratosphere over the Arctic in boreal winter. | AMS - glossary of meteorology |
| Arctic surface water | The water mass of the upper 150 m in the Arctic Ocean. It has a temperature of -1.5 to -1.9C and a salinity varying between 28 and 33.5 psu. | AMS - glossary of meteorology |
| Arctic tree line | The northern limit of tree growth; the sinuous boundary between tundra and boreal forest; taken by many to delineate the actual southern boundary of the Arctic Zone. | AMS - glossary of meteorology |
| Arctic zone | 1.(Formerly called North Frigid Zone.) Geographically, the area north of the Arctic Circle (66 deg 34 min N). 2.(Same as tundra.) Biogeographically, the area extending northward from the arctic tree line to the "limit of life." It is also used for the level above the timber line in mountains. | AMS - glossary of meteorology |
| Arctic-alpine | Of, or pertaining to, areas above the timber line in mountainous regions, and to the biologic, geologic, etc., characteristics of such areas. | AMS - glossary of meteorology |
| Arcticization | The preparation of equipment for operation in an environment of extremely low temperatures. | AMS - glossary of meteorology |
| Area of ice cover | The ratio in percent of the ice cover area to the total sea area or some geographical area at a specific moment of time. This local may be global covering an area of the seas of the entire hemisphere or some part of an ocean or a sea, for example such as Baffin Bay or the Barents Sea. | Bushuyev 2004 |
| Area S | Extent in two spatial dimensions, always understood in mass-balance work (when the two dimensions are horizontal) to be map area, that is, the extent of the glacier or part thereof when the glacier outline is projected onto the surface of an ellipsoid approximating the surface of the Earth or onto a planar (horizontal) approximation to that ellipsoid. In mass-balance studies, except for ice discharge and for the special case of frontal ablation, lengths such as layer thicknesses are always measured parallel to the vertical axis and not normal to the glacier surface. When calculating volumes within a specified outline, the area to be used is therefore the integral of ds (an element of projected area) and not the integral of sec ds, the so-called 'true' area (where is the slope of the glacier surface). The glacier area excludes nunataks but includes debris-covered parts of the glacier. However, delineating the glacier where it is debris-covered can be very difficult, because the debris may cover stagnant ice and there may be no objective way to distinguish between the debris-covered glacier and contiguous ice-cored moraine. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Area-altitude distribution | The frequency distribution of glacier area with surface altitude (elevation), generally presented as a hypsometric curve or table giving the area of the glacier within successive altitude intervals. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Area-averaged | Descriptive of a quantity that has been averaged over part or all of the area of the glacier. The area-averaged mass balance is simply the specific mass balance of the region under consideration. The adjective has sometimes been used to emphasize that the specific mass balance is that of the whole glacier and not of a 'specific' location. 'Mean specific mass balance' has been used in the same sense. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Areal scouring | Large-scale erosion of bedrock in lowland areas by an ice sheet. | Swisseduc - Photo glossary of glaciological terms |
| Arete | Sharp, narrow ridge formed as a result of glacial erosion from both sides. | NSIDC accessed 2016 |
| Arete | A jagged, narrow ridge that separates two adjacent glacier valleys or cirques. The ridge frequently resembles the blade of a serrated knife. A French term referring to the bones in a fish backbone. | Molnia USGS 2004 |
| Arete | Sharp topographic ridge that separates cirques on a mountain that is or has been glaciated. | PhysicalGeography.net |
| Artificial ground freeezing | The process of inducing or maintaining a frozen condition in earth materials by artificial means. | NSIDC accessed 2016 |
| Artificial ground freezing | The process of inducing or maintaining a frozen condition in earth materials by artificial means | Van Everdingen International Permafrost Association 2005 |
| Aspect of slope | Aspect AS is the compass direction towards which a slope faces. The direction is taken downslope and normal to the contours of elevation, i.e., along the fall line.
Aspect should be given either in degrees, clockwise from true North N = 0° = 360°, or as cardinal and inter-cardinal points, i.e., N, NE, E, SE, S, SW, W, NW. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Asymmetric valley | Asymmetric Valleys form due to the aspect driven sun exposure and thermal erosion. The cold slopes are the steepest, whereas warmer slopes typically experience more freeze-thaw cycles, hence weathering and Solifluction / Gelifluction processes. The asymmetry depends on the hemisphere. In the Southern hemisphere, south facing slopes are colder. In the cold environments of the Andeas one can distinguish between: 1. Valles unregularly bottomed 2. V-shaped valleys 3. Flat-bottomed, or U-shaped valleys | Trombotto et al. 2014 |
| Aufeis | Deposit of ice on the surface of the ground or exposed structures, produced by the freezing of periodically flowing natural, agricultural or industrial water. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Aufeis | The ice formed when water from a spring or stream emerges and freezes on top of previously formed ice. (Also called icings.) | AMS - glossary of meteorology |
| Aurora | The sporadic radiant emission from the upper atmosphere over the middle and high latitudes. It is believed to be due primarily to the emission of the nitrogen molecule N2, its molecular ion N2+, and atomic oxygen [O]. According to various theories, auroras seem definitely to be related to magnetic storms and the influx of charged particles from the sun. The exact details of the nature of the mechanisms involved are still being investigated. The aurora is most intense at times of magnetic storms (when it is also observed farthest equatorward) and shows a periodicity related to the sun's 27-day rotation period and the 11-year sunspot cycle. The distribution with height shows a pronounced maximum near 100 km. The lower limit is probably near 80 km. The aurora can often be clearly seen, and it assumes a variety of shapes and colors that are characteristic patterns of auroral emission. The names given to the various forms are 1) arcs, which are bands of light extending across the sky, the highest point of the arc being in the direction of the magnetic meridian; 2) rays, which may appear as single lines like a searchlight beam, or in bundles; 3) draperies, which have a curtainlike appearance, sharp on the bottom and tenuous in the upper parts; 4) crown or corona, which are seen when the rays appear to spread out from a single point in the sky; 5) bands, which are similar to the arcs, and may or may not have a ray structure; and 6) diffuse luminous surfaces, which appear as luminous clouds of indefinite shape. Sometimes the term "streamers" is used to describe the auroral forms that extend to great heights. In northern latitudes these displays are called aurora borealis, aurora polaris, or northern lights; in southern latitudes they are called aurora australis. | AMS - glossary of meteorology |
| Aurora | Multicolored lights that appear in the upper atmosphere (ionosphere) over the polar regions and visible from locations in the middle and high latitudes. Caused by the interaction of solar wind with oxygen and nitrogen gas in the atmosphere. Aurora in the Northern Hemisphere are called aurora borelis and aurora australis in the Southern Hemisphere. | PhysicalGeography.net |
| Aurora australis | The aurora of southern latitudes. (Also called southern lights.) | AMS - glossary of meteorology |
| Aurora borealis | The aurora of northern latitudes. (Also called aurora polaris, northern lights.) | AMS - glossary of meteorology |
| Auroral arc | A special class of bandlike forms. The arc appears as a simple, slightly curving arch. Arcs are usually quiet and not bright. | AMS - glossary of meteorology |
| Auroral bands | Characterized by more or less continuous lower border. They appear like a ribbon or sheet of luminosity, inclined in the direction of the magnetic field. They may be homogeneous, rayed, or striated, and can be single or multiple. | AMS - glossary of meteorology |
| Auroral corona | In any fairly complex rayed form, viewed in the direction of the magnetic lines of force, rays that appear to converge, forming a fan or corona. | AMS - glossary of meteorology |
| Auroral curtains | Aurora that give an appearance of looking at curtains or drapery as viewed from below. (Also known as Auroral draperies) | AMS - glossary of meteorology |
| Auroral oval | An oval-shaped distribution of the aurora. The oval is asymmetrical, but generally around the region of the Arctic and Antarctic. The oval increases in intensity and size when auroral activity is more intense. | AMS - glossary of meteorology |
| Auroral rays | A form of the aurora consisting of rays or shafts of luminosity aligned in the direction of the geomagnetic field. It can consist of a single ray, a small bundle of rays, or many scattered rays. | AMS - glossary of meteorology |
| Auroral zone | An approximately circular region around the two geomagnetic poles within which there is a maximum of auroral activity. It lies about ten to fifteen degrees of geomagnetic latitudes from the geomagnetic poles. The auroral zone broadens and extends equatorward during intense auroral displays. | AMS - glossary of meteorology |
| Autumn ice | Sea ice in early stage of formation. It is comparatively salty and crystalline in appearance. Like young ice, it is not yet affected by lateral pressure. | AMS - glossary of meteorology |
| Avalanche | Mass of snow which becomes detached and slides down a slope, often acquiring great bulk by fresh addition as it descends. | NSIDC accessed 2016 |
| Avalanche | A mass of snow, rock, and/or ice falling down a mountain or incline. In practice, it usually refers to the snow avalanche. In the United States, the term snow slide is commonly used to mean a snow avalanche. | NOAA National Weather Service Glossary 2009 |
| Avalanche | Mass of snow and ice falling suddenly down a mountain slope and often taking with it earth, rocks and rubble of every description. | WMO METEOTERM accessed 2016 |
| Avalanche | A slide or flow of a mass of snow, firn or ice that becomes detached abruptly, often entraining additional material such as snow, debris and vegetation as it descends. The duration of an avalanche is typically seconds to minutes. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Avalanche | Mass of snow and ice suddenly sliding down a mountain-side and often taking with it earth, rocks and rubble. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Avalanche | A mass of snow (perhaps containing ice and rocks) moving rapidly down a steep mountain slope. Avalanches may be characterized as loose and turbulent, or slab; either type may be dry or wet according to the nature of the snow forming it, although dry snow usually forms loose avalanches and wet snow forms slabs. A large avalanche sweeps a current of air along with and in front of it as an avalanche wind, which supplements its already tremendous destructive force. (Also called snowslide.) | AMS - glossary of meteorology |
| Avalanche | Mass of snow which becomes detached and slides down a slope, often acquiring great bulk by fresh additions as it descends. | Illustrated Glossary of Snow and Ice |
| Avalanche | Snow avalanches; Ice avalanches | Illustrated GLIMS Glacier Classification Manual |
| Avalanche wind | Rush of air produced by an avalanche or landslide. | WMO METEOTERM accessed 2016 |
| Avalanche wind | The rush of air produced in front of an avalanche of dry snow or in front of a landslide. The most destructive form, the avalanche blast, occurs when an avalanche is stopped abruptly, as in the case of an almost vertical fall into a valley floor. Such blasts may have very erratic behavior, leveling one house without damaging its neighbor. | AMS - glossary of meteorology |
| Avalanching | Mass transfer by avalanches which redistribute snow, firn and ice. Avalanching from a valley wall to the glacier surface constitutes accumulation. Avalanching from the glacier margin constitutes ablation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Baffin Current | Southward flowing current on the eastern side of Baffin Bay with speeds of 0.2-0.4 m/s. It is fed by low-salinity water from the Arctic Ocean, thus contributing to the freshwater budget between the Pacific and Atlantic, and by the West Greenland Current. It feeds the Labrador Current. | AMS - glossary of meteorology |
| Balance flux | The hypothetical horizontal mass flux (dimension [M T-1]) through a vertical cross section that would be equal to the mass balance (usually the climatic mass balance) over the region upglacier from the cross section. Comparison of balance flux and actual mass flux at the same cross section gives an indication of the health of the glacier. If the mass balance of the glacier is zero it follows that at the terminus the balance flux and mass flux are equal, and if there is also no calving that they are equal to zero. If the two are equal at all cross sections the glacier is in steady state. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Balance velocity | The volumetric balance flux divided by the area of the vertical cross section through which it passes. Comparison of balance velocity to actual velocity, that is, to the actual volumetric flux (mass flux divided by average density) divided by the area of the vertical cross section, gives an indication of the health of the glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Balance year | The mass-balance year. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Balanced-budget | Descriptive of a glacier with a mass balance equal to zero on average over a number of years. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Balanced-budget AAR | The AAR, sometimes denoted AAR0, of a glacier with a mass balance equal to zero. Glaciers do not in general have mass balances equal to zero. The Balanced-budget AAR is usually estimated as the AAR at which a curve (often linear) fitted to a relation between AAR and the Annual surface mass balance Bsfc, observed over a number of years, crosses the axis Bsfc = 0. The AAR0 of non-calving glaciers has been found to vary roughly between 0.5 and 0.6 on average, although the range of variation is substantial. On calving glaciers it is typically larger, approaching 1.0 on the Antarctic Ice Sheet. AAR0 can exceed 0.8 on tropical glaciers of year-round ablation type. The Balanced-budget AAR may differ from the steady-state AAR because it summarizes observations made in conditions that may not approximate to steady state. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Balanced-budget ELA | The ELA, sometimes denoted ELA0, of a glacier with a climatic mass balance equal to zero on average over a number of years. The Balanced-budget ELA is usually estimated as the altitude at which a curve fitted to an observed relation between Annual ELA and Annual mass balance Ba crosses the axis Ba = 0. The uncertainty in such estimates can be substantial, especially when mass-balance sampling is sparse or the equilibrium zone occupies a large fraction of the glacier surface. The Balanced-budget ELA may differ from the steady-state ELA because it is estimated from observations made in conditions that may not approximate to steady state. In particular, most measurements of mass balance published over the past several decades have been negative. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Band ogives | Alternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter. | NSIDC accessed 2016 |
| Banded cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form subhorizontal layers. | NSIDC accessed 2016 |
| Banded cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form subhorizontal layers | Van Everdingen International Permafrost Association 2005 |
| Banded fabric | The presence of banded or isobanded structures in periglacial soils is one of the most frequent features to be discerned in the sub-soils of temperate soils that have formerly been subjected to glacial or periglacial influences. Preferential mobilization of fines to surmount banded sediments and pressure stress accumulation adjacent to melted lenses are the major processes causing the banded microstructure. | Trombotto et al. 2014 |
| Banner cloud | A cloud plume often observed to extend downwind from isolated, sharp, often pyramid-shaped mountain peaks, even on otherwise cloud-free days. The Matterhorn and Mount Everest are two notable peaks where banner clouds have been frequently observed.The physics of the formation of such clouds is not completely understood. The aerodynamics of the flow around the peak produces flow separation and dynamically induced pressure reductions to the lee of the mountain peaks. The magnitude of the leeside pressure deficits increases with height to a maximum near the top of the peak, producing an upslope pressure gradient and upslope flow along the lee slope of the mountain. When the air near the base of the mountain is sufficiently moist, it ascends in the upslope flow, condenses, and forms a triangular- shaped cloud, the banner cloud, to the lee of the peak. Because of its unusual shape and location, this cloud strongly resembles snow blowing off the peak (snow banner), and it is often difficult to tell the difference. (Also called cloud banner.) | AMS - glossary of meteorology |
| Bare ice | Ice without snow cover. | WMO Sea Ice Nomenclature 2017 |
| Bare ice | Ice without snow cover. | Bushuyev 2004 |
| Bare ice | Ice without snow cover. | AMS - glossary of meteorology |
| Barren zone | An area of fresh, vegetation-free bedrock around the margin of a retreating glacier that documents the recent loss of ice. | Molnia USGS 2004 |
| Barrens | Areas of discontinuous vegetation cover in the polar semi-desert of the high arctic. | NSIDC accessed 2016 |
| Barrens | Areas of discontinuous vegetation cover in the polar semi-desert of the High Arctic | Van Everdingen International Permafrost Association 2005 |
| Barrens | Any region that is devoid of vegetation or permits only the sparse growth of very few plant species. This term is most commonly applied to such terrain in polar regions. | AMS - glossary of meteorology |
| Barrier iceberg | Obsolescent term for tabular iceberg. | AMS - glossary of meteorology |
| Barrier jet | A jet on the windward side of a mountain barrier, blowing parallel to the barrier. The jet is produced when stable synoptic flow at low levels approaches the barrier and is blocked ( see blocking) for a significant fraction of a day or longer. This often occurs, for example, when a cold front approaches the barrier. The component of the large-scale flow perpendicular to the ridge forces the flow to ascend the barrier. Because the air column is stable, the air layer near the surface is potentially colder (by definition) than the air layer above it, and the stratification opposes and retards the upslope flow. As the colder air ascends, it produces higher pressure along the slope than at the same level over the plain, and consequently also a pressure-gradient force directed away from the mountains. If this pressure configuration lasts for several hours or more, Coriolis deflection accelerates the flow with a component perpendicular to the pressure gradient, that is, in the along-barrier direction. At timescales greater than a pendulum day that required for geostrophic adjustment these processes produce a persistent barrier jet at heights below the level of the mountain. The process of geostrophic adjustment also brings the flow in the jet into balance with the thermal wind, so an argument based on thermal wind reasoning also explains the barrier jet. Barrier jets have been documented windward of the Sierra Nevada in California, to the north of the Brooks Range in Alaska, and in Antarctica along the Antarctic Peninsula and the Transantarctic Mountains. Maximum speeds, which generally occur at heights just below the midway level of the mountains, reach 15-30 m/s, and the jet can extend laterally 100 km or more upstream of the barrier. The strong shear in the jet is capable of producing moderate to severe turbulence for low-flying aircraft. | AMS - glossary of meteorology |
| Basal ablation | The removal of ice by melting at the base of a glacier. At the base of grounded temperate ice, melting is either fuelled by the geothermal heat flux and the conversion of the kinetic energy of basal sliding to heat, or results from variations of the pressure-melting point. Pressure melting, however, tends to be balanced by regelation. Typical continental geothermal heat fluxes G of 0.050.15 W m-2 imply potential basal ablation G/Lf of 514 mm w. E. A-1, where Lf is the latent heat of fusion. Much greater geothermal heat fluxes are found in areas of Active volcanism. If all of the energy of basal sliding is converted to heat, basal ablation ubb/Lf at rates of 330 mm w. E. A-1 is implied by sliding velocities ub of 10100 m a-1 and basal shear stress b of 105 Pa. Basal ablation rates tens or hundreds of times greater are implied beneath ice streams. At the base of an ice shelf or floating tongue, melting occurs because of convection of warmer sea water to the ice-water interface, supplying the required latent heat of fusion. The rate of melting depends on the temperature of the sea water and the efficiency of the heat transfer between the seawater and the base of the ice shelf. Basal ablation rates beneath ice shelves or floating tongues can reach tens of m w. E. A-1, equivalent to heat transfer at hundreds of W m-2. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Basal accumulation | The freezing of water to the base of the glacier, increasing the mass of the glacier and Antarctic Ice Sheeting its basal temperature if that temperature is below the freezing point. The result of basal accumulation is typically observable in ice cores or at glacier margins as accreted ice that is relatively clear, often with some concentration of dispersed sediments incorporated from the glacier bed during freezing. Accreted ice may also be distinguishable from glacier ice (the latter sometimes referred to as meteoric ice in this context) by differences in isotopic content, geochemical composition and optical properties, and may have distinctive dielectric properties by which it can be recognized in ground-penetrating radar records. Accreted ice at the base of an ice shelf is referred to as marine ice. For purposes of the glaciological method, basal accumulation is indistinguishable from internal accumulation in that both represent addition of mass to the glacier that goes unaccounted for by surface observations. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Basal cryopeg | A layer of unfrozen ground that is perennially cryotic (t 0 degrees Celsius), forming the basal portion of the permafrost. | NSIDC accessed 2016 |
| Basal cryopeg | A layer of unfrozen ground that is perennially cryotic (T < 0° C), forming the basal portion of the permafrost | Van Everdingen International Permafrost Association 2005 |
| Basal cryostructure | The cryostructure of a frozen deposit of boulders that is saturated with ice. | NSIDC accessed 2016 |
| Basal cryostructure | The cryostructure of a frozen deposit of boulders that is saturated with ice | Van Everdingen International Permafrost Association 2005 |
| Basal debris | Rock fragments and ground-up bedrock incorporated into the base of a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Basal ice layer | The layer of ice at the bed of a glacier that is the product of melting and refreezing (regelation, q.v.). It is strongly layered, sheared and incorporates a variable amount of debris. | Swisseduc - Photo glossary of glaciological terms |
| Basal lubrication | Reduction of friction at the base of an ice sheet or glacier due to lubrication by meltwater. This can allow the glacier or ice sheet to slide over its base. Meltwater may be produced by pressureinduced melting, friction or geothermal heat, or surface melt may drain to the base through holes in the ice. | IPCC WGI AR5 2013 |
| Basal mass balance | The change in the mass of the glacier due to basal accumulation and basal ablation over a stated period. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Basal sliding | The sliding of a glacier over bedrock. | NSIDC accessed 2016 |
| Basal sliding | The sliding of a glacier over bedrock, a process usually facilitated by the lubricating effect of meltwater. | Swisseduc - Photo glossary of glaciological terms |
| Basal sliding | The motion of the basal ice of the glacier relative to the material immediately beneath the glacier. | AMS - glossary of meteorology |
| Basal sliding | The sliding of a glacier over the surface it rests on. Caused by the gradient of the slope and the weight of the glacier's mass. | PhysicalGeography.net |
| Basal-layered cryostructure | The cryostructure of a frozen layered deposit of gravel and boulders that is saturated with ice | Van Everdingen International Permafrost Association 2005 |
| Base flow | Discharge which enters a stream channel mainly from groundwater, but also from lakes and glaciers, during long periods when no precipitation or snowmelt occurs. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Basic zones | Basic zones are delineated by mobility, total concentration and age categories. Such additional characteristics as hummock and ridge concentration, rafting of young ice, or stages of melting are usually included in a description of the characteristics of these basic zones. It is assumed that the boundaries of the main and additional characteristics coincide. The basic zones are subdivided into the following types: Fast ice, Drifting Ice, Bergy water, Ice-free water. On large-scale ice charts, giant and sometimes vast ice floes can be contoured and described in the basic zones. | Bushuyev 2004 |
| Batture floes | Canadian sea ice terminology that is not a part of the World Meteorological Organization's (WMO) terminology. It defines large, thick, uneven and discoloured ice floes that form on the upstream side of shoals and islets in rivers, when cold weather precedes or accompanies neap tides. It is composed of ice of different thicknesses formed under pressure during ebb tide, the whole mass freezes together and gradually increasing in size, with each successive tide. As the range increases between the neap and spring tides, large sections of grounded ice break away and drift down river causing the floes. | Environment and Climate Change Canada 2014 |
| Bay ice | 1.Any recently formed sea ice that is sufficiently thick to impede navigation. 2.In Labrador, one-year ice that forms in bays and inlets. 3.In the Antarctic, sometimes applied to heavy floes recently broken away from an ice shelf. | AMS - glossary of meteorology |
| Beaded stream | A stream characterized by narrow reaches linking pools or small lakes | Van Everdingen International Permafrost Association 2005 |
| Beginning of freezup | Date on which ice forming a stable winter ice cover is first observed on the water surface. | NOAA Glossary of Hydrologic Terms |
| Beginning of the breakup | Date of definite breaking, movement, or melting of ice cover or significant rise of water level. | NOAA Glossary of Hydrologic Terms |
| Belt | A large feature of pack ice arrangement that is longer than it is wide, from 0.5 mi to 65 mi (1-100 kin) in width. | WMO Sea Ice Nomenclature 2017 |
| Belt | Sea ice terminology meaning a large area of pack/drift ice that is longer than it is wide. It can be from 1 km to more than 100 km in width. | Environment and Climate Change Canada 2014 |
| Belt | A long area of pack ice from a few km to more than 100 km in width. | Illustrated Glossary of Snow and Ice |
| Benchmark glacier | In the monitoring strategy of the United States Geological Survey, a glacier on which detailed measurements of seasonal glacier mass changes, meteorological environment, and stream flow variations are collected on a continuing basis. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Berg | Commonly used abbreviation for iceberg. | AMS - glossary of meteorology |
| Bergschrund | Crevasse that separates flowing ice from stagnant ice at the head of a glacier. | NSIDC accessed 2016 |
| Bergschrund | A single large crevasse or series of sub-parallel crevasses that develop at the head of a glacier. The location where ice pulls away from the bedrock wall of the cirque against which it accumulated. In winter, the crevasse fills with snow. In spring or summer, it reopens. (Originally a German term). | Molnia USGS 2004 |
| Bergschrund | A crevasse at the head of a glacier that separates flowing ice from stagnant ice, or from a rock headwall. From an ice-dynamical point of view the bergschrund is the headward boundary of the glacier, while for hydrological and other purposes, including glacier inventory, the stagnant ice above the bergschrund is part of the glacier. Bergschrund is an Anglicized word of German origin. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Bergschrund | (from the German) An irregular crevasse, usually running across an ice slope in the accumulation area, where active glacier ice pulls away from ice adhering to the steep mountainside. | Swisseduc - Photo glossary of glaciological terms |
| Bergschrund | A deep crevasse commonly found at the head of an alpine glacier. Forms when the glacial ice pulls away from the mountain side. | PhysicalGeography.net |
| Bergschrund | The crevasse which occurs at the head of a cirque or valley glacier and which separates the moving glacier ice from the rock wall and the ice apron attached to it. When the ice apron is absent the gap is known as a randkluft. | Illustrated Glossary of Snow and Ice |
| Bergy bit | Large chunk of glacier ice (a very small iceberg) floating in the sea; bergy bits are usually less than 5 meters (15 feet) in size and are generally spawned from disintegrating icebergs. | NSIDC accessed 2016 |
| Bergy bit | A large piece of floating glacier ice, generally showing less than 16 ft (- 5 m) above sea level but more than 3 ft (= 1 m) and normally about 120 to 360 sq yds (t 100-300 sq m) in area. | WMO Sea Ice Nomenclature 2017 |
| Bergy bit | A large piece of floating ice of land origin, showing less than 5 m above sea-level and 100-300 m2 in area [Note: it might be better to say no more than 20 metres long, rather than give an area] | Bushuyev 2004 |
| Bergy bit | A piece of ice which has broken away from an iceberg, extending 1-5 meters above the sea surface and 100-300 square meters in area. Can also be the remains of a melting iceberg. | NOAA National Weather Service Glossary 2009 |
| Bergy bit | Sea ice terminology that describes a piece of glacier ice, generally showing at 1m to less than 5m above sea level; with a length of 5m to less than 15m. They normally have an area of 100-300 sq. M. | Environment and Climate Change Canada 2014 |
| Bergy bit | A piece of floating glacier ice up to several metres across, commonly deriving from the disintegration of an iceberg. | Swisseduc - Photo glossary of glaciological terms |
| Bergy bit | A small iceberg or iceberg fragment; it also may be a piece of floeberg or hummocked ice; it is larger than a growler. | AMS - glossary of meteorology |
| Bergy bit | A piece of floating ice, generally less than 5 m above sea level and not more than about to m across. It is generally of glacier ice, but may be a massive piece of sea ice or disrupted hummocked ice. | Illustrated Glossary of Snow and Ice |
| Bergy seltzer | A crackling or sizzling similar to that made by soft drinks or seltzer water but louder. The sound made as air bubbles formed at many atmospheres of pressure are released during the melting of glacier ice. Also called Ice Sizzle. | Molnia USGS 2004 |
| Bergy water | A large area of navigable water in which ice of land origin is present or possible at a total concentration less than 1/10. Such zones do not usually have a clearly expressed edge or boundary with ice-free water. A characterization of ice conditions in such areas can be made both on the basis of data from direct observations, data from previous observations or from climatic data. | Bushuyev 2004 |
| Bergy water | Sea ice terminology that describes an area of freely navigable water, in which ice of land origin is present. Other ice types may be present, although the total concentration of all other ice is less than 1/10. | Environment and Climate Change Canada 2014 |
| Beset | Situation of a vessel surrounded by ice and unable to move. | NSIDC accessed 2016 |
| Beset | Sea ice terminology meaning a situation in which a vessel is surrounded by ice and unable to move. | Environment and Climate Change Canada 2014 |
| Beset | Situation of a vessel surrounded by ice and unable to move. | WMO Sea Ice Nomenclature 2017 |
| Beset | The situation of a ship surrounded by ice and unable to move. | Bushuyev 2004 |
| Beset | Situation of a vessel surrounded by ice and unable to move. | Illustrated Glossary of Snow and Ice |
| Biennial ice | Sea ice that has survived one summer's melt. (Also called second-year ice.) | AMS - glossary of meteorology |
| Bight | An extensive crescent-shaped indentation in the ice edge formed either by wind or current. | NSIDC accessed 2016 |
| Bight | An extensive crescent-shaped indentation in the ice edge, formed by either wind of current. | WMO Sea Ice Nomenclature 2017 |
| Bight | Sea ice terminology that describes an extensive crescent-shaped indentation in the ice edge, formed by either wind or current. | Environment and Climate Change Canada 2014 |
| Bight | An extensive crescent-shaped indentation in the ice edge, formed either by wind or current. | Illustrated Glossary of Snow and Ice |
| Biogenic ice nucleus | An ice nucleus of biological origin, particularly bacteria (e.g., pseudomonas syringae) from plant surfaces. These organisms have threshold temperatures as high as -2C, being active at the highest temperature known for natural nuclei. They were first identified in leaf litter, collected worldwide. Commercial application lies in nucleation of water spray drops for artificial snow on ski slopes. | AMS - glossary of meteorology |
| Bise | Name given to cold northerly, northeasterly, or easterly, postfrontal winds in the Swiss Middleland (the region between the Jura and the Alps) and in various regions of eastern France. The bise is typically driven by an anticyclone building to the northwest or north of the Alps. According to Wanner and Furger (1990), "the cold air flow from the north and northeast is channeled between the Jura and the Alps and leads to the formation of the bise over the Swiss Middleland and the upper Rh?ne Valley. Thus, the bise is normally a postfrontal phenomenon and is closely connected with the advection of cold and dry continental air. Typically the classic bise endures about one to three days." The bise is most frequent in spring, when it usually brings fine, bright weather. In winter a special case of the bise occurs when the pressure gradient is produced by a Mediterranean cyclone system to the south of the Alps, bringing moist air in from the Balkans. Accompanied by heavy clouds, snow whirlwinds in the mountains, and rain, snow, or hail, this wind is called a "black bise" (bise noire in Switzerland and Sa?ne in east central France; bise n?gre in Aveyron in south central France). In spring the bise can last for several days and bring damaging frosts. In the Morvan in east central France the very dry bise in March is termed hale de mars (drying wind of March). In the Dr?me Valley southeast of Valence (southeast France) the name bise brume is given to a moist, mild, and sometimes foggy wind from the northwest. (Also spelled bize.) | AMS - glossary of meteorology |
| Black frost | Dry freeze, with respect to its effects on vegetation, which suffers internal freezing and has a blackened appearance. | WMO METEOTERM accessed 2016 |
| Black frost | 1. A dry freeze with respect to its effects upon vegetation, that is, the internal freezing of vegetation unaccompanied by the protective formation of hoarfrost. A black frost is always a killing frost, and its name derives from the resulting blackened appearance of affected vegetation. 2. Among some fishermen, a steam fog that extends above the bridge level of the fishing boats. If the steam fog does not reach this height, it is a white frost. | AMS - glossary of meteorology |
| Black ice | (1) Thin ice on a fresh or salt water body which appears dark in colour because of its transparency. (2) A mariner's term for a dreaded form of icing sometimes sufficiently heavy to capsize a small ship. | WMO METEOTERM accessed 2016 |
| Black ice | Transparent ice formed in rivers and lakes, or on roads and bridges. | NOAA Glossary of Hydrologic Terms |
| Black ice | 1. Slang reference to patchy ice on roadways or other transportation surfaces that cannot easily be seen. 2. In hydrologic terms, transparent ice formed in rivers and lakes. | NOAA National Weather Service Glossary 2009 |
| Black ice | 1.Thin, new ice on freshwater or saltwater, appearing dark in color because of its transparency, which is a result of its columnar grain structure. On lakes, black ice is commonly overlain by white ice formed from refrozen snow or slush. 2.A mariner's term for a dreaded form of icing sometimes sufficiently heavy to capsize a small ship. 3.A popular alternative for glaze. A thin sheet of ice, relatively dark in appearance, may form when light rain or drizzle falls on a road surface that is at a temperature below 0C. It may also be formed when supercooled fog droplets are intercepted by buildings, fences, and vegetation. | AMS - glossary of meteorology |
| Blind lead | A lead closed off on all sides within the ice pack. | NSIDC accessed 2016 |
| Blizzard | Violent winter storm, lasting at least 3 hours, which combines below freezing temperatures and very strong wind laden with blowing snow that reduces visibility to less than 1 km. | WMO METEOTERM accessed 2016 |
| Blizzard | Winds of at least 35 miles per hour along with considerable falling and/or blowing snow reducing visibility to less than one-quarter mile for a period of at least three hours (extremely cold temperatures are often associated with dangerous blizzard conditions, but are not a formal part of the modern definition). | NSIDC accessed 2016 |
| Blizzard | A severe weather condition characterized by reduced visibility from falling and/or blowing snow and strong winds that may be accompanied by low temperatures. | Environment and Climate Change Canada 2014 |
| Blizzard | Violent and very cold wind which is loaded with snow, some of which has been raised from snow covered ground. | Australian Bureau of Meteorology 2016 |
| Blizzard | A severe weather condition characterized by high winds and reduced visibilities due to falling or blowing snow. The U.S. National Weather Service specifies sustained wind or frequent gusts of 16 m per second (30 kt or 35 mi per hour) or greater, accompanied by falling and/or blowing snow, frequently reducing visibility to less than 400 m (0.25 mi) for 3 hours or longer. Earlier definitions also included a condition of low temperatures, on the order of -7C (20F) or lower, or -12C (10F) or lower (severe blizzard). The name originated in the United States but it is also used in other countries. In the Antarctic the name is given to violent autumnal winds off the ice cap. In southeastern France, the cold north wind with snow is termed blizzard (see also boulbie). Similar storms in Russian Asia are the buran and purga. In popular usage in the United States and in England, the term is often used for any heavy snowstorm accompanied by strong winds. | AMS - glossary of meteorology |
| Blizzard | Winter severe weather condition characterized by strong wind, blowing snow, and cold temperatures. | PhysicalGeography.net |
| Block field | A surficial layer of angular shattered rocks formed in either modern or Pleistocene periglacial environments | Van Everdingen International Permafrost Association 2005 |
| Blocky iceberg | Sea ice terminology that describes a flat-topped iceberg with steep vertical sides. | Environment and Climate Change Canada 2014 |
| Blow hole | Opening through a snow bridge into a crevasse or system of crevasses which are otherwise sealed by snow bridges; a snowdrift usually forms on the lee side. | NSIDC accessed 2016 |
| Blow hole | Opening through a snow bridge into a crevasse or system of crevasses which are otherwise sealed by snow bridges. A snowdrift usually forms on the lee side. | Illustrated Glossary of Snow and Ice |
| Blowing snow | Snow particles violently stirred up by wind to sufficient heights above the ground to reduce visibility to 10 km or less. | Canada National Climate Archive 2015 |
| Blowing snow | An ensemble of snow particles raised by the wind to moderate or great heights above the ground; the horizontal visibility at eye level is generally very poor. | NSIDC accessed 2016 |
| Blowing snow | Blowing snow is wind-driven snow that reduces surface visibility. Blowing snow can be falling snow or snow that has already accumulated but is picked up and blown by strong winds. Blowing snow is usually accompanied by drifting snow. | NOAA National Weather Service Glossary 2009 |
| Blowing snow | Snow entrained, suspended and transported by the wind at heights greater than 2 m above the surface. The height of 2 m is a convenient separator between blowing snow, which reduces horizontal visibility significantly, and drifting snow. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Blowing snow | Snow lifted from the earth's surface by the wind to a height of 2 metres or more. | Environment and Climate Change Canada 2014 |
| Blowing snow | An ensemble of snow particles raised by the wind to moderate or great heights above the ground. The horizontal visibility at eye level is generally very poor (cf. Drifting snow). | Illustrated Glossary of Snow and Ice |
| Blue ice | Dense glacier ice with a blue appearance accounted for by lack of air bubbles. The crystal structure absorbs all colours except the blue part of the visible spectrum. Strictly, blue ice is ice that has originated by recrystallization upglacier and, having followed a trajectory through the interior of the glacier, becomes exposed at the surface downglacier, a locally zero or negative surface mass balance being implied. The term is used loosely, however, to refer to all exposed ice on the Antarctic Ice Sheet; again, the absence of snow and firn implies a locally negative surface mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Blue ice | Pure ice in the form of large single crystals. It is blue owing to the scattering of light by the ice molecules; the purer the ice, the deeper the blue. | AMS - glossary of meteorology |
| Blue ice area | Areas where surface ablation has exposed blue ice. These are sites, usually on large ice sheets, where ice flow has concentrated meteorites that have fallen throughout the catchment area of the particular blue-ice area. | AMS - glossary of meteorology |
| Bora | A regional downslope wind whose source is so cold that it is experienced as a cold wind, despite compression warming as it descends the lee slope of a mountain range. | NOAA National Weather Service Glossary 2009 |
| Bora | A fall wind with a source so cold that, when the air reaches the lowlands or coast, the dynamic warming is insufficient to raise the air temperature to the normal level for the region; hence it appears as a cold wind. The terms borino and boraccia denote a weak bora and a strong bora, respectively. The term was originally applied (along with karstbora) to the cold northeast wind on the Dalmatian coast of Croatia and Bosnia in winter when cold air from Russia crosses the mountains and descends to the relatively warm coast of the Adriatic. According to Smith (1987), the bora "has often been considered the prototype fall wind," although recent studies have revealed that some boras have downslope windstorm or hydraulic jump structure. The event often lasts a day or less, although extended events occur with enough frequency that "the longevity of the bora is one of its primary characteristics. A duration of four to six days is not unusual." It is very stormy and squally, the squalls sometimes reaching 50 m s-1 or more. F. Defant (1951) distinguishes between cyclonic bora (bora scura) with clouds and rain, covering the whole Adriatic and occurring with a depression over southern Adria, and the dry anticyclonic bora, with a powerful anticyclone over central Europe extending over Dalmatia; the latter is very violent over the land but extends only a short distance out to sea. A local bora also occurs on the east coast of the Adriatic with a cold anticyclone over the Balkans. The term bora is now applied to similar winds in other parts of the world. Well-known examples occur at Novorossiisk on the northern shore of the Black Sea, and in Novaya Zemlya (islands in the Russian Arctic). A squally katabatic wind at Alme Dagh in the Gulf of Iskenderon (eastern Mediterranean Sea) is termed rageas (also ragut, ghaziyah). The Bulgarian term is buria. In some mountainous regions of the world bora has been further generalized to represent any large mesoscale or synoptic-scale downslope flow of cold air, including post- arctic-frontal fall winds and cold-air downslope windstorms, which may have a hydraulic jump- like character and structure. In the case of downslope windstorms, some authors have used bora for a cold-advection flow (or one that results in cooling to the immediate lee of the mountain barrier), whereas chinook or foehn refer to a warm- or neutral-advection wind (or one that results in warming or no temperature change leeward of the barrier). Those who have attempted to classify downslope windstorms, however, have found that many cases do not fall neatly into one category or the other. | AMS - glossary of meteorology |
| Bora | Term used to describe a katabatic wind in Yugoslavia. | PhysicalGeography.net |
| Border ice | An ice sheet in the form of a long border attached to the bank or shore.; shore ice. | NOAA Glossary of Hydrologic Terms |
| Border ice | In hydrologic terms, an ice sheet in the form of a long border attached to the bank or shore.; shore ice. | NOAA National Weather Service Glossary 2009 |
| Boreal forest | The forested region that adjoins the tundra along the arctic tree line. It has two main divisions: its northern portion is a belt of taiga or boreal woodland; its southern portion is a belt of true forest, mainly conifers but with some hardwoods. On its southern boundary the boreal forest passes into "mixed forest" or "parkland," prairie, or steppe, depending on the rainfall. | AMS - glossary of meteorology |
| Boreal forest | High to mid-latitude biome dominated by coniferous forest. Predominant vegetation of this biome is various species of spruce, fir, pine, and cedars. Also called Taiga. | PhysicalGeography.net |
| Boreal woodland | The taiga portion of the boreal forest. | AMS - glossary of meteorology |
| Boreal zone | 1.Defined by W. K?ppen (1931) as the zone having a definite winter with snow, and a short summer, generally hot. It includes a large part of North America between the Arctic Zone and about 40N, extending to 35N in the interior. In Central Europe and in Asia the boreal zone extends southward from the tundra to 40-50N. 2.A biogeographical zone or region characterized by a northern type of fauna or flora. The term boreal region is used mainly by American biologists, and includes the area between the mean summer isotherm of 18C or 64.4F (roughly 45N latitude) and the Arctic Zone. | AMS - glossary of meteorology |
| Bottom bergs | Icebergs that originate from near the bottom of a glacier; the color is usually black from trapped rock material or dark blue because of old, coarse, bubble-free ice; they sit low in the water due to the weight of the embedded rocks. | NSIDC accessed 2016 |
| Bottom temperature of snow cover | Temperature measured at the base of the snow cover during mid- to late-winter (February/March) | Van Everdingen International Permafrost Association 2005 |
| Boulder clay | An English term for till, no longer favoured by glacial geologists. | Swisseduc - Photo glossary of glaciological terms |
| Boundary | The surface separating the glacier from its surroundings. The term is often simply a synonym of glacier margin or glacier outline, but it can be useful to have a separate word that is understood to encompass the glacier surface and the glacier bed as well. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Brackish ice | In hydrologic terms, ice formed from brackish water. | NOAA National Weather Service Glossary 2009 |
| Brackish ice | Ice formed from Brackish water. | NOAA Glossary of Hydrologic Terms |
| Braided stream | A relatively shallow stream with many branches that commonly recombine and migrate across a valley floor. Braided streams typically form downstream of a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Braided stream (anastomizing stream) | A stream that is characterized by a complex network of branches that continuously separate and reunite. Streams braid when they have a much greater sediment load than they can carry. Also called an Anastomosing Stream. | Molnia USGS 2004 |
| Branched-valley glacier | Glacier that has one or more tributary glaciers that flow into it; distinguished from a simple valley glacier that has only a single tributary glacier. | NSIDC accessed 2016 |
| Brash ice | Accumulation of floating ice made up of fragments not more than 2 meters across; the wreckage of other forms of ice. | NOAA Glossary of Hydrologic Terms |
| Brash ice | Accumulation of floating ice made up of fragments not more than 2 meters (6.6 feet) across, the wreckage of other forms of ice. | NSIDC accessed 2016 |
| Brash ice | Accumulations of floating ice made up of fragments not more than 2 m across; the wreckage of other forms of ice. Brash is common between colliding floes or in regions where pressure ridges have collapsed. | ASPECT 2012 |
| Brash ice | Accumulations of floating ice made up of fragments not more than 6.5 ft (= 2 m) across, the wreckage of other forms of ice. | WMO Sea Ice Nomenclature 2017 |
| Brash ice | Accumulations of floating ice made up of fragments not more than 2 m across, the wreckage of other forms of ice as a result of melting. | Bushuyev 2004 |
| Brash ice | In hydrologic terms, accumulation of floating ice made up of fragments not more than 2 meters across; the wreckage of other forms of ice. | NOAA National Weather Service Glossary 2009 |
| Brash ice | Sea ice terminology that describes the accumulation of floating ice that is made up of fragments not more than 2 metres across. It is the result of the wreckage of other forms of ice. | Environment and Climate Change Canada 2014 |
| Brash ice | Accumulation of floating ice made up of fragments not more than 2 metres across. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Brash ice | Accumulations of floating ice made up of fragments not more than 2 m across, the wreckage of other forms of ice. | Illustrated Glossary of Snow and Ice |
| Breached watershed | A short, glacially eroded valley, linking two major valleys across a mountain divide. | Swisseduc - Photo glossary of glaciological terms |
| Breakup | The time when a river whose surface has been frozen from bank to bank for a significant portion of its length begins to change to an open water flow condition. Breakup is signaled by the breaking of the ice and often associated with ice jams and flooding. | NOAA Glossary of Hydrologic Terms |
| Breakup | Stage of the breakup season, or sharp break of the ice cover, followed by a massive departure of the ice, mostly in inland waters. | WMO METEOTERM accessed 2016 |
| Breakup | In hydrologic terms, the time when a river whose surface has been frozen from bank to bank for a significant portion of its length begins to change to an open water flow condition. Breakup is signaled by the breaking of the ice and often associated with ice jams and flooding. | NOAA National Weather Service Glossary 2009 |
| Breakup date | Date on which a body of water is first observed to be entirely clear of ice and remains clear thereafter. | NOAA Glossary of Hydrologic Terms |
| Breakup date | In hydrologic terms, date on which a body of water is first observed to be entirely clear of ice and remains clear thereafter. | NOAA National Weather Service Glossary 2009 |
| Breakup jam | Ice jam that occurs as a result of the accumulation of broken ice pieces. | NOAA Glossary of Hydrologic Terms |
| Breakup jam | In hydrologic terms, an ice jam that occurs as a result of the accumulation of broken ice pieces. | NOAA National Weather Service Glossary 2009 |
| Breakup period | The period of disintegration of an ice cover. | NOAA Glossary of Hydrologic Terms |
| Breakup period | In hydrologic terms, the period of disintegration of an ice cover. | NOAA National Weather Service Glossary 2009 |
| Breakup season | Ensemble of the phenomena associated with the disappearance of the ice-pack due to climatic (temperature, wind) and hydrological (waves, currents, tides) factors. | WMO METEOTERM accessed 2016 |
| Brewer-Dobson circulation | The meridional overturning circulation of the stratosphere transporting air upward in the tropics, poleward to the winter hemisphere, and downward at polar and subpolar latitudes. The Brewer-Dobson circulation is driven by the interaction between upward propagating planetary waves and the mean flow. | IPCC WGI AR5 2013 |
| Brine | Small droplets of highly saline water that form in pockets between ice crystals, as sea ice forms and expels salt into the underlying ocean water. | NSIDC accessed 2016 |
| Brown snow | Snow intermixed with dust particles; a common phenomenon in many parts of the world. Snows of other colors, such as red snow and yellow snow, are similarly explainable. | AMS - glossary of meteorology |
| BTS method | Method to predict the presence or absence of permafrost in a mountain area, using measurements of the bottom temperature of snow cover mid- to late-winter. | NSIDC accessed 2016 |
| BTS method | Method to predict the presence or absence of permafrost in a mountain area, using measurements of the bottom temperature of snow cover mid- to late-winter | Van Everdingen International Permafrost Association 2005 |
| Bubbly ice | Glacier ice containing air bubbles. Air bubbles are trapped when the ice is formed from either water or compressed snow. A layer of bubbly ice is called a white band. | AMS - glossary of meteorology |
| Bummock | From the point of view of the submariner, a downward projection from the underside of the ice canopy; the counterpart of a hummock. | WMO Sea Ice Nomenclature 2017 |
| Bummock | Sea ice terminology that describes a downward projection from the underside of sea ice; the submariner's counterpart of a hummock. | Environment and Climate Change Canada 2014 |
| Bummock | From the point of view of the submariner, a downward projection from the underside of a floating ice canopy; the submerged counterpart of an ice hummock. | AMS - glossary of meteorology |
| Bummock | From the point of view of the submariner, a downward projection from the under-side of the ice canopy; the counterpart of a hummock. | Illustrated Glossary of Snow and Ice |
| Bummocks | Smooth hills of ice that form on the bottom of sea ice from eroding keels, particularly during the summer melt. | NSIDC accessed 2016 |
| Buran | A strong northeast wind in Russia and central Asia. It is most frequent in winter when it resembles a blizzard, that is, very cold and lifting snow from the ground; as such it is called white buran or, on the tundra, purga. A similar wind in Alaska is called burga. The buran also occurs, but less frequently, in summer, when it raises dust clouds; it is then called karaburan. | AMS - glossary of meteorology |
| Burga | A northeasterly storm in Alaska, bringing sleet or snow; it is similar to the winter buran or purga of Russia and Siberia. (Also spelled boorga.) | AMS - glossary of meteorology |
| Buried ice | Ice formed or deposited on the ground surface and later covered by sediments | Van Everdingen International Permafrost Association 2005 |
| Buried ice | Ice formed or deposited on the ground surface and later covered by sediments. Buried Ice likely represents buried Glacier Ice or buried Snowdrift or avalanche Snow; or less likely, lake, river or sea Ice, or Icings. | Trombotto et al. 2014 |
| Cake ice | Flat pieces of sea ice larger than brash. Cake ice is often tightly packed, giving it a mosaic appearance, but its surface is generally smooth in contrast to rough, hummocked pressure ice. | AMS - glossary of meteorology |
| Calve | Break off from a larger ice shelf or ice sheet into the water. | NSIDC accessed 2016 |
| Calved ice | A piece of ice floating in a body of water after calving from a mass of land ice or iceberg. (Also called calf.) | AMS - glossary of meteorology |
| Calving | Sea ice terminology that describes the breaking away of a mass of ice from an ice wall, ice front or iceberg. | Environment and Climate Change Canada 2014 |
| Calving | The breaking away of a mass of ice from an ice wall, ice front, or iceberg. | WMO Sea Ice Nomenclature 2017 |
| Calving | The component of ablation consisting of the breaking off of discrete pieces of ice from a glacier margin into lake or sea water, producing icebergs, or onto land in the case of dry calving. Calving excludes frontal melting and sublimation, although in practice it may be difficult to measure the phenomena separately. For example subaqueous frontal melting may lead to the detachment of icebergs by undercutting or by encouraging the propagation of crevasses. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Calving | Process by which ice breaks off a glacier's terminus usually the term is reserved for tidewater glaciers or glaciers that end in lakes, but it can refer to ice that falls from hanging glaciers. | NSIDC accessed 2016 |
| Calving | The process by which pieces of ice break away from the terminus of a glacier that ends in a body of water or from the edge of a floating ice shelf that ends in the ocean. Once they enter the water, the pieces are called icebergs. | Molnia USGS 2004 |
| Calving | The breaking off of discrete pieces of ice from a glacier, ice sheet or an ice shelf into lake or seawater, producing icebergs. This is a form of mass loss from an ice body. | IPCC WGI AR5 2013 |
| Calving | Breaking away of a mass of ice from an ice wall, ice front or iceberg. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Calving | The process of detachment of icebergs and smaller blocks of ice from a glacier into water. | Swisseduc - Photo glossary of glaciological terms |
| Calving | The breaking away of a mass of ice from a floating glacier, ice front, or iceberg. | AMS - glossary of meteorology |
| Calving | The loss of glacier mass when ice breaks off into a large water body like an ocean or a lake. | PhysicalGeography.net |
| Calving | The breaking away of a mass of ice from a floating glacier, ice front or iceberg. | Illustrated Glossary of Snow and Ice |
| Calving | Terminus extends into lake or sea (Tidewater glacier); Produces icebergs; Any glacier that possesses 'Normal' frontal characteristics and is calving; Not to be used for 'Terrestrial calving' ('dry calving'); Terminus of a glacier sufficiently extending into sea or lake water to produce icebergs; includes - for this inventory - dry land calving which would be recognisable from the lowest glacier elevation (WGMS 1970, 1998); Terminus of a glacier sufficiently extending into sea or occasionally lake water to produce icebergs; includes - for this inventory - dry land calving (WGMS 1977); If the frontal terminus is calving on dry land see classification for 'Terrestrial calving' | Illustrated GLIMS Glacier Classification Manual |
| Calving flux | The mass flux, with dimension [M T-1], of ice by calving from a glacier margin. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Calving front | A glacier margin from which discrete pieces of ice calve or break off, to become icebergs if the margin stands or floats in sea or lake water. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Calving glacier | A glacier with a terminus that ends in a body of water (river, lake, ocean) into which it calves icebergs. | Molnia USGS 2004 |
| Calving glacier | Glacier that loses material by calving, usually a glacier that terminates in sea, lake, or river water. | NSIDC accessed 2016 |
| Calving rate | Either the calving flux or the calving velocity, depending on the context. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Calving velocity | The volumetric calving flux divided by the area of projection of the calving glacier margin onto a vertical plane normal to the mean direction of the ice flow. Denoting horizontal velocity components in the direction of the ice flow as u, the calving velocity ucalv can be determined by application of the principle of conservation of mass at the glacier margin: calvu u u L Lbalthin, where ubal is the balance velocity, uthin is the thinning velocity and llis the rate of change of the glacier's length reckoned from a fixed point upglacier from the margin. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Canadian hardness-gauge | A type of disk hardness-gauge, especially useful in relatively soft snow. | AMS - glossary of meteorology |
| Canadian high | High pressure system that develops in winter over central North America. | PhysicalGeography.net |
| Candle ice | A form of rotten ice; disintegrating sea ice (or lake ice) consisting of ice prisms or cylinders oriented perpendicular to the original ice surface; these "ice fingers" may be equal in length to the thickness of the original ice before its disintegration. | AMS - glossary of meteorology |
| Canopy drip | Redirection of a proportion of the rain or snow falling on a plant to the edge of its canopy. | PhysicalGeography.net |
| Cap cloud | 1. An approximately stationary cloud, or standing cloud, on or hovering above an isolated mountain peak. It is formed by the cooling and condensation in moist air forced up over the peak. (Also called cloud cap.) 2.Same as pileus. | AMS - glossary of meteorology |
| Cartographic method | Like topographic method, a synonym of geodetic method in the context of measurement of mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cascading | Changes in the inclination of the glacier surface; Areas of crevasses and seracs are common; Descending in a series of marked steps with some crevasses and seracs | Illustrated GLIMS Glacier Classification Manual |
| Catchment glacier | A semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a snowdrift glacier or a drift glacier. | NSIDC accessed 2016 |
| Cave ice | Ice formed in a closed or open cave. | NSIDC accessed 2016 |
| Cave ice | Ice formed in a closed or open cave | Van Everdingen International Permafrost Association 2005 |
| Chain | Row of hills, mountains or nunataks of lesser extent than a range. | UK Antarctic Place-names Committee accessed 2016 |
| Channel in ice (made by ship) | A band of broken ice or flaw formed by a ship passing across fast or pack ice. | Bushuyev 2004 |
| Chatter marks | A series of small, closely spaced, crescentic grooves or scars formed in bedrock by rocks frozen in basal ice as they move along and chip the glacier's bed. The horns of the crescent generally point down glacier. | Molnia USGS 2004 |
| Chattermarks | Striations or marks left on the surface of exposed bedrock caused by the advance and retreat of glacier ice. | NSIDC accessed 2016 |
| Chattermarks | A group of crescent-shaped friction cracks on bedrock, formed by the juddering effect of moving ice. | Swisseduc - Photo glossary of glaciological terms |
| Chinook | The name given to the foehn in western North America, especially on the plains to the lee or eastern side of the Rocky Mountains in the United States and Canada. On the eastern slopes of the Rocky Mountains the chinook generally blows from the west or southwest, although the direction may be modified by topography. Often the chinook begins to blow at the surface as an arctic front retreats to the east, producing dramatic temperature rises. Jumps of 10-20C can occur in 15 minutes, and at Havre, Montana, a jump from -12 to +5C in 3 minutes was recorded. Occasionally the arctic front is nearly stationary and oscillates back and forth over an observing station, causing the temperature to fluctuate wildly as the station comes alternately under the influence of warm and cold air. As in the case of any foehn, chinook winds are often strong and gusty. They can be accompanied by mountain waves, and they can occur in the form of damaging downslope windstorms. The air in the chinook originates in midtroposphere above the ridgetops, and its warmth and dryness result from subsidence. When moisture is present, a variety of mountain-wave clouds and lee-wave clouds can form, such as the chinook arch of the Canadian Rocky Mountains west of Calgary, Alberta. The chinook brings relief from the cold of winter, but its most important effect is to melt or sublimate snow: A foot of snow may disappear in a few hours. As with the foehn, researchers have attempted to classify chinooks as downslope winds with warming and boras as those accompanied by cooling. Again, these schemes have produced limited success because of the many ambiguous or erroneously classified cases. | AMS - glossary of meteorology |
| Chinook wind | The name of a North American wind that occurs on the leeward side of mountains. This wind is warm and has a low humidity. | PhysicalGeography.net |
| Chionosphere | The part of the Earth's surface lying above the regional snowline. Though useful, the term, due originally to Kalesnik, is in fact confined to the Russian literature. 'Chion' is a Greek word for snow. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cirque | Bowl shape or amphitheater usually sculpted out of the mountain terrain by a cirque glacier. | NSIDC accessed 2016 |
| Cirque | A deep, steep-walled recess in a mountain, caused by glacial erosion. | Molnia USGS 2004 |
| Cirque | A bowl-shaped, amphitheater-like depression eroded into the head or the side of a glacier valley. Typically, a cirque has a lip at its lower end. The term is French and is derived from the Latin word circus. | Molnia USGS 2004 |
| Cirque | Rounded recess on a mountain side formed by glacial action and usually occupied by a glacier. | UK Antarctic Place-names Committee accessed 2016 |
| Cirque | (from the French) An armchair-shaped hollow with steep sides and back wall, formed as a result of glacial erosion high on a mountainside, and often containing a rock basin with a tarn (q.v.) (known as corrie or cwm in Britain). | Swisseduc - Photo glossary of glaciological terms |
| Cirque | Glacially eroded rock basin found on mountains. Most alpine glaciers originate from a cirque. | PhysicalGeography.net |
| Cirque | Located in an arm chair shaped bedrock hollow; No tongue developed, in contrast to simple basin; As wide or even wider as their length; Catchmant area is created through the process of glacial erosion; Occupies a separate, rounded, steep-walled recess which it has formed on a mountain side | Illustrated GLIMS Glacier Classification Manual |
| Cirque glacier | A small glacier that forms within a cirque basin, generally high on the side of a mountain. | Molnia USGS 2004 |
| Cirque glacier | Glacier that resides in basins or amphitheaters near ridge crests; most cirque glaciers have a characteristic circular shape, with their width as wide or wider than their length. | NSIDC accessed 2016 |
| Cirque glacier | A glacier occupying a cirque. A cirque is a rounded recess with steep sides and back wall, formed on a mountainside by glacial erosion. Cirque is an Anglicized French word that has displaced the synonyms 'corrie' (from Scots Gaelic) and 'cwm' (from Welsh) of early glaciological usage. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cirque glacier | A glacier occupying a cirque. | Swisseduc - Photo glossary of glaciological terms |
| Cirque glacier | Small glacier lying wholly within a cirque, or topographic hollow, created by glacial excavation located high in mountainous areas. | AMS - glossary of meteorology |
| Cirque glacier | Small glacier that just occupies a cirque. | PhysicalGeography.net |
| Cirque glacier | A glacier which occupies a separate rounded recess which it has formed on a mountain side. | Illustrated Glossary of Snow and Ice |
| Clear ice | A thin coating of ice on terrestrial objects, caused by rain that freezes on impact. The ice is relatively transparent, as opposed to rime ice, because of large drop size, rapid accretion of liquid water, or slow dissipation of latent heat of fusion. | NOAA National Weather Service Glossary 2009 |
| Clear ice | Smooth compact rime, usually transparent, fairly amorphous, with a ragged surface, and morphologically resembling glaze. | WMO METEOTERM accessed 2016 |
| Clear ice | Smooth compact rime, usually transparent, fairly amorphous, with a ragged surface, and morphologically resembling glaze. (Or clear icing.) This term has two different major applications. 1) Most commonly, it is used as a synonym for glaze, particularly with respect to aircraft icing. Factors that favor clear ice (or glaze) formation are large drop size, rapid accretion of liquid water, slight supercooling, and slow dissipation of latent heat of fusion. Thus, an aircraft flight through supercooled rain at an air temperature of 0 to -4C is most conducive to clear icing. This type of icing does not seriously distort airfoil shape, but it does add appreciably to the weight of the craft. 2) The term may also be applied to homogeneous bodies of glacier ice and lake ice. | AMS - glossary of meteorology |
| Climate snow line | The altitude above which a flat surface (fully exposed to sun, wind, and precipitation) would experience a net accumulation of snow over an extended period of time. Below this altitude ablation would predominate. While this concept is largely theoretical in application, it corresponds closely to the actual firn line of a glacier and to the average summer position of the snow line in mountainous terrain. (Also called climatic snow line.) | AMS - glossary of meteorology |
| Climate system | The climate system is the highly complex system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the lithosphere, and the biosphere, and the interactions among them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations, and anthropogenic forcings such as the changing composition of the atmosphere and land use change. | IPCC WGII AR5 2014 |
| Climatic mass balance | The sum of the surface mass balance and the internal mass balance; see also climatic-basal mass balance. The term is introduced to preserve the distinction between its two components, which is compromised if surface mass balance is redefined to include internal accumulation. The qualifier 'climatic' reflects the fact that the surface and internal balances both depend strongly on interaction between the glacier, the hydrosphere and the atmosphere. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Climatic snowline | A synonym of regional snowline. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Climatic-basal mass balance | The sum of the climatic mass balance and the basal mass balance. The expression b csfc asfc ci ai cb ab states that the climatic-basal mass balance b is the sum of surface accumulation csfc, surface ablation asfc, internal accumulation ci, internal ablation ai, basal accumulation cb and basal ablation ab. The sum of cb and ab is the basal mass balance. The sum of ci and ai is the internal mass balance. The sum of csfc and asfc is the surface mass balance. The sum of the surface mass balance and internal mass balance (the first four quantities on the right of the expression) is the climatic mass balance. The sum of the six quantities on the right (that is, of the climatic mass balance and the basal mass balance) is the climatic-basal mass balance. The climatic-basal mass balance includes all those components of mass change that do not arise from glacier flow or frontal ablation. The qualifier 'basal' does not exclude a role for the climate, for example through interactions between the atmosphere and the ocean. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Close cavity ice | Ice formed in a closed space, cavity or cave in permafrost. | NSIDC accessed 2016 |
| Close pack ice | Composed of close ice that is mostly in contact; ice cover 7/10ths to 9/10ths. | NSIDC accessed 2016 |
| Close pack ice | Floating ice in which the concentration is 7/10 to 8/10, composed of floes mostly in contact. | Bushuyev 2004 |
| Close pack ice | Pack ice in which the concentration is seven-tenths to eight-tenths, composed of floes mostly in contact. | WMO Sea Ice Nomenclature 2017 |
| Close pack ice | Floating pack ice in which the ice concentration is between 7/10 and 8/10, composed of floes mostly in contact. | AMS - glossary of meteorology |
| Close pack ice | Composed of floes mostly in contact. Ice cover 7/10ths to 9/10ths. | Illustrated Glossary of Snow and Ice |
| Close pack/drift | Sea ice terminology that describes floating ice that has a concentration of 7/10 to 8/10. It is composed mostly of ice floes that are in contact with one another. | Environment and Climate Change Canada 2014 |
| Closed talik | A layer or body of unfrozen ground occupying a depression in the permafrost table below a lake or river. | NSIDC accessed 2016 |
| Closed talik | A layer or body of unfrozen ground occupying a depression in the permafrost table below a lake or river | Van Everdingen International Permafrost Association 2005 |
| Closed talik | Is a form of localized unfrozen ground (talik) in an area of permafrost. It is completely enclosed by permafrost in all directions. | PhysicalGeography.net |
| Closed-cavity ice | Ice formed in a closed space, cavity or cave in permafrost | Van Everdingen International Permafrost Association 2005 |
| Closed-system freezing | Freezing that occurs under conditions that preclude the gain or loss of any water by the system. | NSIDC accessed 2016 |
| Closed-system freezing | Freezing that occurs under conditions that preclude the gain or loss of any water by the system | Van Everdingen International Permafrost Association 2005 |
| Closed-system pingo | A pingo formed by doming of frozen ground due to freezing of injected water supplied by expulsion of pore water during permafrost aggradation in the closed talik under a former water body. | NSIDC accessed 2016 |
| Closed-system pingo | A pingo formed by doming of frozen ground due to freezing of injected water supplied by expulsion of pore water during permafrost aggradation in the closed talik under a former water body | Van Everdingen International Permafrost Association 2005 |
| Coalescing, non contributing | Glaciers whose tongues come together and flow in parallel without coalescing; No merging of ice masses; Glaciers whose tongues come together and flow in parallel without coalescing (WGMS 1977) | Illustrated GLIMS Glacier Classification Manual |
| Coefficient of compressibility | The volume change per unit volume of a substance per unit increase in effective compressive stress, under isothermal conditions | Van Everdingen International Permafrost Association 2005 |
| Coffee-can method | A means of measuring the submergence velocity or emergence velocity of the glacier surface by anchoring a stand for a global navigation satellite system (GNSS; usually a Global Positioning System) receiver to the body of the glacier, using a suitable object (such as a coffee can) as an anchor connected to the surface by a cable under tension. The essence of the method is that measured changes in the exposed length of the cable (or equivalent measurements of the local surface mass balance), and in the surface elevation (measured by the GNSS receiver), yield two of the three terms in the continuity equation and allow the third term, the submergence or emergence velocity (that is, the flux divergence) to be determined. Corrections may be needed for the densification (that is, settling) of firn beneath the anchor and for downslope advection of the anchor. The coffee-can method has been used mainly in the accumulation zones of ice sheets, where the surface mass balance can be obtained by ice-core stratigraphy. However in the ablation zone the emergence of cables emplaced for other reasons, such as the measurement of temperature profiles, can serve a similar purpose. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Col | Depression in a range of hills or mountains generally forming a pass. | UK Antarctic Place-names Committee accessed 2016 |
| Col | (from the French) A high-level pass formed by glacial breaching of an ar?te or mountain mass. | Swisseduc - Photo glossary of glaciological terms |
| Col | Saddle like depression found between two mountain peaks. Formed when two opposing cirque glaciers back erode an arte. | PhysicalGeography.net |
| Cold cap | As defined by A. Supan (1879), a region of the earth within which the mean temperature of the warmest month is less than 10C. This limiting condition closely approximates the temperature at the arctic tree line, and was later adopted by W. K?ppen (1918) as his boundary between the polar climates and tree climates. Supan also defined temperate belt and hot belt in his early form of climatic classification. | AMS - glossary of meteorology |
| Cold desert | Desert found in the high latitudes and at high altitudes where precipitation is low. Surface air temperatures are generally cold in these dry environments. | PhysicalGeography.net |
| Cold glacier | Glacier in which most of the ice is below the pressure melting point; nonetheless, the glacier's surface may be susceptible to melt due to incoming solar radiation, and the ice at the rock/ice interface may be warmed as a result of the natural (geothermal) heat from the earth's surface. | NSIDC accessed 2016 |
| Cold glacier | A glacier consisting of cold ice, except possibly in a surface layer up to 1015 m thick that might warm to the melting point seasonally, and possibly right at the bed. See polythermal glacier, temperate glacier, dry-based glacier, warm-based glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cold glacier | A glacier in which the bulk of the ice is below the pressure-melting point and therefore frozen to the bed. | Swisseduc - Photo glossary of glaciological terms |
| Cold glacier | Glacier in which the ice found from the its surface to base has a temperature as cold as -30 Celsius throughout the year. This is well below the pressure melting point. Pressure melting can cause the melting of ice at the base of these glaciers. One of the three types of glaciers: cold glacier; temperate glacier; and subpolar glacier. | PhysicalGeography.net |
| Cold ice | Ice at a temperature below its pressure-melting point; see temperate ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cold ice | Ice which is below the pressure melting point, and therefore dry. Some surface melting and runoff may occur, however. | Swisseduc - Photo glossary of glaciological terms |
| Cold infiltration-recrystallization zone | See infiltration-recrystallization zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cold pole | The hemispheric location which has the lowest mean annual temperature. | WMO METEOTERM accessed 2016 |
| Cold pole | The location that has the lowest annual mean temperature in its hemisphere. In the Northern Hemisphere the cold pole is usually placed at Verkhoiansk in Siberia (67 deg 33 min N, 133 deg 24 min E) with an annual mean temperature of -16C (3F) [January: -50C (-59F), July: 16C (60F)], but the country around Verkhoiansk is very mountainous, and lower winter temperatures are found in some of the valleys. At Oimekon, for example, the average January temperature is probably below -51C (-60F). In the Southern Hemisphere the cold pole is near 80-85S and 75-90E. International Geophysical Year stations located inland on Antarctica have recorded several temperatures well below -73C (-100F). | AMS - glossary of meteorology |
| Cold-based glacier | A glacier whose bed is below its pressure-melting point, implying that there is no liquid water at the bed; dry-based glacier is a synonym. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Collapse scar | That portion of a peatland where the whole or part of a palsa or peat plateau has thawed and collapsed to the level of the surrounding peatland. | NSIDC accessed 2016 |
| Collapse scar | That portion of a peatland where the whole or part of a palsa or peat plateau has thawed and collapsed to the level of the surrounding peatland | Van Everdingen International Permafrost Association 2005 |
| Columnar ice | Ice consisting of columnar shaped grain. The ordinary black ice is usually columnar-grained. | NOAA Glossary of Hydrologic Terms |
| Columnar snow crystals | Fairly short prismatic ice crystals either solid or hollow, the ends of which may be plane, pyramidal, truncated or hollow. | WMO METEOTERM accessed 2016 |
| Combined system | A combination of two time systems of mass-balance measurement, usually of the stratigraphic system with either the fixed-date system or the floating-date system. As originally defined, the combined system accounted rigorously for differences between the stratigraphic and fixed-date systems, but this rigorous accounting has been found impractical in most measurement programmes and various simplifications have been adopted. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Compact ice | Sea ice terminology that describes floating ice that has a concentration of 10/10, and no water is visible. | Environment and Climate Change Canada 2014 |
| Compact pack ice | Floating ice in which the concentration is 10/10 and no water is visible. | Bushuyev 2004 |
| Compact pack ice | Pack ice in which the concentration is ten-tenths, and no water is visible. | WMO Sea Ice Nomenclature 2017 |
| Compacted ice edge | Close, clear-cut ice edge compacted by wind or current; usually on the windward side of an area of pack ice. | WMO Sea Ice Nomenclature 2017 |
| Compacted ice edge | Sea ice terminology that describes a clear-cut ice edge that is compacted by wind or current, usually on the windward side of an area of ice. | Environment and Climate Change Canada 2014 |
| Compacting | A decrease in the separation between individual ice floes resulting in increased ice concentration. | Bushuyev 2004 |
| Compacting | Pieces of floating ice are considered to be compacting when they are subjected to a converging motion, which increases ice concentration and/or produces stresses that may result in ice deformation. | WMO Sea Ice Nomenclature 2017 |
| Compacting | Sea ice terminology that describes an increase in ice concentration and/or a stress which may result in ice deformation (i.e. The ice becoming warped). | Environment and Climate Change Canada 2014 |
| Complete freeze-up | Freezing of the water in a river reach from the bed to the surface. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Complete freeze-up | Freezing of the water in a river or shallow lake from the surface to the bed. | AMS - glossary of meteorology |
| Composite wedge | A wedge showing evidence of both primary and secondary filling. | NSIDC accessed 2016 |
| Composite wedge | A wedge showing evidence of both primary and secondary filling | Van Everdingen International Permafrost Association 2005 |
| Compound basins | Several catchment areas of a simple basin type (see below) in a specific zone of accumulation feeding a glacier tongue; Two or more individual accumulation basins feeding one glacier system; Can be used if a mountain glacier consists of several cirques, but has no valley developed | Illustrated GLIMS Glacier Classification Manual |
| Compound basins | Dendritic system of Outlet- or valley glaciers of more than one 'compound basin' that merge together; Two or more individual valley glaciers issuing from tributary valleys and coalescing | Illustrated GLIMS Glacier Classification Manual |
| Compression flow | Flow that occurs when glacier motion is decelerating down-slope. | NSIDC accessed 2016 |
| Compression of ice | A further stage of ice compacting after its concentration reaches 9-10/10. During compression of ice, rafting and hummocking usually occur and stuffed ice may be formed within the coastal zone. Within the zones where big and giant floes are predominant, compression of ice may start if total concentration is equal 7-8/10. | Bushuyev 2004 |
| Compression zone | Zone where compression of ice is observed. | Bushuyev 2004 |
| Concentration | Sea ice terminology, for a ratio (expressed in tenths) which describes the area of the water surface covered by ice, as a fraction of the whole area. Total concentration includes all stages of development that are present. Partial concentration refers to the amount of a particular stage or of a particular form of ice, and represents only a part of the total. | Environment and Climate Change Canada 2014 |
| Concentration | The ratio in tenths of the sea surface actually covered by ice to the total area of sea surface, both ice covered and ice free, at a specific location or over a defined area. | WMO Sea Ice Nomenclature 2017 |
| Concentration | The ratio of the area of ice features to the total area of a sea part (zone) delineated on the chart, expressed in tenths. The total concentration includes all stages of development and the partial concentration includes areas of ice of specific age or arrangement which comprise only part of the total concentration. Concentrations within 0-1/10 and 9/10 | Bushuyev 2004 |
| Concentration boundary | A line approximating the transition between two areas of pack ice with distinctly different concentrations. | WMO Sea Ice Nomenclature 2017 |
| Concentration boundary | Sea ice terminology, describing a line that marks the transition between two areas of floating ice with different concentrations. | Environment and Climate Change Canada 2014 |
| Conduit | A drainage tunnel within or at the bed of a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Confluent | Tributary glacier tongues that merge into other glaciers; Merging ice masses | Illustrated GLIMS Glacier Classification Manual |
| Congelation | (1) The freezing of liquid water in the absence of pre-existing ice; see infiltration ice, recrystallization. (2) Addition of ice to the base of sea ice by freezing. If new and young ice are not deformed into rafts or ridges, they will continue to grow by congelation. Congelation ice has distinctive columnar crystal texture due to the downward growth of the crystals into the water. It is very common in Arctic pack ice and fast ice. In limnology it is called 'black ice'. Congelation derives from 'congeal', meaning freeze or thicken, increase in viscosity. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Congelation ice | An advanced form of new ice that forms as a stable sheet with a smooth bottom surface. | NSIDC accessed 2016 |
| Congelifraction | The splitting of rocks as the result of the freezing of the water contained in them. The individual fragment produced by this process is called a congelifract. (Also called frost riving, frost splitting.) | AMS - glossary of meteorology |
| Congeliturbation | (Rare.) The churning and stirring of soil as a result of repeated cycles of freezing and thawing. This includes such actions as frost heaving and surface subsidence during thaws. A body of material disturbed by frost action is called a congeliturbate. | AMS - glossary of meteorology |
| Conglomeric cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles form compound arrangements. | NSIDC accessed 2016 |
| Conglomeric cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles form compound arrangements | Van Everdingen International Permafrost Association 2005 |
| Conglomeric cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles form compound arrangements. This fabric, found in cryosols, results from freeze-thaw processes probably accompanied by Cryoturbation. | Trombotto et al. 2014 |
| Conservation of mass | The principle that mass in a system is neither created nor destroyed, expressed by the relation the rate of change of mass in an element of the system equals the rate at which mass enters the element minus the rate at which mass leaves the element. The definition rests on the convention that all flows are positive in the positive coordinate direction. With the commonest alternative convention, that inward flows are positive and outward flows are negative, the definition would be read with 'plus' replacing 'minus'. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Consolidated ice | Floating ice in which the concentration is 10/10 and the floes are frozen together. | Bushuyev 2004 |
| Consolidated ice | Sea ice terminology, meaning floating ice in which the concentration is 10/10, and the floes are frozen together. | Environment and Climate Change Canada 2014 |
| Consolidated ice | An area of the sea covered by ice of various origins consolidated, by wind and currents, into a solid mass. | AMS - glossary of meteorology |
| Consolidated ice cover | Ice cover formed by the packing and freezing together of floes, brash ice and other forms of floating ice. | NOAA Glossary of Hydrologic Terms |
| Consolidated pack ice | Pack ice in which the floes are frozen together; ice cover 10/10ths. | NSIDC accessed 2016 |
| Consolidated pack ice | Pack ice in which the concentration is ten-tenths and the floes are frozen together. | WMO Sea Ice Nomenclature 2017 |
| Consolidated pack ice | Pack ice in which the floes are frozen together. Ice cover 10/10ths. | Illustrated Glossary of Snow and Ice |
| Consolidated ridge | A ridge in which the base has frozen together. | WMO Sea Ice Nomenclature 2017 |
| Consolidated ridge | Sea ice terminology, describing a ridge in which the base has frozen together. | Environment and Climate Change Canada 2014 |
| Construction methods in permafrost | Special design and construction procedures required when engineering works are undertaken in permafrost areas | Van Everdingen International Permafrost Association 2005 |
| Continental arctic air mass | Air mass that forms over extensive landmass areas of the high latitudes. In the Northern Hemisphere, these system form only in winter over Greenland, northern Canada, northern Siberia, and the Arctic Basin. Continental Arctic air masses are very cold and extremely dry. These air masses are also very stable. | PhysicalGeography.net |
| Continental glacier | A continuous sheet of land ice that covers a very large area and moves outward in many directions. This type of ice mass is so thick as to mask the land surface contours, in contrast to the smaller and thinner highland ice. The continental glacier of Greenland is sometimes called the Inland Ice. This term is often used to describe the great ice masses that characterized the ice ages. | AMS - glossary of meteorology |
| Continental glacier | Largest type of glacier with a surface coverage in the order of 5 million square kilometers. (Also continental ice sheet) | PhysicalGeography.net |
| Continental ice sheet | Unconstrained by topography Continental size Derive their morphological shape from ice flow properties, internal dynamics, and bedrock conditions Inundates areas of Continental size May incorporate individual ice domes | Illustrated GLIMS Glacier Classification Manual |
| Continental polar air mass | Air mass that forms over extensive landmass areas of middle to high latitudes. In North America, these system form over northern Canada. Continental Polar air masses are cold and very dry in the winter and cool and dry in the summer. These air masses are also atmospherically stable in both seasons. | PhysicalGeography.net |
| Continuous permafrost | Form of permafrost that exists across a landscape as an unbroken layer. | PhysicalGeography.net |
| Continuous permafrost | Geographic area in which permafrost occurs everywhere beneath the exposed land surface with the exception of widely scattered sites, such as newly deposited unconsolidated sediments that have just been exposed to the freezing climate; mean annual soil surface temperatures are typically below -5 degrees (23 degrees Fahrenheit). | NSIDC accessed 2016 |
| Continuous permafrost | Permafrost occurring everywhere beneath the exposed land surface throughout a geographic region with the exception of widely scattered sites, such as newly deposited unconsolidated sediments, where the climate has just begun to impose its influence on the thermal regime of the ground, causing the development of continuous permafrost | Van Everdingen International Permafrost Association 2005 |
| Continuous permafrost | Permafrost occurring everywhere beneath the exposed land surface throughout a geographic region with the exception of widely scattered sites, such as newly deposited sediments, where the climate is just beginning to influence the ground thermal regime, causing the development of Continuous Permafrost. For practical purposes, the existence of small Taliks within Continuous Permafrost has to be recognized. The term, therefore, generally refers to areas where more than 90% of the ground surface is underlain by Permafrost. The term 'continuous' Permafrost is mostly used for Arctic/Antarctic Permafrost zones. For the mountainous zones the terms 'likely, possible and unlikely' are preferred. | Trombotto et al. 2014 |
| Continuous permafrost zone | The major subdivision of a permafrost region in which permafrost occurs everywhere beneath the exposed land surface with the exception of widely scattered sites. | NSIDC accessed 2016 |
| Continuous permafrost zone | The major subdivision of a permafrost region in which permafrost occurs everywhere beneath the exposed land surface with the exception of widely scattered sites | Van Everdingen International Permafrost Association 2005 |
| Conventional balance | The mass balance of a glacier, the term having been introduced by Elsberg et al. (2001) to distinguish the mass balance from the reference-surface balance, which is the balance the glacier would have if the glacier surface geometry were fixed in time. Conventional balances are obtained when point measurements over a particular time interval are extrapolated to the glacier area and area-altitude distribution measured during the same time interval. Calculations of conventional balance require repeated mapping of glacier hypsometry at intervals appropriate to the rate of change of the surface geometry. However, maps are often re-calculated at longer time intervals, the reported balances being a combination of conventional and reference-surface balances. Conventional balances are relevant for hydrological applications because they represent the actual mass change of a glacier. Conventional balances are not simply correlated to variations in climate because they incorporate both climate forcing and changes in glacier hypsometry. For glacier/climate investigations the reference-surface balance is a more relevant quantity. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Coordination number | Coordination number CN is the number of connections between a particle and its neighbours. It can be represented with indices, averaged over a volume or determined for an individual structure. These geometric parameters are common in numerical models of snow. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Corn snow ice | Rotten granular ice. | NOAA Glossary of Hydrologic Terms |
| Cornice | An overhanging accumulation of ice and wind-blown snow, characteristically found on the edge of a ridge or cliff face. | NSIDC accessed 2016 |
| Cornice | The overhanging portion of a snow field produced by drifting snow. | WMO METEOTERM accessed 2016 |
| Cornice | An overhanging structure of ice or snow formed at a topographic edge (such as a mountain ridge) by wind-driven deposition. Cornices can be extremely hazardous to mountain climbers. Cornice release can also initiate avalanches. | AMS - glossary of meteorology |
| Cornice | An overhanging accumulation of ice and wind-blown snow, characteristically found on the edge of a ridge or cliff face. | Illustrated Glossary of Snow and Ice |
| Corrie | A British term for cirque (q.v.), derived from the Gaelic coire. | Swisseduc - Photo glossary of glaciological terms |
| Coulee | (1) Steep-sided flow of volcanic lava that has solidified. (2) Abandoned glacial meltwater channel. (3) Term used in the United States to describe a steep-sided stream valley. | PhysicalGeography.net |
| Crack | A separation formed in an ice cover of floe that does not divide it into two or more pieces. | NOAA Glossary of Hydrologic Terms |
| Crack | Any fracture or rift in floating ice not sufficiently wide to be described as a lead. | NSIDC accessed 2016 |
| Crack | Any fracture of fast ice, consolidated ice or a single floe with a width ranging from a few centimeters to 50 m and a length from several tens or hundreds of meters to several hundreds of kilometers. | Bushuyev 2004 |
| Crack | Any fracture that has not parted. | WMO Sea Ice Nomenclature 2017 |
| Crack | Sea ice terminology that describes any fracture of fast ice, consolidated ice or a single floe which may have been followed by separation ranging from a few centimetres to 1 metre. | Environment and Climate Change Canada 2014 |
| Crack | A fracture in an ice floe that has not parted substantially. More specifically, it is any fracture of fast ice, consolidated ice, or a single floe that may have been followed by separation ranging from a few centimeters to 1 m. | AMS - glossary of meteorology |
| Crack | Any fracture or rift in floating ice not sufficiently wide to be described as a lead. | Illustrated Glossary of Snow and Ice |
| Crag-and-tail | A glacially eroded rocky hill with a tail of till formed down-glacier of it. | Swisseduc - Photo glossary of glaciological terms |
| Crater | Glaciers in and / or on volcano craters; Network of glacier encompassing the summit at the outward flanks; Occurring in extinct or dormant volcanic craters which rise above the regional snow line (WGMS 1970); Occurring in and /or on volcanic craters (WGMS 1977); Occurring in extinct or dormant volcanic craters (WGMS 1998) | Illustrated GLIMS Glacier Classification Manual |
| Crater glacier | A glacier contained in or overflowing from a volcanic crater. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Creep | A way that snow or ice can move by deforming its internal structure. | NSIDC accessed 2016 |
| Creep | (1) Slow mass movement of soil downslope. Occurs where the stresses on the slope material are too small to create a rapid failure. See soil creep. (2) Another term used to describe traction. | PhysicalGeography.net |
| Creep of frozen ground | The slow deformation (or time-dependent shear strain) that results from long-term application of a stress too small to produce failure in the frozen material. | NSIDC accessed 2016 |
| Creep of frozen ground | The slow deformation (or time-dependent shear strain) that results from long-term application of a stress too small to produce failure in the frozen material | Van Everdingen International Permafrost Association 2005 |
| Creep of frozen ground | The slow deformation that results from long-term application of a stress unable to produce failure in the frozen material. In frozen soils, Creep deformations are due mainly to the Creep of Pore Ice and the migration of unfrozen pore water. In ice-saturated frozen soils, most Creep deformations are distortional with little or no volume change. In frozen soils with large unfrozen water contents or in unsaturated frozen soils, slow deformations due to consolidation, and Creep due to volume change, may also occur. Usually, a large portion of the Creep deformation is permanent. | Trombotto et al. 2014 |
| Creep strength | The failure strength of a material at a given strain rate or after a given period under deviatoric stress. | NSIDC accessed 2016 |
| Creep strength | The failure strength of a material at a given strain rate or after a given period under deviatoric stress | Van Everdingen International Permafrost Association 2005 |
| Creeping flow | Fluid flow at very small values of the Reynolds number, that is, in general, a very viscous flow. | AMS - glossary of meteorology |
| Crescentic gouge | Any curved mark or fracture produced by plucking or chipping of the glacier's bed. Larger than chatter marks,typically the horns of these gouges point up glacier. Also called Lunate Fracture or Crescentic Mark. | Molnia USGS 2004 |
| Crescentic gouge | A crescent-shaped scallop, usually several centimetres across, formed as a result of bedrock fracture under moving ice. | Swisseduc - Photo glossary of glaciological terms |
| Crest | Top or summit applied to a hill, mountain or nunatak. | UK Antarctic Place-names Committee accessed 2016 |
| Crevasse | Open fissure in the glacier surface. | NSIDC accessed 2016 |
| Crevasse | A crack or series of cracks that open in the surface of a moving glacier in response to differential stresses caused by glacier flow. They range in shape from linear to arcuate, in length from feet to miles. Their orientation may be in any direction with respect to the glacier flow. The deepest crevasses may exceed 100 feet. | Molnia USGS 2004 |
| Crevasse | A crack formed in glacier ice when tensile stresses exceed the tensile strength of the ice. The tensile stresses, and the tensile strength of the ice, are variable, and compressive stress at depth is believed to play a role in limiting the depth to which surface crevasses propagate. This depth can be up to a few tens of metres, or more if the crevasse is filled with water. Crevasses are conduits for the transfer of water, including surface meltwater, to the glacier interior and sometimes the glacier bed; see moulin. When crevasses in floating ice fill with surface meltwater, they may propagate to the base, causing the ice shelf or floating tongue to disintegrate. The fragments may contribute to an ice m | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Crevasse | Fissure formed in a glacier but not applied in place-names, cf. chasm. | UK Antarctic Place-names Committee accessed 2016 |
| Crevasse | Fissure in a glacier. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Crevasse | A deep V-shaped cleft formed in the upper brittle part of a glacier as a result of the fracture of ice undergoing extension. For various types of crevasses refer to longitudinal crevasse, transverse crevasse, en-echelon crevasse and bergschrund. | Swisseduc - Photo glossary of glaciological terms |
| Crevasse | A deep rift in a glacier, or in any other form of land ice, caused by its motion. | AMS - glossary of meteorology |
| Crevasse | (1) Opening on a levee that allows for the drainage of water from the floodplain to the stream channel. (2) Fracture on the brittle surface of a glacier. | PhysicalGeography.net |
| Crevasse | A fissure formed in a glacier. Crevasses are often hidden by snow bridges. | Illustrated Glossary of Snow and Ice |
| Crevasse hoar | A kind of hoarfrost; ice crystals that develop by sublimation in glacial crevasses and in other cavities with cooled space and calm, still conditions under which water vapor can accumulate; physical origin is similar to depth hoar. | NSIDC accessed 2016 |
| Crevasse hoar | Ice crystals that form and grow in glacial crevasses and in other cavities where a large cooled space is formed and in which water vapor can accumulate under calm, still conditions; a type of hoarfrost. They have an origin similar to that of depth hoar; the typical crystal is a hollow cup with one side opening inward and continued in a hexagonal scroll. | AMS - glossary of meteorology |
| Crevasse stratigraphy | The observation of Annual and other layer thicknesses in the walls of crevasses and similar nearly vertical exposures. See ice-core stratigraphy. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Crevasse trace | A long vein of clear ice a few centimetres to a few metres wide, formed as a result of fracture and recrystallisation of ice under tension without separation of the two walls; these structures commonly form parallel to open crevasses and extend into them. Thicker veins of clear ice resulting from the freezing of standing water in open crevasses are also referred to as crevasse traces. | Swisseduc - Photo glossary of glaciological terms |
| Crevasses | Crevasses are open fissures in glacier ice. Crevasses form where the speed of the ice is variable, such as in icefalls and at valley bends. The surface may appear blistered with crevasses where the ice flows over bedrock knobs and ridges. Crevasses are a glacier's most awesome features and are a constant hazard for climbers. They form where adjacent parts of a glacier are moving at different speeds. This unequal rate of flow produces stresses in the ice that cause it to break. Groups of crevasses often form where the glacier flows over a steep place in its bed. The ice moves faster here, and pulls apart, and a crevasse is formed. Although a large crevasse may seem to be bottomless to the observer, most crevasses are less than 100 feet deep because ice pressure tends to close the open spaces in the ice below that depth. | Molnia USGS 2004 |
| Crust | A hard snow surface lying upon a softer layer; crust may be formed by sun, rain or wind, and is described as breakable crust or unbreakable crust, depending upon whether it will break under the weight of a turning skier. | NSIDC accessed 2016 |
| Crust | A friable, firm layer of snow or ice of varying thickness formed at the surface of the snowpack. It is designated as 'breakable' or 'unbreakable' according to its ability to support a person on skis. Examples are wind crusts and slabs, melt-freeze crusts as well as sun and rain crusts (see Appendix A.1, DF or RG, MF, and IF, respectively). Melt-freeze-crusts can be up to several centimetres thick while sun and rain crusts usually form a thin, i.e., a few millimetres thick glaze of ice on the surface. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Crust | A hard snow surface lying upon a softer layer. Crust may be formed by sun, rain or wind, and is described as breakable crust or unbreakable crust, depending upon whether it will break under the weight of a turning skier. | Illustrated Glossary of Snow and Ice |
| Crust-like cryostructure | The cryostructure of a frozen deposit of angular blocks that are coated with ice, whereas large spaces between the blocks are not filled with ice. | NSIDC accessed 2016 |
| Crust-like cryostructure | The cryostructure of a frozen deposit of angular blocks that are coated with ice, whereas large spaces between the blocks are not filled with ice | Van Everdingen International Permafrost Association 2005 |
| Cryochore | A region of perpetual snow. | AMS - glossary of meteorology |
| Cryoconite | Dark, fine-grained debris on the glacier surface, often forming small, roughly circular patches. See cryoconite hole. The word was introduced by Nordenski | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cryoconite hole | A small cylindrical hole on the surface of a glacier, formed by patches of cryoconite that absorb more short-wave radiation than the surrounding ice, melting downwards at a faster rate and adding to sub-metre-scale spatial variability in ablation. See also weathering crust. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cryoconite hole | A small cylindrical hole on the surface of a glacier, formed by small patches of debris that absorb more radiation than the surrounding ice, and melt downwards at a faster rate. | Swisseduc - Photo glossary of glaciological terms |
| Cryoconite hole | A small pit in an ice surface produced by the sinking of a particle of dust of cosmic origin (known as cryoconite, a fine-grained dark-colored substance). | AMS - glossary of meteorology |
| Cryofront | The boundary between cryotic and noncryotic ground as indicated by the position of the 0 degrees Celsius isotherm in the ground. | NSIDC accessed 2016 |
| Cryofront | The boundary between cryotic and noncryotic ground as indicated by the position of the 0°C isotherm in the ground | Van Everdingen International Permafrost Association 2005 |
| Cryofront | The boundary between cryotic and non-Cryotic Ground as indicated by the position of the 0C isotherm in the ground. The Permafrost Base and the boundaries between noncryotic and cryotic portions of the Active Layer constitute Cryofronts. The Freezing Front may lag behind the Cryofront as it moves downwards during annual freezing of the Active Layer as a result of freezing-point depression. | Trombotto et al. 2014 |
| Cryogenesis | The combination of thermophysical, physico-chemical and physico-mechanical processes occurring in freezing, frozen and thawing earth materials. | NSIDC accessed 2016 |
| Cryogenesis | The combination of thermophysical, physico-chemical and physico-mechanical processes occurring in freezing, frozen and thawing earth materials | Van Everdingen International Permafrost Association 2005 |
| Cryogenesis | The combination of thermo-physical, physico-chemical and physico-mechanical processes occurring in freezing, frozen and thawing earth materials. Specific processes of Cryogenesis include water migration during freezing and thawing of the ground, Frost Heave, heat and mass (moisture) exchange, regelation and Gelifluction. | Trombotto et al. 2014 |
| Cryogenic aquiclude | A layer of ground which, because of its frozen state, has a low enough permeability to act as a confining bed for an aquifer. | NSIDC accessed 2016 |
| Cryogenic aquiclude | A layer of ground which, because of its frozen state, has a low enough permeability to act as a confining bed for an aquifer | Van Everdingen International Permafrost Association 2005 |
| Cryogenic aquiclude | A layer of ground which, because of its frozen state, has a low enough permeability to act as a confining bed for an aquifer. Annual freezing can turn the Active Layer into a Cryogenic Aquiclude. | Trombotto et al. 2014 |
| Cryogenic fabric | The distinct soil micromorphology resulting from the effects of freezing and thawing processes. | NSIDC accessed 2016 |
| Cryogenic fabric | The distinct soil micromorphology resulting from the effects of freezing and thawing processes | Van Everdingen International Permafrost Association 2005 |
| Cryogenic hygrometer | A special type of chilled mirror hygrometer capable of measuring very low frost points. These low temperatures at the mirror are attained by evaporating low boiling point or cryogenic fluids. This strong cooling capability allows cryogenic hygrometers to maintain reasonable response times even at low frost points. Cryogenic hygrometers are used for airborne humidity measurements from aircraft or balloons, but also in semiconductor industries for monitoring very dry environmental conditions needed in manufacturing processes. | AMS - glossary of meteorology |
| Cryogenic period | An interval in geologic time during which geologic, geomorphic, and climatic conditions favored large-scale glacier formation; a period that tended to produce an ice age or glacial period. | AMS - glossary of meteorology |
| Cryogenic temperature | In international materials science, this term refers to temperatures generally below -50 degrees Celsius, but usually to temperatures within a few degrees of absolute zero (-273 degrees Celsius). | NSIDC accessed 2016 |
| Cryogenic temperature | In international materials science, this term refers to temperatures generally below -50°C, but usually to temperatures within a few degrees of absolute zero (-273°C). | Van Everdingen International Permafrost Association 2005 |
| Cryolithology | The study of the genesis, structure and lithology of frozen earth materials. | NSIDC accessed 2016 |
| Cryolithology | The study of the genesis, structure and lithology of frozen earth materials | Van Everdingen International Permafrost Association 2005 |
| Cryology | The study of solid water, e.g. ice, snow, hail, etc. | WMO METEOTERM accessed 2016 |
| Cryology | The science of the physical aspects of snow, ice, hail, and sleet and other forms of water produced by temperatures below Zero degrees Celsius. | NOAA Glossary of Hydrologic Terms |
| Cryology | Branch of science which studies processes, evolution and development of the cryosphere. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Cryology | 1. The study of ice and snow. 2.In Europe, a synonym for glaciology. Note: The term cryology has become almost meaningless unless it is defined in context. (Arctic and Subarctic Terms, Arctic, Desert Tropic Information Center Pub. A-105, 1955.) 3.The study of sea ice. | AMS - glossary of meteorology |
| Cryomero | Cryomere refers to a cold period and is the opposite of a Thermomere, which is a warm climate period. According to the importance, duration, intensity, temperatures and precipitation characteristics different categories have been proposed such as: Category Cryomere Thermomere 1 Glacial Interglacial 2 Stadial Interstadial 3 Phase Interval 4 Step Stage In the mountain environment, the spatial scope of the glaciations, from a glacial (Category 1) up to a step (Category 4), were considered to be of 100 km, between 50 and 100 km, between 15 and 50 km and less than 15 km, respectively. | Trombotto et al. 2014 |
| Cryopediment | Gently inclined erosion surfaces developed at the foot of valley sides or marginal slopes of geomorphological units developed by cryogenic processes under Periglacial conditions. | Trombotto et al. 2014 |
| Cryopedology | The study of soils at temperatures below 0 degrees Celsius, with particular reference to soils subject to intensive frost action, and to soils overlying permafrost. | NSIDC accessed 2016 |
| Cryopedology | The study of soils at temperatures below 0°C, with particular reference to soils subject to intensive frost action, and to soils overlying permafrost | Van Everdingen International Permafrost Association 2005 |
| Cryopedology | "The study of [ground movement caused by] intensive frost action and of permafrost, their causes and occurrences, and the engineering devices and practices which may be devised to overcome difficulties brought about by them." (from Glossary of Arctic and Subarctic Terms 1955). | AMS - glossary of meteorology |
| Cryopedometer | Instrument for measuring the depth to which the soil is frozen. | WMO METEOTERM accessed 2016 |
| Cryopeg | A layer of unfrozen ground that is perennially cryotic (forming part of the permafrost), in which freezing is prevented by freezing-point depression due to the dissolved-solids content of the pore water. | NSIDC accessed 2016 |
| Cryopeg | A layer of unfrozen ground that is perennially cryotic (forming part of the permafrost), in which freezing is prevented by freezing-point depression due to the dissolved-solids content of the pore water | Van Everdingen International Permafrost Association 2005 |
| Cryopeg | A layer of Unfrozen Ground that is perennially cryotic (forming part of the Permafrost), in which freezing is prevented by freezing-point depression due to the dissolved-solids content of the pore water. Three types of Cryopeg can be distinguished on the basis of their position with respect to Permafrost: a basal Cryopeg forms the basal portion of the Permafrost; an isolated Cryopeg is entirely surrounded by perennially Frozen Ground; and a marine Cryopeg is found in coastal or subsea perennially Frozen Ground; marine Cryopegs may also be basal and/or isolated. | Trombotto et al. 2014 |
| Cryoplanation | The process through which cryoplanation terraces form | Van Everdingen International Permafrost Association 2005 |
| Cryoplanation | A type of erosion peculiar to high latitudes and/or high elevations. Specifically, it is land reduction by the processes of intensive frost action, that is, congeliturbation, including soil creep, and supplemented by the erosive actions of running water, moving ice, and other agents. | AMS - glossary of meteorology |
| Cryoplanation terrace | A step-like or table-like bench cut in bedrock in cold climate regions. | NSIDC accessed 2016 |
| Cryoplanation terrace | A step-like or table-like bench cut in bedrock in cold climate regions | Van Everdingen International Permafrost Association 2005 |
| Cryoplanation terraces | Closely related to pediment like surfaces are large terraces carved in bedrock. They usually occupy higher elevations in the landscape. Other terms used to describe these features are goletz terraces, altiplanation terraces, Nivation terraces and equiplanation terraces. These slope profiles occur mainly in the unglaciated regions of northern North America, Russia, but have also been recognized in South America. Cryoplanation Terraces vary in form; they may be sickle-like or elongated and relatively narrow in shape. Their dimensions also vary; the smallest may be less than 50 m in maximum dimensions while others exceed 400-600 m in length. | Trombotto et al. 2014 |
| Cryoplankton | One-celled plants, usually algae, that live in snow and ice and tint their habitat red or green. | AMS - glossary of meteorology |
| Cryoseisms | A cryoseism (pronounced krī′ ō sī′ zəm), also known as an ice quake or a frost quake, is a non-tectonic seismic event caused by the sudden freezing and expansion of water-saturated soil or rock, causing a crack and resulting in a loud sound. This happens in response to a sudden drop in temperature. The stress created by the freezing water builds up and then is explosively released. Cryoseisms are often mistaken for weak earthquakes. | GCW |
| Cryosol | Soil formed in either mineral or organic materials having permafrost either within 1 meter (3.3 feet) below the surface or, if the soil is strongly cryoturbated, within 2 meters (6.6 feet) below the surface, and having a mean annual ground temperature below 0 degrees Celsius. | NSIDC accessed 2016 |
| Cryosol | Soil formed in either mineral or organic materials having permafrost either within 1 m below the surface or, if the soil is strongly cryoturbated, within 2 m below the surface, and having a mean annual ground temperature below 0°C | Van Everdingen International Permafrost Association 2005 |
| Cryosol soil | Soil order (type) of the Canadian System of Soil Classification. This soil is common to high latitude tundra environments. The main identifying feature of this soil is a layer of permafrost within one meter of the soil surface. | PhysicalGeography.net |
| Cryosphere | One of the earth's spheres of irregular form existing in the zone of interaction of the atmosphere, hydrosphere and lithosphere, distinguished by negative or zero temperature and the presence of water in the solid or super-cooled state; the term refers collectively to the portions of the earth where water is in solid form, including snow cover, floating ice, glaciers, ice caps, ice sheets, seasonally frozen ground and perennially frozen ground (permafrost). | NSIDC accessed 2016 |
| Cryosphere | All regions on and beneath the surface of the Earth and ocean where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers and ice sheets, and frozen ground (which includes permafrost). | IPCC WGII AR5 2014 |
| Cryosphere | The component of the climate system consisting of all snow, ice and frozen ground (including permafrost) on and beneath the surface of the Earth and ocean. | EU Climate-ADAPT |
| Cryosphere | Total ice, snow and permafrost masses of the world. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Cryosphere | That part of the earth's crust, hydrosphere and atmosphere subject to temperatures below 0<FONT FACE=WP MathA">E</FONT>C for at least part of each year" | Van Everdingen International Permafrost Association 2005 |
| Cryosphere | That part of the earth's crust, hydrosphere and atmosphere subject to temperatures below 0C for at least part of each year. The Cryosphere may be divided into the cryoatmosphere, the cryohydrosphere (Snow Cover, Glaciers, and river, lake and sea Ice) and the cryolithosphere (perennially and seasonally Cryotic Ground, Rock Glacier). Some authorities exclude the earth's atmosphere from the Cryosphere; others restrict the term Cryosphere to the regions of the earth's crust where Permafrost exists. | Trombotto et al. 2014 |
| Cryosphere | That portion of the earth where natural materials (water, soil, etc.) occur in frozen form. Generally limited to the polar latitudes and higher elevations. | AMS - glossary of meteorology |
| Cryosphere | The term “cryosphere” traces its origins to the Greek word kryos, meaning frost or icy cold. It collectively describes the components of the Earth’s surface that contain ice, including snow, glaciers, ice sheets, ice shelves, icebergs, sea ice, lake ice, river ice, permafrost and seasonally frozen ground. Permafrost, however, can be “dry” and therefore the cryosphere also includes any natural material in frozen form. | Allison et al. 2019. The International Association of Cryospheric Sciences: past, present and future. Hist. Geo Space Sci., 10, 1–11; https://doi.org/ |
| Cryosphere | A component of the Earth system that includes solid precipitation, snow cover, sea ice, lake and river ice, glaciers, ice caps, ice sheets, permafrost and seasonally frozen ground.
Note: While elements of the cryosphere are often defined as containing frozen water, permafrost can be “dry”. The GCW definition includes elements of the cryosphere that occur on or beneath the Earth’s surface, or that are measured at the surface in the case of solid precipitation. It, therefore, excludes ice clouds. | GCW |
| Cryostatic pressure | Pressure exerted on a substance by ice at rest. | PhysicalGeography.net |
| Cryostructure | The structural characteristics of frozen earth materials. | NSIDC accessed 2016 |
| Cryostructure | The structural characteristics of frozen earth materials | Van Everdingen International Permafrost Association 2005 |
| Cryostructure | Is the structural characteristics of frozen earth material. The Cryostructure is determined by the amount and distribution of Pore Ice (or Ice cement) and lenses of Segregated Ice. The type and arrangement of Ice in the frozen material will depend largely on the initial total water content of the material and the extent of moisture migration during subsequent freezing. For engineering purposes, the structure of frozen soil may be described as massive, layered or reticulate, based on the type and distribution of Ice in the soil. A massive structure (not to be confused with massive ground-ice forms) is characterized by the predominant presence of Pore Ice and by relatively low total Ice Content. In soils with a reticulate structure, Ice Veins generally form a random net, whereas in those with a layered structure, well-oriented horizontal Ice Lenses alternate with soil layers having a massive structure. In both cases their total Ice Content is relatively high. | Trombotto et al. 2014 |
| Cryosuction | A suction developed in freezing or partially frozen fine-grained materials as a result of temperature-dependent differences in unfrozen water content. | NSIDC accessed 2016 |
| Cryosuction | A suction developed in freezing or partially frozen fine-grained materials as a result of temperature-dependent differences in unfrozen water content | Van Everdingen International Permafrost Association 2005 |
| Cryosuction | A suction developed in freezing or partially frozen fine-grained materials as a result of temperature-dependent differences in unfrozen water content. Cryosuction occurs where gradients of the temperature-dependent unfrozen water content in a freezing or partially frozen fine-grained earth material cause hydraulic gradients large enough to induce migration of pore water from unfrozen soil into the partially frozen soil via unfrozen water films. | Trombotto et al. 2014 |
| Cryotexture | The textural characteristics of frozen, fine-grained organic and mineral earth materials cemented together with ice. | NSIDC accessed 2016 |
| Cryotexture | The textural characteristics of frozen, fine-grained organic and mineral earth materials cemented together with ice | Van Everdingen International Permafrost Association 2005 |
| Cryotic | Something that is frozen. | PhysicalGeography.net |
| Cryotic ground | Soil or rock at temperatures of 0 degrees Celsius or lower. | NSIDC accessed 2016 |
| Cryotic ground | Soil or rock at temperatures of 0°C or lower | Van Everdingen International Permafrost Association 2005 |
| Cryotic ground | Soil or rock at temperatures of 0C or lower. The terms 'cryotic' and 'non-cryotic' were introduced to solve a major semantic problem identified by Brown and Kupsch (1974), namely the lack of specific separate terms to designate 'above 0C' and 'below 0C' as opposed to 'unfrozen' (not containing Ice) and 'frozen' (containing Ice). Cryotic and noncryotic refer solely to the temperature of the material described, independent of its water or Ice Content. Perennially Cryotic Ground refers to ground that remains at or below 0C continuously for two or more years and is therefore synonymous with Permafrost. | Trombotto et al. 2014 |
| Cryoturbate | A body of earth material moved or disturbed by frost action. | NSIDC accessed 2016 |
| Cryoturbate | A body of earth material moved or disturbed by frost action | Van Everdingen International Permafrost Association 2005 |
| Cryoturbation | (1) (singular) a collective term used to describe all soil movements due to frost action (2) (plural) irregular structures formed in earth materials by deep frost penetration and frost action processes, and characterized by folded, broken and dislocated beds and lenses of unconsolidated deposits, included organic horizons and even bedrock. | NSIDC accessed 2016 |
| Cryoturbation | 1. (Singular) A collective term used to describe all soil movements due to frost action; 2. (Plural) Irregular structures formed in earth materials by deep frost penetration and frost action processes, and characterized by folded, broken and dislocated beds and lenses of unconsolidated deposits, included organic horizons and even bedrock | Van Everdingen International Permafrost Association 2005 |
| Cryoturbation | (Singular) A collective term used to describe all soil movements due to Frost Action irrespective of the existence of Permafrost. (Plural) Irregular structures formed in earth materials by deep Frost Penetration and Frost Action processes, and characterized by folded, broken and dislocated beds and lenses of unconsolidated deposits, included organic horizons and even bedrock. Note: Cryoturbation encompasses Frost Heave, thaw settlement and all differential movements, including expansion and contraction due to temperature changes and the growth and disappearance of Ground Ice bodies, whether perennial or seasonal. Low temperatures alone are not enough to produce Cryoturbation; the water-ice phase change is necessary. Cryoturbation is an important process in the development of Patterned Ground. | Trombotto et al. 2014 |
| Crystal | A solid body whose atoms or molecules have a regularly repeated arrangement called crystal lattice. The latter may be outwardly expressed by plane faces (see crystal facet). Single crystals grow from a single nucleus (see also grain). Skeleton type or hopper crystals grow faster along their edges than in the centres of their faces, so that the faces appear to be recessed. This type of skeletal recrystallization usually determines the morphology of depth hoar crystals. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Crystal | A more or less regular periodic array of atoms, molecules, or ions, usually forming a solid. In everyday parlance crystal is used in a bewildering variety of ways, sometimes contradictory. Fine glassware is called crystal, although glass, an amorphous solid, is the antithesis of a crystal. A solid with facets exhibiting external symmetry may be called a crystal, although a solid without such facets may still be a crystal. A pure liquid such as water is said to be crystal clear even though transparency is not an essential property of a crystal. | AMS - glossary of meteorology |
| Crystal card | Usually dark metallic or plastic screen that simplifies snow crystal analysis by providing a grid to determine grain shape and size. Also known as crystal screen. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Crystal facet | A crystal face, i.e., a small, plane or flat surface of a crystal. Facets appear on many growing crystals because some surfaces grow much more slowly than others. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Crystal habit | Any characteristic external crystalline form. For an ice crystal, may refer just to the ratio of the lengths of the crystal parallel to its c and a axes (at 90 to or parallel to the hexagonal basal plane), but usually it simply means the crystal shape, including dendritic, skeletal, prismatic, sectors, etc. The term is not applied to the internal crystal lattice. Slight variations in the growth rates of different crystal planes in a given crystal structure lead to quite different crystal habits. Such growth rate variations may result from variations in temperature and water vapor supersaturation of the environment in which the crystal grows. | AMS - glossary of meteorology |
| Crystalline frost | Hoarfrost that exhibits a relatively simple macroscopic crystalline structure; to be distinguished from amorphous frost. Crystalline frosts are classified into five forms: 1) needle; 2) featherlike; 3) plate; 4) cup; and 5) dendritic. Such ice forms are typically developed as a result of deposition at temperatures well below 0C, the degree of supersaturation and temperature controlling the form. | AMS - glossary of meteorology |
| Crystallization | The process of formation of a crystal (an ordered state) from a disordered (gas) or partially ordered (liquid) state. Examples are the freezing of liquid water, the deposition of water vapor (frost), and crystal formation in supersaturated solutions. | AMS - glossary of meteorology |
| Crystallization nucleus | Same as ice nucleus, but applied mainly to the formation of ice crystals in a body of water. | AMS - glossary of meteorology |
| Cumulative mass balance | The mass of the glacier, or part of the glacier, at a stated time relative to its mass at some earlier time t0, considered as a function of time, M (t) M (t0). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Cup crystal | An ice crystal in the form of a hollow hexagonal cup. Usually one side is not developed and appears to be rolled up. Cup crystals are the most common form of depth hoar, but are rarely observed in snow. | AMS - glossary of meteorology |
| Curvature | Mean curvature κ and Gaussian curvature G are defined locally by the mean and product of the principal curvatures, respectively. Both values are useful in describing the microstructure of snow. The mean curvature plays a significant role in interfacial thermodynamics, while Gaussian curvature can be used to characterize the mechanical properties. Both quantities are measured locally and averaged over a volume. Local curvature measurements are easy to interpret for certain shapes such as crystal facets (zero curvature) and sharp corners (very high positive curvature). Obtaining precise curvature values currently requires threedimensional images of snow microstructure. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Cwm | A British term for cirque, derived from the Welsh and occasionally used more widely. | Swisseduc - Photo glossary of glaciological terms |
| Dansgaard-Oeschger events | Abrupt events characterized in Greenland ice cores and in palaeoclimate records from the nearby North Atlantic by a cold glacial state, followed by a rapid transition to a warmer phase, and a slow cooling back to glacial conditions. Counterparts of Dansgaard-Oeschger events are observed in other regions as well. | IPCC WGI AR5 2013 |
| Dansgaard-Oeschger events | Warm-cold oscillations during the last glacial period recorded in the oxygen isotope record of the Greenland ice, and also found in biotic and isotopic indices from deep-sea sediments in the North Atlantic. The warm phases of these events correspond to interstadials, persist for a few hundred to a few thousand years, and have very rapid onset and termination (as little as a few decades). The range of temperature change inferred for the regions where the snow was formed that ultimately produced the Greenland ice was several degrees Celsius. Named for the ice core paleoclimatologists Willi Dansgaard and Hans Oeschger, Dansgaard-Oeschger events between 80 000 and 20 000 years ago are grouped in 10 000- to 15 000-year periods of increasing cooling. The ending of each of these groups of events is marked by a major flux of icebergs into the North Atlantic, as evidenced by associated material found in ocean floor sediments. The temperature conditions in Greenland and the North Atlantic region then return to the higher level of the beginning of the group of Dansgaard-Oeschger events. Most of the Dansgaard-Oeschger events that lasted 2000 years or more coincide with warmer conditions in East Antarctica, also revealed by analysis of oxygen isotopes in ice. | AMS - glossary of meteorology |
| Dark nilas | Nilas that is under 2 in (5 cm) in thickness and is very dark in color. | WMO Sea Ice Nomenclature 2017 |
| Dark nilas | Nilas which is under 5 cm in thickness and is very dark in color. | Bushuyev 2004 |
| Dark nilas | Sea ice terminology which describes a nilas of up to 5 cm in thickness, which is very dark in colour. | Environment and Climate Change Canada 2014 |
| Day of snow lying | Day during which at least half of the ground at the station is covered by snow. | WMO METEOTERM accessed 2016 |
| Day of snow lying | Day during which at least half of the ground at a hydrological station is covered by snow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Days with snow cover | The number of days per month with snow cover on the ground. Typically expressed as the percentage of days per month that snow cover of various depths is on the ground for a location in categories from trace to whole inches. | AMS - glossary of meteorology |
| De-icing | The removal of ice accumulation on aircraft, ships and other objects by mechanical, thermal or chemical devices. | NSIDC accessed 2016 |
| De-icing | The removal of ice deposited on any object, especially applied to aircraft icing. Principal methods of de-icing in use today are heating, chemical treatment, and mechanical rupture of the ice deposit. | AMS - glossary of meteorology |
| De-icing | The removal of ice accumulation on aircraft, ships and other objects by mechanical, thermal or chemical devices (cf. Anti-icing). | Illustrated Glossary of Snow and Ice |
| Dead glacier | A glacier that has ceased moving due to excessive ablation or diminished accumulation; usually covered by moraine. | AMS - glossary of meteorology |
| Dead ice | Any part of a glacier which has ceased to flow; dead ice is usually covered with moraine. | NSIDC accessed 2016 |
| Dead ice | Any part of a glacier that does not flow at a detectable rate. Stagnant ice is a synonym. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Dead ice | Any part of a Glacier which has ceased to flow or Creep. Dead Ice is usually covered with morainal deposits and the underlying Ice may not be visible or easily recognizable. | Trombotto et al. 2014 |
| Dead ice | Glacier ice which is stagnant, i.e. no longer moving. Typically dead ice is found buried under debris in terminal or lateral moraines after the glacier receded from them. Also the ice of flat glacier tongues may become dead during a phase of glacier recession. | Swisseduc - Photo glossary of glaciological terms |
| Dead ice | Any part of a glacier which has ceased to flow. Dead ice is usually covered with moraine. | Illustrated Glossary of Snow and Ice |
| Debris cone | A cone or mound of debris-covered ice, with a thick enough sediment cover to protect the ice from melting. | Molnia USGS 2004 |
| Debris coverage of tongue | Uncertain: unknown or not identifiable; Debris free: Almost no debris coverage on the glacier surface; Partly debris covered: More than 10% and less than 50% of the glacier surface in the ablation area is debris covered. Patchy distribution; Mostly debris covered: More than 50% and less than 90% of the glacier surface in the ablation area is debris covered. Continuously distributed debris cover; Completely debris covered: Almost the entire ablation area is covered by debris. Debris covered ice; | Illustrated GLIMS Glacier Classification Manual |
| Debris flow | A sudden and destructive variety of landslide, in which loose material on a slope, with more than 50 percent of particles larger than sand size, is mobilized by saturation and flows down a channel or canyon | Van Everdingen International Permafrost Association 2005 |
| Debris flow | A type of mass movement where there is a downslope flow of a saturated mass of soil, sediment, and rock debris. | PhysicalGeography.net |
| Debris-covered glacier | A glacier that supports a layer of rock, dust or ash detritus on most or all of the surface of its ablation zone. In the accumulation zone any deposited debris is buried by later snowfalls, but in the ablation zone debris remains at the surface and englacial debris is added to the surface layer from beneath as ice ablates away. The debris cover affects the rate of ablation, with very thin debris resulting in accelerated melt and debris thicker than a few tens of millimetres reducing the melting rate. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Defile | Narrow mountain pass | UK Antarctic Place-names Committee accessed 2016 |
| Deformability | The ability of a material to change its shape or size under the influence of an external or internal agency, such as stress, temperature, or pore pressure | Van Everdingen International Permafrost Association 2005 |
| Deformed ice | A general term for ice which has been squeezed together and forced upwards and downwards in places. Subdivisions are rated ice, ridge ice, hummocked ice, and other similar deformations. | NOAA Glossary of Hydrologic Terms |
| Deformed ice | A general term for ice that has been squeezed together and, in places, forced upwards (and downwards). Subdivisions are rafted ice, ridged ice, and hummocked ice. | WMO Sea Ice Nomenclature 2017 |
| Deformed ice | A general term for ice which has been squeezed together and broken up with formation of surface and underwater conglomerations. Subdivisions are rafted ice, rough ice, ridged ice, jammed brash barrier and hillocky multiyear ice. | Bushuyev 2004 |
| Deformed ice | Sea ice terminology. It is a general term for ice which has been squeezed together, and in places, forced upwards and downwards. The subdivisions of deformed ice are known as rafted ice, ridged ice, and hummocked ice. | Environment and Climate Change Canada 2014 |
| Deformed ice | A general term for sea ice that has been broken and reoriented. It includes ridged, hummocked, and rafted ice. Deformed ice is distinguished by its high surface roughness. | AMS - glossary of meteorology |
| Deglaciation | The removal of land ice from an area; the opposite of glacierization. | AMS - glossary of meteorology |
| Deglaciation/glacial termination | Transitions from full glacial conditions (ice age) to warm interglacials characterized by global warming and sea level rise due to change in continental ice volume. | IPCC WGI AR5 2013 |
| Degree of saturation | 1. The total degree of saturation of frozen soil is the ratio of the volume of ice and unfrozen water in the soil pores to the volume of the pores; 2. The degree of saturation of frozen soil by ice is the ratio of the volume of ice in the soil pores to the volume of the pores. | Van Everdingen International Permafrost Association 2005 |
| Degree-Day | A unit of measurement to express the departure of the mean temperature for a day from a given References (or base) temperature. The Freezing Index and the Thawing Index are expressed in degree-days with respect to a References temperature of 0C (32F); units: degree-day Celsius or degree-day Fahrenheit. | Trombotto et al. 2014 |
| Degree-day (C or F) | A derived unit of measurement used to express the departure of the mean temperature for a day from a given reference (or base) temperature | Van Everdingen International Permafrost Association 2005 |
| Degrees of frost | In England, the number of Fahrenheit degrees that the temperature falls below the freezing point. Thus a day with a minimum temperature of 27F may be designated as a day of five degrees of frost. | AMS - glossary of meteorology |
| Delayed strength | The failure strength of a material at a given strain rate or after a given period under deviatoric stress | Van Everdingen International Permafrost Association 2005 |
| Dendrite | Hexagonal ice crystals with complex and often fernlike branches. | NSIDC accessed 2016 |
| Dendritic crystal | (Or dendrite.) A crystal, particularly a planar ice crystal, with its macroscopic form (crystal habit) characterized by intricate branching structures of a treelike nature. Dendritic ice crystals possess hexagonal symmetry, and tend to develop when a crystal grows by vapor deposition at temperatures within a few degrees of -15C, providing saturation is close to supercooled water. Similar forms occur by ice growth into supercooled liquid water at temperatures down to -10C. Spatial dendrites grow in three dimensions from a central frozen drop. | AMS - glossary of meteorology |
| Dendritic snow crystals | Ice crystals whose macroscopic form is characterized by intricate branching structures which are treelike in form and which possess hexagonal symmetry in ideal form. | WMO METEOTERM accessed 2016 |
| Dendrochronology | The study of tree rings and subfossil wood to provide information about the glacial and climatic history of an area. | Molnia USGS 2004 |
| Densification | The conversion of snow to firn and then to glacier ice. Newly fallen snow has a variable density depending on the meteorological conditions of its formation and deposition. The density of dry snow increases rapidly at first, by the conversion of snowflakes to grains. Then, usually under the pressure of an increasing overburden of newer snow, density increases more slowly by settling of the grains to about 550 kg m-3, representing the maximum practically attainable packing. Snow becomes firn (in the structural sense) over a range of density beginning at about 400 kg m-3.Beyond the maximum packing density, even slower mechanisms of densification sintering and plastic deformation of the grains, and recrystallization become dominant. When the firn reaches a density of about 830 kg m-3, the pore spaces between crystals are closed off, air can no longer flow (as opposed to diffusing through the crystal lattices), and the substance is deemed to be glacier ice. When there has been no melting, densification rarely proceeds beyond 400 kg m-3 over the course of a typical mid-latitude winter. Depending on the accumulation (that is, loading) rate, glacier ice may be produced in times from a few years to a few centuries. Melting followed by refreezing can yield bulk densities near that of pure ice in times shorter than a day. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Density | The ratio of the mass of any substance to the volume that it occupies. Density is expressed in kg m3. The density of the matter constituting the glacier can range from as low as 10 kg m3, at the surface in unusual weather, to the density of pure ice at depths at which all air has been squeezed out of bubbles. It is very common to assume that the bulk density of the glacier is 900 kg m3. This reduced density is a rough-and-ready allowance for the presence of snow and firn, large voids (crevasses, moulins and subglacial cavities) and sediment. Where a large proportion of the glacier thickness consists of snow and firn, a bulk density even lower than 900 kg m3 is appropriate. Where there is relatively little snow or firn, and the temperature is very low, a higher density, approaching or even exceeding the conventional 917 kg m3, may be appropriate. In studies of mass balance, however, densities are never known with the accuracy of laboratory measurements of pure ice, which are made by measuring the lattice parameters of single crystals. Typical field instruments are hand-held corers and spring balances, and inaccuracies of the order of 48% are usual. Better accuracy is possible in principle with advanced devices such as neutron-scattering probes, but these are not in routine use. In some circumstances, such as when a load of low-density snow produces compensating densification at depth, the density of the mass gained or lost by the glacier may be assumed equal to the bulk density. See Sorge's law. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Density | Density is the ratio of the mass of an object to its volume. Snow has a density averaging about 0.1, firn has a density greater than 0.55, and glacier ice has a density of about 0.89. The density of unmineralized fresh water is 1. Glaciologists measure snowpack density frequently so that they may anticipate future water supplies, and to assess avalanche hazards. The density of a fresh snowpack is about 0.1; firn has a density of about 0.55 and glacier ice, of about 0.89. Each annual snow layer has a characteristic grain size and density. | Molnia USGS 2004 |
| Density of frozen ground | The mass of a unit volume of frozen soil or rock. | NSIDC accessed 2016 |
| Density of frozen ground | The mass of a unit volume of frozen soil or rock | Van Everdingen International Permafrost Association 2005 |
| Density of frozen ground | The mass of a unit volume of frozen soil or rock. | Trombotto et al. 2014 |
| Density of snow | The ratio, expressed as a percentage, of the volume which a given quantity of snow would occupy if it were reduced to water, to the volume of the snow. When a snow sampler is used, it is the ratio expressed as percentage of the scale reading on the sampler to the length of the snow core or sample. | NOAA Glossary of Hydrologic Terms |
| Density of snow | The ratio of the volume of melted snow to the volume of the original, unmelted snow sample. | AMS - glossary of meteorology |
| Depergelation | The act or process of thawing permafrost. | AMS - glossary of meteorology |
| Deposition | (1) A process by which gases are deposited as a solid without first forming as a liquid (inverse sublimation). Surface hoar (SH) growth at the surface of the snowpack as well as recrystallization of snow within the snowpack (FC, DH) result from deposition of water vapour on ice. (2) The process by which snow is deposited on the ground either with or without wind action. As a result, stationary snow deposits such as snow dunes, snowdrifts, or the snow cover itself may form. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Deposition | The process by which a vapour changes phase directly into a solid; resublimation is a synonym. See latent heat of sublimation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Deposition | (1) The change in state of matter from gas to solid that occurs with cooling. Usually used in meteorology when discussing the formation of ice from water vapor. This process releases latent heat energy to the environment. (2) Laying down of sediment transported by wind, water, or ice. | PhysicalGeography.net |
| Deposition nuclei | Six-sided microscopic particle that allows for deposition of water as ice crystals in the atmosphere. Nucleus for the formation of snowflakes. Deposition normally occurs on these particles when relative humidity becomes 100%. | PhysicalGeography.net |
| Depositional landform | Is a landform formed from the deposition of weathered and eroded surface materials. On occasion, these deposits can be compressed, altered by pressure, heat and chemical processes to become sedimentary rocks. This includes landforms with some of the following geomorphic features: beaches, deltas, floodplains, and glacial moraines. | PhysicalGeography.net |
| Depth hoar | A kind of hoarfrost; ice crystals that develop by sublimation within a layer of dry snow; characterized by rapid recrystallization, usually caused by large temperature gradients; similar in physical origin to crevasse hoar; crystals are faceted, rather than rounded. | NSIDC accessed 2016 |
| Depth hoar | A layer of ice crystals, usually cup-shaped and facetted, formed by vapour transfer (sublimation followed by deposition) within dry snow beneath the snow surface. Depth hoar is associated with very fast crystal growth under large temperature gradients. Sometimes a layer of depth hoar forms just above, and may assist in identifying, the summer surface. The low density and low strength of depth hoar can make it difficult to retrieve unbroken core sections during coring, and can complicate estimates of accumulation by microwave remote sensing. Layers of depth hoar also increase the likelihood of avalanching. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Depth hoar | 1.Ice crystals (usually cup-shaped, faceted crystals) of low strength formed by sublimation within dry snow beneath the snow surface; a type of hoarfrost. Associated with very fast crystal growth under large temperature gradients. This is one way in which firn formation may begin. Depth hoar is similar in physical origin to crevasse hoar. 2.Hoarfrost composed of crystals that have built up a three-dimensional complex of faceted, rather than rounded, crystals. | AMS - glossary of meteorology |
| Depth of seasonal frost penetration | The maximum thickness of the seasonally frozen layer. | NSIDC accessed 2016 |
| Depth of seasonal frost penetration | The maximum thickness of the seasonally frozen layer | Van Everdingen International Permafrost Association 2005 |
| Depth of snow | Vertical distance between the top surface of a snow layer and the ground beneath; the layer is assumed to be evenly spread over the ground which it covers. | WMO METEOTERM accessed 2016 |
| Depth of snow | Vertical interval between the top surface of a snow layer and the ground beneath; the layer is assumed to be evenly spread over the ground which it covers. | NSIDC accessed 2016 |
| Depth of snow | Vertical distance between the top of a snow layer and the horizontal ground beneath. The layer is assumed to be evenly spread on the surface. When the snow is not uniformly distributed, snow depth is measured by taking an average of multiple measurements | AMS - glossary of meteorology |
| Depth of snow | The vertical distance between the surface of a snow layer and the ground or ice beneath; average or representative depth for the area. | Illustrated Glossary of Snow and Ice |
| Depth of snowfall, Height of new snow | Height of new snow HN is the depth in centimetres of freshly fallen snow that accumulated on a snow board during a standard observing period of 24 hours. Additional observation intervals can be used, but should be specified. For example, the notation HN(8h) or HN(2d) denotes an observation interval of 8 hours or 2 days, respectively. Height of new snow is traditionally measured with a ruler. After the measurement, the snow is cleared from the board and the board is placed flush with the snow surface to provide an accurate measurement at the end of the next interval. The corresponding slope-perpendicular measurement is denoted by DN. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Depth of thaw | The minimum distance between the ground surface and frozen ground at any time during the thawing season in an area subject to seasonal freezing and thawing. | NSIDC accessed 2016 |
| Depth of thaw | The minimum distance between the ground surface and frozen ground at any time during the thawing season in an area subject to seasonal freezing and thawing | Van Everdingen International Permafrost Association 2005 |
| Depth of thaw | The minimum distance between the ground surface and Frozen Ground at any time during the thawing season in an area subject to seasonal freezing and thawing. When no Frozen Ground remains, thawing is complete, and Depth of Thaw cannot be determined. Depth of Thaw may relate to the Active Layer in Permafrost environments or to any other areas with seasonal freezing. | Trombotto et al. 2014 |
| Depth of zero annual amplitude | The distance from the ground surface downward to the level beneath which there is practically no annual fluctuation in ground temperature. | NSIDC accessed 2016 |
| Depth of zero annual amplitude | The distance from the ground surface downward to the level beneath which there is practically no annual fluctuation in ground temperature | Van Everdingen International Permafrost Association 2005 |
| Depth of zero annual amplitude | The distance from the ground surface downward to the level beneath which there is no annual fluctuation in ground temperature. A change of no more than 0.1C throughout the year is arbitrarily considered as 'practically no annual fluctuation'. In the Northern hemisphere the temperature at the Depth of Zero Annual Amplitude ranges from about -0.1C at the southern limit of the Permafrost region to about -15C in the extreme polar reaches of the zone of Continuous Permafrost. The Depth of Zero Annual Amplitude varies widely but generally lies between 10 and 20 m below the ground surface, depending on climatic and terrain conditions such as amplitude of annual surface temperature variation, vegetation, Snow Cover and characteristics of the soils and rocks including thermal diffusivity. | Trombotto et al. 2014 |
| Deranged drainage | Drainage pattern that is highly irregular. Areas that have experienced continental glaciation may have this type of drainage pattern. | PhysicalGeography.net |
| Desiccation crack | Crack or fissure developed in fine-grained soil material as a result of shrinkage during drying. | Van Everdingen International Permafrost Association 2005 |
| Desiccation polygon | Closed, multi-sided patterned-ground feature formed by desiccation cracks in fine-grained soil material. Usually less than 2 m in diameter | Van Everdingen International Permafrost Association 2005 |
| Design depth of frost penetration | (North American usage) the mean of the three largest depths of seasonal frost penetration measured during the past thirty years, or the largest depth of seasonal frost penetration beneath a snow-free soil surface measured during the past ten years (2) (Russian usage) the mean of the depths of seasonal frost penetration measured during at least the last ten years with the ground surface free of snow and the groundwater level below the depth of seasonal frost penetration. | NSIDC accessed 2016 |
| Design depth of frost penetration | 1. (North-American usage) The mean of the three largest depths of seasonal frost penetration measured during the past thirty years, or the largest depth of seasonal frost penetration beneath a snow-free soil surface measured during the past ten years; 2. (Russian usage) The mean of the depths of seasonal frost penetration measured during at least the last ten years with the ground surface free of snow and the groundwater level below the depth of seasonal frost penetration | Van Everdingen International Permafrost Association 2005 |
| Design freezing index | The cumulative number of degree-days below 0 degrees Celsius, calculated by taking the average of the seasonal freezing indices for the three coldest winters in the most recent 30 years of record. | NSIDC accessed 2016 |
| Design freezing index | The cumulative number of degree-days below 0°C, calculated by taking the average of the seasonal freezing indices for the three coldest winters in the most recent 30 years of record | Van Everdingen International Permafrost Association 2005 |
| Design thawing index | The cumulative number of degree-days above 0 degrees Celsius, calculated by taking the average of the seasonal thawing indices for the three warmest summers in the most recent 30 years of record. | NSIDC accessed 2016 |
| Design thawing index | The cumulative number of degree-days above 0°C, calculated by taking the average of the seasonal thawing indices for the three warmest summers in the most recent 30 years of record | Van Everdingen International Permafrost Association 2005 |
| Destructive metamorphism | Snow metamorphism that rounds the comers and edges of an ice crystal. | NSIDC accessed 2016 |
| Detachment failure | A slope failure in which the thawed or thawing portion of the active layer detaches from the underlying frozen material. | NSIDC accessed 2016 |
| Detachment failure | A slope failure in which the thawed or thawing portion of the active layer detaches from the underlying frozen material | Van Everdingen International Permafrost Association 2005 |
| Detachment failure | A slope failure in which the thawed or thawing portion of the Active Layer detaches from the underlying frozen material. Detachment Failures are common on colluvial slopes in areas of fine-grained, ice-rich deposits. They occur more frequently during warm summers or following disturbance of the vegetation or ground surface by, for example, tundra or forest fires or engineering activity, when the Depth of Thaw is greater than normal. Detachment Failures that expose Massive Ice or icy sediments can develop into retrogressive thaw slumps. | Trombotto et al. 2014 |
| Dewpoint | The temperature to which a given air parcel must be cooled at constant pressure and constant water vapor content in order for saturation to occur. When this temperature is below 0C, it is sometimes called the frost point. The dewpoint may alternatively be defined as the temperature at which the saturation vapor pressure of the parcel is equal to the actual vapor pressure of the contained water vapor. Isobaric heating or cooling of an air parcel does not alter the value of that parcel's dewpoint, as long as no vapor is added or removed. Therefore, the dewpoint is a conservative property of air with respect to such processes. However, the dewpoint is nonconservative with respect to vertical adiabatic motions of air in the atmosphere. The dewpoint of ascending moist air decreases at a rate only about one-fifth as great as the dry-adiabatic lapse rate. The dewpoint can be measured directly by several kinds of dewpoint hygrometers or it can be deduced indirectly from psychrometers or devices that measure the water vapor density or mixing ratio. See dewpoint formula. (Or dewpoint temperature.) | AMS - glossary of meteorology |
| Dewpoint | Dew point is the temperature at which water vapor saturates from an air mass into liquid or solid usually forming rain, snow, frost or dew. Dew point normally occurs when a mass of air has a relative humidity of 100%. If the dew point is below freezing, it is referred to as the frost point. | PhysicalGeography.net |
| Diachronous | Of a surface or layer, spanning time. The word diachronous is needed most commonly when the surface or layer did not form instantaneously. The summer surface may be diachronous, forming at different times over a span of days or weeks, but it is assumed to be instantaneous. In a record of a ground-penetrating radartraverse, a marker horizon may be valuable in the determination of mass balance if it is an isochrone, but not if it is diachronous. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Diamond dust | A type of precipitation composed of slowly falling, very small, unbranched crystals of ice which often seem to float in the air; it may fall from a high cloud or from a cloudless sky, it usually occurs under frosty weather conditions (under very low air temperatures). | NSIDC accessed 2016 |
| Diamond dust | A fall of non-branched (snow crystals are branched) ice crystals in the form of needles, columns, or plates. | NOAA National Weather Service Glossary 2009 |
| Diamond dust | An optically and physically thin layer of ground-level cloud composed of small ice crystals that settle slowly. Typically diamond dust forms by the mixing of relatively moist air from aloft into a low-level inversion layer in which the temperature is 40 | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Diamond dust | Diamond dust forms under very low air temperatures in strong, surface-based temperature inversion layers. Either vertical mixing within or radiational longwave cooling of this layer causes the air to become supersaturated with respect to ice, so that small ice crystals form. These mostly unbranched crystals are seemingly floating in the air, slowly falling from an often apparently cloudless sky (AMS, 2000). Columns (ppco) and plates (pppl) are the dominant shapes found in diamonddust (Walden et al., 2003), but stellar dendrites (ppsd) may also be observed. Long-prism columns having a ratio of length to width 5 are defined as 'Shimizu crystals'. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Dielectric constant | The dielectric constant of a soil is a measure of the ability of the soil to store electrical energy in the presence of an electrostatic field. | Van Everdingen International Permafrost Association 2005 |
| Dielectric device | Instrument that uses the dielectric properties of snow to determine its liquid water content through capacitance and density measurements; it may also be used to determine dry snow density. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Difficult area | A general expression to indicate that the severity of ice conditions prevailing in an area is such that navigation in it is difficult. | Bushuyev 2004 |
| Difficult area | A general qualitative expression to indicate, in a relative manner, that the severity of ice conditions prevailing in an area is such that navigation in it is difficult. | WMO Sea Ice Nomenclature 2017 |
| Difficult area | Sea ice terminology. A general qualitative expression that indicates that the relative severity of prevailing ice conditions in a particular area are such that navigation will be difficult. | Environment and Climate Change Canada 2014 |
| Diffuse ice | Poorly defined ice edge limiting an area of dispersed ice; usually on the leeward side of an area of floating ice. | NOAA Glossary of Hydrologic Terms |
| Diffuse ice | In hydrologic terms, poorly defined ice edge limiting an area of dispersed ice; usually on the leeward side of an area of floating ice. | NOAA National Weather Service Glossary 2009 |
| Diffuse ice edge | Poorly defined ice edge limiting an area of dispersed ice; usually on the leeward side of an area of pack ice. | WMO Sea Ice Nomenclature 2017 |
| Diffuse ice edge | Sea ice terminology, meaning a poorly defined ice edge which limits an area of dispersed ice, usually on the leeward side of an area of ice. | Environment and Climate Change Canada 2014 |
| Dilation crack | A tensile fracture in a frozen material due to surface extension caused by doming. | NSIDC accessed 2016 |
| Dilation crack | A tensile fracture in a frozen material due to surface extension caused by doming | Van Everdingen International Permafrost Association 2005 |
| Dilation crack ice | Ice that forms in dilation cracks. | NSIDC accessed 2016 |
| Dilation crack ice | Ice that forms in dilation cracks | Van Everdingen International Permafrost Association 2005 |
| Dirt cone | A cone-shaped formation of ice that is covered by dirt; a dirt cone is caused by a differential pattern of ablation between the dirt covered surface and bare ice. | NSIDC accessed 2016 |
| Dirt cone (or ablation cone) | A thin veneer of debris draping a cone of ice up to several metres high, formed because the debris has retarded ablation under it. | Swisseduc - Photo glossary of glaciological terms |
| Dirty ice | Ice that contains sediments stirred up and tangled in the ice as it grows. | NSIDC accessed 2016 |
| Dirty ice | Ice that has a mineral or organic content of natural or anthropogenic origin on the surface or in its strata. | Bushuyev 2004 |
| Disarticulation | Disarticulation is the process through which large blocks of ice, sometimes greater than .5 miles in width, detach from the thinning and retreating terminus of a glacier that ends in a body of water. Disarticulation occurs as the terminus thins to where its buoyandcy no longer permits it to remain in contact with its bed. As the glacier begins to float free and rises off the bottom it rapidly comes apart along old fracture scars and crevasses. For example, at Bering Glacier, in the Chugach Mountains, Alaska, a single observed disarticulation event resulted in nearly 2/3 of a mile of terminus retreat in a single day. As many as 100 discrete, tabular pieces of glacier ice have been observed separating from the glacier's terminus in a single event. Bering Glacier flows through Wrangell-St. Elias National Park, Alaska. | Molnia USGS 2004 |
| Discharge | The rate of flow of ice or water through a vertical section perpendicular to the direction of the flow. Care is needed because discharge can refer to either ice discharge or meltwater discharge, as well as being used in hydrology to refer to water flow from basins in which there are no glaciers. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Discontinuous permafrost | Permafrost occurring in some areas beneath the exposed land surface throughout a geographic region where other areas are free of permafrost. | NSIDC accessed 2016 |
| Discontinuous permafrost | Permafrost occurring in some areas beneath the exposed land surface throughout a geographic region where other areas are free of permafrost | Van Everdingen International Permafrost Association 2005 |
| Discontinuous permafrost | Permafrost occurring in some areas beneath the exposed land surface throughout a geographic region where other areas are free of Permafrost. Discontinuous Permafrost occurs between the Continuous Permafrost zone and the southern latitudinal limit of Permafrost in lowlands. Depending on the scale of mapping, several subzones can often be distinguished, based on the percentage of the land surface underlain by Permafrost (extensive 65-90%, intermediate 35-65%). See also sporadic Permafrost and isolate patches of Permafrost. Discontinuous Permafrost is difficult to identify in the Andes, where the term Mountain Permafrost is usually used since permafrost within mountains frequently present variations as a function of altitude, slope orientation, topography, microclimatic conditions and radiation. | Trombotto et al. 2014 |
| Discontinuous permafrost | Form of permafrost that contains numerous scattered pockets of unfrozen ground. | PhysicalGeography.net |
| Discontinuous permafrost zone | The major subdivision of a permafrost region in which permafrost occurs in some areas beneath the exposed land surface, whereas other areas are free of permafrost. | NSIDC accessed 2016 |
| Discontinuous permafrost zone | The major subdivision of a permafrost region in which permafrost occurs in some areas beneath the exposed land surface, whereas other areas are free of permafrost | Van Everdingen International Permafrost Association 2005 |
| Disequilibrium permafrost | Permafrost that is not in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and the geothermal heat flux. | NSIDC accessed 2016 |
| Disequilibrium permafrost | Permafrost that is not in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and the geothermal heat flux | Van Everdingen International Permafrost Association 2005 |
| Disequilibrium permafrost or degrading permafrost | Permafrost that is not in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and the Geothermal Heat Flux. Typically a disequilibrium is stated when a warming (or cooling) trend emerges. | Trombotto et al. 2014 |
| Distributary | A tongue of glacier ice that flows away from the main trunk of the glacier. This may result from differential melting changing the gradient of part of a glacier. | Molnia USGS 2004 |
| Diverging | Ice fields or floes in an area are subjected to diverging or dispersive motion, thus reducing ice concentration and/or relieving stresses in the ice. | WMO Sea Ice Nomenclature 2017 |
| Diverging | Sea ice terminology that describes ice fields or floes in an area, that move in opposite directions, reducing ice concentration and/or relieving stresses in the ice. | Environment and Climate Change Canada 2014 |
| Diverging | The process of increasing separation between ice fields or floes, thus reducing ice concentration and/or relieving stresses in the ice. | Bushuyev 2004 |
| Divide | A line separating two contiguous glaciers, the horizontal flow of ice diverging on each side of the line. See glacier margin, glacier outline. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Dome | Dome-shaped ice cap or snowfield or dome-shaped snow summit. | UK Antarctic Place-names Committee accessed 2016 |
| Domed iceberg | Sea ice terminology, meaning an iceberg which is smooth and rounded on top. | Environment and Climate Change Canada 2014 |
| Downvalley wind | A nocturnal, thermally forced along-valley wind produced as a result of nocturnal cooling of the valley air; a nocturnal component of the fair- weather mountain-valley wind systems encountered during periods of light synoptic or other larger-scale flow. Valley cooling is accomplished by the combined effects of draining cold air off the slopes by early-evening downslope (katabatic) winds, and upward motion with upward cold-air advection from the convergence of katabatic flows in the valley center. Air in the valley thus becomes cooler than air at the same level over the adjacent plain ( see topographic amplification factor), producing higher pressure in the valley. The pressure gradient drives a downvalley wind that begins one to four hours after sunset, persists for the rest of the night until after sunrise, and often reaches 7-10 m s-1 or more above the surface. The downvalley wind tends to fill the valley, that is, its depth is approximately the depth of the valley, and where mountains end and a valley empties onto the plains, the downvalley wind can become a cold-air valley outflow jet flowing out of the mouth of the valley. (Same as mountain breeze.) | AMS - glossary of meteorology |
| Downwasting | Thinning of the glacier due to ablation. See dynamic thinning. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Downwasting | The thinning of a glacier due to the melting of ice. This loss of thickness may occur in both moving and stagnant ice. Also called Thinning. | Molnia USGS 2004 |
| Drain channel | Preferred path for meltwater to flow from the surface through a snow cover. | NSIDC accessed 2016 |
| Drainage wind | A wind common to mountainous regions that involves heavy cold air flowing along the ground from high to low elevations because of gravity. Also see katabatic wind. | PhysicalGeography.net |
| Dried ice | Sea ice from the surface of which meltwater has disappeared after the formation of cracks and thaw holes. During the period of drying, the surface whitens. | WMO Sea Ice Nomenclature 2017 |
| Dried ice | Sea ice that was earlier at the flooded ice stage, from the surface of which melt-water has disappeared after the formation of cracks and thaw holes. During the period of drying, the surface whitens. | Bushuyev 2004 |
| Dried ice | Sea ice terminology that describes an ice surface from which water has disappeared after the formation of cracks and thaw holes; during the period of drying the surface whitens. | Environment and Climate Change Canada 2014 |
| Dried ice | Sea ice from the surface of which meltwater has disappeared after the formation of cracks and thaw holes. During the period of drying, the surface whitens. | AMS - glossary of meteorology |
| Drift | A collective term used to describe all types of glacier sedimentary deposits, regardless of the size or amount of sorting. The term includes all sediment that is transported by a glacier, whether it is deposited directly by a glacier or indirectly by running water that originates from a glacier. | Molnia USGS 2004 |
| Drift | A 19th century term, still in use, to describe all unconsolidated deposits associated with glaciers, glacial meltwater and icebergs. | Swisseduc - Photo glossary of glaciological terms |
| Drift | Any material deposited by a glacier. | PhysicalGeography.net |
| Drift divide | A boundary between ice massifs or zones drifting in different directions or with a different speed. Drift divide indications include increased fracturing of the ice cover, flaws, ridging belts, leads and diverging zones. One frequently observes ice floe rotation at the drift divide. | Bushuyev 2004 |
| Drift glacier | A semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a snowdrift glacier. | NSIDC accessed 2016 |
| Drift ice | Ice that moves from winds, currents, or other forces. | NSIDC accessed 2016 |
| Drift ice | Any sea ice that has drifted from its place of origin. The term is used in a wide sense to include any areas of sea ice, other than fast ice, no matter what form it takes or how disposed. | AMS - glossary of meteorology |
| Drift ice/Pack ice | Sea ice terminology. This term is used in a wide sense to include any area of ice, other than fast ice, no matter what form it takes or how it gets there. When concentrations are high (7/10 or more) the term pack ice is normally used. When concentrations are 6/10 or less the term drift ice is normally used. | Environment and Climate Change Canada 2014 |
| Drift of ice | Displacement of a sea ice field from its place of origin under the effect of ocean currents and winds. | NSIDC accessed 2016 |
| Drift vector | A segment on a graphical or digital ice chart connecting the location of an ice cover point at successive moments of time. For subsequent analysis and calculations, the observed drift vector field is usually interpolated to regular grid points with a step size chosen as required. The vectors at the regular grid points can also be obtained by means of model calculations. | Bushuyev 2004 |
| Drifting ice | Pieces of floating ice moving under the action of wind and/ or currents. | NOAA Glossary of Hydrologic Terms |
| Drifting ice | In hydrologic terms, pieces of floating ice moving under the action of wind and/ or currents. | NOAA National Weather Service Glossary 2009 |
| Drifting snow | An ensemble of snow particles raised by the wind to a small height above the ground. The visibility is not sensibly diminished at eye level. | WMO METEOTERM accessed 2016 |
| Drifting snow | Snow raised from the surface of the earth by the wind to a height of less than 1.5 to 2.0 meters (5 to 6.6 feet) above the surface; it dose not restrict horizontal visibility at 2 meters (6.6 feet) or more above the surface. | NSIDC accessed 2016 |
| Drifting snow | Drifting snow is an uneven distribution of snowfall/snow depth caused by strong surface winds. Drifting snow may occur during or after a snowfall. Drifting snow is usually associated with blowing snow. | NOAA National Weather Service Glossary 2009 |
| Drifting snow | Snow entrained and transported within 2 m of the surface by the wind. The height of 2 m is a convenient separator between drifting snow, which does not reduce sensibly the horizontal visibility at eye level, and blowing snow. See windborne snow. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Drifting snow | Snow that is raised from the earth's surface by the wind to a height of less than 2 metres. | Environment and Climate Change Canada 2014 |
| Drifting snow | Snow raised from the surface of the earth by the wind to a height of less than 6 ft above the surface. In aviation weather observations, drifting snow is not regarded as an obstruction to vision because it does not restrict horizontal visibility at 6 ft or more above the surface. When snow is raised 6 ft or more above the surface, it is classified as blowing snow. | AMS - glossary of meteorology |
| Drifting snow | An ensemble of snow particles raised by the wind to small heights above the ground. The visibility is not sensibly diminished at eye level (cf. Blowing snow). | Illustrated Glossary of Snow and Ice |
| Driven snow | Snow that has been moved by wind and collected into snowdrifts. A wind speed of about 13 mph will move light surface snow. In weather reports, snow lifted less than 6 ft above the surface is drifting snow, more than 6 ft is blowing snow. | AMS - glossary of meteorology |
| Drizzle | Precipitation from stratus clouds, consisting of minute, fine water droplets which appear to float. | Environment and Climate Change Canada 2014 |
| Droxtal | A tiny ice particle, about 10-20 microns in diameter, formed by direct freezing of supercooled water droplets with little growth directly from the vapor. The term combines the words drop and crystal. Droxtals cause most of the visibility reduction in ice fog. | AMS - glossary of meteorology |
| Drumlin | Remnant elongated hills formed by historical glacial action; it is not clear exactly how they are formed and why they form only in some glaciated regions. | NSIDC accessed 2016 |
| Drumlin | An elongated ridge of glacial sediment sculpted by ice moving over the bed of a glacier. Generally, the down-glacier end is oval or rounded and the up-glacier end tapers. The shape is often compared to an inverted, blunt-ended canoe. Although not common in Alaska, drumlins cover parts of the Eastern and Midwestern United States (Irish). | Molnia USGS 2004 |
| Drumlin | A hill shaped deposit of till. The shape of these features resembles an elongated teaspoon laying bowl down. The tapered end of the drumlin points to the direction of glacier advance. Drumlins come in assorted sizes. Lengths can range from 100 to 5,000 meters and heights can be as great as 200 meters. | PhysicalGeography.net |
| Drumlin (from the Gaelic) | A streamlined hillock, commonly elongated parallel to the former ice flow direction, composed of glacial debris, and sometimes having a bedrock core; formed beneath an actively flowing glacier. | Swisseduc - Photo glossary of glaciological terms |
| Drunken forest | Trees leaning in random directions caused by melting permafrost. | NSIDC accessed 2016 |
| Drunken forest | Trees leaning in random directions | Van Everdingen International Permafrost Association 2005 |
| Dry calving | Ice discharge from a glacier margin onto land, usually in discrete pieces. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Dry crack | Crack visible at the surface but not going right through the ice cover, and therefore it is dry. | NOAA Glossary of Hydrologic Terms |
| Dry crack | In hydrologic terms, a crack visible at the surface but not going right through the ice cover, and therefore it is dry. | NOAA National Weather Service Glossary 2009 |
| Dry density | The mass of a unit volume of dried material (e.g. Soil). | NSIDC accessed 2016 |
| Dry density | The mass of a unit volume of dried material (e.g. soil) | Van Everdingen International Permafrost Association 2005 |
| Dry freeze | The freezing of the soil and terrestrial objects caused by a reduction of temperature when the adjacent air does not contain sufficient moisture for the formation of hoarfrost on exposed surfaces. With respect to vegetation alone, this is termed a black frost. A dry freeze is usually considered to be a more local and short-period (probably radiative) phenomenon than a freeze. | AMS - glossary of meteorology |
| Dry frozen ground | Frozen ground with a very low total water content consisting almost completely of interfacial water, and not cemented by ice. | NSIDC accessed 2016 |
| Dry frozen ground | Frozen ground with a very low total water content consisting almost completely of interfacial water, and not cemented by ice | Van Everdingen International Permafrost Association 2005 |
| Dry ice | Solidified carbon dioxide that, at -78.5C and ambient pressure, changes directly to a gas as it absorbs heat. It is used as a coolant to induce the ice phase for supercooled cloud and fog modification procedures. | AMS - glossary of meteorology |
| Dry permafrost | Permafrost containing neither free water nor ice. | NSIDC accessed 2016 |
| Dry permafrost | Permafrost containing neither free water nor ice | Van Everdingen International Permafrost Association 2005 |
| Dry permafrost | Permafrost containing neither Free Water nor Ice. A negligible quantity of moisture in the form of interfacial water may be present. Dry Permafrost is thaw-stable (cf. Thaw Weakening). | Trombotto et al. 2014 |
| Dry permafrost | Permafrost that contains little or no ice; it is loose and crumbly. | AMS - glossary of meteorology |
| Dry snow | Snow from which a snowball cannot readily be made and which has a temperature less than 0 degrees C. | WMO METEOTERM accessed 2016 |
| Dry snow | Snow from which a snowball cannot readily be made. | AMS - glossary of meteorology |
| Dry-based glacier | A glacier whose bed is below its pressure-melting point, implying that there is no liquid water at the bed. Cold-based glacier is a synonym. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Dry-snow line | The set of points on a glacier separating the dry-snow zone from the percolation zone. See zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Dry-snow zone | Region of the glacier where there is neither surface melting nor rainfall. See zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Drydocked iceberg | Sea ice terminology, which describes an iceberg that has eroded in such a way that a U-shaped slot is formed near or at water level, with twin columns or pinnacles. | Environment and Climate Change Canada 2014 |
| Dump moraine | A mound or layer of moraine formed along the edge of a glacier by rock that falls off the ice; sometimes called a ground moraine. | NSIDC accessed 2016 |
| Duration of ice cover | The time from freeze-up to break-up of an ice cover. | NOAA Glossary of Hydrologic Terms |
| Dust | An accumulation of aerosol that, when deposited on the surface of a glacier, modifies the mass balance through its effect on surface albedo. Saharan dust, for instance, sometimes has a substantial impact on the mass balance of European glaciers. Volcanic eruptions can deliver dust and ash to nearby, and sometimes to distant, glaciers. In extreme cases the added material can turn the glacier into a debris-covered glacier. Dust can help to define the summer surface, and a dateable dust layer in firn or glacier ice can be useful as a marker horizon. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Dynamic ice | Pressure due to a moving ice cover or drifting ice. | NOAA Glossary of Hydrologic Terms |
| Dynamic modulus of elasticity | The ratio of stress to strain for a material under dynamic loading conditions | Van Everdingen International Permafrost Association 2005 |
| Dynamic Poisson's ratio | The absolute value of the ratio between the linear strain changes, perpendicular to and in the direction of a given uniaxial stress change, respectively, under dynamic loading conditions | Van Everdingen International Permafrost Association 2005 |
| Dynamic thinning | The reduction of glacier thickness, in excess of that due to ablation, that results when the flux divergence is positive, that is, when more mass flows out of the thinning region than flows in. See downwasting. Dynamic thinning, when not compensated by thickening in a downstream part of the glacier, implies an enhanced calving flux at the glacier terminus, or an advance of the terminus, or both. See also calving velocity. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Earth albedo | Is the reflectivity of the Earth's atmosphere and surface combined. Measurements indicate that the average Earth albedo is approximately 30%. | PhysicalGeography.net |
| Earth hummock | A hummock having a core of silty and clayey mineral soil which may show evidence of cryoturbation. | NSIDC accessed 2016 |
| Earth hummock | A hummock having a core of silty and clayey mineral soil which may show evidence of cryoturbation | Van Everdingen International Permafrost Association 2005 |
| East Antarctic Ice Sheet | That portion of the Antarctic Ice Sheet lying predominantly in the Eastern Hemisphere. A line following the Transantarctic Mountains to the Antarctic Peninsula serves as the boundary between the East and West Antarctic Ice Sheets. | AMS - glossary of meteorology |
| East Greenland current | A southward flowing current along Greenland's east coast that forms part of the North Atlantic subpolar gyre and at the same time constitutes the major outflow route of Arctic water into the Atlantic. This water has a salinity of 30-33 psu and a temperature below -1C. Some of it is diverted just north of Denmark Strait and northeast of Iceland into the East Iceland Current, which carries it toward the Norwegian Sea as part of the formation process of Arctic Bottom Water. The remainder is joined south of Denmark Strait and southwest of Iceland by the northwestward flowing Irminger Current, which brings the water of the subpolar gyre. Transport estimates are 5 Sv (5 ? 10^6 m^3/s) for the East Greenland Current and 8-11 Sv (8-11 x 10^6 m^3/s) for the Irminger Current. The combined flow continues around the southern tip of Greenland into the West Greenland Current. | AMS - glossary of meteorology |
| Easy area | (Opposite of difficult area) Navigation is not difficult. | WMO Sea Ice Nomenclature 2017 |
| Easy area | A general expression to indicate that ice conditions prevailing in an area are such that navigation in it is not difficult. | Bushuyev 2004 |
| Easy area | Sea ice terminology, meaning a general qualitative expression that indicates that prevailing ice conditions in an area are such that navigation is not difficult. | Environment and Climate Change Canada 2014 |
| Edge wasting | Process by which warm water erodes iceberg above the waterline | NSIDC accessed 2016 |
| Effective snowmelt | That part of snowmelt that reaches stream channels as runoff. | AMS - glossary of meteorology |
| Eisrinde | Ice-rich layer at the surface of permafrost (see also Transition Layer). | Trombotto et al. 2014 |
| Electrical conductivity | The inverse of electrical resistivity | Van Everdingen International Permafrost Association 2005 |
| Electrical properties of frozen ground | The dielectric constant (or relative permittivity), electrical conductivity and electrical resistivity are the major electrical properties governing the flow of electric current through frozen ground | Van Everdingen International Permafrost Association 2005 |
| Electrical properties of frozen ground | The dielectric constant, electrical conductivity and electrical resistivity are the major electrical properties governing the flow of electric current through Frozen Ground. The dielectric constant of a soil/rock is a measure of the ability of it to store electrical energy in the presence of an electrostatic field; it is the ratio of the soil's permittivity to the permittivity of a vacuum. The electrical conductance of a soil is the inverse of the resistance offered by a soil to electrical current flow. Current flow under an electrical gradient in a frozen soil occurs almost entirely through the unfrozen water films. Electrical conduction is related to the thickness of these water films and their degree of interconnection; it decreases with decreasing temperature and increases with increasing pressure. Electrical resistivity is the property of a material that determines the electrical current flowing through a cube centimetre of the material when an electrical potential is applied to opposite faces of the cube. All these electrical properties are influenced by soil/rock type, density, salinity, temperature and, in particular, the unfrozen water content. | Trombotto et al. 2014 |
| Electrical resistivity | The property of a material that determines the electrical current flowing through a centimetre cube of the material when an electrical potential is applied to opposite faces of the cube | Van Everdingen International Permafrost Association 2005 |
| Elevation change | Vertical changing glacier surface elevation (altitude), typically derived from two elevation measurements, adjusted if necessary for the difference of their respective datum surfaces, at the same (or nearly the same) horizontal coordinates. The elevation of the surface can change due to (i) ablation and accumulation at the surface and bottom of the glacier; (ii) compaction (densification) of snow and firn; (iii) emergence and submergence resulting from ice flow; (iv) changes in subglacial water pressure; (v) tectonic and isostatic movements of the glacier bed; and (vi) geomorphic processes (abrasion, plucking; lodgement of sediment) at the bed. Changes due to (iv) and (vi) can usually be neglected in mass-balance studies, although a correction is sometimes applied for glacial isostatic adjustment (GIA). Surface elevation change is usually similar to thickness change, but (ivvi) above produce elevation changes without changes of the thickness or glacier mass, while (ii) above produces a decrease of thickness with no accompanying change of mass. See continuity equation, geodetic method. In turn, large changes of glacier thickness lead to isostatic changes of the bed elevation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Emergence velocity | The vertical component, when it is directed upward, of the glacier-flow velocity vector at the glacier surface, at a point fixed in space. When the component is directed downward, it is called the submergence velocity. The emergence velocity is related through the continuity equation to the climatic-basal mass balance and the rate of thickness change. The component is typically upward in the ablation zone and downward in the accumulation zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| En-echelon crevasses | Series of crevasses oriented at an angle to the glacier margin. These form as a result of rotational strain within the ice along the glacier's edge. | Swisseduc - Photo glossary of glaciological terms |
| End moraine | An arch-shaped ridge of moraine found near the end of a glacier. | NSIDC accessed 2016 |
| End moraine (see terminal moraine) | A prominent ridge of glacial debris formed when a glacier reached its maximum limit during a sustained advance. | Swisseduc - Photo glossary of glaciological terms |
| End-of-summer snowline | A synonym of Annual snowline. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Energy balance | A relation describing the change in the amount of energy stored within a defined volume owing to flows of energy across the boundary of the volume. A change in the amount of stored energy, due for example to the advection or conduction of heat or the absorption or emission of radiation, will result in a change in the temperature or the phase, or both, of the material in the volume. Phase changes, in particular melting and freezing but also sublimation and deposition, couple the energy balance strongly to the mass balance. For example they determine the amount of ablation by melting and sublimation, and so the energy balance must be determined using either an energy-balance model or a temperature-index model in any attempt to model ablation. The surface energy balance is that of an interface or degenerate volume, the thickness of which approaches zero, at the surface of the glacier. Glaciers also have internal and basal energy balances. In cold glaciers and some polythermal glaciers, the largest component of the internal energy balance is usually the heat source due to refreezing. In both the internal and basal energy balances, friction is a mechanical source of heat and heat is conducted (or advected) between adjacent volumes that are not isothermal. The geothermal heat flux is usually a significant term in the basal energy balance and basal mass balance of grounded ice, but the resulting contribution to the climatic-basal mass balance is generally small. Exchanges of heat with sea or lake water must be considered where the ice is afloat. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Energy balance | The difference between the total incoming and total outgoing energy. If this balance is positive, warming occurs; if it is negative, cooling occurs. Averaged over the globe and over long time periods, this balance must be zero. Because the climate system derives virtually all its energy from the Sun, zero balance implies that, globally, the amount of incoming solar radiation on average must be equal to the sum of the outgoing reflected solar radiation and the outgoing thermal infrared radiation emitted by the climate system. A perturbation of this global radiation balance, be it anthropogenic or natural, is called radiative forcing | EU Climate-ADAPT |
| Energy of glacierization | A less-used synonym of activity index, appearing mainly in the Russian-language literature. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Energy-balance model | A model of mass balance in which ablation by melting and sublimation is estimated by solving the surface energy balance. Energy balance models require more input information than temperature-index models, but are preferred for being based on a more complete description of processes, and for superior accuracy when the input information can be supplied accurately. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Englacial | Pertaining to the interior of the glacier, between the summer surface and the bed. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Englacial conduit | A channel, commonly cylindrical, formed within the body of a glacier, carrying water towards the glacier bed or margins. Capture of a stream upglacier commonly leads to their abandonment. | Swisseduc - Photo glossary of glaciological terms |
| Englacial debris | Debris dispersed throughout the interior of a glacier. It originates either as surface debris that is buried in the accumulation area or falls into crevasses, or in basal debris that is raised from the bed by thrusting or folding. | Swisseduc - Photo glossary of glaciological terms |
| Englacial stream | A meltwater stream that has penetrated below the surface of a glacier and is making its way towards the bed. | Swisseduc - Photo glossary of glaciological terms |
| Epigenetic ice | Ground ice developed in epigenetic permafrost, or in previously formed syngenetic permafrost. | NSIDC accessed 2016 |
| Epigenetic ice | Ground ice developed in epigenetic permafrost, or in previously formed syngenetic permafrost | Van Everdingen International Permafrost Association 2005 |
| Epigenetic ice wedge | An ice wedge developed in epigenetic permafrost, or in previously formed syngenetic permafrost. | NSIDC accessed 2016 |
| Epigenetic ice wedge | An ice wedge developed in epigenetic permafrost, or in previously formed syngenetic permafrost | Van Everdingen International Permafrost Association 2005 |
| Epigenetic permafrost | Permafrost that formed through lowering of the permafrost base in previously deposited sediment or other earth material. | NSIDC accessed 2016 |
| Epigenetic permafrost | Permafrost that formed through lowering of the permafrost base in previously deposited sediment or other earth material | Van Everdingen International Permafrost Association 2005 |
| Equilibrium | A state in which the mass balance is equal to zero over one or more years. Equilibrium may hold for a single column, for an entire flowline, or for an entire glacier. See steady state. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Equilibrium AAR | A synonym of Balanced-budget AAR. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Equilibrium growth | Slow growth of grains and bonds within the snowpack resulting in a decrease of the specific surface area of snow. Causes particles to round off. Works at low temperature gradients, i.e., when excess water vapour density is below the critical value for kinetic growth to occur. An extreme case of equilibrium growth is isothermal or equi-temperature growth in dry snow. This is the type of metamorphism that in nature occurs only in the centre of polar ice shields and may allow grains to develop facets. The latter is still a matter of research. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Equilibrium line | The set of points on the surface of the glacier where the climatic mass balance is zero at a given moment. The equilibrium line separates the accumulation zone from the ablation zone. It coincides with the snowline only if all mass exchange occurs at the surface of the glacier and there is no superimposed ice. Unless qualified by a different adjective, references to the equilibrium line refer to the Annual equilibrium line. See also equilibrium-line altitude, firn line, snowline, transient equilibrium line, zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Equilibrium line | Equilibrium line is the boundary between the accumulation area and the ablation area. | Molnia USGS 2004 |
| Equilibrium line | The spatially averaged boundary at a given moment, usually chosen as the seasonal mass budget minimum at the end of summer, between the region on a glacier where there is a net annual loss of ice mass (ablation area) and that where there is a net annual gain (accumulation area). The altitude of this boundary is referred to as equilibrium line altitude (ELA). | IPCC WGI AR5 2013 |
| Equilibrium line | The boundary on a glacier between the ablation area and accumulation area. No net mass is gained or lost at this location. In the absence of superimposed ice, this line is equal to the snow line at the end of the mass balance year. | AMS - glossary of meteorology |
| Equilibrium line | The line or zone on a glacier where a year's ablation balances a year's accumulation. The equilibrium line is determined at the end of the ablation season (cf. Firn line and Snow line). | Illustrated Glossary of Snow and Ice |
| Equilibrium line of glacier | Line or zone on a glacier along which the annual ablation balances the annual accumulation. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Equilibrium line/zone | The line or zone on a glacier's surface where a year's ablation balances a year's accumulation (cf. Firn line). It is determined at the end of the ablation season, and commonly occurs at the boundary between superimposed ice (q.v.) and glacier ice. | Swisseduc - Photo glossary of glaciological terms |
| Equilibrium permafrost | Permafrost that is in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and with the geothermal heat flux. | NSIDC accessed 2016 |
| Equilibrium permafrost | Permafrost that is in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and with the geothermal heat flux | Van Everdingen International Permafrost Association 2005 |
| Equilibrium permafrost | Permafrost that is in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and with the Geothermal Heat Flux. | Trombotto et al. 2014 |
| Equilibrium zone | Zone of a glacier in which the amount of precipitation that falls is equal to the amount that melts the following summer. | NSIDC accessed 2016 |
| Equilibrium zone | Part of a glacier bounded by two contours of surface elevation, within which the equilibrium line lies. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Equilibrium-line altitude ELA | The spatially averaged altitude of the equilibrium line. The ELA may be determined by direct visual observation, but is generally determined, in the context of mass-balance measurements, by fitting a curve to data representing surface mass balance as a function of altitude (see mass-balance profile). This is often an idealization, because the equilibrium line tends to span a range of altitudes. Many approximations of the ELA have been suggested; the glaciation level and the mid-range altitude are examples. The ELA is understood to be the Annual ELA unless it is qualified as the transient ELA. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Erosion | The process by which the surface of the snow cover is worn away, primarily by the action of wind (see also 2.9, surface features, and zastrugi). Wind erosion is a very important factor in the redistribution of surface snow. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Erosion | The process of removal and transport of soil and rock by weathering, mass wasting, and the action of streams, glaciers, waves, winds and underground water. | EU Climate-ADAPT |
| Erosion | Wearing away and transport of soil and rock by running water, glaciers, wind or waves. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Erosion | The removal of weathered sediment or rocks by the forces of wind, water, and ice. | PhysicalGeography.net |
| Erosional landform | Is a landform formed from the removal of weathered and eroded surface materials by wind, water, glaciers, and gravity. This includes landforms with some of the following geomorphic features: river valleys, glacial valleys, and coastal cliffs. | PhysicalGeography.net |
| Erratic | A rock of unspecified shape and size, transported a significant distance from its origin by a glacier or iceberg and deposited by melting of the ice. Erratics range from pebble-size to larger than a house and usually are of a different composition that the bedrock or sediment on which they are deposited. | Molnia USGS 2004 |
| Erratic | A rock of unspecified shape and size, transported a significant distance from its origin by a glacier or iceberg and deposited by melting of the ice. Erratics range from pebble-size to larger than a house and usually are of a different composition that the bedrock or sediment on which they are deposited. | Molnia USGS 2004 |
| Erratic | A boulder or large block of bedrock that is being, or has been, transported away from its source by a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Erratic | A large rock boulder that has been transported by glaciers away from its origin and deposited in a region of dissimilar rock. | PhysicalGeography.net |
| Esker | A meandering, water-deposited, generally steep-sided sediment ridge that forms within a subglacial or englacial stream channel. Its floor can be bedrock, sediment, or ice. Subsequent melting of the glacier exposes the deposit. Generally composed of stratified sand and gravel, eskers can range from feet to miles in length and may exceed 100 feet in height. | Molnia USGS 2004 |
| Esker | A sinuous ridge of sedimentary material (typically gravel or sand) deposited by streams that cut channels under or through the glacier ice. | NSIDC accessed 2016 |
| Esker | (from the Gaelic) A long, commonly sinuous ridge of sand and gravel, deposited by a stream in a subglacial tunnel. | Swisseduc - Photo glossary of glaciological terms |
| Esker | Long twisting ridges of sand and gravel found on the Earth's surface. Created when the deposits of subsurface glacial streams are placed on the ground after glacial melting. | PhysicalGeography.net |
| Eustacy | Fluctuations in the worldwide sea-level regime caused by changes in the quantity of seawater available. The greatest changes are caused by water being added to, or removed from, glaciers. | Molnia USGS 2004 |
| Excess ice | The volume of ice in the ground which exceeds the total pore volume that the ground would have under natural unfrozen conditions | Van Everdingen International Permafrost Association 2005 |
| Excess ice | The volume of ice in the ground that exceeds the total pore volume that the ground would have under natural unfrozen conditions. Due to the presence of Ground Ice, the total water content of a frozen soil may exceed that corresponding to its unfrozen state. In standard geotechnical terminology, a soil is considered normally consolidated when its total pore volume or its total water content is in equilibrium with the acting gravity stresses. As a result, upon thawing, a soil containing Excess Ice will settle under its own weight until it attains normal consolidation. | Trombotto et al. 2014 |
| Expanded | Frontal expansion on a level surface (not necessary lowland); Less restricted by topography; Widening of the tongue (lateral expansion is less than for piedmont); Lobe or fan formed where the lower portion of the glacier leaves the confining wall of a valley and extends on to a less restricted and more level surface (WGMS 1970, 1998); Lobe or fan formed where the lower portion of the glacier leaves the confining wall of a valley and extends on to a less restricted and more level surface. Lateral extension markedly less than for piedmont. (WGMS 1977) | Illustrated GLIMS Glacier Classification Manual |
| Expanded foot | The fan of glacier ice formed when a valley glacier or outlet glacier flows beyond its constricting valley walls onto lowland terrain and expands laterally. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Expanded-foot glacier | A glacier with an expanded foot, the lateral expansion of which is too limited to justify calling the glacier a piedmont glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Extending flow | When glacier motion is accelerating down-slope. | NSIDC accessed 2016 |
| Extensive discontinuous permafrost | (1) (North American usage) permafrost underlying 65 - 90% of the area of exposed land surface (2) (Russian usage) permafrost underlying 70 - 80% of the area of exposed land surface. | NSIDC accessed 2016 |
| Extensive discontinuous permafrost | 1. (North-American usage) Permafrost underlying 65 to 90 percent of the area of exposed land surface; 2. (Russian usage) Permafrost underlying 70 to 80 percent of the area of exposed land surface. | Van Everdingen International Permafrost Association 2005 |
| Fabric | Soil micromorphology | Van Everdingen International Permafrost Association 2005 |
| Facies | A collection of attributes serving to distinguish one part of the glacier from others; by extension, the part of the glacier so distinguished. The term, originally Latin for 'face, outward appearance', was borrowed from geology. Examples of diagnostic attributes include ice lenses in the firn, indicating refreezing and therefore the percolation facies; the absence of such lenses, possibly suggesting the dry snow facies; or the seasonal exposure of glacier ice, indicating the ablation facies. In glaciology the term zone is equivalent and is now more common. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| False ogives | Bands of light and dark on a glacier that were formed by rock avalanching. | NSIDC accessed 2016 |
| Fast ice | Ice that is anchored to the shore or ocean bottom, typically over shallow ocean shelves at continental margins; fast ice is defined by the fact that it does not move with the winds or currents. | NSIDC accessed 2016 |
| Fast ice | Sea ice which forms and remains fast along the coast, where it is attached to the shore, to an ice wall, to an ice front, between shoals or grounded icebergs. Vertical fluctuations may be observed during changes of sea-level. Fast ice may be formed in situ from sea water or by freezing of pack ice of any age to the shore, and it may extend a few metres or several hundred kilometres from the coast. Fast ice may be more than one year old and may then be prefixed with the appropriate age category (old, second-year, or multi-year). | ASPECT 2012 |
| Fast ice | Consolidated solid ice attached to the shore, to an ice wall or to an ice front. It forms by freezing to the shore of the ice cover forming in the coastal zone or as a result of freezing of drifting ice of any age category to the shore or fast ice. Vertical movement may be observed during tidal oscillations. It can be preserved without fracturing for two or more years transforming from first-year ice to multiyear ice and even shelf ice. The fast ice width can vary from several hundreds of meters to several hundreds of kilometers. That part of fast ice presenting a narrow fringe of ice directly attached to the coast with a shallow bottom and unresponsive to tidal oscillations that remains after the fast ice has moved away is called the Ice foot. Fast ice at the initial stage of formation consisting of nilas and young ice with a width up to 100-200 m is called young coastal ice. When coding and depicting fast ice on ice charts, total concentration is not indicated as this is always equal to 10/10 in accordance with the definition. | Bushuyev 2004 |
| Fast ice | Sea ice that forms and remains fast along the coast, where it is attached to the shore, to an ice wall, to an ice front, between shoals or grounded icebergs. Vertical fluctuations may be observed during changes of sea level. Fast ice may be formed on site from sea water or by freezing of pack ice of any age to the shore, and it may extend a few yards (meters) or several hundred miles (kilometers) from the coast. Fast ice may be more than one year old and may then be prefixed with appropriate age category (old, second- year, or multiyear). If it is thicker than about 7 ft (2 m) above sea level, it is called an ice shelf. | WMO Sea Ice Nomenclature 2017 |
| Fast ice | Sea ice terminology, describing ice which forms and remains fast along the coast. It may be attached to the shore, to an ice wall, to an ice front, or between shoals or grounded icebergs. It can extend between a few metres to several hundred kilometres from the coast. It may be more than one year old, in which case it may be attached to the appropriate age category (old, second year or multi-year). If higher than 2 m above sea level, it is called an ice shelf. | Environment and Climate Change Canada 2014 |
| Fast ice | Sea ice that is immobile due to its attachment to a coast, usually extending offshore to about the 20-m isobath. In protected bays and inlets, fast ice is smooth and level, typically reaching a thickness of between 2 and 2.5 m. Along exposed coastlines, fast ice may be greatly deformed. (Also called landfast ice.) | AMS - glossary of meteorology |
| Fast ice | Sea ice which remains fast along the coast, where it is attached to the shore, to an ice wall, to an ice front, or over shoals, or between grounded icebergs. Fast ice may extend a few m or several hundred km from the shore. Fast ice may be more than one year old. When its surface level becomes higher than about 2 m above sea level, it is called an ice shelf. | Illustrated Glossary of Snow and Ice |
| Fast ice boundary | Sea ice terminology. The ice boundary, which at any given time is found between fast ice and the pack/drift ice. | Environment and Climate Change Canada 2014 |
| Fast ice edge | Sea ice terminology, describing the differentiation (at any given time) between fast ice and open water. | Environment and Climate Change Canada 2014 |
| Fast-ice boundary | The ice boundary at any given time between fast ice and pack ice. | WMO Sea Ice Nomenclature 2017 |
| Fast-ice edge | The demarcation at any given time between fast ice and open water. | WMO Sea Ice Nomenclature 2017 |
| Fault | A displacement in a glacier formed by ice fracturing without its walls separating. It can be recognized by the discordance of layers in the ice on either side of the fracture. | Swisseduc - Photo glossary of glaciological terms |
| Feature tracking | A method for estimating glacier surface velocities by measurement of the positions of easily distinguishable features on repeated images of known date. See speckle tracking. Surface debris and crevasses are the most commonly measured features. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Fern | Old snow which has been transformed into a dense material. Firn is characterized by the fact that: (a) the particles are to some extent joined together, but that (b) the air interstices still communicate with each other. (a) distinguishes it from snow and (b) from ice. | Illustrated Glossary of Snow and Ice |
| Finger rafted ice | Sea ice terminology, meaning a type of rafted ice in which floes overlap each other in 'fingers.' This is common in nilas. | Environment and Climate Change Canada 2014 |
| Finger rafting | A process by which currents or winds push around thin ice so they slide over each other. | NSIDC accessed 2016 |
| Finger rafting | A particular form of rafted ice, typical of thin ice, whereby overlapping occurs in alternating, interlocking segments (like the interlaced fingers of clasped hands). | AMS - glossary of meteorology |
| Finger-rafted ice | Type of rafted ice in which floes thrust 'fingers' alternately over and under the other. | WMO Sea Ice Nomenclature 2017 |
| Finsterwalder's method | A method for the measurement of elevation change by comparison of contours on maps of two dates. The area between the later and the earlier instance of each contour is measured. The average elevation change of the region between any two contours is the sum of the area changes (later minus earlier) of the two contours, divided by the sum of the earlier and later areas of the region and multiplied by the difference of the contour elevations. The method, described by Finsterwalder (1953), is now less used, having been superseded by the preparation and subtraction of digital elevation models. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Firn | Old snow on top of glaciers, granular and compact and not yet converted into ice. It is a transitional stage between snow and ice. Also called Neve. | NOAA Glossary of Hydrologic Terms |
| Firn | Firn is old snow that has been recrystalized into a more dense substance. Firn has a density greater than 0.55. Snowflakes are compressed under the weight of the overlying snowpack. Individual crystal near the melting point have slick liquid edges allowing them to glide along other crystal planes and to readjust the space between them. Where the crystals touch they bond together, squeezing the air between them to the surface or into bubbles. During summer we might see the crystal metamorphosis occur more rapidly because of water percolation between the crystals. By summer's end the result is firn -- a compacted snow with the appearance of wet sugar, but with a hardness that makes it resistant to all but the most dedicated snow shovelers! Several years are usually required for the snow to settle and to season into the substance we call glacier ice. | Molnia USGS 2004 |
| Firn | In hydrologic terms, old snow on top of glaciers, granular and compact and not yet converted into ice. It is a transitional stage between snow and ice. Also called Neve. | NOAA National Weather Service Glossary 2009 |
| Firn | Rounded, well-bonded snow that is older than one year; firn has a density greater than 550 kilograms per cubic-meter (35 pounds per cubic-foot); called n | NSIDC accessed 2016 |
| Firn | (1) Snow that has survived at least one ablation season but has not been transformed to glacier ice. This sense prevails in the study of mass balance. Snow becomes firn, by definition, at the instant when the mass-balance year ends. See zone. (2) Structurally, the metamorphic stage intermediate between snow and ice, in which the pore space is at least partially interconnected, allowing air and water to circulate; typical densities are 400830 kg m3. In this sense, the firn is generally up to a few tens of metres thick on a temperate glacier that is close to a steady state, and up to or more than 100 m thick in the dry snow zone on the ice sheets. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Firn | Old snow that has recrystallized into a dense material. Unlike ordinary snow, the particles are to some extent joined; but, unlike ice, the air spaces in it still connect with each other. | WMO Sea Ice Nomenclature 2017 |
| Firn | Sea ice terminology that describes old snow which has re-crystallized into a dense material. Unlike ordinary snow, particles are (to some extent) joined together; but, unlike ice, the air spaces in it still connect with each other. | Environment and Climate Change Canada 2014 |
| Firn | Well-bonded and compacted snow that has survived the summer season, but hasnot been transformed to glacier ice. Typical densities are 400-830 kg m3 (perennialsnow, n | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Firn | An intermediate stage in the transformation of snow to glacier ice. Snow becomes firn when it has been compressed so that no pore space remains between flakes or crystals, a process that takes less than a year. | Molnia USGS 2004 |
| Firn | Old snow which has become granular and dense under the action of various processes of melting and refreezing, including sublimation and crystallization. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Firn | (from the German) Dense, old snow in which the crystals are partly joined together, but in which the air pockets still communicate with each other. It has a sugary texture. | Swisseduc - Photo glossary of glaciological terms |
| Firn | Old snow that has become granular and compacted (dense) as the result of various surface metamorphoses, mainly melting and refreezing but also including sublimation. The resulting particles are generally spherical and rather uniform. Firnification, the process of firn formation, is the first step in the transformation of snow into land ice (usually glacier ice). Some authorities restrict the use of firn to snow that has lasted through one summer, thereby distinguishing it from spring snow. Originally, the French term, "n v ," was equivalent to the German term, "firn," but there is a growing tendency, especially among British glaciologists, to use "n v s" for an area of firn, that is, generally for the accumulation area above or at the head of a glacier. | AMS - glossary of meteorology |
| Firn | Neve on a glacier that survives the year's ablation season. With time much of the firn is transformed into glacial ice. | PhysicalGeography.net |
| Firn area | The zone of the glacier where the summer surface is underlain by firn instead of glacier ice. Changes in extent of the firn area, and thickness of the firn, complicate mass-balance calculations by the geodetic method since Sorge's law no longer applies. The firn area is not the same as the accumulation zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Firn field | 1.An area of firn that is not part of a glacier. 2.Same as accumulation area. | AMS - glossary of meteorology |
| Firn limit | The minimum elevation of firn lying on a glacier surface; each year's firn line marks a glacier's annual equilibrium line; also called firn line. | NSIDC accessed 2016 |
| Firn limit | A synonym of firn line. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Firn limit | The lower boundary of the zone of accumulation on a glacier where snow accumulates on an annual basis. Also called the Firn Line. | PhysicalGeography.net |
| Firn line | The highest level to which the fresh snow on a glacier's surface retreats during the melting season. The line separating the accumulation area from the ablation area. | NOAA Glossary of Hydrologic Terms |
| Firn line | A line across the glacier, from edge to edge, that marks the transition between exposed glacier ice (below) and the snow-covered surface of a glacier (right). During the summer melt season, this line migrates up-glacier. At the end of the melt season the firn line separates the accumulation zone from the ablation zone. | Molnia USGS 2004 |
| Firn line | A line that marks the limit on a mountain above which snow persists from one winter to the next is called the annual snowline, and this line on a glacier is called the firnline. Above the firnline, snow that falls each year packs down and changes into glacier ice as air is slowly forced out of it. This part of the glacier is its accumulation area where more snow falls each year than is lost by melting. Below the firnline is the ablation area, where melting predominates. | Molnia USGS 2004 |
| Firn line | The minimum elevation of firn lying on a glacier surface; each year's firn line marks a glacier's annual equilibrium line; also called firn limit. | NSIDC accessed 2016 |
| Firn line | In hydrologic terms, the highest level to which the fresh snow on a glacier's surface retreats during the melting season. The line separating the accumulation area from the ablation area. | NOAA National Weather Service Glossary 2009 |
| Firn line | The set of points on the surface of a glacier delineating the firn area and, at the end of the mass-balance year, separating firn (usually above) from glacier ice (usually below).In steady state and equilibrium, and in the absence of superimposed ice, the firn line coincides with the equilibrium line. However, the equilibrium line will generally be above the firn line in a year of negative mass balance; in a year of positive mass balance it will in general be below the firn line of the previous year. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Firn line | Boundary on the surface of a glacier which separates the zone of accumulation from the zone of ablation. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Firn line | The boundary of the area of snow on a glacier surviving one year's ablation, thus becoming firn. In the absence of superimposed ice, this limit is equivalent to the equilibrium line. See climate snow line. | AMS - glossary of meteorology |
| Firn line | The line or zone on a glacier that separates bare ice from snow at the end of the ablation season (cf. Equilibrium line and Snow line). | Illustrated Glossary of Snow and Ice |
| Firn water table | The height of meltwater within saturated firn that is trapped over ice in a glacier. | NSIDC accessed 2016 |
| Firnification | The process of firn formation. | AMS - glossary of meteorology |
| Firnspiegel | A thin sheet of ice formed on the glacier surface by rapid refreezing of solar-heated snow or firn, usually at high elevations during spring. | NSIDC accessed 2016 |
| Firnspiegel | A thin, highly reflective sheet of clear ice formed at the snow surface; formed in spring when subfreezing air temperatures combine with subsurface melting (due to penetration of solar energy into the snow). | AMS - glossary of meteorology |
| First-year ice | Floating ice of no more than one year's growth developing from young ice; thickness from 0.3 to 2 meters (1 to 6.6 feet); characteristically level where undisturbed by pressure, but where ridges occur, they are rough and sharply angular. | NSIDC accessed 2016 |
| First-year ice | Sea ice of not more than one winter's growth, developing from young ice; thickness (typically) 30cm2m. May be subdivided into thin first-year ice/white ice, medium first-year ice and thick first-year ice. | ASPECT 2012 |
| First-year ice | Sea ice of not more than one winter's growth, developing from young ice; thickness 30 cm - 2 m, and sometimes slightly more. May be subdivided into thin first-year ice/white ice, medium first-year ice and thick first-year ice. | Bushuyev 2004 |
| First-year ice | Sea ice of not more that one winter's growth, developing from young ice; thickness 1 to 7 ft (30 cm-2 in). May be subdivided into thin first-year ice (white ice), medium first-year ice, and thick first-year ice. | WMO Sea Ice Nomenclature 2017 |
| First-year ice | Sea ice terminology, meaning sea ice that has grown for not more than one winter, developing from young ice. It must also be 30 cm or greater. First-year ice may be subdivided into thin first-year ice (sometimes referred to as white ice), medium first-year ice, and thick first-year ice. | Environment and Climate Change Canada 2014 |
| First-year ice | Sea ice that has not yet experienced summer melt. First-year ice is distinguished from older ice primarily by having a higher salinity. Undeformed first-year ice differs from older ice in that it is smoother and lacks refrozen melt ponds. First-year ridges are distinguished by being larger, more angular, and more porous than multiyear ridges. | AMS - glossary of meteorology |
| First-year ice | Floating ice of not more than one year's growth developing from young ice. Thickness from 30 cm to 2 m. Characteristically level where undisturbed by pressure, but where ridges occur they are rough and sharply angular. | Illustrated Glossary of Snow and Ice |
| Fixed-date system | The time system in which mass balance is determined by conducting field surveys on fixed calendar dates. The fixed date representing the start of the mass-balance year is usually at the start of the local hydrological year. To determine seasonal balances, a fixed date is chosen to represent the mean date of the end of the accumulation season. Due to logistical constraints it is often impossible to conduct field surveys on these exact dates. Therefore the data need to be corrected, which is often done by estimating ablation and accumulation between the survey date and the fixed date using meteorological data from a nearby weather station or a database of upper-air measurements. See also measurement year, stratigraphic system, floating-date system, combined system. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Fjord | Glacial troughs that fill with sea water. | NSIDC accessed 2016 |
| Fjord | A glacially eroded or modified U-shaped valley that extends below sea level and connects to the ocean. Filled with seawater, depths may reach more than 1,000 feet below sea level. The largest Alaskan fiords are more than 100 miles long and more than 5 miles wide. Also spelled Fiord. | Molnia USGS 2004 |
| Fjord | A fjord (from the Norwegian; spelt fiord in North America and New Zealand) is a long, narrow arm of the sea, formed as a result of erosion by a valley glacier. | Swisseduc - Photo glossary of glaciological terms |
| Fjord | A deep-water inlet, usually surrounded by mountains; specifically a submerged U-shaped valley carved out by glacial action. The fjord is characteristic of the coastal regions of Norway, western Scotland and Ireland, Greenland, Labrador, Alaska, British Columbia, southern Chile, the Antarctic peninsula, southwest New Zealand, and other high-latitude oceanic islands (Iceland, Spitzbergen, Kerguelen, etc.). (Sometimes spelled fiord, fiard.) | AMS - glossary of meteorology |
| Fjord | A glacial valley or glacial trough found along the coast that is now filled with a mixture of fresh water and seawater. | PhysicalGeography.net |
| Fjord (or Fiord) | Long narrow arm of the sea between high cliffs, but the term bay has also been applied to such features. | UK Antarctic Place-names Committee accessed 2016 |
| Flaw | A narrow separation zone between pack ice and fast ice filled with continuous small ice cake with some small floes, where the pieces of ice are in chaotic state; it forms when drift ice moves under the effect of a strong wind or current along the fast ice boundary. Flaws also form at drift divides. | Bushuyev 2004 |
| Flaw | A narrow separation zone between pack ice and fast ice, where the pieces of ice are in a chaotic state; it forms when pack ice shears under the effect of a strong wind or current along the fast ice boundary. | WMO Sea Ice Nomenclature 2017 |
| Flaw | Sea ice terminology, describing a narrow separation zone between floating ice and fast ice, where the pieces of ice are in a chaotic state. Flaws form when ice shears, due to a strong wind or current along the fast ice boundary. | Environment and Climate Change Canada 2014 |
| Flaw lead | A navigable passage between pack ice and fast ice. | NSIDC accessed 2016 |
| Flaw lead | A passage-way between pack ice and fast ice which is navigable by surface vessels [Note: shore lead is used in the Antarctic] | Bushuyev 2004 |
| Flaw lead | A passageway between pack ice and fast ice that is navigable by surface vessels. | WMO Sea Ice Nomenclature 2017 |
| Flaw lead | Sea ice terminology, describing a passageway between ice and fast ice, which is navigable by surface vessels. | Environment and Climate Change Canada 2014 |
| Flaw lead | A navigable passage between pack ice and fast ice. | Illustrated Glossary of Snow and Ice |
| Flaw polynya | A polynya between pack ice and fast ice. | WMO Sea Ice Nomenclature 2017 |
| Flaw polynya | Sea ice terminology, which describes a polynya between ice and fast ice. | Environment and Climate Change Canada 2014 |
| Floating | Glacier terminus is floating in the sea; Approximate grounding line may be detectable; Tidewater glacier; Implies that the glacier is calving | Illustrated GLIMS Glacier Classification Manual |
| Floating glaciers | Tidewater glaciers with floating tongues. Their lateral margins might be attached to the coastline or where there is no more topographic limitation it might expand. | Illustrated GLIMS Glacier Classification Manual |
| Floating ice | Any form of ice found floating in water. | NSIDC accessed 2016 |
| Floating ice | Any form of ice floating in water. The principal kinds of floating ice at the sea surface are sea ice which is formed by the freezing of sea water at the surface, lake ice and river ice formed on rivers or lakes and glacier ice (ice of land origin). The concept also includes ice that is grounded. | Bushuyev 2004 |
| Floating ice | Any form of ice found floating in water. The principal kinds of floating ice are lake ice, river ice, and sea ice, which form by the freezing of water at the surface, and glacier ice (ice of land origin) formed on land or in an ice shelf. The concept includes ice that is stranded or grounded. | WMO Sea Ice Nomenclature 2017 |
| Floating ice | Sea ice terminology, meaning any form of ice found floating in water. The principal kinds of floating ice are lake ice, river ice and sea ice, which form by the freezing of water at the surface, and glacier ice which is formed on land or in an ice shelf. | Environment and Climate Change Canada 2014 |
| Floating ice | Any form of ice found floating in water. The principal kinds of floating ice are lake ice, river ice, sea ice that forms by the freezing of water at the surface, and glacier ice (ice of land origin) formed on land or in an ice shelf. The concept includes ice that is stranded or grounded. | AMS - glossary of meteorology |
| Floating ice | Any form of ice found floating in water. | Illustrated Glossary of Snow and Ice |
| Floating tongue | The terminal part of a glacier, the weight of which is partially or entirely supported by lake or seawater. Lateral stress from valley walls, and possibly from ice rises and other grounded parts of the glacier, supports a significant part of the weight of the floating ice, in which respect floating tongues generally differ from ice shelves. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Floating-date system | The time system in which mass balance is determined by conducting field surveys on floating calendar dates. Annual field surveys are usually carried out close to the beginning of the hydrological year. For the determination of seasonal mass balances, a survey is carried out close to the end of the accumulation season, without interpolation or extrapolation to a fixed date. The duration of the mass-balance year varies in the floating-date system. See also measurement year, stratigraphic system, fixed-date system, combined system. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Floc | A cluster of frazil particles. | NOAA Glossary of Hydrologic Terms |
| Floe | An accumulation of frazil flocs (also known as a 'pan') or a single piece of broken ice. | NOAA Glossary of Hydrologic Terms |
| Floe | Separate patch of floating ice or flat sheet of unbroken pack ice, greater than 20 meters (22 yards) across. | NSIDC accessed 2016 |
| Floe | A floe is any contiguous piece of sea ice. Floes may be described in terms of several size categories: Giant: over 10km across Vast: 2-10km across Big: 500-2000m across Medium: 100-500m across Small: 20-100m across. Floes less than 20m across are called cake ice | ASPECT 2012 |
| Floe | Any relatively flat piece of sea ice 20 m or more across. Floes are subdivided according to horizontal extent as follows: Giant: Over 10 km across, Vast: 2 to 10 km across, Big: 500 to 2000 m across, Medium: 100 to 500 m across, Small: 20 to 100 m across. | Bushuyev 2004 |
| Floe | Any relatively flat, isolated piece of sea ice 65 ft (= 20 m) or more across. Floes are subdivided according to horizontal extent as follows: GIANT: over 5.5 n mi (10 km) VAST: 1-5.5 n mi (2-10 kin) MEDIUM: 110-550 yd (100-500 m) SMALL: 22-110 yd (20-100 m) | WMO Sea Ice Nomenclature 2017 |
| Floe | Sea ice terminology. Describes any relatively flat piece of ice that is 20 m or more across. Floes are subdivided according to their horizontal extent, as follows: Small: 20 m - 100 m across, Medium: 101 m - 500 m across, Big: 501 m - 2000 m across, Vast: 2001 m - 10 km across, Giant: Greater than 10 km across. | Environment and Climate Change Canada 2014 |
| Floe | Any relatively flat piece of ice 20 m or more across. It may be composed of several fragments bonded together. | AMS - glossary of meteorology |
| Floe | A piece of floating ice other than fast ice or glacier ice. Floes are subdivided by size as follows: ice cakes are less than 20 m across; small floes 20-100 m; medium floes 100-500 m; big floes 500 m-2 km; vast floes 2-10 km; giant floes over 10 km. | Illustrated Glossary of Snow and Ice |
| Floeberg | A massive piece of sea ice composed of a hummock or a group of hum- mocks, frozen together and separated from any ice surroundings. It may float up to 17 ft (5 m) above sea level. | WMO Sea Ice Nomenclature 2017 |
| Floeberg | A massive piece of sea ice composed of a hummock, or a group of hummocks frozen together, presenting a separate floating ice fragment in ice-free water or among separate ice fragments. It may protrude up to 5 m above sea-level. | Bushuyev 2004 |
| Floeberg | Sea ice terminology, describing a massive piece of ice composed of a hummock or a group of hummocks, frozen together and separated from any surrounding ice. They may typically protrude up to 5 m above water level. | Environment and Climate Change Canada 2014 |
| Floeberg | A mass of hummocked ice, formed by the piling up of many ice floes by lateral pressure; an extreme form of pressure ice. It may be more than 50 ft high and resemble an iceberg. | AMS - glossary of meteorology |
| Flooded ice | Ice which has been flooded by melt water or river water and is heavily loaded by water and wet snow. | NOAA Glossary of Hydrologic Terms |
| Flooded ice | In hydrologic terms, ice which has been flooded by melt water or river water and is heavily loaded by water and wet snow. | NOAA National Weather Service Glossary 2009 |
| Flooded ice | Sea ice that has been flooded by meltwater or river water and is heavily loaded by water and wet snow. | WMO Sea Ice Nomenclature 2017 |
| Flooded ice | Sea ice, usually first-year ice, flooded by a melt or river water layer. | Bushuyev 2004 |
| Flooded ice | Sea ice terminology. Describes ice which has been flooded and is heavily loaded by water, or water and wet snow. | Environment and Climate Change Canada 2014 |
| Flooded sea ice | Ice that is pushed into the underlying ocean water by the weight of thick snow cover on its surface; the salty ocean water floods the snow cover and creates a salty, slushy layer; flooded sea ice is more common in the antarctic because of more snowfall and thinner sea ice than in the arctic. | NSIDC accessed 2016 |
| Flotation | The transition from being grounded to being afloat, made when the pressure w gd exerted by water of depth d on adjacent ice of thickness h = d + hflot becomes just equal to the weight i gh of the ice; w is the density of the water, i is the depth-averaged density of the ice (allowing for example for crevasses and possibly snow or firn) and hflot is the freeboard, that is, the elevation of the ice surface above the water level. The definition neglects tidal flexure and some other lesser phenomena. It represents mutual hydrostatic equilibrium of the column of water and the adjacent column of ice the water below d supports the weight of both columns, which are at rest with respect to each other. If the two densities are known, a measurement of the freeboard of floating ice is a measurement of ice thickness, which is required for the calculation of ice discharge. The condition for flotation is d = h i / w. A condition for being afloat is d | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Flow | Motion of an ice body by a combination of internal deformation, rigid displacement over the bed and deformation of bed material. Rigid displacement over the bed is called basal sliding, and implies that the ice at the bed is at its pressure-melting point. The speed and direction of the flow are determined by a balance of forces. In the momentum balance, acceleration terms are negligible. Typically, gravity is balanced by pressure and frictional forces. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Flow finger | A small percolation channel that is a beginning path for surface meltwater through snow or firn. | NSIDC accessed 2016 |
| Flow finger | Vertical flow channel formed by percolating water in a subfreezing snowpack. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Flow unit | A distinct stream of ice in a valley glacier, commonly bounded by lateral and medial moraines. The term applies down-stream of the zone of convergence of two or more valley glaciers. | Swisseduc - Photo glossary of glaciological terms |
| Flowline | (1) A sequence of columns of infinitesimal cross section, each extending vertically from base to surface of the glacier, arranged so that each column but the first gains mass by flow from an upglacier neighbour and each column except possibly the last loses mass by flow to a downglacier neighbour. (2) The trace of such a sequence on the glacier surface. Ideally, the upglacier and downglacier walls of all the columns would be at right angles to the local horizontal velocity vector. It is assumed that flow through the other two walls of the columns may be neglected, by allowing an implicit relative width of the flowline to vary and thus to account for transverse straining. In practice, velocity measurements are usually sparse or lacking and it is necessary to construct the flowline from the surface topography. The topography is averaged within a radius of the order of the glacier thickness, to suppress the effect on calculations that might be exerted by short-wavelength topographic features that are not due to the glacier flow. The definitions may be extended to accommodate interrupted glaciers, in which part of the 'flow' is by avalanching from an upper part to a lower part. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Fluctuations of Glaciers | A database containing information on glacier changes, such as in length, area, mass, mass balance and volume, archived and published by the World Glacier Monitoring Service and its predecessor organisations since 1895. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Flurries | Precipitation in the form of snow from a convective cumulus-type cloud, are known as flurries. They are characterized by the suddenness with which they start and stop, by their rapid changes in intensity, and usually by rapid changes in the appearance of the sky. | Environment and Climate Change Canada 2014 |
| Fluted berg | An iceberg that is grooved into a curtain-like pattern; thought to be carved by small meltwater streams. | NSIDC accessed 2016 |
| Fluted lateral moraine | Tall lateral moraines on the sides of receding valley glaciers are commonly so steep that rapid erosion and gullying takes place on their side facing the glacier and causes vertical channels (flutes). | Swisseduc - Photo glossary of glaciological terms |
| Fluted moraine | A set of low ridges formed parallel to ice flow, metre-scale in width, 100 metre-scale in length. They commonly extend down-valley from a boulder, and consist of till. | Swisseduc - Photo glossary of glaciological terms |
| Fluted snow | Steep, strongly ribbed and gullied snow slopes produced by a combination of rime on the ribs and avalanching in the gullies. These slopes form the upper parts of the accumulation area of tropical and Himalayan glaciers. | Swisseduc - Photo glossary of glaciological terms |
| Flux-divergence method | Application of the continuity equation to determine mass balance at a point using measurements on the glacier surface or remotely of thickness, thickness change and surface velocity. The required data may be obtained 1 for thickness, from boreholes or radar; 2 for thickness change, from repeated optical surveying, laser altimetry, radar altimetry, photogrammetry, or Global Positioning System determinations of altitude; 3 for surface velocity, from repeated optical surveying or Global Positioning System determinations of stake locations or feature tracking. In the case of several repeated thickness change and velocity determinations, thickness can also be obtained as the solution of a problem in geophysical inverse theory. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Foehn | Wind warmed and dried by descent, in general on the lee side of a mountain. Air is forced to flow against and over a mountain range in a short period of time. The air cools as it rises up the mountain range, cloud forms and rain or snow falls. Heat is added to the air through condensation of water vapour (latent heat) thus reducing the rate at which the air cools. When the air descends on the other side it has lost some of its moisture (because rain and/or snow has fallen from it) and it is warmed by compression as it descends. This dry, warm wind is the foehn wind. The windward side is usually very wet while the lee side can be a dry desert. Rainfall in Australia is greater in the east due to the influence of the Great Dividing Range. | Australian Bureau of Meteorology 2016 |
| Fog deposit | The formation of an ice coating when fog contacts exposed surfaces that are at temperatures below freezing. | AMS - glossary of meteorology |
| Fold | Layers of ice (and sometimes debris) that have been deformed into a curved form by flow at depth in a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Foliation | Layering in glacier ice that has distinctive crystal sizes and/or bubbles; foliation is usually caused by stress and deformation that a glacier experiences as it flows over complex terrain, but can also originate as a sedimentary feature. | NSIDC accessed 2016 |
| Foliation | The layering or banding that develops in a glacier during the process of transformation of snow to glacier ice. Individual layers, called folia, are visible because of differences in crystal or grain size, alternation of clear ice and bubbly ice, or because of entrained sediment. | Molnia USGS 2004 |
| Foliation | Groups of closely spaced, often discontinuous, layers of coarse bubbly, coarse clear and fine-grained ice, formed as a result of shear or of compression at depth within a glacier. The two dominant types are longitudinal and arcuate. | Swisseduc - Photo glossary of glaciological terms |
| Foothills | Relatively low elevations in a mountainous area. | UK Antarctic Place-names Committee accessed 2016 |
| Forbes bands | Alternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter. | NSIDC accessed 2016 |
| Forel stripes | Shallow, parallel grooves on the face of a large melting ice crystal. | NSIDC accessed 2016 |
| Fossil ice | Ground ice found in regions of permafrost, or in other regions where present-day temperatures are not low enough to have formed it; ice that was formed in the geologic past. | AMS - glossary of meteorology |
| Fossil ice wedges | Sedimentary structures of past episodes that show ancient wedges, which have been filled by sediments and ice preserving the original cryogenic form. Fossile ice wedges are an indicator for mean annual paleotemperatures between -3.5 and -8C depending on the host material. | Trombotto et al. 2014 |
| Fountain | A glacial spring, generally discharging supercooled water with a significant hydrostatic head. | Molnia USGS 2004 |
| Fracture | Any break or rupture formed in an ice cover or floe due to deformation. | NOAA Glossary of Hydrologic Terms |
| Fracture | Any break or rupture through very close pack ice, compact pack ice, consolidated pack ice, fast ice, or a single floe resulting from deformation processes. Fractures may contain brash ice and/or be covered with nilas and/or young ice. Length may vary from a few metres to many kilometres. Fractures, by definition, are narrower than leads and may not aid navigation of surface vessels. | ASPECT 2012 |
| Fracture | A restricted space, the length of which is comparable with the width of ice-free water, or very open broken ice among solid, very close and close ice. Diamond- or lens-shaped fractures form as a result of the shear of ice floes along the line of an earlier crack or lead. Due to cracks and leads not being rectilinear, they expand in some places and converge in other places under slight pressure. Hummocking can form a chain of fractures. This is the most stable type of fracture and can exist for several months. In the autumn-winter period, nilas and young ice and then first-year ice forms at their surface. Less stable fractures the shape and dimensions of which constantly change, are formed as a result of shears between giant and vast ice floes and by local divergance of close ice of smaller formations. | Bushuyev 2004 |
| Fracture | Any break or rupture through very close pack ice, compact pack ice, consolidated pack ice, fast ice, or a single floe resulting from deformation processes. Fractures may contain brash ice and/or may be covered with nilas and/or round ice. Length may vary from a few yards (meters) to many miles (kilometers). | WMO Sea Ice Nomenclature 2017 |
| Fracture | In hydrologic terms, any break or rupture formed in an ice cover or floe due to deformation. | NOAA National Weather Service Glossary 2009 |
| Fracture | Sea ice terminology. Describes any break or rupture through very close pack ice, compact ice, consolidated ice, fast ice or a single floe, resulting from the deformation processes. Fractures may contain brash ice and/or be covered with nilas and/or young ice. Their lengths may vary from a few metres to many kilometres long. | Environment and Climate Change Canada 2014 |
| Fracture zone | An area which has a great number of fractures. | NOAA Glossary of Hydrologic Terms |
| Fracture zone | An area that has a great number of fractures. | WMO Sea Ice Nomenclature 2017 |
| Fracture zone | In hydrologic terms, an area which has a great number of fractures. | NOAA National Weather Service Glossary 2009 |
| Fracture zone | Sea ice terminology. Describes an area which has a great number of fractures. Fractures are subdivided as follows: Very Small Fracture: 1 m to 50 m wide. Small Fracture: 51 m to 200 m wide. Medium Fracture: 201 m to 500 m wide. Large Fracture: Greater than 500 m wide | Environment and Climate Change Canada 2014 |
| Fracturing | Deformation process whereby ice is permanently deformed, and fracture occurs. | NOAA Glossary of Hydrologic Terms |
| Fracturing | A pressure process whereby ice is permanently deformed, and rupture occurs. Most commonly used to describe breaking across fast ice, ice breccia, compact ice and ice fields. | Bushuyev 2004 |
| Fracturing | Any break or rupture through close ice, compact ice, consolidated ice, fast ice, or a single floe resulting from shears and deformation processes. The fracture may contain brash ice and be covered with nilas or young ice. The length may vary from a few meters to several tens of kilometers. | Bushuyev 2004 |
| Fracturing | In hydrologic terms, deformation process whereby ice is permanently deformed, and fracture occurs. | NOAA National Weather Service Glossary 2009 |
| Fracturing | Pressure process whereby ice is permanently deformed, and rupture oc- curs. Most commonly used to describe breaking across very close pack ice, compact pack ice, and consolidated pack ice. | WMO Sea Ice Nomenclature 2017 |
| Fracturing | Sea ice terminology that describes the pressure process whereby ice is permanently deformed, and rupture occurs. This term is most commonly used to describe the breaking across of very close ice, compact ice and consolidated ice. | Environment and Climate Change Canada 2014 |
| Fragmic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete units that are densely packed. | NSIDC accessed 2016 |
| Fragmic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete units that are densely packed | Van Everdingen International Permafrost Association 2005 |
| Fragmoidal cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete units that are coalescing. | NSIDC accessed 2016 |
| Fragmoidal cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete units that are coalescing | Van Everdingen International Permafrost Association 2005 |
| Fragmoidal cryogenic fabric | It is a micromorphological soil structure, which is the result of Freeze-Thaw Processes, and in which the units are either coalescent or with bridges, and the voids are planar. Such structures can be found in the Andes, associated with patterned ground. | Trombotto et al. 2014 |
| Frazil | Small needle-like ice crystals, typically 3 to 4 millimeters in diameter, suspended in water, that represent the first stages of sea ice growth; they merge under calm conditions to form thin sheets of ice on the surface, frazil crystals consist of nearly pure fresh water. | NSIDC accessed 2016 |
| Frazil | (Or frazil crystals; also called needle ice.) Ice crystals that form in supercooled water that is too turbulent to permit coagulation into sheet ice. This is most common in swiftly flowing streams, but is also found in a turbulent sea (where it is called lolly ice). It may accumulate as anchor ice on submerged objects obstructing the water flow. | AMS - glossary of meteorology |
| Frazil ice | Fine spicules, plates, or discoids of ice suspended in water. In rivers and lakes, frazil is formed in supercooled, turbulent water. | NOAA Glossary of Hydrologic Terms |
| Frazil ice | Fine spicules or plates of ice in suspension in water. | NSIDC accessed 2016 |
| Frazil ice | Fine spicules or plates of ice, suspended in water. Frazil ice formation represents the first stage of sea ice growth. The frazil crystals are usually suspended in the top few centimetres of the surface layer of the ocean and give the water an oily appearance. In the open ocean the crystals may form, or be stirred to a depth of several metres by wave-induced turbulence. | ASPECT 2012 |
| Frazil ice | Fine spicules or plates of ice, suspended in water. | Bushuyev 2004 |
| Frazil ice | Fine spicules, or plates of ice, suspended in water. | WMO Sea Ice Nomenclature 2017 |
| Frazil ice | In hydrologic terms, fine spicules, plates, or discoids of ice suspended in water. In rivers and lakes, frazil is formed in supercooled, turbulent water. | NOAA National Weather Service Glossary 2009 |
| Frazil ice | Sea ice terminology, meaning fine spicules or plates of ice suspended in water. | Environment and Climate Change Canada 2014 |
| Frazil ice | Accumulation of primary ice crystals in water and/or at the bottom of a water body, formed by supercooled turbulent waters. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Frazil ice | 1.An accumulation of frazil in a body of water. 2.The initial stage of ice formation in turbulent water. Frazil ice consists of platelets or discs roughly 1 mm in diameter. These small platelets clump together to form shuga, and eventually (if sufficient open water area exists) form pancake ice. Frazil ice may form in open water leads and around the ice margins in the Arctic, but it is most common in the Antarctic. It may also form in turbulent rivers in winter, particularly in rapids. | AMS - glossary of meteorology |
| Frazil ice | Fine spicules or plates of ice in suspension in water. | Illustrated Glossary of Snow and Ice |
| Frazil slush | An agglomerate of loosely packed frazil which floats or accumulates under the ice cover. | NOAA Glossary of Hydrologic Terms |
| Frazil slush | In hydrologic terms, an agglomerate of loosely packed frazil which floats or accumulates under the ice cover. | NOAA National Weather Service Glossary 2009 |
| Free water | Free water is that portion of the pore water that is free to move between interconnected pores under the influence of gravity | Van Everdingen International Permafrost Association 2005 |
| Free water | Free Water is that portion of the pore water that is free to move between interconnected pores under the influence of gravity. The term Free Water also covers water in fissures, solution channels, and other openings in soils or rocks. The temperature at which Free Water will change phase depends primarily on its dissolved-solids content, which determines the Freezing Point depression. | Trombotto et al. 2014 |
| Free water content of snow | Fraction by weight of liquid water which is contained in the interstices between snow grains, but is not bound to individual grains and is free to move by capillarity or gravity. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Freeboard | The elevation of the surface of a floating ice body above the surface of the water in which it is afloat. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Freeze | A freeze is when the surface air temperature is expected to be 32 | NOAA National Weather Service Glossary 2009 |
| Freeze | Change from a liquid to a solid. | Australian Bureau of Meteorology 2016 |
| Freeze | The condition that exists when, over a widespread area, the surface temperature of the air remains below freezing (0C) for a sufficient time to constitute the characteristic feature of the weather. This is a general term, and the time period necessary is usually considered to be two or more days; only the hardiest herbaceous crops survive. It differs from a dry freeze or black frost, for these terms are usually used to describe purely local freezing due to chilling of the surface air by rapid radiation from a restricted portion of the earth. | AMS - glossary of meteorology |
| Freeze probability curve | Statistical curve relating probability of first and last freeze (0C) occurrence in the fall and spring to specific dates; a tool to assess freeze risk. May be applied to other critical threshold temperatures such as -1C, -2C, -4C, etc. | AMS - glossary of meteorology |
| Freeze-free period | The period, usually expressed in days, between the last occurrence of freezing temperatures (0C) in the spring and the first occurrence in the autumn. | AMS - glossary of meteorology |
| Freeze-thaw cycle | Freezing of a material followed by thawing | Van Everdingen International Permafrost Association 2005 |
| Freeze-thaw cycle | Freezing of a material followed by thawing. Natural Freeze-Thaw Cycles consist of the freezing and subsequent thawing during a freezing season and the following thawing season. | Trombotto et al. 2014 |
| Freeze-thaw pattern | Pattern of alternating temperatures from above to below freezing causing freezing and thawing of upper soil layer, often resulting in damage to plant root systems, particularly small winter grains, most commonly observed with soils near saturation in surface layers. | AMS - glossary of meteorology |
| Freeze-up | Formation of ice cover on a water surface due to seasonal cooling. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Freeze-up | The seasonal formation of continuous ice cover on a body of water. | AMS - glossary of meteorology |
| Freezeback | Refreezing of thawed materials. | NSIDC accessed 2016 |
| Freezeback | Refreezing of thawed materials | Van Everdingen International Permafrost Association 2005 |
| Freezeback | Refreezing of thawed materials. This term is used to describe: 1) seasonal refreezing of the thawed Active Layer or 2) refreezing of soil thawed as a result of construction activity or drilling of a well in Permafrost, and of soil placed as backfill or a slurry around foundations or engineering facilities buried or embedded in Frozen Ground. | Trombotto et al. 2014 |
| Freezeup date | Date on which the water body was first observed to be completely frozen over. | NOAA Glossary of Hydrologic Terms |
| Freezing | The process by which a liquid changes phase into a solid; a synonym of solidification. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Freezing | 1.The phase transition of a substance passing from the liquid to the solid state; solidification; the opposite of fusion. In meteorology, this almost invariably applies to the freezing of water. The phase change from the gaseous to the solid state is deposition. Like condensation, the freezing of water involves the process of nucleation. See ice point, freezing point, true freezing point, melting point. 2.Said of an environment when its temperature is equal to or less than 0C (32F). | AMS - glossary of meteorology |
| Freezing | The change in state of matter from liquid to solid that occurs with cooling. Usually used in meteorology when discussing the formation of ice from liquid water. | PhysicalGeography.net |
| Freezing (of ground) | The changing of phase from water to ice in soil or rock. | NSIDC accessed 2016 |
| Freezing (of ground) | The changing of phase from water to ice in soil or rock | Van Everdingen International Permafrost Association 2005 |
| Freezing (of ground) | The changing of phase from water to Ice in soil or rock. The temperature at which ground freezing starts may be lower than 0C as a result of freezing-point depression through changes in the chemical composition of the water or soil (e.g. the presence of salt). | Trombotto et al. 2014 |
| Freezing degree-days | A measure of how cold it has been and how long it has been cold; the cumulative fdd is usually calculated as a sum of average daily degrees below freezing for a specified time period (10 days, month, season, etc.). | NSIDC accessed 2016 |
| Freezing drizzle | Drizzle, the drops of which freeze on impact with the ground or with objects at or near the ground. | Canada National Climate Archive 2015 |
| Freezing drizzle | Drizzle, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight. | NSIDC accessed 2016 |
| Freezing drizzle | A drizzle that falls as a liquid but freezes into glaze or rime upon contact with the cold ground or surface structures. | NOAA National Weather Service Glossary 2009 |
| Freezing drizzle | Drizzle that freezes on impact to form a coating of clear ice (glaze) on the ground and on exposed objects. | Environment and Climate Change Canada 2014 |
| Freezing drizzle | Drizzle that falls in liquid form but freezes upon impact to form a coating of glaze. In U.S. aviation weather observations, this hydrometeor is encoded ZL. The physical cause of this phenomenon is the same as that for freezing rain. | AMS - glossary of meteorology |
| Freezing drizzle | Drizzle, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight. | Illustrated Glossary of Snow and Ice |
| Freezing fog | A fog the droplets of which freeze upon contact with exposed objects and form a coating of rime and/or glaze. | AMS - glossary of meteorology |
| Freezing front | The advancing boundary between frozen (or partially frozen) ground and unfrozen ground. | NSIDC accessed 2016 |
| Freezing front | The advancing boundary between frozen (or partially frozen) ground and unfrozen ground | Van Everdingen International Permafrost Association 2005 |
| Freezing front | The advancing boundary between frozen (or partially frozen) ground and Unfrozen Ground. In the usual case, where the Active Layer extends to the Permafrost Table, two Freezing Fronts will be present during annual freezing of the ground, one moving downward from the ground surface, the other moving upward from the Permafrost Table. The Freezing Front may not coincide with the 0C isotherm (Cryofront) due to freezing-point depressions. | Trombotto et al. 2014 |
| Freezing index | The cumulative number of degree-days below 0 degrees Celsius for a given time period. | NSIDC accessed 2016 |
| Freezing index | A measure of the combined duration and magnitude of below freezing temperatures occurring during a specific freezing season and calculated by accumulating the number of degree-days below 0 degrees C and subtracting from that total the number of degree-days above 0 degrees C over the same period. | WMO METEOTERM accessed 2016 |
| Freezing index | The cumulative number of degree-days below 0°C for a given time period | Van Everdingen International Permafrost Association 2005 |
| Freezing index | As used by the U. S. Army Corps of Engineers, the number of Fahrenheit degree-days (above and below 32F) between the highest and lowest points on the cumulative degree-days time curve for one freezing season. For a critical review of the topic see Sakari Tuhkanen (1980). "The freezing index is used as a measure of the combined duration and magnitude of below freezing temperatures occurring during any given freezing season. The index determined for air temperatures at 4.5 feet above the ground is commonly designated as the air freezing index, while that determined for temperatures immediately below a surface is known as the surface freezing-index." (Also called "coldness sun.") | AMS - glossary of meteorology |
| Freezing index | The cumulative number of degree-days below 0C for a given time period. Four main types of air freezing indices have been used: Approximate Freezing Index - calculated from the mean monthly air temperatures for a specific station without making corrections for positive degree-days (T > 0C) in spring and fall (Boyd, 1979); I_af = SUM (NT) where N = number of days per month for months with a mean monthly temperature below 0C during one complete year. T= mean monthly temperature. Total annual Freezing Index - calculated by adding all the negative mean daily air temperatures (C) for a specific station during a calendar year (Harris, 1981); I_af = SUM (T) where T = mean daily air temperatures (C) below 0C for one complete calendar year. _ Seasonal Freezing Index - calculated as the arithmetic sum of all the negative and positive mean daily air temperatures (C) for a specific station during the time period between the highest point in the fall and the lowest point the next spring on the cumulative degree-day time curve (Huschke, 1959); I_af = SUM (T) where T = mean daily air temperatures (C) during the time period between the highest temperature in the Fall and the lowest temperature in the Spring. _ Design Freezing Index - calculated by taking the average of the seasonal freezing indices for the three coldest winters in the most recent 30 years of record. If data for 30 years are not available, then the index is based on the coldest winter in the latest 10-year period of record (U.S. Army/Air Force, 1966). | Trombotto et al. 2014 |
| Freezing level | The lowest level above a specific location where the temperature is 0 degrees C. | WMO METEOTERM accessed 2016 |
| Freezing level | Commonly, and in aviation terminology, the lowest altitude in the atmosphere, over a given location, at which the air temperature is 0C; the height of the 0C constant-temperature surface. This simple concept may become slightly complicated by the existence of one or more "above- freezing layers" formed by temperature inversions at altitudes higher than the above-defined freezing level. In cloud physics terminology, this is more accurately termed the melting level, for melting of ice always occurs very near 0C, but liquid cloud drops may remain supercooled to much colder temperatures. | AMS - glossary of meteorology |
| Freezing nucleus | Nucleus on which the freezing of water occurs. | WMO METEOTERM accessed 2016 |
| Freezing nucleus | Any particle immersed within supercooled water, initiating the growth of an ice crystal to be compared with particles nucleating directly from the vapor phase (deposition nucleus). Similar particles may nucleate at somewhat different temperatures (a few degrees) depending on the process. Observations of natural freezing nuclei indicate that there is normally present in the atmosphere a large variety of such particles with varying activation temperatures (temperatures at which they become effective nucleators). Certain bacteria from vegetation (pseudomonas syringae) nucleate ice at temperatures as high as -2C; mineral particles (e.g., clays: kaolinite and montmorillonite) at -10 to -20C; artificial nuclei (e.g., silver iodide, lead iodide, and metaldehyde), as smoke, can be found to nucleate at intermediate temperatures, i.e., -5 to -10C. The origin, distribution, and composition of these particles is highly variable; some are composed of a mixture with a hygroscopic component that dilutes prior to nucleation of the water by the freezing nucleus. | AMS - glossary of meteorology |
| Freezing point | The temperature at which a liquid solidifies under the influence of a particular set of conditions. | WMO METEOTERM accessed 2016 |
| Freezing point | (1) the temperature at which a pure liquid solidifies under atmospheric pressure (2) the temperature at which a ground material starts to freeze. | NSIDC accessed 2016 |
| Freezing point | The temperature at which a substance begins to solidify (see melting point). The freezing point of water is 273.15 K at an ambient pressure of 1013.25 hpa. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Freezing point | The temperature, equal to 273.15 K (0 degrees C) | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Freezing point | Temperature of solidification of a liquid under given conditions. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Freezing point | 1. The temperature at which a pure liquid solidifies under atmospheric pressure; 2. The temperature at which a ground material starts to freeze | Van Everdingen International Permafrost Association 2005 |
| Freezing point | 1. The temperature at which a pure liquid solidifies under atmospheric pressure. 2. The temperature at which a ground material starts to freeze. | Trombotto et al. 2014 |
| Freezing point | (Also called apparent freezing point.) The temperature at which a liquid solidifies under any given set of conditions. It may or may not be the same as the melting point or the more rigidly defined true freezing point or (for water) ice point. It is not an equilibrium property of a substance; it applies to the liquid phase only. The freezing point is somewhat dependent upon the purity of the liquid; the volume and shape of the liquid mass; the availability of freezing nuclei; and the pressure acting upon the liquid. The freezing point is a colligative property of a solution and becomes proportionately lower with an increasing amount of dissolved matter. Therefore, since natural water almost invariably contains some solutes, its freezing point is found to be slightly below 0C. For example, bulk samples of normal seawater freeze at about -1.9C (28.6F). | AMS - glossary of meteorology |
| Freezing precipitation | Precipitation drops freezing on impact to form a coating of clear ice (glaze) on the ground and on exposed objects. | WMO METEOTERM accessed 2016 |
| Freezing precipitation | Any form of liquid precipitation that freezes upon impact with the ground or exposed objects, that is, freezing rain, freezing drizzle, or freezing fog. | AMS - glossary of meteorology |
| Freezing pressure | The positive pressure developed at ice-water interfaces in soil as it freezes. | NSIDC accessed 2016 |
| Freezing pressure | The positive pressure developed at ice-water interfaces in a soil as it freezes | Van Everdingen International Permafrost Association 2005 |
| Freezing pressure | The positive pressure developed at ice-water interfaces in a soil as it freezes (freezing of in situ pore water - 9% expansion). It is also known to result in a heaving pressure or frost-heave pressure that is responsible for the heaving of utilities, foundations and pavements. Ice-water interfaces occur at the contact between Ice lenses and the Frozen Fringe. | Trombotto et al. 2014 |
| Freezing rain | Rain, the drops of which freeze on impact with the ground or with objects at or near the ground. | Canada National Climate Archive 2015 |
| Freezing rain | Rain, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight. | NSIDC accessed 2016 |
| Freezing rain | Rain that falls as a liquid but freezes into glaze upon contact with the ground. | NOAA National Weather Service Glossary 2009 |
| Freezing rain | Rain that freezes on impact to form a coating of clear ice (glaze) on the ground and on exposed objects. | Environment and Climate Change Canada 2014 |
| Freezing rain | Rain that freezes upon impact, forming a surface coating of glaze, or after percolating below the glacier surface. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Freezing rain | Supercooled raindrops which freeze on impact to form a coating of clear ice on the ground and/or on exposed objects. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Freezing rain | Rain that falls in liquid form but freezes upon impact to form a coating of glaze upon the ground and on exposed objects. In aviation weather observations, this hydrometeor is encoded ZR. While the temperature of the ground surface and glazed objects is typically near or below freezing (0C or 32F), it is necessary that the water drops be supercooled before striking. Freezing rain can sometimes occur on surfaces exposed to the air (such as tree limbs) with air temperatures slightly above freezing in strong winds. Local evaporational cooling may result in freezing. Freezing rain frequently occurs, therefore, as a transient condition between the occurrence of rain and ice pellets (sleet). When encountered by an aircraft in flight, freezing rain can cause a dangerous accretion of clear icing. | AMS - glossary of meteorology |
| Freezing rain | A type of precipitation. Occurs when liquid rain hits a cold surface and then immediately freezes into ice. For this to occur, a surface temperature inversion is usually required. In such an inversion, the surface must have a temperature below freezing, while the temperature of the atmosphere where the precipitation forms is above freezing. | PhysicalGeography.net |
| Freezing rain | Rain, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight. | Illustrated Glossary of Snow and Ice |
| Freezing season | As used by the U.S. Army Corps of Engineers, the period of time between the highest point and the succeeding lowest point on the time curve of cumulative degree-days above and below 32F; the opposite of thawing season. A less rigorous, but more commonly used, definition is the number of days or months between the first day of fall or winter and the last day of the same winter or the following spring on which the air temperature is below 0C. | AMS - glossary of meteorology |
| Freezing spray | An accumulation of freezing water droplets on a vessel caused by some appropriate combination of cold water, wind, cold air temperature, and vessel movement. | NOAA National Weather Service Glossary 2009 |
| Freezing spray | Freezing spray occurs when a combination of below freezing temperatures and strong winds, causes a wind-generated spray to freeze and accumulate (or build-up) on any marine infrastructure located in or near the vicinity of the water. | Environment and Climate Change Canada 2014 |
| Freezing spray | Sea spray transported through the air at temperatures below 0C. | AMS - glossary of meteorology |
| Freezing thaw action | Processes associated with daily and seasonal cycles of freezing and melting. | PhysicalGeography.net |
| Freezing-level chart | A synoptic chart showing the height of the 0C constant-temperature surface by means of contour lines. | AMS - glossary of meteorology |
| Freezing-point depression | The number of degrees by which the freezing point of an earth material is depressed below 0 degrees Celsius. | NSIDC accessed 2016 |
| Freezing-point depression | The number of degrees by which the freezing point of an earth material is depressed below 0°C | Van Everdingen International Permafrost Association 2005 |
| Freezup jam | Ice jam formed as frazil ice accumulates and thickens. | NOAA Glossary of Hydrologic Terms |
| Freezup jam | In hydrologic terms, ice jam formed as frazil ice accumulates and thickens. | NOAA National Weather Service Glossary 2009 |
| Friable permafrost | Permafrost in which the soil particles are not held together by ice. | NSIDC accessed 2016 |
| Friable permafrost | Permafrost in which the soil particles are not held together by ice | Van Everdingen International Permafrost Association 2005 |
| Friendly ice | From the point of view of the submariner, an icy canopy containing many large ice skylights or other features which permit a submarine to surface; there must be more than ten such features per 37 kilometers (30 nautical miles) along the submarine's track. | NSIDC accessed 2016 |
| Friendly ice | From the point of view of the submariner, an ice canopy containing many large skylights or other features that permit a submarine to surface. There must be more than ten such features per 30 n mi (56 km) along the submarine's track. | WMO Sea Ice Nomenclature 2017 |
| Friendly ice | Sea ice terminology that describes an ice canopy containing many large skylights or other features, which permits a submarine to surface. There must be more than 10 such features per 30 nautical miles (56 km) along the submarine's track. | Environment and Climate Change Canada 2014 |
| Friendly ice | From the point of view of the submariner, an ice canopy containing many large skylights or other features that permit a submarine to surface. There must be more than 10 such features per 56 km (30 nautical miles) along the submarine's track. | AMS - glossary of meteorology |
| Friendly ice | From the point of view of the submariner, an ice canopy containing many large ice skylights or other features which permit a submarine to surface. There must be more than ten such features per 30 nautical miles along the submarine's track. | Illustrated Glossary of Snow and Ice |
| Frigid zone | (Obsolete.) Based on an ancient climatic classification scheme using solar illumination geometry, the region poleward of the Arctic or Antarctic Circles (66 deg 33 min N and 66 deg 33 min S, respectively). | AMS - glossary of meteorology |
| Front | See glacier front. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Front of snow melting | Boundary that separates the area subject to snow melting from the area where snow melting has not started. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Frontal ablation | Loss of mass from a near-vertical glacier margin, such as a calving front. The processes of mass loss can include calving, subaerial melting and subaerial sublimation, and subaqueous frontal melting. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Frost | Frost is the condition that exists when the temperature of the air near the earth or earth-bound objects falls to freezing or lower (0 | Canada National Climate Archive 2015 |
| Frost | The condition which exists when the temperature near the earth's surface and earth-bound objects falls below freezing (0 degrees Celsius or 32 degrees Fahrenheit). | NSIDC accessed 2016 |
| Frost | (Abbrev. FRST) - Frost describes the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans. Frost develops under conditions similar to dew, except the temperatures of the Earth's surface and earthbound objects falls below 32 | NOAA National Weather Service Glossary 2009 |
| Frost | A deposit of ice crystals that forms through a process called sublimation. | Environment and Climate Change Canada 2014 |
| Frost | Deposit of soft white ice crystals or frozen dew drops on objects near the ground; formed when surface temperature falls below freezing point. | Australian Bureau of Meteorology 2016 |
| Frost | Covering by ice produced by the sublimation of water vapour on objects that are colder than 0 degrees Celsius. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Frost | The occurrence of air temperatures below 0°C | Van Everdingen International Permafrost Association 2005 |
| Frost | 1.The fuzzy layer of ice crystals on a cold object, such as a window or bridge, that forms by direct deposition of water vapor to solid ice. 2.The condition that exists when the temperature of the earth's surface and earthbound objects fall below freezing. Depending upon the actual values of ambient-air temperature, dewpoint, and the temperature attained by surface objects, frost may occur in a variety of forms. These include a general freeze, hoarfrost (or white frost), and dry freeze (or black frost). If a frost period is sufficiently severe to end the growing season (or delay its beginning), it is commonly referred to as a killing frost. See frost day, ground frost. | AMS - glossary of meteorology |
| Frost | Deposition of ice at the Earth's surface because of atmospheric cooling. | PhysicalGeography.net |
| Frost action | The process of alternate freezing and thawing of moisture in soil, rock and other materials, and the resulting effects on materials and on structures placed on, or in, the ground. | NSIDC accessed 2016 |
| Frost action | The process of alternate freezing and thawing of moisture in soil, rock and other materials, and the resulting effects on materials and on structures placed on, or in, the ground | Van Everdingen International Permafrost Association 2005 |
| Frost action | The process of alternate freezing and thawing of moisture in soil, rock and other materials, and the resulting effects on materials and on structures placed on, or in, the ground. Frost action in soils describes the processes of Frost Heave that occurs in the ground during the freezing period, and Thaw Weakening that occurs as the seasonally Frozen Ground thaws. Although it normally refers to seasonal freezing and thawing processes and effects, the term Frost action has also been used to describe the long-term heaving that occurs when soils are subjected continuously to a freezing temperature over a long period of time (years). Frost action contributes to the mechanical weathering (disintegration or breakdown) of soil and rock materials, by frost wedging, Cryoturbation activity, and to the development of cryotexture and cryogenic fabric in soils. | Trombotto et al. 2014 |
| Frost action | In general, cycles of freezing and thawing of water contained in natural or man-made materials. This is especially applied to the disruptive effects of this action. In geology, two basic types of frost action are described: 1) congelifraction, the shattering or splitting of rock material; and 2) congeliturbation, the churning, heaving, and thrusting of soil material. | AMS - glossary of meteorology |
| Frost belt | (Or frost dam.) A ditch constructed to assist the early and rapid freezing of the soil in order to block the seepage of subsurface flow from entering a critical area. | AMS - glossary of meteorology |
| Frost blister | A seasonal frost mound produced through doming of seasonally frozen ground by a subsurface accumulation of water under elevated hydraulic potential during progressive freezing of the active layer. | NSIDC accessed 2016 |
| Frost blister | A seasonal frost mound produced through doming of seasonally frozen ground by a subsurface accumulation of water under elevated hydraulic potential during progressive freezing of the active layer | Van Everdingen International Permafrost Association 2005 |
| Frost blister | A seasonal frost mound produced through doming of seasonally frozen ground by a subsurface accumulation of water under high hydraulic potential during progressive freezing of the active layer. | AMS - glossary of meteorology |
| Frost boil | A small mound of soil material, presumed to have been formed by frost action. | NSIDC accessed 2016 |
| Frost boil | A small mound of soil material, presumed to have been formed by frost action | Van Everdingen International Permafrost Association 2005 |
| Frost boil | 1.An accumulation of water and mud released from ground ice by spring thawing. 2.A small mound of fresh soil material, formed by frost action. | AMS - glossary of meteorology |
| Frost boil / mud boil | A small mound of soil material, presumed to have been formed by frost action. A type of nonsorted circle; they are commonly found in fine-grained sediments underlain by permafrost, but also occur in non-permafrost areas. | Trombotto et al. 2014 |
| Frost bulb | A more or less symmetrical zone of frozen ground formed around a buried chilled pipeline or beneath or around a structure maintained at temperatures below 0 degrees Celsius. | NSIDC accessed 2016 |
| Frost bulb | A more or less symmetrical zone of frozen ground formed around a buried chilled pipeline or beneath or around a structure maintained at temperatures below 0°C | Van Everdingen International Permafrost Association 2005 |
| Frost climate | The coldest temperature province in C. W. Thornthwaite's 1931 climatic classification. It is the climate of the ice cap regions of the earth, that is, those regions perennially covered with snow and ice. It is equivalent to the more commonly used term perpetual frost climate, to the colder of K?ppen's (1918) polar climates, and to Nordenskj?ld's (1928) high arctic climate. | AMS - glossary of meteorology |
| Frost creep | The net downslope displacement that occurs when a soil, during a freeze-thaw cycle, expands normal (perpendicular) to the ground surface and settles in a nearly vertical direction. | NSIDC accessed 2016 |
| Frost creep | The net downslope displacement that occurs when a soil, during a freeze-thaw cycle, expands normal to the ground surface and settles in a nearly vertical direction | Van Everdingen International Permafrost Association 2005 |
| Frost creep | The net downslope displacement that occurs when a soil, during a freeze-thaw cycle, expands normal to the ground surface and settles in a nearly vertical direction. | Trombotto et al. 2014 |
| Frost creep | Slow mass movement of soil downslope that is initiated by freeze-thaw action. Occurs where the stresses on the slope material are too small to create a rapid failure. | PhysicalGeography.net |
| Frost damage | Physiological damage to plants and plant tissues during occurrences of frost with temperatures generally below 3C. | AMS - glossary of meteorology |
| Frost day | An observational day on which frost occurs; one of a family of climatic indicators (e.g., thunderstorm day, rain day). The definition is somewhat arbitrary, depending upon the accepted criteria for a frost observation. Thus, it may be 1) a day on which the minimum air temperature in the thermometer shelter falls below 0C (32F); 2) a day on which a deposit of white frost is observed on the ground; 3) in British usage, a day on which the minimum temperature at the level of the ground or on the tops of low, close-growing vegetation falls to -0.9C (30.4F) or below (also called a "day with ground frost"); and perhaps others. The present trend is to drop such terms in favor of something less ambiguous, such as "day with minimum temperature below 0C (32F)." | AMS - glossary of meteorology |
| Frost depth | Depth into soil that frost has penetrated at any given time. | AMS - glossary of meteorology |
| Frost flowers | Crystals of ice that form when water vapor becomes a solid (bypassing the liquid phase) and deposits itself on the sea ice surface; frost flowers roughen the surface and dramatically affect its electromagnetic signal. | NSIDC accessed 2016 |
| Frost flowers | Growth of ice crystals by condensation from the atmosphere at points on the surface of young ice. After formation sea water may be drawn through the ice into the flowers. | Bushuyev 2004 |
| Frost free days | Number of frost free days is calculated based on the last occurrence of frost in spring and the first occurrence of frost in autumn. This is an especially important parameter for agriculture, because the variability in the number of frost free days is crucial for many agricultural activities such as planting and harvesting, but the impact of a strong frost can become an economic problem that affects the prices. | Canada National Climate Archive 2015 |
| Frost hazard | The risk of damage by frost. It may be expressed as the probability or frequency of killing frost on different dates during the growing season, or as the distribution of dates of the last killing frost of spring or the first of autumn. A strict application of the concept would take into account the actual species or group of plants that might potentially be killed, as different plants sustain frost damage at different temperatures. Wind-chill factors should also be considered. | AMS - glossary of meteorology |
| Frost heave | The upward or outward movement of the ground surface (or objects on, or in, the ground) caused by the formation of ice in the soil. | NSIDC accessed 2016 |
| Frost heave | The upward or outward movement of the ground surface (or objects on, or in, the ground) caused by the formation of ice in the soil | Van Everdingen International Permafrost Association 2005 |
| Frost heave | The upward or outward movement of the ground surface caused by the formation of Ice in the soil. Frost Action in fine-grained soils increases the volume of the soil not only by freezing of in situ pore water (9% expansion) but also by drawing water to the Freezing Front where Ice lenses form. Soils that have undergone substantial heaving may consist of alternate layers of Ice-saturated soil and relatively clear Ice lenses. The lenses are formed normal to the direction of heat flow and when freezing penetrates from the ground surface (which may be horizontal, sloping or vertical), they form parallel to that surface. When unrestrained, the amount of surface heave may be almost as much as the total thickness of the Ice lenses. Frost Heave can occur seasonally or continuously if freezing of the ground proceeds without interruption over a period of years. Differential, or non-uniform, frost heaving is one of the main aspects of the Frost Action process and reflects the heterogeneous nature of most soils, or variations in heat removal rate and groundwater supply over short distances. Depending on the degree of restraint, large Freezing Pressures (up to 1 MPa) can be developed as the ground freezes. | Trombotto et al. 2014 |
| Frost heave extent | The difference between the elevations of the ground surface before and after the occurrence of frost heave. | NSIDC accessed 2016 |
| Frost heaving | The upward or outward movement of the ground surface (or objects on, or in, the ground) caused by the formation of ice in the soil. | AMS - glossary of meteorology |
| Frost hollow | A local bowl-shaped region or depression in the surface in which, in suitable conditions, cold air accumulates during the night as the result of cold air drainage called katabatic wind. Such regions are subject to a greater incidence of frost, and to more severe frosts, than are the surrounding areas of nonconcave shape. (Also known as frost pocket in agricultural/gardening) | AMS - glossary of meteorology |
| Frost jacking | Cumulative upward displacement of objects embedded in the ground, caused by frost action. | NSIDC accessed 2016 |
| Frost jacking | Cumulative upward displacement of objects embedded in the ground, caused by frost action | Van Everdingen International Permafrost Association 2005 |
| Frost line | Maximum depth of frozen ground during the winter. The term may refer to an individual winter, to an average over a number of years, or to the greatest depth since observations began. The frost line varies with the nature of soil and the protection afforded by vegetal ground cover and snow cover, as well as with the amount of seasonal cooling. | AMS - glossary of meteorology |
| Frost mound | Any mound-shaped landform produced by ground freezing combined with accumulation of ground ice due to groundwater movement or the migration of soil moisture. | NSIDC accessed 2016 |
| Frost mound | Any mound-shaped landform produced by ground freezing combined with accumulation of ground ice due to groundwater movement or the migration of soil moisture | Van Everdingen International Permafrost Association 2005 |
| Frost mound | Any mound-shaped landform produced by ground freezing combined with Accumulation of Ground Ice due to groundwater movement or the migration of soil moisture. Various types of Frost Mounds, (e.g., frost blisters, icing blisters, palsas and Pingos) can be distinguished on the basis of their structure and duration, and the character of the Ice contained in them. | Trombotto et al. 2014 |
| Frost mound | A conical mound on a land surface, caused by the freezing of water in the ground. It is a product of frost heaving, but is unusual in that it requires a great concentration of water in a relatively small subsurface volume. Usually a frost mound is of seasonal duration. (Also called ice mound, ground ice mound.) | AMS - glossary of meteorology |
| Frost penetration | The movement of the freezing front into the ground during freezing. | NSIDC accessed 2016 |
| Frost penetration | The movement of the freezing front into the ground during freezing | Van Everdingen International Permafrost Association 2005 |
| Frost penetration | The movement of the Freezing Front into the ground during freezing. | Trombotto et al. 2014 |
| Frost phenomena | Effects of frost action on earth materials and on structures placed in or on the ground. | NSIDC accessed 2016 |
| Frost phenomena | Effects on earth materials and on structures placed in or on the ground, resulting from frost action | Van Everdingen International Permafrost Association 2005 |
| Frost point | The highest temperature at which atmospheric moisture will sublimate in the form of hoarfrost on a cooled surface; it is analogous to the dew point. | NSIDC accessed 2016 |
| Frost point | Is the temperature at which water vapor saturates from an air mass into solid usually forming snow or frost. Frost point normally occurs when a mass of air has a relative humidity of 100%. | PhysicalGeography.net |
| Frost point hygrometer | An instrument similar to the dewpoint hygrometer, but especially suited for low frost points. The strong cooling necessary for these measurements is provided either by multistage Peltier devices or by evaporating low-boiling-point (cryogenic) fluids like liquid nitrogen. Using this technique, frost points down to -100C can be measured. Electrical resistance wires are used to provide heating. | AMS - glossary of meteorology |
| Frost protection | Methods of a passive or active nature that serve to reduce the damage to plants during a frost period. Passive methods include variety selection, site selection, and planting date. Active methods include heaters, fans, flooding, sprinkling, windbreaks, mulching, etc. | AMS - glossary of meteorology |
| Frost ring | A false annual growth ring in the trunk of a tree, due to out-of-season defoliation by frost and subsequent regrowth of foliage. A frost ring is identified by a thin light ring within the annual growth ring. | AMS - glossary of meteorology |
| Frost shattering | The mechanical disintegration of rock by the pressure of water freezing in pores and along grain boundaries. | NSIDC accessed 2016 |
| Frost shattering | The mechanical disintegration of rock by the pressure of the freezing of water in pores and along grain boundaries | Van Everdingen International Permafrost Association 2005 |
| Frost shattering | The mechanical disintegration of rock by the pressure of the freezing of water in pores and along grain boundaries. Freezing of the water drawn between the grains by various particle surface forces exerts sufficient differential pressure to loosen and separate the grains. Frost Shattering may be the dominant weathering process in high mountain regions, particularly in areas with frequent Freeze-Thaw Cycles and heavily jointed and weak rock types. | Trombotto et al. 2014 |
| Frost smoke | Fog-like clouds, due to the contact of cold air with relatively warm water, which appear over newly-formed leads, or leeward of the ice edge, and which may persist while new ice is forming. | NSIDC accessed 2016 |
| Frost smoke | Sea ice terminology that describes fog-like clouds that are formed when cold air and relatively warm water come in contact with each other. Frost smoke can appear over openings in the ice or leeward of the ice edge, and may persist while ice is forming. | Environment and Climate Change Canada 2014 |
| Frost smoke | A rare type of fog formed in the same manner as a steam fog, but at colder temperatures so that it is composed of ice particles instead of water droplets. Thus, it is a type of ice fog. (Sometimes called barber.) | AMS - glossary of meteorology |
| Frost smoke | Fog-like clouds, due to the contact of cold air with relatively warm water, which appear over newly-formed leads, or leeward of the ice edge, and which may persist while new ice is forming. | Illustrated Glossary of Snow and Ice |
| Frost sorting | The differential movement of soil particles of different sizes as a result of frost action. | NSIDC accessed 2016 |
| Frost sorting | The differential movement of soil particles of different size ranges as a result of frost action | Van Everdingen International Permafrost Association 2005 |
| Frost sorting | The differential movement of soil particles of different size ranges as a result of Frost Action. | Trombotto et al. 2014 |
| Frost table | An irregular surface in the ground that, at any given time, represents the penetration of thawing into seasonally frozen ground. In regions of permafrost, when the active layer is thawed completely, this coincides with the permafrost table. | AMS - glossary of meteorology |
| Frost weathering | The disintegration and break-up of soil or rock by the combined action of frost shattering, frost wedging and hydration shattering. | NSIDC accessed 2016 |
| Frost weathering | The disintegration and break-up of soil or rock by the combined action of frost shattering, frost wedging and hydration shattering | Van Everdingen International Permafrost Association 2005 |
| Frost weathering | The disintegration and break-up of soil or rock by the combined action of Frost Shattering, frost wedging and hydration shattering. Hydration shattering is the process of grain loosening and soil or rock disintegration by the wedging pressure of water in films of varying thickness on the surfaces of silicate minerals. The process can act in all climates without the aid of freezing and thawing. When combined with freezing and thawing (Frost Shattering and frost wedging), however, the resulting process of Frost Weathering can be a very efficient mechanism for the break-up of soil or rock. | Trombotto et al. 2014 |
| Frost wedging | The mechanical disintegration, splitting or break-up of rock by the pressure of water freezing in cracks, crevices, pores, joints or bedding planes. | NSIDC accessed 2016 |
| Frost wedging | The mechanical disintegration, splitting or break-up of rock by the pressure of the freezing of water in cracks, crevices, pores, joints or bedding planes | Van Everdingen International Permafrost Association 2005 |
| Frost wedging | A process of physical weathering in which water freezes in a crack and exerts force on the rock causing further rupture. | PhysicalGeography.net |
| Frost zone | The layer of ground subject to seasonal freezing. In regions of permafrost, this corresponds to the active layer. | AMS - glossary of meteorology |
| Frost-free season | The period, usually expressed in days, between the last observed occurrence of frost in the spring and the first observed occurrence of frost in the autumn. | AMS - glossary of meteorology |
| Frost-heave extent | The difference between the elevations of the ground surface before and after the occurrence of frost heave | Van Everdingen International Permafrost Association 2005 |
| Frost-stable ground | Ground (soil or rock) in which little or no segregated ice forms during seasonal freezing. | NSIDC accessed 2016 |
| Frost-stable ground | Ground (soil or rock) in which little or no segregated ice forms during seasonal freezing | Van Everdingen International Permafrost Association 2005 |
| Frost-stable soil | Soil in which little or no segregated ice forms during seasonal freezing. | NSIDC accessed 2016 |
| Frost-stable soil | Soil in which little or no segregated ice forms during seasonal freezing | Van Everdingen International Permafrost Association 2005 |
| Frost-susceptible ground | Ground (soil or rock) in which segregated ice will form (causing frost heave) under the required conditions of moisture supply and temperature. | NSIDC accessed 2016 |
| Frost-susceptible ground | Ground (soil or rock) in which segregated ice will form (causing frost heave) under the required conditions of moisture supply and temperature | Van Everdingen International Permafrost Association 2005 |
| Frost-susceptible soil | Soil in which segregated ice will form (causing frost heave) under the required conditions of moisture supply and temperature. | NSIDC accessed 2016 |
| Frost-susceptible soil | Soil in which segregated ice will form (causing frost heave) under the required conditions of moisture supply and temperature | Van Everdingen International Permafrost Association 2005 |
| Frostburn | Damage to skin tissue resulting from contact of bare skin with metal surfaces at below- freezing temperatures. | AMS - glossary of meteorology |
| Frostless zone | That warmest part of a slope above a valley floor lying between the layer of cold air that forms over the valley floor on calm, clear nights and the cold hilltops or plateaus. The air flowing down the slopes is warmed by mixing with the air above ground level and to some extent also by adiabatic compression. The frostless zone is not a fixed belt but varies in level from night to night and season to season according to the initial temperature, the length of the night, and the clearness of the sky. Its lower limit is sometimes clearly marked by the upper limit of frost damage to crops, following the hillsides at a small angle to the horizontal. (Also called thermal belt, thermal zone, green belt, verdant zone.) | AMS - glossary of meteorology |
| Frozen fringe | The zone in a freezing, frost-susceptible soil between the warmest isotherm at which ice exists in pores and the isotherm at which the warmest ice lens is growing. | NSIDC accessed 2016 |
| Frozen fringe | The zone in a freezing, frost-susceptible soil between the warmest isotherm at which ice exists in pores and the isotherm at which the warmest ice lens is growing | Van Everdingen International Permafrost Association 2005 |
| Frozen fringe | The zone in a freezing, frost-susceptible soil between the warmest isotherm at which Ice exists in pores and the isotherm at which the warmest Ice lens is growing. | Trombotto et al. 2014 |
| Frozen ground | Soil or rock in which part or all of the pore water has turned into ice. | NSIDC accessed 2016 |
| Frozen ground | Soil or rock in which part or all of the pore water is frozen. Frozen ground includes permafrost. Ground that freezes and thaws annually is called seasonally frozen ground. | IPCC WGI AR5 2013 |
| Frozen ground | Soil or rock in which part or all of the pore water has turned into ice | Van Everdingen International Permafrost Association 2005 |
| Frozen ground | Soil or rock in which part or all of the pore water has turned into Ice. Perennially and seasonally Frozen Ground can vary from being partially to extensively frozen depending on the extent of the phase change. It may be described as hard Frozen Ground, plastic Frozen Ground, or dry Frozen Ground, depending on the Pore Ice and unfrozen water contents and its compressibility under load. Hard-frozen soils are firmly cemented by Ice, are subject to brittle failure, and exhibit practically no consolidation under load. Plastic-frozen soils are cemented by Ice but have viscous properties due to their high unfrozen water content and therefore will compress and deform under load. Dry, or friable-frozen, soils have a very low total water content and are not cemented by Ice; their compressibility is the same as for unfrozen soils having the same composition, total water content and density. | Trombotto et al. 2014 |
| Frozen ground | Soil within which the moisture has predominantly changed to ice, the unfrozen portion being in vapor phase. Ice within the soil bonds (adfreezes) adjacent soil particles and renders frozen ground very hard. "Permanently" frozen ground is called permafrost. "Dry" frozen ground is relatively loose and crumbly because of the lack of bonding ice. Frozen ground is sometimes inadvisedly called frost or ground frost. | AMS - glossary of meteorology |
| Frozen precipitation | Any form of precipitation that reaches the ground in frozen form, that is, snow, snow pellets, snow grains, ice crystals, ice pellets, and hail. | AMS - glossary of meteorology |
| Frozen talus slopes | Slope, formed by rocks and blocks of considerable thickness. Massive or interstitial ice can result in gravity driven creep deformations. These slopes may be associated with other creeping landforms, such as Rock Glaciers or Gelifluction slopes. | Trombotto et al. 2014 |
| Funicular regime | (of water) The condition of high liquid water content where liquid exists in continuous paths covering the ice structure; grain-to-grain bonds are weak. The volume fraction of free water exceeds 8 %, i.e., the wetness index is 3. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Fusion | The phase transition of a substance passing from the solid to the liquid state, melting; in meteorology, fusion is understood to refer to the melting of ice, which, if the ice is pure and subjected to one standard atmosphere of pressure, takes place at the ice point of 0 degrees Celsius (32 degrees Fahrenheit). | NSIDC accessed 2016 |
| Fusion | The process by which a solid changes phase into a liquid; a synonym of melting. See latent heat of fusion. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Gamma survey of snow cover | Remote measurement of the water equivalent of snow from the attenuation of the Earth's natural gamma-radiation through the snow cover. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Gamma-ray snow gauge | Instrument which uses a source of gamma radiation positioned on a surface underlying a snow cover to measure the amount of radiation absorbed by the snow and hence determine the water content of the snow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Gamma-ray snow gauge | An instrument designed to determine the water content of snow by measuring the amount of gamma radiation absorbed by the snow overlying the transmitter that is placed at the surface. Because the earth naturally emits gamma radiation, by the same concept, aircraft measurements of gamma radiation can be used to estimate the water content of snow on the ground along the aircraft's flight path. | AMS - glossary of meteorology |
| Gap wind | A strong, low-level wind through either a relatively level channel between two mountain ranges or a gap in a mountain barrier; originally applied to strong (10-20 m/s) easterly winds through the Strait of Juan de Fuca between the Olympic Mountains of western Washington State and the mountains of Vancouver Island, British Columbia, Canada. There they have been defined as "a flow of air in a sea level channel that accelerates under the influence of a pressure gradient parallel to the axis of the channel." As in the case of mountain- gap winds, this term has also been applied to pressure-gradient winds accelerating through a gap in a mountain barrier. The pressure gradient often results from a stable, post-cold-frontal anticyclone approaching the barrier and being partially blocked (see blocking) as it ascends the barrier, except for the flow through the gap or channel. The tehuantepecer of Central America is a well- known gap wind by this definition. These flows have sometimes been referred to as jet-effect wind and canyon wind. | AMS - glossary of meteorology |
| Gaps | Elevated areas around clasts that form by Frost Action. | Trombotto et al. 2014 |
| Gas hydrate | A special form of solid clathrate compound in which crystal lattice cages or chambers, consisting of host molecules, enclose guest molecules | Van Everdingen International Permafrost Association 2005 |
| Gelifluction | The slow downslope flow of unfrozen earth materials on a frozen substrate. | NSIDC accessed 2016 |
| Gelifluction | The slow downslope flow of unfrozen earth materials on a frozen substrate | Van Everdingen International Permafrost Association 2005 |
| Gelifluction | The slow downslope flow of unfrozen earth materials on a frozen substrate. Gelifluction is a type of Solifluction implying the presence of either Seasonal Frost or Permafrost. | Trombotto et al. 2014 |
| Gelifluction | Form of mass movement in periglacial environment where a permafrost layer exists. It is characterized by the movement of soil material over the permafrost layer and the formation of lobe-shaped features. Also see solifluction. | PhysicalGeography.net |
| Gelisols | Soil order (type) of the United States Natural Resources Conservation Service Soil Classification System. This soil is common to high latitude tundra environments. The main identifying feature of this soil is a layer of permafrost within one meter of the soil surface. | PhysicalGeography.net |
| Geocryology | The study of earth materials having a temperature below 0 degrees Celsius. | NSIDC accessed 2016 |
| Geocryology | The study of earth materials having a temperature below 0°C | Van Everdingen International Permafrost Association 2005 |
| Geocryology | The study of earth materials including rock at temperatures below 0C. It is the science that studies the environment and ecology of cold regions, the natural, geological, physical and chemical processes related to the freezing-thawing cycles, and the relationship with Permafrost and human activities. | Trombotto et al. 2014 |
| Geodetic method | Any method for determining mass balance by repeated mapping of glacier surface elevations to estimate the volume balance; cartographic method and topographic method are synonyms. The conversion of elevation change to mass balance requires information on the density of the mass lost or gained, or an assumption about the time variations in density (see Sorge's law). Elevation changes are commonly measured using repeated altimetry, photogrammetry or ground surveys. In the past, glacier mapping relied on ground surveying with theodolites and similar instruments, but global navigation satellite system receivers are now usual, offering more rapid and more accurate coverage. The entire glacier surface may be mapped, but more sparse elevation measurements, for example along a central flowline, are often extrapolated to the full glacier surface. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Geostationary satellite | A satellite that orbits the earth at the same rate that the earth rotates, and as a result remains over a fixed place above the equator. | Environment and Climate Change Canada 2014 |
| Geothermal gradient | The rate of temperature increase with depth in the subsurface | Van Everdingen International Permafrost Association 2005 |
| Geothermal heat flux | The amount of heat moving steadily outward from the interior of the earth through a unit area in unit time | Van Everdingen International Permafrost Association 2005 |
| Geyser | Fountain that develops when water from a conduit is forced up to the surface of a glacier; also called a negative mill. | NSIDC accessed 2016 |
| Gla?on | Very generally, a piece of sea ice that is smaller than a medium-sized floe. | AMS - glossary of meteorology |
| Glacial | 1.Pertaining to ice, especially in great masses, such as sheets of land ice or glaciers. 2.Pertaining to an interval of geologic time that was marked by an equatorward advance of ice during an ice age; the opposite of interglacial phase. These intervals are variously called glacial periods, glacial epochs, glacial "stages," etc. | AMS - glossary of meteorology |
| Glacial | (1) Period of time during an ice age when glaciers advance because of colder temperatures. (2) Involving glaciers and moving ice. Usually pertaining to processes associated with glaciers. | PhysicalGeography.net |
| Glacial advance | When a mountain glacier's terminus extends farther downvalley than before; occurs when a glacier flows downvalley faster than the rate of ablation at its terminus. | NSIDC accessed 2016 |
| Glacial advance | Glacial advance is the net movement of glacier terminus downvalley. Advance occurs when the rate of glacier flow downvalley is greater than its rate of ablation. Advances are characterized by a convex-shaped terminus. | Molnia USGS 2004 |
| Glacial anticyclone | A type of semipermanent anticyclone that has been said to overlie the ice caps of Greenland and Antarctica. As presented by W. H. Hobbs, it was thought that these anticyclones played a dominant part in the world atmospheric circulation, but modern theory backed by limited observation has tended to diminish their importance and even to question their reality. (Or glacial high.) | AMS - glossary of meteorology |
| Glacial drift | Glacial drift is the loose and unsorted rock debris distributed by glaciers and glacial meltwaters. As glaciers melt, their remaining load of rocks is distributed in several ways. Rocks may be dropped in place by the melting ice; they may be rolled to the ice margins, or they may be deposited by meltwater streams. Collectively, these deposits are called 'glacial drift'. 'Till' refers to the debris deposited directly by the glacier. Rock debris rolls off the glacier edges and builds piles of loose unconsolidated rocks called 'glacier moraine'. 'Lateral moraines' form along the side of a glacier and curl into a 'terminal moraine' at the glacier's downvalley end. Drift and moraines are valuable to geologists because they outline the boundaries of past glaciations. | Molnia USGS 2004 |
| Glacial drift | All rock material in transport by glacial ice, and all deposits predominantly of glacial origin made in the sea or in bodies of glacial meltwater, including rocks rafted by icebergs. "Glacial drift occurs as scattered rock fragments, as till [rocks mixed with finer material], and as outwash [fine material with no rocks]. Contrast with angular drift."(from Glossary of Arctic and Subarctic Terms 1955). | AMS - glossary of meteorology |
| Glacial drift | A generic term applied to all glacial and glaciofluvial deposits. | PhysicalGeography.net |
| Glacial environment | This is the environment where Glaciers are located. It often includes unglaciated mountain peaks, called nunataks. Glaciers, Ice Caps, icefields and other surface Snow and Ice form an frozen water system that interacts with the atmosphere and hydrosphere. Glacial environments are characterized by a suite of distinct geomorphic processes and their associated landforms. | Trombotto et al. 2014 |
| Glacial epoch | (1) Any of the geological epochs characterised by an ice age. Thus the Pleistocene may be termed a glacial epoch. (2) Generally an interval of geological time which was marked by a major equatorward advance of ice. It applies to an entire ice age or, rarely, to the individual glacial stages which make up an ice age. | WMO METEOTERM accessed 2016 |
| Glacial epoch | 1.Any of the geologic epochs characterized by an ice age. Thus, the Pleistocene epoch may be termed a "glacial epoch." 2.Generally, an interval of geologic time that was marked by a major equatorward advance of ice. This has been applied to an entire ice age or (rarely) to the individual glacial "stages" that make up an ice age. The term "epoch" here is not used in the most technical sense of a geologic epoch. | AMS - glossary of meteorology |
| Glacial erratic | A boulder swept from its place of origin by glacier advance or retreat and deposited elsewhere as the glacier melted; after glacial melt, the boulder might be stranded in a field or forest where no other rocks of its type or size exist. | NSIDC accessed 2016 |
| Glacial flour | Glacial flour is the fine-grained sediment carried by glacial rivers that results from the abrasion of rock at the glacier bed. Its presence turns lake water aqua blue or brown, depending on its parent rock type. Rivers originating beneath glaciers are choked with glacial flour, the silty fine-grained sediment produced by the abrasion of rocks at the glacier bed. | Molnia USGS 2004 |
| Glacial geology | The study of land features resulting from glaciation. | AMS - glossary of meteorology |
| Glacial groove/Glacial furrow | A linear depression, inches to miles in length, produced by the removal of rock or sediment by the erosive action of a glacier. | Molnia USGS 2004 |
| Glacial grooves | Grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial striations. | NSIDC accessed 2016 |
| Glacial hydrology | Branch of hydrology which deals with the origin, processes and regime of liquid water in a glacial system. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glacial ice | A very dense form frozen water that is much harder than snow, nv, or firn. | PhysicalGeography.net |
| Glacial interstade | An interval (literally a stage) of time characterized by an equatorward spread of ice (of shorter duration than a glacial epoch). | WMO METEOTERM accessed 2016 |
| Glacial isostatic adjustment (GIA) | A change of glacier surface elevation due to vertical motion of the glacier bed under the influence of mass redistribution in the underlying solid Earth. Present-day mass redistribution in the Earth's interior is dominated by continuing adjustment to the redistribution of surface water at the end of the most recent ice age. Corrections are also required for vertical motions of tectonic origin in some regions, such as the Karakoram. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacial isostatic adjustment (GIA) | The deformation of the Earth and its gravity field due to the response of the earth-ocean system to changes in ice and associated water loads. It is sometimes referred to as glacio-hydro isostasy. It includes vertical and horizontal deformations of the Earth's surface and changes in geoid due to the redistribution of mass during the ice-ocean mass exchange. | IPCC WGI AR5 2013 |
| Glacial lake | An accumulation of standing liquid water on (supraglacial), in (englacial), or under (subglacial) a glacier. | Molnia USGS 2004 |
| Glacial lake | A natural impoundment of meltwater at the front of a glacier. | PhysicalGeography.net |
| Glacial lake outburst flood (GLOF) | During a period of glacier recession, back from a terminal moraine, a lake may form. This lake is impounded by an unstable pile of debris and buried ice. Catastrophic failure of the moraine will result in a devastating flood. Usually associated with high mountain regions such as the Andes and Himalaya. | Swisseduc - Photo glossary of glaciological terms |
| Glacial maximum | The time of greatest ice volume and/or position of greatest areal extent of any glacierization. | AMS - glossary of meteorology |
| Glacial milk | Term used to describe glacial meltwater which has a light colored or cloudy appearance because of clay-sized sediment held in suspension. | PhysicalGeography.net |
| Glacial mudflow | Mudflow caused by the melting of snow and ice on a glacier, by a glacial outburst or by the instability of morainic deposits. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glacial outburst | Sudden emptying of a glacial-dammed lake. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glacial outburst floods | Glacial outburst floods are sudden outbursts of water released by a glacier. The water may be released from glacier cavities, sub-glacial lakes, and from glacier-dammed lakes in side valleys. Also known as 'J | Molnia USGS 2004 |
| Glacial period | 1.Any of the geologic periods that embraced an ice age. For example, the Quaternary period may be called a "glacial period." 2.Generally, an interval of geologic time that was marked by a major equatorward advance of ice. This may be applied to an entire ice age or (rarely) to the individual glacier "stages" that make up an ice age. The term "period" here is not used in the most technical sense of a geologic period. | AMS - glossary of meteorology |
| Glacial phase | Period, during an ice age, marked by a major equatorward advance of ice. | WMO METEOTERM accessed 2016 |
| Glacial polish | Glacial polish is the leveling and smoothing of rock by fine-grained debris at the glacier bed. Glacier ice alone is too soft to be a powerful rock-cutting agent. Many glaciers are armed with rock fragments embedded within the ice that are effective cutting tools. The rock-choked ice grazes over the glacier bed, removign rock obstacles and leaving the bedrock rounded and smoothed. In some places fine-grained debris polishes the bedrock to a lustrous surface finish called glacial polish. Coarser rocks may gouge scratches called striations. | Molnia USGS 2004 |
| Glacial polish | The abrasion of bedrock surfaces by materials carried on the bottom of a glacier. This process leaves these surfaces smooth and shiny. | PhysicalGeography.net |
| Glacial rebound | Vertical raising of a portion of the earth's crust following the removal of an ice mass. Glacial rebound is the reaction to deglaciation. | AMS - glossary of meteorology |
| Glacial retreat | When the position of a mountain glacier's terminus is farther upvalley than before; occurs when a glacier ablates more material at its terminus than it transports into that region. | NSIDC accessed 2016 |
| Glacial retreat | Glacial retreat is the net movement of the glacier terminus upvalley. Retreat results when the glacier is ablating at a rate faster than its movement downvalley. Retreating termini are usually concave in shape. | Molnia USGS 2004 |
| Glacial retreat | The backwards movement of the snout of a glacier. | PhysicalGeography.net |
| Glacial stream | A channelized accumulation of liquid water on (supraglacial), in (englacial), or under (subglacial) a glacier, moving under the influence of gravity. | Molnia USGS 2004 |
| Glacial striations | Grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial grooves. | NSIDC accessed 2016 |
| Glacial surge | A rapid forward movement of the snout of a glacier. | PhysicalGeography.net |
| Glacial till | Accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders; the usual composition of a moraine. | NSIDC accessed 2016 |
| Glacial till | Glacial till - an unsorted, unstratified mixture of fine and coarse rock debris deposited by a glacier. As glaciers melt, their remaining load of rocks is distributed in several ways. Rocks may be dropped in place by the melting ice; they may be rolled to the ice margins, or they may be deposited by meltwater streams. Collectively, these deposits are called 'glacial drift'. 'Till' refers to the debris deposited directly by the glacier. Rock debris rolls off the glacier edges and builds piles of loose unconsolidated rocks called 'glacier moraine'. 'Lateral moraines' form along the side of a glacier and curl into a 'terminal moraine' at the glacier's downvalley end. Drift and moraines are valuable to geologists because they outline the boundaries of past glaciations. | Molnia USGS 2004 |
| Glacial trough | A large u-shaped valley formed from a v-shaped valley by glacial erosion. | NSIDC accessed 2016 |
| Glacial trough | A glaciated valley or fjord (q.v.), often characterised by steep sides and a flat bottom, with multiple basins, resulting primarily from erosion by strongly channelled ice. | Swisseduc - Photo glossary of glaciological terms |
| Glacial trough | Large area, such as those in the Alps, carved out to depths of hundreds to thousands of meters by the erosive action of glaciers. | AMS - glossary of meteorology |
| Glacial trough | A deep U-shaped valley with steep valley walls that was formed from glacial erosion. At the base of many of these valleys are cirques. | PhysicalGeography.net |
| Glacial uplift | Upward movement of the Earth's crust following isostatic depression from the weight of the continental glaciers. | PhysicalGeography.net |
| Glacial valley | Valley that was influenced by the presence of glaciers. The cross-section of such valleys tends to be U-shaped because of glacial erosion. Similar to glacial trough. | PhysicalGeography.net |
| Glacial-interglacial cycles | Phase of the Earth's history marked by large changes in continental ice volume and global sea level. See also Ice age and Interglacials. | IPCC WGI AR5 2013 |
| Glaciated | Land covered in the past by any form of glacier is said to be glaciated. | NSIDC accessed 2016 |
| Glaciated | Covered by glacier ice in the past, but not at present. See glacierized, which refers to present-day coverage. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glaciated | Land presently or formerly covered by any form of Glacier is said to be Glaciated. | Trombotto et al. 2014 |
| Glaciated | The character of land that was once covered by glacier ice in the past (cf. glacierised). | Swisseduc - Photo glossary of glaciological terms |
| Glaciated | Land covered in the past by any form of glacier is said to be glaciated (cf. Ice covered). | Illustrated Glossary of Snow and Ice |
| Glaciation | Transformation of cloud droplets into ice crystals, e.g. as occurring in the upper portion of a cumulonimbus. | WMO METEOTERM accessed 2016 |
| Glaciation | The transformation of cloud particles from water drops to ice crystals. Thus, a cumulonimbus cloud is said to have a 'glaciated' upper portion. | NOAA National Weather Service Glossary 2009 |
| Glaciation | 1.Alteration of any part of the earth's surface by passage of a glacier, chiefly by glacial erosion or deposition; distinguish from glacierization. 2.As used in many texts, particularly with respect to the ice ages, same as glacierization, for example, "Pleistocene glaciation." 3.The transformation of cloud particles from supercooled water drops to ice crystals. Thus, a cumulonimbus cloud is said to have a glaciated upper portion. | AMS - glossary of meteorology |
| Glaciation level | In any small glacierized region, the average of the elevations of the highest unglacierized peak and the lowest glacierized peak. The glaciation level has been used as a regional-scale proxy for the steady-state ELA, although a correction is required for this purpose because the glaciation level is known to be systematically higher by about 200 m. See mid-range altitude. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glaciation limit | A less-used synonym of glaciation level. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glaciation limit | 1.For a given locality, the lowest altitude at which glaciers can develop. 2.Same as glacial maximum. | AMS - glossary of meteorology |
| Glacier | Bodies of land ice that consist of recrystallized snow accumulated on the surface of the ground, and that move slowly downslope. | NOAA Glossary of Hydrologic Terms |
| Glacier | A large, perennial accumulation of ice, snow, rock, sediment and liquid water originating on land and moving down slope under the influence of its own weight and gravity; a dynamic river of ice. Glaciers are classified by their size, location, and thermal regime. | Molnia USGS 2004 |
| Glacier | A mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer; many believe that a glacier must show some type of movement; others believe that a glacier can show evidence of past or present movement. | NSIDC accessed 2016 |
| Glacier | A glacier is a body of ice showing evidence of movement as reported by the presence of ice flowline, crevasses, and recent geologic evidence. | Molnia USGS 2004 |
| Glacier | A mass of ice predominantly of atmospheric origin, usually moving from higher to lower ground. A seaward margin of a glacier that is aground, the rock basement being at or below sea-level, is termed an ice wall. The projecting seaward extension of a glacier, which is usually afloat, is termed a glacier tongue. In the Antarctic, glacier tongues may extend over many tens of kilometers. | Bushuyev 2004 |
| Glacier | A mass of snow and ice continuously moving from higher to lower ground or, if afloat, continuously spreading. The principal forms of glacier are inland ice sheets, ice shelves, ice streams, icecaps, ice piedmonts, cirque (half-bowl) glaciers, and various types of mountain (valley) glaciers. | WMO Sea Ice Nomenclature 2017 |
| Glacier | A perennial mass of ice, and possibly firn and snow, originating on the land surface by the recrystallization of snow or other forms of solid precipitation and showing evidence of past or present flow. For mass-balance purposes glaciers are delineated, when possible, by outlines across which there is no flow, so that transfer of mass as ice across those outlines is zero. Any change of the outline during the study period must be allowed for appropriately. If part of the outline fails the no-flow test, such as at a grounding line, the ice discharge must be included as a component of the mass balance. In contrast to what is natural in dynamic glaciology and glacial geomorphology, for mass-balance purposes the glacier consists only of frozen water. Sediment carried by the glacier is deemed to be outside the glacier. Meltwater in transit or in storage, for example in supraglacial lakes or subglacial cavities, is also regarded as being outside the glacier. Glaciers may contain or consist of other glaciers. The more generic term glacier complex is available for objects that may be divisible into more than one glacier, and the term ice body is available for any object that is made mainly of ice and may or may not be a glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier | In hydrologic terms, bodies of land ice that consist of recrystallized snow accumulated on the surface of the ground, and that move slowly downslope. | NOAA National Weather Service Glossary 2009 |
| Glacier | Sea ice terminology. Describes a mass of snow and ice that is continuously moving from higher to lower ground or, if afloat, continuously spreading. The principal forms of glaciers are: inland ice sheets, ice shelves, ice streams, ice caps, ice piedmonts, cirque glaciers, and various types of mountain (valley) glaciers. | Environment and Climate Change Canada 2014 |
| Glacier | Mass of snow and ice moving continuously from higher to lower ground or, if afloat, continuously spreading. In the broad sense, glaciers include ice caps, ice piedmonts, ice rises, ice shelves, ice streams and snowfields, but in place-names the term is restricted to features of valleys or cirques. | UK Antarctic Place-names Committee accessed 2016 |
| Glacier | A perennial mass of land ice that originates from compressed snow, shows evidence of past or present flow (through internal deformation and/or sliding at the base) and is constrained by internal stress and friction at the base and sides. A glacier is maintained by accumulation of snow at high altitudes, balanced by melting at low altitudes and/or discharge into the sea. An ice mass of the same origin as glaciers, but of continental size, is called an ice sheet. For the purpose of simplicity in this Assessment Report, all ice masses other than ice sheets are referred to as glaciers. See also Equilibrium line and Mass balance/budget (of glaciers or ice sheets). | IPCC WGI AR5 2013 |
| Glacier | Accumulation of ice with an atmospheric origin which usually moves slowly on land over a long period. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glacier | A mass of Ice that originates on land, usually having an area larger than one tenth of a square kilometre (10 ha). Many authors believe that a Glacier must show some type of movement or signs of deformation; others believe that a Glacier can show evidence of past or present movement. Principle forms of Glaciers are: Ice Sheets, ice shelves, Ice Caps, icefields, ice streams, piedmont Glaciers, and various types of mountain Glaciers. Outlet Glacier: Drains an ice sheet, ice field or ice cap, usually of valley glacier form; the catchment area may not be clearly delineated. Valley Glacier: Flows down a valley; the catchment area is well defined. Mountain glacier: Cirque, niche or crater type, hanging glacier; includes ice aprons and groups of small units. Glacieret and Snow Patches: Small ice masses of indefinite shape in hollows, river beds and on protected slopes, which has developed from snow drifting, avalanching and/or especially heavy accumulation in certain years; usually no marked flow pattern is visible; exists for at least two consecutive summers. | Trombotto et al. 2014 |
| Glacier | A mass of ice, irrespective of size, derived largely from snow, and continuously moving from higher to lower ground. | Swisseduc - Photo glossary of glaciological terms |
| Glacier | A mass of land ice, formed by the further recrystallization of firn, flowing continuously from higher to lower elevations. This term covers all such ice accumulations from the extensive continental glacier to tiny snowdrift glaciers. Nearly all glaciers are classified according to the topographical features with which they are associated, for example, highland glacier, plateau glacier, piedmont glacier, valley glacier, cirque glacier. They are also classified according to their seasonal temperatures, or melting characteristics, as temperate glaciers or polar glaciers. If a glacier is flowing, it is active or living; but an active glacier may be advancing or retreating depending upon the rate of flow compared to the rate of ablation at the terminus. A glacier that has ceased to flow is termed stagnant or dead. | AMS - glossary of meteorology |
| Glacier | A large long lasting accumulation of snow and ice that develops on land. Most glaciers flow along topographic gradients because of their weight and gravity. | PhysicalGeography.net |
| Glacier | A mass of snow and ice continuously moving from higher to lower ground or, if afloat, continuously spreading. The principle forms of glaciers are: ice sheets, ice shelves, ice caps, ice piedmonts, and various types of mountain glacier. | Illustrated Glossary of Snow and Ice |
| Glacier | A glacier or perennial snow mass, identified by a single GLIMS glacier ID, consists of a body of ice and snow that is observed at the end of the melt season, or, in the case of tropical glaciers, after transient snow melts. This includes, at a minimum, all tributaries and connected feeders that contribute ice to the main glacier, plus all debris-covered parts of it. Excluded is all exposed ground, including nunataks. An ice shelf (see item 9 below) shall be considered as a separate glacier. The following consequences and observations must be kept in mind: 1. Bodies of ice above the bergschrund that are connected to the glacier shall be considered part of the glacier, because they contribute snow (through avalanches) and ice (through creep flow) to the glacier. 2. A tributary in a glacier system that has historically been treated (and named) as a separate glacier should, within the GLIMS framework, be included as part of the glacier into which it flows. The name field for the glacier should be populated with all relevant names of tributaries. 3. Any steep rock walls that avalanche snow onto a glacier but do not retain snow themselves are NOT included as part of the glacier. 4. A stagnant ice mass still in contact with a glacier is part of the glacier, even if it supports an old-growth forest. 5. All debris-covered parts of the glacier must be included. 6. If no flow takes place between separate parts of a continuous ice mass, they should, in general, be treated as separate units, separated at the topographic divide. However, for practical purposes, such an ice mass may be analyzed as a unit at the analyst's discretion, if delineation of the flow divides is impossible or impractical. If the same system is analyzed in the same way later, it will have the same glacier ID, and can therefore be compared. If the system is analyzed in more detail later by breaking it into its component glaciers, those pieces will get new IDs (ID of system will be parent icemass ID for each part), and future analyses of those pieces, if done in the same way, will be comparable. 7. It is possible that an ice body that is detached from another may still contribute mass to the latter through ice avalanches, or it may no longer do so. It is practically impossible to tell which is the case from a single satellite image. Therefore, within GLIMS, adjacent but detached ice areas should, in general, be considered as different glaciers , regardless of whether they contribute mass to the main glacier through snow or ice avalanches. However, at the analyst's discretion, detached ice masses may be included as parts of one glacier. This is similar to the situation described in 5 above. If the pieces are analyzed separately later, each piece should be given a new GLIMS ID, the old one being used as the parent icemass ID for all the pieces. 8. Regarding the lower parts of lateral snowfields, whose extent varies from year to year, map only at the end of the ablation period, preferably in a year without snow outside of the glaciers, to exclude seasonal snow. Then map everything that is connected to the glacier. If snowfields are identifiable, they should be disconnected from the main glacier. For hydrological purposes they can be included in the GLIMS Glacier Database under a separate GLIMS glacier ID, but they must be marked as a snowfield. Lateral glacier outlines that might be hidden by seasonal snow or by avalanches should be labeled as preliminary, or even the entire glacier can be excluded. Ice avalanche cones below a glacier terminus (drycalving) are not a part of the glacier. 9. An ice shelf is typically ice downstream of the grounding zone of two or more glaciers that is floating on ocean water (e.g. the Getz Ice Shelf in Antarctica). Ice masses that form via direct accumulation at the surface, without significant ice input from the land surface (e.g. the Wilkins Ice Shelf), are also considered ice shelves. Ice tongues: floating ice extending from a single glacier (e.g. the Drygalski Ice Tongue) ? are not considered ice shelves, and should be considered part of the glacier to which they are attached. 10.Rock glaciers and heavily debris-covered glaciers tend to look similar, but their geneses are different. GLIMS does not currently deal with the former, but does include the latter. | GLIMS analysis tutorial |
| Glacier advance | The forward movement of the snout (toe) of a glacier following successive years of positive mass balance (q.v.). | Swisseduc - Photo glossary of glaciological terms |
| Glacier bed | Bedrock, or debris, over which the glacier flows. | Swisseduc - Photo glossary of glaciological terms |
| Glacier berg | An irregularly shaped iceberg. | WMO Sea Ice Nomenclature 2017 |
| Glacier berg | An irregularly shaped iceberg. | Bushuyev 2004 |
| Glacier breeze | Shallow wind which blows, by day and night, down the slopes of a glacier. | WMO METEOTERM accessed 2016 |
| Glacier cave | A cave of ice, usually underneath a glacier and formed by meltwater; cave entrances are often enlarged near a glacier terminus by warm winds; most common on stagnant portions of glaciers. | NSIDC accessed 2016 |
| Glacier cave | A cave formed in or under a glacier, typically by running water. Steam or high heat flow can also form glacier caves. Also called Ice Cave. | Molnia USGS 2004 |
| Glacier cave | A cave formed in or under a glacier, typically by running water. Steam or high heat flow can also form glacier caves. Also called Ice Cave. | Molnia USGS 2004 |
| Glacier complex | A number of contiguous glaciers; a generic term for all collections of glaciers that meet at divides. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier dammed lake | The lake formed when a glacier flows across the mouth of an adjoining valley and forms an ice dam. | NOAA Glossary of Hydrologic Terms |
| Glacier dammed lake | In hydrologic terms, the lake formed when a glacier flows across the mouth of an adjoining valley and forms an ice dam. | NOAA National Weather Service Glossary 2009 |
| Glacier dammed lake | Body of water which accumulates behind ice sheets or in mountain valleys dammed by valley glaciers. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glacier fire | A phenomenon in which strong reflection of the sun on an icy surface causes a glacier to look like it is on fire. | NSIDC accessed 2016 |
| Glacier flea | The glacier flea (Desoria saltans) is a hexapod from the class of springtails. It is 1,5 to 2,5mm long, lives on Alpine glaciers where it occasionally occurs in great numbers. Its main food source is cryoconite. When disturbed, glacier fleas can escape by means of a dorsal appendix which lets them jump a considerable distance. This lead to their common name although they are not fleas, but Collembolans (springtails). Various sugars protect them fom freezing, even at temperatures between -10 to -15 C. Their preferred ambient temperature ist 0 C. | Swisseduc - Photo glossary of glaciological terms |
| Glacier flood | A sudden outburst of water released by a glacier. | NSIDC accessed 2016 |
| Glacier flood | Sudden outburst of water released by a glacier. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glacier flood | A sudden release of substantial amounts of meltwater from a glacier. | AMS - glossary of meteorology |
| Glacier flood | A sudden outburst of water released by a glacier. | Illustrated Glossary of Snow and Ice |
| Glacier flour | A fine powder of silt- and clay-sized particles that a glacier creates as its rock-laden ice scrapes over bedrock; usually flushed out in meltwater streams and causes water to look powdery gray; lakes and oceans that fill with glacier flour may develop a banded appearance; also called rock flour. | NSIDC accessed 2016 |
| Glacier flow | The movement of ice in a glacier, typically in a downward and outward direction, caused by the force of gravity. 'Normal' flow rates are in feet per day. 'Rapid' flow rates (i.e. surge) are in 10s or 100s of feet per day. | Molnia USGS 2004 |
| Glacier flow | The movement of ice caused by gravitational force. | AMS - glossary of meteorology |
| Glacier fluctuations | Glacier changes with time, such as changes of length, area, thickness, volume and mass. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier forebay | The water in front of a calving glacier into which icebergs are discharged. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier forefield | An unglacierized area abutting on a glacier margin. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier front | The terminus of the glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier front | The leading edge of a glacier. (Also called glacier terminus.) | AMS - glossary of meteorology |
| Glacier ice | Well-bonded ice crystals compacted from snow with a bulk density greater than 860 kilograms per cubic-meter (55 pounds per cubic-foot). | NSIDC accessed 2016 |
| Glacier ice | A mono-mineralic type of rock, composed of crystals of the mineral ice, formed through metamorphism of snowflakes. Metamorphism results in recrystallization, increased density, and the growth of hexagonal crystals. This ice comprises the majority of the mass of a glacier. Intermediate stages include Firn and Neve. | Molnia USGS 2004 |
| Glacier ice | (1) Ice that is part of a glacier, as opposed to other forms of frozen water such as ground ice and sea ice. (2) Ice that is part of a glacier, having formed by the compaction and recrystallization of snow to a point at which few of the remaining voids are connected, and having survived at least one ablation season. In this more restricted sense, the term refers to the body of the glacier, excluding not only snow and firn but also superimposed ice, accreted ice and marine ice. See zone. The density at which voids cease to form a connected network, that is, the density at which firn becomes glacier ice, is conventionally taken to be near to 830 kg m-3. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier ice | Ice in, or originating from, a glacier, whether on land or floating on the sea as icebergs, bergy bits, or growlers. | WMO Sea Ice Nomenclature 2017 |
| Glacier ice | Snowflakes are compressed under the weight of the overlying snowpack. Individual crystal near the melting point have slick liquid edges allowing them to glide along other crystal planes and to readjust the space between them. Where the crystals touch they bond together, squeezing the air between them to the surface or into bubbles. During summer we might see the crystal metamorphosis occur more rapidly because of water percolation between the crystals. By summer's end the result is firn -- a compacted snow with the appearance of wet sugar, but with a hardness that makes it resistant to all but the most dedicated snow shovelers! Several years are usually required for the snow to settle and to season into the substance we call glacier ice. Above the firnline, snow that falls each year packs down and changes into glacier ice as air is slowly forced out of it. | Molnia USGS 2004 |
| Glacier ice | Ice in, or originating from, a glacier, whether on land or floating on the sea as icebergs, bergy bits or growlers. | Bushuyev 2004 |
| Glacier ice | Sea ice terminology that describes ice in or originating from a glacier, whether on land or floating on the sea as icebergs, bergy bits, growlers or ice islands. | Environment and Climate Change Canada 2014 |
| Glacier ice | Any ice in, or originating from, a glacier, whether on land or floating on the sea as icebergs. | Swisseduc - Photo glossary of glaciological terms |
| Glacier ice | Any ice that is or was once a part of a glacier. It has been consolidated from firn by further melting and refreezing and by static pressure. Firn becomes glacier ice once the pockets of air between individual ice grains are no longer interconnected. Glacier ice may be found in the sea as an iceberg. | AMS - glossary of meteorology |
| Glacier ice | Any ice in, or originating from, a glacier,whether on land or floating in the sea as icebergs. | Illustrated Glossary of Snow and Ice |
| Glacier inventory | A detailed record of the attributes of the glaciers in a region. See World Glacier Inventory. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier karst | Debris-covered stagnant ice, sometimes found at the snout of a retreating glacier, with numerous lake-bearing caverns and tunnels. | Swisseduc - Photo glossary of glaciological terms |
| Glacier lake | (1) Temporary lake on the surface of a glacier. (2) Lake upstream from morainic deposits. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glacier margin | The line separating the glacier from ice-free terrain. See divide, glacier outline, boundary, terminus. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier milk | Turbid water of a stream issuing from under a glacier. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glacier milk | Meltwater from a glacier, which commonly has a milky appearance from suspended fine sediment. | Swisseduc - Photo glossary of glaciological terms |
| Glacier mill | A nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses. | NSIDC accessed 2016 |
| Glacier moraine | As glaciers melt, their remaining load of rocks is distributed in several ways. Rocks may be dropped in place by the melting ice; they may be rolled to the ice margins, or they may be deposited by meltwater streams. Collectively, these deposits are called 'glacial drift'. 'Till' refers to the debris deposited directly by the glacier. Rock debris rolls off the glacier edges and builds piles of loose unconsolidated rocks called 'glacier moraine'. 'Lateral moraines' form along the side of a glacier and curl into a 'terminal moraine' at the glacier's downvalley end. Drift and moraines are valuable to geologists because they outline the boundaries of past glaciations. | Molnia USGS 2004 |
| Glacier outline | The line in horizontal space separating the glacier from unglacierized terrain or, at divides, from contiguous glaciers. See glacier margin, boundary. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier pot-hole | A deep and more or less vertical hole in a glacier. Glacier pot-holes drain away surface melt-water. | Illustrated Glossary of Snow and Ice |
| Glacier pothole | Potholes formed at the bottom of glaciers through erosion caused by sand and gravel in melt-water; melt-water seeps through crevasses in the glaciers, sometimes forming whirlpools; at the bottom of the glacier, the water is under very high pressure, leading to erosion of underlying rocks. | NSIDC accessed 2016 |
| Glacier recession | The shrinking of the snout (toe) of a glacier following successive years of negative mass balance (q.v.). This is usually evident from the recession of the ice margin on land, or calving in the sea, but also from down-wasting. Also referred to by the term glacier retreat. | Swisseduc - Photo glossary of glaciological terms |
| Glacier remainie | A glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier, then re-adhering; also called reconstituted, reconstructed or regenerated glacier. | NSIDC accessed 2016 |
| Glacier retreat | see glacier recession: The shrinking of the snout (toe) of a glacier following successive years of negative mass balance (q.v.). This is usually evident from the recession of the ice margin on land, or calving in the sea, but also from down-wasting. Also referred to by the term glacier retreat. | Swisseduc - Photo glossary of glaciological terms |
| Glacier snout | The lowest end of a glacier; also called glacier terminus or toe. | NSIDC accessed 2016 |
| Glacier snout | The terminus is the downvalley end of a glacier. It is sometimes referred to as the glacier snout. | Molnia USGS 2004 |
| Glacier sole | The bottom of the ice of a glacier. | NSIDC accessed 2016 |
| Glacier sole | The lower few metres of a (usually sliding) glacier that contain debris picked up from the bed. | Swisseduc - Photo glossary of glaciological terms |
| Glacier table | A rock that resides on a pedestal of ice; formed by differential ablation between the rock-covered ice and surrounding bare ice. | NSIDC accessed 2016 |
| Glacier table | A rock that is balanced on a pedestal of ice, and elevated above the surface of a glacier. The rock protects the pedestal of ice from melting by insulating it from the sun. | Molnia USGS 2004 |
| Glacier table | A rock that rests on a pedestal of ice formed when ablation of the ice beneath the rock is less than ablation of the surrounding bare ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacier table | A boulder perched on a pedestal of ice. The boulder protects the ice from ablation during sunny weather. Around the boulder the ice surface ablates and, therefore, is lowered, whereas the boulder remains at the original level. While the pedestal becomes higher and higher in relation to the glacier surface, the sun shines further under the boulder from the south (in the northern hemisphere). Consequently the pedestal gets ablated on its southern side, and the boulder will eventually fall off the pedestal, usually on its southern side (in the northern hemisphere). After this a new cycle of table growth and destruction may begin. | Swisseduc - Photo glossary of glaciological terms |
| Glacier terminus | The lowest end of a glacier; also called glacier snout or toe. | NSIDC accessed 2016 |
| Glacier terminus | Lowest end of a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Glacier toe | The lowest end of a glacier; also called glacier snout or terminus. | NSIDC accessed 2016 |
| Glacier tongue | An extension of a glacier or ice stream projecting seaward, usually afloat. | NSIDC accessed 2016 |
| Glacier tongue | Projecting seaward extension of a glacier, usually afloat. | WMO Sea Ice Nomenclature 2017 |
| Glacier tongue | Sea ice terminology that describes the seaward extension of a glacier, usually afloat. In the Antarctic, glacier tongues may extend over many tens of kilometres. | Environment and Climate Change Canada 2014 |
| Glacier tongue | An extension of a glacier or ice stream projecting seaward, usually afloat. | UK Antarctic Place-names Committee accessed 2016 |
| Glacier tongue | The long slender part of a valley glacier that is subject to net ablation. | Swisseduc - Photo glossary of glaciological terms |
| Glacier tongue | An extension of a glacier or ice stream projecting seaward, usually afloat. | AMS - glossary of meteorology |
| Glacier tongue | An extension of a glacier or ice stream projecting seaward, usually afloat. | Illustrated Glossary of Snow and Ice |
| Glacier trough | U-shaped valleys transformed from v-shaped stream valleys due to erosion caused by passing glaciers. | NSIDC accessed 2016 |
| Glacier wind | A localized current of air occurring as a result of a glacier's melting processes; when the surface of glacial ice melts, the air above the glacier cools and becomes heavier than the surrounding air and flows down the glacial valley; glacier wind can also be wind that flows out of ice caves; a kind of katabatic wind. | NSIDC accessed 2016 |
| Glacier wind | A shallow downslope wind above the surface of a glacier, caused by the temperature difference between the air in contact with the glacier and the free air at the same altitude. The glacier wind does not reverse diurnally like slope and along-valley wind systems. | NOAA National Weather Service Glossary 2009 |
| Glacier wind | A shallow gravity wind, along the icy surface of a glacier, caused by the temperature difference between the air in contact with the glacier and free air at the same altitude. The glacier wind does not reverse itself diurnally as do mountain and valley winds, but it reaches its maximum intensity in the early afternoon. The glacier wind is characterized by strongly turbulent flow. See katabatic wind. (Or glacier breeze.) | AMS - glossary of meteorology |
| Glacier-wide | Descriptive of a quantity that, whether or not it is expressed in specific units, has been measured or estimated over the entire glacier. The adjective is used to emphasize that the mass balance is that of the entire glacier and not that at a 'specific' location (for which the recommended term is point mass balance). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacieret | A very small glacier. | NSIDC accessed 2016 |
| Glacieret | A very small glacier, typically less than 0.25 km2 in extent, with no marked flow pattern visible at the surface. To qualify as a glacieret, an ice body must persist for at least two consecutive years. Glacierets can be of any shape, and usually occupy sheltered parts of the landscape. Windborne snow and avalanches can be dominant contributors to the accumulation of glacierets. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glacieret and snowfield | Very small ice or snow masses; Virtually no ice movement; Accumulation and ablation area not always clearly detectable; Small ice masses of indefinite shape in hollows, river beds and on protected slopes, which has developed from snow drifting, avalanching and/or especially heavy accumulation in certain years; usually no marked flow pattern is visible, exist for at least two consecutive years; Hard to detect by remote sensing analysis, due to size and short term changes in the appearance | Illustrated GLIMS Glacier Classification Manual |
| Glacierised | The character of land currently covered by glacier ice (cf. Glaciated). | Swisseduc - Photo glossary of glaciological terms |
| Glacierization | The covering of a land area by glacier ice. This term was coined by G. Taylor in the Antarctic and introduced by Wright and Priestly (1922) to distinguish the act of glacial inundation from its geologic consequences (glaciation). It is growing in use in Great Britain but still is considered unnecessary by some American geologists, who use "glacier covering." | AMS - glossary of meteorology |
| Glacierized | Land overlaid at present by a glacier is said to be covered; the alternative term glacierized has not found general favour. | NSIDC accessed 2016 |
| Glacierized | Of a region or terrain, containing glaciers or covered by glacier ice today. See glaciated, which refers to past coverage. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glaciofluvial | Geomorphic feature whose origin is related to the processes associated with glacial meltwater. | PhysicalGeography.net |
| Glaciological method | A method of determining mass balance in-situ on the glacier surface by measurements of accumulation and ablation, generally including measurements at stakes and in snow pits; direct method has long been a synonym. The measurements may also rely on depth probing and density sampling of the snow and firn, and coring. They are made at single points, the results from a number of points being extrapolated and integrated to yield the surface mass balance over a larger area such as an elevation band or the entire glacier. The internal mass balance and basal mass balance, and ice discharge if any, are treated separately. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glaciological noise | In an ice core, fluctuations in layer thicknesses that are due not to variations in the rate of spatially averaged Annual accumulation but to redistribution of snow by the wind, including the migration of snow dunes and sastrugi across the core site. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glaciology | Science dealing with the properties and occurrence of ice, ice accumulation and ice action in all its forms. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Glaciology | The study of snow and ice on the earth's surface. It includes the study of glaciers, snow, and sea ice. | AMS - glossary of meteorology |
| Glare ice | Any highly reflective sheet of ice on water, land, or glacier. | AMS - glossary of meteorology |
| Glaze | A coating of ice, generally clear and smooth but usually containing some air pockets, formed on exposed objects by freezing of a film of super-cooled water deposited by rain, drizzle, fog, or possibly condensed from super-cooled water vapor ; glaze is denser, harder and more transparent, than either rime or hoarfrost. | NSIDC accessed 2016 |
| Glaze | (1) A solid surface deposit formed by the freezing of supercooled raindrops or possibly of condensed water vapour, distinguished from rime by having a density near that of ice. See also hoar. In this sense, glaze represents accumulation. (2) A surface deposit of ice formed by a short episode of melting that results only in recrystallization and not in percolation and is followed by a return to sub-freezing temperatures. In this sense, glaze is largely responsible for the creation of the summer surface. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Glaze | A coating of ice, generally clear and smooth, formed on exposed objects by the freezing of a film of supercooled water deposited by rain, drizzle, fog, or possibly condensed from supercooled water vapour. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Glaze | A coating of ice, generally clear and smooth, formed on exposed objects by the freezing of a film of supercooled water deposited by rain, drizzle, fog, or possibly condensed from supercooled water vapor. Glaze is denser, harder, and more transparent than either rime or hoarfrost. Its density may be as high as 0.8 or 0.9 g/cm^3. Factors that favor glaze formation are large drop size, rapid accretion, slight supercooling, and slow dissipation of heat of fusion. The opposite effects favor rime formation. The accretion of glaze on terrestrial objects constitutes an ice storm; as a type of aircraft icing it is called clear ice. Glaze, as well as rime, may form on ice particles in the atmosphere. Ordinary hail is composed entirely (or nearly so) of glaze; the alternating clear and opaque layers of some hailstones represent glaze and rime, deposited under varying conditions around the growing hailstone. (Also called glaze ice, glazed frost, verglas.) | AMS - glossary of meteorology |
| Glaze | Coating of ice that forms when rain falls on a surface with a temperature below freezing. | PhysicalGeography.net |
| Glaze | A generally homogeneous and transparent deposit of ice formed by the freezing of supercooled drizzle droplets or raindrops on objects the surface temperature of which is below or slightly above 0 C. It may also be produced by the freezing of non-supercooled drizzle droplets or raindrops immediately after impact with surfaces the temperature of which is well below 0 C. | Illustrated Glossary of Snow and Ice |
| Glazed surface | A multi-layered structure found in polar regions and consisting of single snow-grain layers cemented by thin (0.1 mm) films of regelation ice. The regelation ice films form on the surface following the kinetic heating of saltating drift snow under constantly strong katabatic wind flow. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Global warming | An overall increase in world temperatures which may be caused by additional heat being trapped by greenhouse gases. | NOAA National Weather Service Glossary 2009 |
| Grain | (1) with respect to both shape and size of snow grains, the same as particle, i.e., the smallest characteristic subunit of snow microstructure recognizable with a hand lens (8-10x magnification). (2) One single crystal of ice making up the ice structure of snow. The crystal orientation is continuous across each individual grain. Several grains together form a polycrystal having grain boundaries where crystal orientation changes. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Grain bond | The interconnection between snow particles, most often neck-like and located around grain boundaries (see grain). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Grain size | The classical grain size E of a snow layer is the average size of its grains. The size of
a grain or particle is its greatest extension measured in millimetres. Alternatively, E
can be expressed by using the terms 'very fine', 'fine', 'medium', 'coarse', 'very coarse', 'extreme'. Some users will want to also specify the average maximum size Emax or even a distribution of sizes. Note that grain size must be regarded as a property of the snow layer and not of the grain shape or shapes. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Grains of ice | Frozen raindrops or almost completely melted and refrozen snowflakes. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Grains of ice | A British term for ice pellets (sleet). Sleet, in turn, has a different meaning in Great Britain than it does in the United States. In British terminology, sleet is precipitation in the form of a mixture of rain and snow. | AMS - glossary of meteorology |
| Granic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete loosely packed units. | NSIDC accessed 2016 |
| Granic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete loosely packed units | Van Everdingen International Permafrost Association 2005 |
| Granoidic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form more or less discrete loosely packed units. | NSIDC accessed 2016 |
| Granoidic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form more or less discrete loosely packed units | Van Everdingen International Permafrost Association 2005 |
| Graupel | Snowflakes that become rounded pellets due to riming; typical sizes are 2 to 5 millimeters in diameter (0.1 to 0.2 inch); graupel is sometimes mistaken for hail. | NSIDC accessed 2016 |
| Graupel | Same as snow pellets or small hail. | NOAA National Weather Service Glossary 2009 |
| Graupel | Heavily rimed snow particles, often called snow pellets; often indistinguishable from very small soft hail except for the size convention that hail must have a diameter greater than 5 mm. Sometimes distinguished by shape into conical, hexagonal, and lump (irregular) graupel. | AMS - glossary of meteorology |
| Graupel | A type of precipitation that consists of a snow crystal and a raindrop frozen together. Also called snow pellets. | PhysicalGeography.net |
| Gravimetric (total) water content | The ratio of the mass of the water and ice in a sample to the dry mass of the sample, commonly expressed as a percentage | Van Everdingen International Permafrost Association 2005 |
| Gravimetric (total) water content | The ratio of the mass of the water and Ice in a sample to the dry mass of the sample, commonly expressed as a percentage. Because of the way it is defined, the gravimetric total water content can greatly exceed 100%. During thawing of a sample of Frozen Ground the gravimetric total water content remains constant, unless excess water is allowed to drain out of the sample. | Trombotto et al. 2014 |
| Gravimetric method | A technique in which glacier mass variations are calculated from direct measurements of Earth's gravity field. Satellite gravimetry is at present the most feasible method for determining glacier mass balance from changes in gravity. The Gravity Recovery and Climate Experiment (GRACE) consists of two polar-orbiting satellites separated by about 200 km along-track, and is the primary mission for this work to date. Precise measurements of range and range rate are used to construct local gravity fields after correcting for non-gravitational accelerations. Suitable models are used to remove gravity variations resulting from atmospheric, hydrospheric and lithospheric mass variations, leaving a time series that represents the glacier mass balance (usually summed and shown as the cumulative mass balance). GRACE spatial and temporal resolutions as good as 2 arc degrees and 10 days have been achieved. Satellite gravimetry is limited by the quality of observations used to constrain the models of non-glacial mass variations, and at present it can resolve only large and rapidly changing glacier complexes or glacierized regions. A distinctive advantage of the method is that it yields a direct measure of mass and does not require density corrections such as those required for geodetic methods. Glacier mass balance has also been estimated using ground-based gravimeters. Measurements at two or more times yield the change in absolute gravity that results from the change in vertical position of a sensor on the glacier surface or at a fixed position above it, and from changes in glacier mass. This technique may become more widely developed as gravimeter resolution, precision and portability improve. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Gray ice | Young ice 4 to 6 in (10-15 cm) thick. Less elastic than nilas and breaks on swell. Usually rafts under pressure. | WMO Sea Ice Nomenclature 2017 |
| Gray ice | Young ice 10-15 cm thick, less elastic than nilas. | AMS - glossary of meteorology |
| Gray-white ice | Young ice 6 to 12 in (15-30 cm) thick. Under pressure more likely to ridge than to raft. | WMO Sea Ice Nomenclature 2017 |
| Grease ice | A very thin, soupy layer of frazil crystals clumped together, which makes the ocean surface resemble an oil slick. | NSIDC accessed 2016 |
| Grease ice | A later stage of freezing than frazil ice when the crystals have coagulated to form a soupy layer on the surface. Grease ice reflects little light, giving the surface a matt appearance. Grease ice behaves in a viscous fluid-like manner, and does not form distinct ice floes. | ASPECT 2012 |
| Grease ice | A later stage of freezing than frazil ice when the crystals have coagulated to form a soupy layer on the surface. Grease ice reflects little light, giving the sea a matt appearance. | Bushuyev 2004 |
| Grease ice | A later stage of freezing than frazil ice. It occurs when the crystals have coagulated to form a soupy layer on the surface. Grease ice reflects little light, giving the sea a matte appearance. | WMO Sea Ice Nomenclature 2017 |
| Grease ice | Sea ice terminology which describes a later stage of freezing than frazil ice where the crystals have coagulated to form a soupy layer on the surface. Grease ice reflects little light, giving the water a matte appearance. | Environment and Climate Change Canada 2014 |
| Grease ice | A thin skin of frazil crystals coagulated on the sea surface having a dark, greasy appearance. It precedes the development of shuga. (Also called ice fat, lard ice.) | AMS - glossary of meteorology |
| Grease ice | A later stage of freezing than frazil ice, when the spicules and plates of ice have coagulated to form a thick soupy layer on the surface of the water. Grease ice reflects little light, giving the sea a matt appearance. | Illustrated Glossary of Snow and Ice |
| Green iceberg | Desalinated seawater frozen to the base of some Antarctic ice shelves that becomes exposed to view when an iceberg separates from the shelf and capsizes. The green color of the ice, and of the seawater from which it froze, is due to dissolved organic matter. | AMS - glossary of meteorology |
| Green snow | A snow surface that has attained a greenish tint as a result of the growth within it of certain microscopic algae (cryoplankton). | AMS - glossary of meteorology |
| Greenland Ice Sheet | The contiguous ice sheet covering most of the Greenland subcontinent. Strictly speaking, it does not also refer to the adjacent small ice caps and glaciers that are physically separated from the main ice mass. | AMS - glossary of meteorology |
| Greenland Sea Deep Water | The coldest (below -1.1C) and densest component of the water masses that mix to produce the Arctic Bottom Water. | AMS - glossary of meteorology |
| Grey ice | Young ice 10-15cm thick. Less elastic than nilas and breaks on swell. Usually rafts under pressure. | ASPECT 2012 |
| Grey ice | Sea ice terminology, describing young ice that is 10 cm to15 cm thick, less elastic than nilas, and which breaks on swell. It usually rafts under pressure. | Environment and Climate Change Canada 2014 |
| Grey ice | Young ice 10-15 cm thick. Less elastic than nilas and breaks in swell. Usually rafts under pressure. | Bushuyev 2004 |
| Grey-white ice | A category of young ice 15 to 30 centimeters (6 to 12 inches) thick, named for its color. | NSIDC accessed 2016 |
| Grey-white ice | Young ice 15-30cm thick. Under pressure more likely to ridge than to raft. | ASPECT 2012 |
| Grey-white ice | Sea ice terminology, describing young ice that is 15 cm to 30 cm thick. Under pressure it is more likely to ridge than to raft. | Environment and Climate Change Canada 2014 |
| Grey-white ice | Young ice 15-30 cm thick. Under pressure it is more likely to ridge than to raft. | Bushuyev 2004 |
| Grid | A finite collection of points to which the meteorological variables used in a numerical model, or interpolated from observations, apply; a field of such regular values (points) is termed gridded field. | NSIDC accessed 2016 |
| Groove | A glacial abrasional form, with striated (q.v.) sides and base, orientated approximately parallel to the ice-flow direction, and commonly up to a few metres wide and deep. | Swisseduc - Photo glossary of glaciological terms |
| Ground frost | In British usage, a freezing condition injurious to vegetation, which is considered to have occurred when a minimum thermometer exposed to the sky at a point just above a grass surface records a temperature (grass temperature) of -0.9C (30.4F) or below. Since 1961 in Britain the statistics refer to the "number of days with grass minimum temperature below 0C" rather than to ground frost. A fuller discussion is given in McIntosh (1963). | AMS - glossary of meteorology |
| Ground frost | Frost that penetrates the soil surface in response to freezing temperatures. | PhysicalGeography.net |
| Ground ice | A general term referring to all types of ice contained in freezing and frozen ground. | NSIDC accessed 2016 |
| Ground ice | A general term referring to all types of ice contained in freezing and frozen ground | Van Everdingen International Permafrost Association 2005 |
| Ground ice | A general term referring to all types of Ice contained in freezing and Frozen Ground. Ground Ice occurs in pores, cavities, voids or other openings in soil or rock and includes Massive Ice. It generally excludes Buried Ice. Ground Ice may be epigenetic or syngenetic, contemporaneous or relict, aggrading or degrading, perennial or seasonal. It may occur as lenses, wedges, veins, sheets, seams, irregular masses, or as individual crystals or coatings on mineral or organic particles. Perennial Ground Ice can only occur within Permafrost bodies. | Trombotto et al. 2014 |
| Ground ice | A body of clear ice in frozen ground. Ice of this nature is most commonly found in more or less permanently frozen ground (permafrost) and may be of sufficient age to be termed fossil ice. (Also called subsoil ice, subterranean ice, underground ice, stone ice.) | AMS - glossary of meteorology |
| Ground ice | General term used to describe all bodies of ice in the ground surface of the permafrost layer. Also called anchor ice. Some forms of ground ice include: pore ice, needle ice, ice wedge, segregated ice, sand wedge, and ice lenses. | PhysicalGeography.net |
| Ground moraine | A thick layer of till deposited by a melting glacier. | PhysicalGeography.net |
| Ground moraine | A blanket of glacier till deposited on all of the surfaces over which a glacier moves, typically by moving ice. | Molnia USGS 2004 |
| Ground moraine | Continuous layer of till near the edge or underneath a steadily retreating glacier. | NSIDC accessed 2016 |
| Ground-penetrating radar (GPR) | A radar, usually a pulsed system with one transmitting and one receiving antenna, operating at a frequency suitable for imaging the subsurface. In glaciology, low frequencies (2220 mhz) are suitable for ice thickness measurements whereas higher frequencies of several hundred mhz are suitable for snow thickness measurements, including detection of the current summer surface and older Annual layering (see radar method). Higher frequencies yield better resolution but may not allow very deep penetration; lower frequencies exhibit the reverse properties. Choice of frequency is therefore paramount. Radar imaging of the subsurface relies on accurate determination of the two-way travel time of the radar wave, which depends on the density. Reflections are caused by contrasts in the (complex) relative dielectric constant at interfaces between layers. Illustrative values of the real part of the relative dielectric constant, at frequencies used by ground-penetrating radars, are 1 for air, ~3.15 for pure ice, ~10 for bedrock and 88 for water at 0 | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Grounded glaciers | Glaciers which rest on bedrock to a large extent but which may have parts reaching into lake or sea water (tidewater glaciers). | Illustrated GLIMS Glacier Classification Manual |
| Grounded hummock | Hummocked grounded ice formation. Single grounded hum- mocks occur as well as lines (or chains) of grounded hummocks. | WMO Sea Ice Nomenclature 2017 |
| Grounded hummock | Sea ice terminology. Defines a hummocked, grounded ice formation. There are single grounded hummocks and lines (or chains) of grounded hummocks. | Environment and Climate Change Canada 2014 |
| Grounded ice | Ice that has run aground or is contact with the ground underneath it. | NOAA Glossary of Hydrologic Terms |
| Grounded ice | Floating ice that is aground in shoal water. | WMO Sea Ice Nomenclature 2017 |
| Grounded ice | In hydrologic terms, ice that has run aground or is contact with the ground underneath it. | NOAA National Weather Service Glossary 2009 |
| Grounded ice | Sea ice terminology that describes floating ice which is stranded in shoal water. | Environment and Climate Change Canada 2014 |
| Grounding line | The set of points separating the floating part of a glacier from the grounded part. See flotation. Usually the floating part is downstream and the grounded part is upstream. However, the 'shorelines' of subglacial lakes are grounding lines. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Grounding line | The junction between a glacier or ice sheet and ice shelf; the place where ice starts to float. This junction normally occurs over a finite zone, rather than at a line. | IPCC WGI AR5 2013 |
| Group | Neighbouring small glaciers; Slightly connected but too small to be treated separately; A number of similar small ice masses occurring in close proximity and too small to be assessed individually | Illustrated GLIMS Glacier Classification Manual |
| Growler | An iceberg less than 2 meters (6.6 feet) across that floats with less than 1 meter (3.3 feet) showing above water; smaller than a bergy bit. | NSIDC accessed 2016 |
| Growler | A smaller piece of ice of land origin than a bergy bit. The color is usually white, but sometimes transparent or blue-green or nearly black, normally occupying an area of about 20 m2. Growlers are distinguished with difficulty when they are surrounded by ice and also in heavy swell. [Note it might be better to say no more than 5 metres long] | Bushuyev 2004 |
| Growler | Sea ice terminology that describes a piece of ice smaller than a bergy bit and floating less than 1 m above the sea surface. A growler generally appears white but sometimes transparent or blue-green in colour. Extending less than 1 m above the sea surface, and normally occupying an area of about 20 sq. M., Growlers are difficult to distinguish when surrounded by sea ice or in high sea state. | Environment and Climate Change Canada 2014 |
| Growler | Smaller piece of ice than a bergy bit, often transparent but appearing green or almost black in color. Usually extends less than 3 ft (1 m) above the sea surface and normally occupies an area of about 24 sq yd (20 sq m). | WMO Sea Ice Nomenclature 2017 |
| Growler | A small piece of floating sea ice, usually a fragment of an iceberg or floeberg. It floats low in the water, and its surface often is heavily pitted. It is smaller than a bergy bit and often appears greenish in color. | AMS - glossary of meteorology |
| Growler | A piece of ice almost awash, smaller than a bergy bit (q.v.). | Illustrated Glossary of Snow and Ice |
| Growth time | The time scale for a glacier to attain steady state from an initial state of zero mass. See response time. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Gully | Glacier-worn or water-worn ravine in a hill or mountain side. | UK Antarctic Place-names Committee accessed 2016 |
| Gully | Deeply eroded watercourse which flows only due to storm runoff and/or during the melting of snow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Hail | Precipitation of small balls or pieces of ice with a diameter ranging from 5 to 50 mm or more. Hail is generally observed during heavy thunderstorms. | Canada National Climate Archive 2015 |
| Hail | Precipitation of small balls or pieces of ice (hailstones) with a diameter ranging from 5 to 50 millimeters (0.2 to 2.0 inches), or sometimes bigger, falling either separately or agglomerated into irregular lumps; when the diameter is less than about 5 millimeters (0.2 inch), the balls are called ice pellets. | NSIDC accessed 2016 |
| Hail | Showery precipitation in the form of irregular pellets or balls of ice more than 5 mm in diameter, falling from a cumulonimbus cloud. | NOAA National Weather Service Glossary 2009 |
| Hail | Precipitation (falling) of particles of ice (hailstones). Usually spheroid, conical or irregular in form and with a diameter varying generally between 5 and 50 millimetres. Hail falls from clouds either separately or collected into irregular lumps. | Australian Bureau of Meteorology 2016 |
| Hail | Precipitation of small balls or pieces of ice (hailstones) with a diameter greater than 5 millimetres, falling either separately or agglomerated into irregular lumps. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Hail | Precipitation in the form of balls or irregular lumps of ice, always produced by convective clouds, nearly always cumulonimbus. An individual unit of hail is called a hailstone. By convention, hail has a diameter of 5 mm or more, while smaller particles of similar origin, formerly called small hail, may be classed as either ice pellets or snow pellets. Thunderstorms that are characterized by strong updrafts, large liquid water contents, large cloud-drop sizes, and great vertical height are favorable to hail formation. The destructive effects of hailstorms upon plant and animal life, buildings and property, and aircraft in flight render them a prime object of weather modification studies. In aviation weather observations, hail is encoded A. | AMS - glossary of meteorology |
| Hail | Hail is a solid form of precipitation that has a diameter greater than 5 millimeters. Occasionally, hailstones can be the size of golf balls or larger. Hailstones of this size can be quite destructive. The intense updrafts in mature thunderstorm clouds are a necessary requirement for hail formation. | PhysicalGeography.net |
| Hail | Precipitation of small balls or pieces of ice (hailstones) with a diameter ranging from 5 to 50 mm, or sometimes more, falling either separately or agglomerated into irregular lumps. When the diameter is less than about 5 mm, the balls are called ice pellets. | Illustrated Glossary of Snow and Ice |
| Hail stage | Part of an obsolete conceptual model of air parcel ascent referring to a portion of the ascent during which the parcel temperature remains at the freezing point until all the rain produced previously has frozen. Other portions of the ascent were described as the dry stage, snow stage, and rain stage. | AMS - glossary of meteorology |
| Hailpad | A device used to obtain data on the size distribution and mass of hailstones. A hailpad usually consists of a plastic foam panel covered by aluminum foil or white latex paint and set in a frame that is hammered into the ground. Hail that impinges on the pad leaves dents in it. The dimensions of the dents are analyzed to obtain the hailstone size and mass data. | AMS - glossary of meteorology |
| Hailstone | A single unit of hail, ranging in size from that of a pea to, on rare occasions, exceeding that of a grapefruit (i.e., from 5 mm to more than 15 cm in diameter). Hailstones may be spheroidal, conical, or generally irregular in shape. The spheroidal stones often exhibit a layered internal structure, with layers of ice containing many air bubbles alternating with layers of relatively clear ice. These probably correspond to dry growth and wet growth and are called rime and glaze, respectively. The conical stones fall with their bases downward without much tumbling and are often smaller and not as layered. Irregular hailstones often have a lobate structure and are not composed of smaller hailstones frozen together. Hailstones grow by accretion of supercooled water drops and sometimes also by accretion of minor amounts of small ice particles. Large hail may contain liquid water and be spongy (an intimate mixture of ice and water) in some regions; it is usually solid ice with density greater than 0.8 g/cm^3. Small hail may be indistinguishable from large graupel (snow pellets) except for the convention that hail must be larger than 5 mm in diameter. The density of small hail can be much less than 0.8 g/cm^3 if they are dry; if partly melted, such hailstones become spongy. The largest recorded hailstone by weight to fall in the United States occurred in a hailstorm in Vivian, South Dakota, on 23 July 2010. The stone from this event weighed 870 g, with a diameter in excess of 20 cm. | AMS - glossary of meteorology |
| Hailstorm | Any storm that produces hailstones that fall to the ground; usually used when the amount or size of the hail is considered significant. | AMS - glossary of meteorology |
| Halo | Group of optical phenomena, in the form of rings, arcs, pillars or bright spots around the sun or moon, produced by the refraction or reflection of light by ice crystals suspended in the atmosphere (cirrus clouds, diamond dust, etc.). | NSIDC accessed 2016 |
| Hanging | No connection with mountain foot; up to 60 deg slope; Perched on a steep mountain-side or issuing from a hanging valley (WGMS, 1970); Perched on a steep mountain-side or issuing from a steep hanging valley (WGMS, 1977) | Illustrated GLIMS Glacier Classification Manual |
| Hanging (ice) dam | A mass of ice composed mainly of frazil or broken ice deposited underneath an ice cover in a region of low flow velocity. | NOAA Glossary of Hydrologic Terms |
| Hanging (ice) dam | In hydrologic terms, a mass of ice composed mainly of frazil or broken ice deposited underneath an ice cover in a region of low flow velocity. | NOAA National Weather Service Glossary 2009 |
| Hanging dam | Accumulation of frazil ice under an ice cover on a watercourse, which reduces the cross-section of streamflow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Hanging glacier | A glacier that terminates at or near the top of a cliff. | NSIDC accessed 2016 |
| Hanging glacier | A glacier that originates high on the wall of a glacier valley and descends only part of the way to the surface of the main glacier. Avalanching and icefalls are the mechanisms for ice and snow transfer to the valley floor below. | Molnia USGS 2004 |
| Hanging glacier | A glacier, usually small, that clings to a steep slope, or a glacier that terminates abruptly at the top of a cliff. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Hanging glacier | A glacier that spills out from a high-level cirque or clings to a steep mountainside. | Swisseduc - Photo glossary of glaciological terms |
| Hanging glacier | A glacier lying above a cliff or steep mountainside. As the glacier advances, its calving can cause ice avalanches. | AMS - glossary of meteorology |
| Hanging valley | A valley formed by a small glacier that has a valley bottom relatively higher than nearby valleys formed by larger glaciers. | NSIDC accessed 2016 |
| Hanging valley | A former tributary glacier valley that is incised into the upper part of a U-shaped glacier valley, higher than the floor of the main valley. Hanging valley streams often enter the main valley as waterfalls. | Molnia USGS 2004 |
| Hanging valley | A tributary valley whose mouth ends abruptly part way up the side of a trunk valley, as a result of the greater amount of glacial down-cutting of the latter. | Swisseduc - Photo glossary of glaciological terms |
| Hanging valley | A secondary valley that enters a main valley at an elevation well above the main valley's floor. These features are result of past erosion caused by alpine glaciers. Hanging valleys are often the site of spectacular waterfalls. | PhysicalGeography.net |
| Hard freeze | A freeze in which seasonal vegetation is destroyed, the ground surface is frozen solid underfoot, and heavy ice is formed on small water surfaces such as puddles and water containers. It is to be distinguished from a hard frost (black frost). | AMS - glossary of meteorology |
| Hard frozen ground | Frozen ground (soil or rock) which is firmly cemented by ice. | NSIDC accessed 2016 |
| Hard frozen ground | Frozen ground (soil or rock) which is firmly cemented by ice | Van Everdingen International Permafrost Association 2005 |
| Hard rime | Opaque, granular masses of rime deposited chiefly on vertical surfaces by a dense supercooled fog. Hard rime is more compact and amorphous than soft rime and may build out into the wind as glazed cones or ice feathers. The icing of ships and shoreline structures by supercooled spray from the sea usually has the characteristics of hard rime. | AMS - glossary of meteorology |
| Head (or Headland ) | Comparatively high, steep-faced land jutting into the sea or into an ice shelf; similar to promontory but applied to a feature of lesser extent, cf. cape, point. An unnamed head is usually described as a headland. | UK Antarctic Place-names Committee accessed 2016 |
| Headwall | A steep cliff, usually the uppermost part of a cirque. | NSIDC accessed 2016 |
| Health | The extent to which the mass balance, usually averaged over a period of some years, differs from zero, growth or equilibrium representing 'good health' and a negative mass balance representing 'poor health'. The term is generally used only informally. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Heat capacity | The amount of heat required to raise the temperature of a unit mass of a substance by one degree. | Van Everdingen International Permafrost Association 2005 |
| Heat capacity | The amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius or Kelvin. This term is a commonly used abbreviation of Specific Heat Capacity, which does not include the effects of changes in Latent Heat due to the melting of Ice or the freezing of water with changes in temperature. Because the phase change in a frozen soil often occurs gradually over a range of temperatures, the Apparent Heat Capacity (covering both sensible and Latent Heat contents) may vary significantly with temperature. Heat Capacity is commonly expressed in Joules per kg per degree K. | Trombotto et al. 2014 |
| Heaving pressure | Upward pressure developed during freezing of the ground. | NSIDC accessed 2016 |
| Heaving pressure | Upward pressure developed during freezing of the ground | Van Everdingen International Permafrost Association 2005 |
| Heavy snow | This generally means...snowfall accumulating to 4' or more in depth in 12 hours or less or | NOAA National Weather Service Glossary 2009 |
| Height | Height H is the coordinate measured vertically (line of plumb) from the base. Ground surface is usually taken as the base, but on firn fields and glaciers, it refers to the level of either the firn surface or glacier ice. Usually expressed in centimetres, height is used to denote the locations of layer boundaries but also of measurements such as snow temperatures relative to the base. Where only the upper part of the snowpack is of interest, the snow surface may be taken as the reference. This should be indicated by using negative coordinate values (depth). The symbol H should be used for all vertical measurements, regardless of whether they are taken at a place where the snow surface is horizontal or inclined. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Height of new snow | See depth of snowfall | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Height of snowpack, snow depth | Snow depth HS denotes the total height of the snowpack, i.e., the vertical distance in centimetres from base to snow surface. Unless otherwise specified snow depth is related to a single location at a given time. Thus, manual snow depth measurements are often made with one or more fixed snow stakes. On the other hand, portable snow depth probes allow for measurements along snow courses and transects. The slope-perpendicular equivalent of snow depth is the total thickness of the snowpack denoted by DS. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Heights | Relatively high hills or mountains. | UK Antarctic Place-names Committee accessed 2016 |
| High arctic climate | In Nordenskj?ld's climatic classification (1928), the climate of those parts of the world where the average temperature of the warmest month is below 0C. It is equivalent, therefore, to the perpetual frost climate of W. K?ppen (1918), and to C. W. Thornthwaite's frost climate (1931). | AMS - glossary of meteorology |
| High foehn | The presence of south foehnlike conditions at higher elevations of the Alps while the lower elevations and the plains or "foreland" to the north are under a cold air mass. Under these conditions, the mountains are often warmer than the lowlands. The warming is attributed to subsiding air in a synoptic anticyclone above the cold surface air. Although the winds in the warm air are apt to have a southerly component, the high foehn does not necessarily have strong, gusty foehn winds. However, this situation often precedes the foehn at the surface. (Also called free foehn.) | AMS - glossary of meteorology |
| High polar glacier | In Ahlmann's (1935) glacier classification, a polar glacier with firn in the accumulation area that is 100 m or more thick and that does not melt appreciably in summer. | AMS - glossary of meteorology |
| High-center polygon | An ice-wedge polygon in which melting of the surrounding ice wedges has left the central area in a relatively elevated position. | NSIDC accessed 2016 |
| High-centre polygon | An ice-wedge polygon in which melting of the surrounding ice wedges has left the central area in a relatively elevated position | Van Everdingen International Permafrost Association 2005 |
| Highland | Group of hills or mountains with glaciers or an undulating plateau. | UK Antarctic Place-names Committee accessed 2016 |
| Highland ice | An unbroken, but limited, sheet of land ice lying on relatively flat plateau country. It is thin enough to show the main contours of the underlying land, in contrast to a continental glacier. | AMS - glossary of meteorology |
| Highland icefield | A near-continuous stretch of glacier ice, but with an irregular surface that follows approximately the contours of the underlying bedrock, and which is punctuated by nunataks (q.v.). | Swisseduc - Photo glossary of glaciological terms |
| Hill | Natural elevation usually below 300 m, but the term may be applied to much higher features in a mountainous areas, cf. knoll, mountain. | UK Antarctic Place-names Committee accessed 2016 |
| Hillocky multiyear ice | A qualitative assessment of the relief of multiyear ice formed as a result of non-uniform melting of initially level ice and smoothing of ice ridges and hummocks. It can be assessed as smoothed multiyear ice, moderately hillocky multiyear ice and strongly hillocky multiyear ice. | Bushuyev 2004 |
| Hinge crack | Crack caused by significant changes in water level. | NOAA Glossary of Hydrologic Terms |
| Hoar | A surface deposit of interlocking ice crystals formed by the deposition of water vapour. See also glaze, rime; depth hoar. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Hoar crystal | An individual ice crystal in a deposit of hoarfrost. Such crystals always grow by deposition. | AMS - glossary of meteorology |
| Hoar frost | A deposit of interlocking crystals formed by direct sublimation on objects, usually those of small diameter freely exposed to the air, such as tree branches, plants, wires, poles, etc. The deposition of hoar frost is similar to the process by which dew is formed, except that the temperature of the frosted object must be below freezing. It forms when air with a dew point below freezing is brought to saturation by cooling. | NOAA National Weather Service Glossary 2009 |
| Hoarfrost | A deposit of interlocking ice crystals (hoar crystals) formed by direct sublimation on objects, usually those of small diameter freely exposed to the air, such as tree branches, plant stems and leaf edges, wires, poles, etc.; the surfaces of these objects are sufficiently cooled, mostly by nocturnal radiation, to cause the direct sublimation of the water vapor contained in the ambient air. | NSIDC accessed 2016 |
| Hoarfrost | Deposit of ice crystals forming on objects whose surface is sufficiently cooled to cause the sublimation of the water vapour contained in the ambient air. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Hoarfrost | A deposit of interlocking ice crystals (hoar crystals) formed by direct deposition on objects, usually those of small diameter freely exposed to the air, such as tree branches, plant stems and leaf edges, wires, poles, etc. Also, frost may form on the skin of an aircraft when a cold aircraft flies into air that is warm and moist or when it passes through air that is supersaturated with water vapor. The deposition of hoarfrost is similar to the process by which dew is formed, except that the temperature of the befrosted object must be below freezing. It forms when air with a dewpoint below freezing is brought to saturation by cooling. In addition to its formation on freely exposed objects (air hoar), hoarfrost also forms inside unheated buildings and vehicles, in caves, in crevasses (crevasse hoar), on snow surfaces (surface hoar), and in air spaces within snow, especially below a snow crust (depth hoar). Hoarfrost is more fluffy and feathery than rime, which in turn is lighter than glaze. Observationally, hoarfrost is designated light or heavy (frost) depending upon the amount and uniformity of deposition. | AMS - glossary of meteorology |
| Hoarfrost | A deposit of ice having a crystalline appearance, generally assuming the form of scales, needles, feathers or fans; produced in a manner similar to dew (i.e. by condensation of water vapour from the air), but at a temperature below 0 C. | Illustrated Glossary of Snow and Ice |
| Hoarfrost (hoar) | A deposit of ice crystals (hoar crystals) formed by direct deposition on objects, usually those of small diameter freely exposed to the air, such as tree branches, plant stems and leaf edges, wires, poles, etc. It forms when air with a dew point below freezing is brought to saturation by cooling, i.e., usually radiative cooling. Hoarfrost also forms on snow surfaces (SH), within the snowpack (FC, DH), as well as inside unheated buildings and vehicles, in caves, and in crevasses (shcv). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Holocene | The current part of geologic time. The Holocene epoch began ~12,000 years ago, at the end of the Pleistocene epoch. | Molnia USGS 2004 |
| Holocene epoch | Period of time from about 10,000 years ago to today. During this period glaciers retreated because of a warmer global climate. Time of modern humans. | PhysicalGeography.net |
| Horn | A pointed, mountain peak, typically pyramidal in shape, bounded by the walls of three or more cirques. Headward erosion has cut prominent faces and ridges into the peak. When a peak has four symmetrical faces, it is called a Matterhorn. | Molnia USGS 2004 |
| Horn | A peak or pinnacle thinned and eroded by three or more glacial cirques. | NSIDC accessed 2016 |
| Horn | Horn-shaped mountain or nunatak. | UK Antarctic Place-names Committee accessed 2016 |
| Horn | A steep-sided, pyramid-shaped peak, formed as a result of the backward erosion of cirque glaciers on three or more sides. | Swisseduc - Photo glossary of glaciological terms |
| Horn | Pyramidal peak that forms when several cirques erode a mountain from three or more sides. | PhysicalGeography.net |
| Hostile ice | From the point of view of the submariner, an ice canopy containing no large ice skylights or other features which permit a submarine to surface. | NSIDC accessed 2016 |
| Hostile ice | From the point of view of the submariner, an ice canopy containing no large skylights or other features that permit a submariner to surface. | WMO Sea Ice Nomenclature 2017 |
| Hostile ice | Sea ice terminology that describes an ice canopy containing no large skylights or other features, and as a result submarines are unable to surface. | Environment and Climate Change Canada 2014 |
| Hostile ice | From the point of view of the submariner, an ice canopy containing no large ice skylights or other features which permit a submarine to surface. | Illustrated Glossary of Snow and Ice |
| Hot-water drilling | A field technique to drill deep holes into a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Hummock | A hillock of broken ice which has been forced upward by pressure. | NOAA Glossary of Hydrologic Terms |
| Hummock | (1) [sea ice] a smooth hill of ice that forms on the sea ice surface from eroding ridges, particularly during the summer melt; the formation of hummocks is similar to young mountain peaks with steep slopes that erode into smooth, rolling hills. (2) [frozen ground] Small lumps of soil pushed up by frost action, often found in uniformly spaced in large groups. Hummocks can form in areas of permafrost or seasonally frozen ground, and are one of the most common surface features of the Arctic. | NSIDC accessed 2016 |
| Hummock | A hillock of broken ice that has been forced upwards by pressure. May be fresh or weathered. The submerged volume of broken ice under the hummock, forced downwards by pressure, is termed a bummock. | WMO Sea Ice Nomenclature 2017 |
| Hummock | Sea ice terminology, meaning a hillock of broken ice which has been forced upwards by pressure; it may be fresh or weathered. | Environment and Climate Change Canada 2014 |
| Hummock | A hillocky conglomeration of broken ice formed by pressure at the place of contact of the angle of one ice floe with anther ice floe. The underwater portion of a hummock is termed a bummock. | Bushuyev 2004 |
| Hummock | A mound of broken ice projecting upward, formed by ice deformation. The submerged counterpart of a hummock is termed a bummock. | AMS - glossary of meteorology |
| Hummock | A mound or hillock of broken floating ice forced up by pressure. May be fresh or weathered. A corresponding projection may also occur on the underside of the ice canopy and is called a bummock. | Illustrated Glossary of Snow and Ice |
| Hummocked ice | Ice piled haphazardly one piece over another to form an uneven surface. | NOAA Glossary of Hydrologic Terms |
| Hummocked ice | Sea ice piled haphazardly one piece over another to form an uneven surface. When weathered, it has the appearance of smooth hillocks. | WMO Sea Ice Nomenclature 2017 |
| Hummocked ice | Sea ice piled haphazardly one piece over another, predominantly in the form of ice ridges and separate hummocks. | Bushuyev 2004 |
| Hummocked ice | Sea ice terminology, which describes ice that is piled chaotically, one piece over another, to form an uneven surface. When weathered, hummocked ice has the appearance of smooth hillocks. | Environment and Climate Change Canada 2014 |
| Hummocked ice | Pressure ice characterized by haphazardly arranged mounds or hillocks ("hummocks"). This has less definite form than rafted ice or tented ice, but in fact may develop from either of those as melting, sublimation, or drifting changes the sharper ice edges into more rounded shapes. | AMS - glossary of meteorology |
| Hummocked ice | A form of pressure ice in which pieces of ice are piled haphazardly, one piece over another, to form an uneven surface. When weathered it has the appearance of smooth hillocks. | Illustrated Glossary of Snow and Ice |
| Hummocking | [sea ice] pressure process by which floating ice becomes broken up into hummocks. | NSIDC accessed 2016 |
| Hummocking | Sea ice terminology. Describes the pressure process by which ice is forced into hummocks. When the floes rotate in the process, it is termed screwing. | Environment and Climate Change Canada 2014 |
| Hummocking | The pressure process by which sea ice is forced into hummocks. When the floes rotate in the process it is termed screwing. | WMO Sea Ice Nomenclature 2017 |
| Hummocking | Pressure process by which floating ice becomes broken up into hummocks. | Illustrated Glossary of Snow and Ice |
| Hydration shattering | A form of weathering that affects all rocks; water freezes in pores and cracks, which leads to an increase in specific volume (vol/unit mass) of the water, producing stress that is greater than the tensile strength of all common rocks; ultimately leads to shattering and fracturing of the rocks. | NSIDC accessed 2016 |
| Hydraulic conductivity | The volume of fluid passing through a unit cross section in unit time under the action of a unit hydraulic potential gradient | Van Everdingen International Permafrost Association 2005 |
| Hydraulic diffusivity | The ratio of the hydraulic conductivity and the storage capacity of a groundwater aquifer | Van Everdingen International Permafrost Association 2005 |
| Hydraulic thawing | Artificial thawing (and removal) of frozen ground by the use of a stream or jet of water under high pressure. | NSIDC accessed 2016 |
| Hydraulic thawing | Artificial thawing (and removal) of frozen ground by the use of a stream or jet of water under high pressure | Van Everdingen International Permafrost Association 2005 |
| Hydrochemical talik | A layer or body of cryotic (but unfrozen) ground in a permafrost area, maintained by moving mineralized groundwater. | NSIDC accessed 2016 |
| Hydrochemical talik | A layer or body of cryotic (but unfrozen) ground in a permafrost area, maintained by moving mineralized groundwater | Van Everdingen International Permafrost Association 2005 |
| Hydrological method | A method of determining the mass balance indirectly by solving the water balance for the change in storage W in a drainage basin W = P E Q , with P the precipitation, E the evapotranspiration and Q the discharge, each of these quantities being a total over a stated span of time. In practical work the hydrological method can be applied only to an entire drainage basin. It does not provide any information on the spatial distribution or gradients. The quantity W will include changes in storage in lakes, seasonal snowpatches, soil and aquifers as well as in the glacier. Each of these changes must be accounted for to isolate the mass balance of the glacierized part of the catchment, but the changes in storage other than in the glacier and the snow cover are often assumed to be negligible over Annual periods. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Hydrological year | A period of one year, synchronized with the natural progression of the hydrological seasons by specifying the calendar date of its first day. Generally in glaciology the hydrological year is found to be convenient because it begins near the start of the accumulation season and ends near the end of the ablation season. For example the appropriate dates are 1 October to 30 September in the mid-latitudes of the Northern Hemisphere. The concept of the hydrological year is most useful where the accumulation and ablation seasons are well differentiated, as on mid-latitude glaciers and most high-latitude glaciers, but it is less well suited to those regions in which there are more than two hydrological seasons, as in the tropics, or in which most of the accumulation occurs in the same season as most of the ablation, as in monsoon climates (see summer-accumulation type.). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Hydrometeorology | Study of the atmospheric and land phases of the hydrological cycle, mostly on the interrelationships involved. | WMO METEOTERM accessed 2016 |
| Hydrosphere | Part of the Earth covered by water and ice. | WMO METEOTERM accessed 2016 |
| Hydrosphere | The component of the climate system comprising liquid surface and subterranean water, such as oceans, seas, rivers, fresh water lakes, underground water, etc. | EU Climate-ADAPT |
| Hydrosphere | That part of the Earth covered by water and ice. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Hydrothermal alteration | Hydrothermal alteration is the alteration of rocks or minerals due to the reactions of geothermally heated water with minerals. The process weathers and weakens the rocks such that they may become unstable. | Molnia USGS 2004 |
| Hydrothermal talik | A layer or body of noncryotic unfrozen ground in a permafrost area, maintained by moving groundwater. | NSIDC accessed 2016 |
| Hydrothermal talik | A layer or body of noncryotic unfrozen ground in a permafrost area, maintained by moving groundwater | Van Everdingen International Permafrost Association 2005 |
| Hypsometric curve | A graph of the area-altitude distribution; hypsographic curve is a synonym. The hypsometric curve shows the area-altitude distribution by plotting area on the horizontal axis versus altitude on the vertical axis. Intervals on the altitude axis are commonly 25, 50 or 100 metres. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Hypsometry | The measurement of the distribution of glacier area with surface altitude (elevation), or more loosely the result of such measurement. Hypsometric and topographic data are essential for converting measurements of the mass-balance profile to glacier-wide estimates of the mass balance. Hypsography is a synonym. See area-altitude distribution, hypsometric curve. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Hypsometry | The distribution of land or ice surface as a function of altitude. | IPCC WGI AR5 2013 |
| Ice | The solid form of water. It can be found in the atmosphere in the form of ice crystals, snow, ice pellets, and hail for example. | Canada National Climate Archive 2015 |
| Ice | (1) Ice is the solid form of water. It is a transparent crystalline material having adensity of 917 kg m-3 for pure, bubble-free ice at 0 | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Ice | Water substance in the solid phase. Ice can occur in many forms. At and near the Earth's surface, ice always crystallizes in the hexagonal system. This phase is designated ice Ih, the Roman numeral I distinguishing it from more than a dozen other phases and the letter h distinguishing it from the metastable cubic phase ice Ic. See, among other articles, glacier ice and diamond dust. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice | The solid crystalline form of water. | NSIDC accessed 2016 |
| Ice | Solid form of water. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice | Water in the solid state | Van Everdingen International Permafrost Association 2005 |
| Ice | Water in solid state. Ice commonly occurs as hexagonal crystals. In Permafrost regions, Ice may occupy voids in soils and rocks and may develop in a variety of forms. Ice may be colourless to pale blue or greenish-blue. It may appear white due to included gas bubbles; in exposures, Ground Ice may also appear black. | Trombotto et al. 2014 |
| Ice | The solid, crystalline form of water substance; it is found in the atmosphere as snow crystals, hail, ice pellets, etc., and on the earth's surface in forms such as hoarfrost, rime, glaze, sea ice, glacier ice, ground ice, frazil, anchor ice, etc. This form of water is, strictly speaking, called ice I, the only one of the several known modifications of solid water substance that is stable at commonly occurring temperatures and pressures. (Some of the other forms have very unusual properties, ice VII, for example, being stable only at pressures above 22 400 kg/cm^2, but then existing at temperatures up to about 100C.) Ice has an open structure because the water molecules bond to their neighbors covalently only in four directions; it therefore floats on higher density water, where broken molecular bonds permit closer packing. All commonly occurring forms of ice are crystalline, although large single crystals are relatively rare except in glaciers. The ice crystal lattice possesses hexagonal symmetry that manifests itself in the gross forms of such single crystals as are sometimes found in snow. At an air pressure of one atmosphere, ice melts at 0C by definition of the Celsius temperature scale. (Strictly at equilibrium among water, ice, and vapor occurs at +0.01C, the triple point.) On the other hand, ice does not invariably form in liquid water cooled below this temperature; it has a tendency to supercool, more so in the absence of ice nuclei. | AMS - glossary of meteorology |
| Ice | Frozen form of the water molecule. Ice has a specific gravity (0.9166) which is slightly less than water. This difference in specific gravity causes ice to float on water. | PhysicalGeography.net |
| Ice | The solid form of water in nature formed either by: (a) the freezing of water, (b) the condensation of atmospheric water vapour direct into ice crystals, (c) the compaction of snow with or without the motion of a glacier, or (d) the impregnation of porous snow masses with water which subsequently freezes. | Illustrated Glossary of Snow and Ice |
| Ice accretion | The process by which a layer of ice (icing) builds up on solid objects that are exposed to freezing precipitation or to supercooled fog or cloud droplets. At the earth's surface this usually refers to glaze formation, and the amount of ice can be roughly measured by an ice-accretion indicator. For airborne objects, ice accretion refers to any type of aircraft icing. | AMS - glossary of meteorology |
| Ice age | Particular period of a geological era during which extensive ice sheets (continental glaciers) covered many parts of the world. | WMO METEOTERM accessed 2016 |
| Ice age | A time of widespread glaciation. | NOAA National Weather Service Glossary 2009 |
| Ice age | An ice age or glacial period is characterized by a long-term reduction in the temperature of the Earth's climate, resulting in growth of ice sheets and glaciers. | IPCC WGI AR5 2013 |
| Ice age | Particular period of a geological era during which extensive ice sheets (continental glaciers) covered many parts of the world. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice age | A cold period in Earth history when large ice sheets extend from the polar regions into temperate latitudes. The term is sometimes used synonymously with "glacial period" or "glacial period", or embraces several such periods to define a major phase of cold climate in Earth's climatic history. | Swisseduc - Photo glossary of glaciological terms |
| Ice age | A major interval of geologic time during which extensive ice sheets (continental glaciers) formed over many parts of the world. The best known ice ages are 1) the Huronian in Canada, occurring very early in the Proterozoic era (2700-1800 million years ago); 2) the pre-Cambrian and early Cambrian, which occurred in the early Paleozoic era (about 540 million years ago) and left traces widely scattered over the world; and 3) the Permo-Carboniferous, occurring during the late Paleozoic era (from 290 million years ago), which was extensively developed on Gondwana, a large continent comprising what is now India, South America, Australia, Antarctica, Africa, and portions of Asia and North America. The term ice age is also applied to advances and retreats of glaciers during the Quaternary era. | AMS - glossary of meteorology |
| Ice age | Period of time when glaciers dominate the landscape of the Earth. The last major Ice Age was during the Pleistocene epoch. | PhysicalGeography.net |
| Ice and snow albedo-temperature feedback | A positive feedback mechanism involving ice and snow cover, surface albedo, and temperature. For example, given an initial warming, a decrease in snow and ice cover occurs, lowering the surface albedo. This causes an increase in the absorption of solar radiation, which amplifies the initial increase in temperature. | AMS - glossary of meteorology |
| Ice apron | A mass of ice adhering to a mountainside. | NSIDC accessed 2016 |
| Ice apron | A steep mass of smooth ice, commonly the source of ice avalanches, that adheres to steep rock near the summits of high peaks. | Swisseduc - Photo glossary of glaciological terms |
| Ice apron | A thin mass of snow and ice adhering to a mountainside. | AMS - glossary of meteorology |
| Ice apron | A thin mass of snow and ice adhering to a mountain side (cf. Bergschrund). | Illustrated Glossary of Snow and Ice |
| Ice apron | Steep, ice covered mountain faces; Hanging glaciers; Thin ice flanks; See longitudinal characteristics for further differentiation; Irregular, usually thin ice mass which adheres to a mountain slope or ridge; Includes ice fringes; Thin ice and snow covered mountain flank (ice flanks or steep ice fields) | Illustrated GLIMS Glacier Classification Manual |
| Ice avalanche | A mass of ice which has detached itself from a steep glacier and which is descending on to the terrain below. | Swisseduc - Photo glossary of glaciological terms |
| Ice band | A long strip of ice floes, parallel to but separated from the edge of the main ice pack. | AMS - glossary of meteorology |
| Ice bands | Ice layers formed by separate accumulation events and exposed at a glacier front or a crevasse wall. | AMS - glossary of meteorology |
| Ice barrier | Obsolete term for ice shelf or ice front. | UK Antarctic Place-names Committee accessed 2016 |
| Ice bay | A baylike recess in the edge of a large ice floe or ice shelf. (Also called ice bight.) | AMS - glossary of meteorology |
| Ice blink | White glare on the underside of low clouds indicating presence of ice which may be beyond the range of vision. | NSIDC accessed 2016 |
| Ice blink | A whitish glare on low clouds above an accumulation of distant ice. | WMO Sea Ice Nomenclature 2017 |
| Ice blink | Sea ice terminology, describing a whitish glare on low clouds above an accumulation of distant ice. | Environment and Climate Change Canada 2014 |
| Ice blink | A relatively bright region on the underside of clouds produced by the reflection of light by ice. This term is used in polar regions where it contributes to the sky map; ice blink is not as bright as snow blink, but is brighter than the reflection of light by land or water. | AMS - glossary of meteorology |
| Ice blink | White glare on the underside of clouds, indicating the presence of pack ice or an ice sheet which may be beyond the range of vision (cf. Water sky). | Illustrated Glossary of Snow and Ice |
| Ice body | Any continuous mass of ice, possibly including snow and firn, at or beneath the Earth's surface. Glaciers, ice shelves, ice floes, icebergs, a continuous cover of sea ice, ice wedges in permafrost, and accumulations of ice in caves are all examples of ice bodies. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice bonded permafrost | Ice-bearing Permafrost in which the soil particles are cemented together by ice. | Trombotto et al. 2014 |
| Ice boom | A floating structure designed to retain ice. | NOAA Glossary of Hydrologic Terms |
| Ice boom | In hydrologic terms, a floating structure designed to retain ice. | NOAA National Weather Service Glossary 2009 |
| Ice bound | A harbor, inlet, etc. Is said to be ice-bound when navigation by ships is prevented on account of ice, except possibly with the assistance of an icebreaker. | Bushuyev 2004 |
| Ice bound | A harbor, inlet, etc., is said to be ice bound when navigation by ships is prevented on account of ice, except possibly with the assistance of an icebreaker. | WMO Sea Ice Nomenclature 2017 |
| Ice boundary | Sea ice terminology that describes the differentiation at any given time between fast ice and floating ice, or between areas of ice of different concentrations, types and/or floe sizes. | Environment and Climate Change Canada 2014 |
| Ice boundary | The demarcation at any given time between fast ice and pack ice or between areas of pack ice of different concentrations. | WMO Sea Ice Nomenclature 2017 |
| Ice boundary | The demarcation between fast ice and drift ice or between different zones of drift ice. When used as a climatologic term, for describing the position of the boundary of spreading of ice of any concentration or age in any given month or a period based on the observation data for a number of years, the tem should be preceded by a word mean, median, minimum or maximum with indication of the ice cover characteristic after it. For example: Median boundary of multiyear close ice. | Bushuyev 2004 |
| Ice break-up | Disintegration of an ice cover. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice breakup | Disintegration of an ice cover on land, river, or coastal waters as a result of thermal and mechanical processes. | AMS - glossary of meteorology |
| Ice breccia | Ice of different stages of development frozen together. | WMO Sea Ice Nomenclature 2017 |
| Ice breccia | Ice of different stages of development frozen together | Bushuyev 2004 |
| Ice breccia | Sea ice terminology, describing ice pieces in different stages of development that are frozen together. | Environment and Climate Change Canada 2014 |
| Ice bridge | A continuous ice cover of limited size extending from shore to shore like a bridge. | NOAA Glossary of Hydrologic Terms |
| Ice bridge | In hydrologic terms, a continuous ice cover of limited size extending from shore to shore like a bridge. | NOAA National Weather Service Glossary 2009 |
| Ice cake | A floe smaller than 20 meters (66 feet) across. | NSIDC accessed 2016 |
| Ice cake | Any relatively flat piece of sea ice less than 22 yd (20 m) across. | WMO Sea Ice Nomenclature 2017 |
| Ice cake | Any relatively flat piece of sea ice less than 20 m across. | Bushuyev 2004 |
| Ice cake | Sea ice terminology that describes any relatively flat piece of ice less than 20 m across. | Environment and Climate Change Canada 2014 |
| Ice cake | A floe smaller than 20 m across. | Illustrated Glossary of Snow and Ice |
| Ice canopy | Pack ice from the point of view of the submariner. | NSIDC accessed 2016 |
| Ice canopy | Pack ice from the point of view of the submariner. | WMO Sea Ice Nomenclature 2017 |
| Ice canopy | Sea ice terminology, meaning ice as it is seen from the point of view of the submariner. (i.e. Underwater looking up at the ice) | Environment and Climate Change Canada 2014 |
| Ice canopy | Pack ice from the point of view of the submariner. | Illustrated Glossary of Snow and Ice |
| Ice cap | A dome-shaped mass of glacier ice that spreads out in all directions; an ice cap is usually larger than an icefield but less than 50,000 square-kilometers (12 million acres). | NSIDC accessed 2016 |
| Ice cap | A dome-shaped accumulation of glacier ice and perennial snow that completely covers a mountainous area or island, so that no peaks or Nunataks poke through. | Molnia USGS 2004 |
| Ice cap | A dome-shaped ice body with radial flow, largely obscuring the subsurface topography and generally defined as covering less than 50 000 km2 (see ice sheet). The flow pattern is less influenced by the subsurface topography than is true of icefields and valley glaciers. The definition embraces small as well as large ice bodies. The usage '(polar) ice cap' for the sea ice cover of the Arctic Ocean or Southern Ocean is confusing and best avoided. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice cap | A dome-shaped ice mass that is considerably smaller in extent than an ice sheet. | IPCC WGII AR5 2014 |
| Ice cap | Dome-shaped glacier or small ice sheet usually covering a highland area. | UK Antarctic Place-names Committee accessed 2016 |
| Ice cap | Dome-shaped glacier usually covering a highland area. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice cap | A dome-shaped mass of glacier ice, usually situated in a highland area, and generally defined as covering up to 50,000 square kilometres (cf. ice sheet). | Swisseduc - Photo glossary of glaciological terms |
| Ice cap | A dome-shaped perennial cover of ice and snow over an extensive portion of the earth's surface. Ice caps are considerably smaller than ice sheets, and it is felt improper to refer to the Greenland and Antarctic Ice Sheets as ice caps. Most ice caps are most probably remnants of the Quaternary Ice Age. The term was first used for the supposedly perennial ice cover at both poles of the earth. However, since it has been found that the ice of arctic waters is largely seasonal, the use of this term to denote arctic polar ice is now considered improper. | AMS - glossary of meteorology |
| Ice cap | Large dome-shaped glacier found covering a large expanse of land. Smaller than an ice sheet. | PhysicalGeography.net |
| Ice cap | A dome-shaped glacier usually covering a highland area. Ice caps are considerably smaller in extent than ice sheets. | Illustrated Glossary of Snow and Ice |
| Ice cap | Dome shaped ice mass; Approximately radial ice flow; Upstanding ice mass over bedrock; Not to be interpreted as_ mountain ice cap; Dome shaped ice mass with radial flow; May incorporate Ice domes; Longitudinal profile is in almost all cases even/regular | Illustrated GLIMS Glacier Classification Manual |
| Ice cave | A cave of ice, usually underneath a glacier and formed by meltwater; cave entrances are often enlarged near a glacier terminus by warm winds; most common on stagnant portions of glaciers. | NSIDC accessed 2016 |
| Ice cave | A cave formed in or under a glacier, typically by running water. Steam or high heat flow can also form glacier caves. Also called Glacier Cave. | Molnia USGS 2004 |
| Ice circle | An ice circle is a thin, circular slab of ice that form in slow moving, rotating part of a river. They are relatively rare natural phenomena. Similar features are ice discs, ice crepes, and ice pans. They can vary in size up to more than 15 m (49 ft), with a maximum observed of 91 m (298 ft). | GCW |
| Ice cliff (ice wall) | A vertical face of ice, normally formed where a glacier terminates in the sea, or is undercut by streams. These terms are also used more specifically for the face that forms at the seaward margin of an ice sheet or ice cap, and that rests on bedrock at or below sea level. | Swisseduc - Photo glossary of glaciological terms |
| Ice cluster | A concentration of sea ice, covering 100's of square kilometers, which is found in the same region every summer. | NSIDC accessed 2016 |
| Ice cluster | A concentration of sea ice, covering hundreds of square kilometres, which is found in the same region every summer. | Illustrated Glossary of Snow and Ice |
| Ice concentration | The fraction of an area that is covered by sea ice. | NSIDC accessed 2016 |
| Ice content | The amount of ice contained in frozen or partially frozen soil or rock. | NSIDC accessed 2016 |
| Ice content | The amount of ice contained in frozen or partially frozen soil or rock | Van Everdingen International Permafrost Association 2005 |
| Ice content | The amount of Ice contained in frozen or partially frozen soil or rock. Ice Content is normally expressed in one of two ways: on a dry-weight basis (gravimetric), as the ratio of the mass of the Ice in a sample to the mass of the dry sample, expressed as a percentage, or on a volume basis (volumetric), as the ratio of the volume of Ice in a sample to the volume of the whole sample, expressed as a fraction. The volumetric Ice Content cannot exceed unity whereas the gravimetric Ice Content can greatly exceed 100%. | Trombotto et al. 2014 |
| Ice core | A core sample drilled from the accumulation of snow and ice over many years that have recrystallized and have trapped air bubbles from previous time periods, the composition of which can be used to reconstruct past climates and climate change; typically removed from an ice sheet (Antarctica and Greenland) or from high mountain glaciers elsewhere. | NSIDC accessed 2016 |
| Ice core | A cylinder of ice drilled out of a glacier or ice sheet. | IPCC WGI AR5 2013 |
| Ice cover | Floating ice covering a water area regardless of its age, concentration, mobility and other characteristics. This is the most general notion, usually requiring further specification. The ice cover boundaries are the ice edge and the coastline. | Bushuyev 2004 |
| Ice cover | Sea ice terminology. Describes the ratio of an area of ice to the total area of water surface within a large geographic area. This area may be global, hemispheric, or defined by a specific oceanographic entity such as Baffin Bay or the Barents Sea. | Environment and Climate Change Canada 2014 |
| Ice cover | The ratio of an area of ice of any concentration to the total area of sea surface within some large geographic locale; this locale may be global, hemispheric, or prescribed by a specific oceanographic entity such as Baffin Bay or the Barents Sea. | WMO Sea Ice Nomenclature 2017 |
| Ice cover | Ice on an open water surface. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice cover | A layer of ice on top of some other feature. Usually used in reference to an ice layer at the surface of a lake or pond. | AMS - glossary of meteorology |
| Ice covered | Land overlaid at present by a glacier is said to be covered; the alternative term glacierized has not found general favour. | NSIDC accessed 2016 |
| Ice covered | Land overlaid at present by a glacier is said to be ice covered. The alternative term "glacierized" has not found general favour (cf. Glaciated). | Illustrated Glossary of Snow and Ice |
| Ice crust | 1. A type of snow crust; a layer of ice, thicker than a film crust, upon a snow surface. It is formed by the freezing of meltwater or rainwater that has flowed into the snow surface. 2. Same as ice rind. | AMS - glossary of meteorology |
| Ice crystal | Any one of a number of macroscopic, crystalline forms in which ice appears, including hexagonal columns, hexagonal platelets, dendritic crystals, ice needles, and combinations of these forms. The crystal lattice of ice is hexagonal in its symmetry under most atmospheric conditions. Varying conditions of temperature and vapor pressure can lead to growth of crystalline forms in which the simple hexagonal pattern is present in widely different habits (a thin hexagonal plate or a long thin hexagonal column). In many ice crystals, trigonal symmetry can be observed, suggesting an influence of a cubic symmetry. The principal axis (c axis) of a single crystal of ice is perpendicular to the axis of hexagonal symmetry. Planes perpendicular to this axis are called basal planes (a axes related to the prism facets) and present a hexagonal cross section. Ice is anisotropic in both its optical and electrical properties and has a high dielectric constant (even higher than water) resulting from its water dipole structure. The electrical relaxation time for water is much shorter than for ice (10^9 Hz compared with 10^4 Hz), resulting from a chain reaction requirement for molecules to relax through defects in the ice lattice. In the free air, ice crystals compose cirrus-type clouds, and near the ground they form the hydrometeor called, remarkably enough, "ice crystals" (or ice prisms). They are one constituent of ice fog, the other constituent being droxtals. On terrestrial objects the ice crystal is the elemental unit of hoarfrost in all of its various forms. Ice crystals that form in slightly supercooled water are termed frazil. Ice originating as frozen water (e.g., hail, graupel, and lake ice) still has hexagonal symmetry but lacks any external hexagonal form. Analysis of their sections (0.5 mm) in polarized light reveals different crystal shapes and orientations, depending on the freezing and any annealing and subsequent recrystallization process. | AMS - glossary of meteorology |
| Ice crystals | Precipitation in the form of slowly falling, singular or unbranched ice needles, columns, or plates. They make up cirriform clouds, frost, and ice fog. Also, they produce optical phenomena such as halos, coronas, and sun pillars. May be called 'diamond dust.' Precipitation of ice crystals in the form of needles, columns or plates sometimes so tiny, they seem suspended in air. They are mainly visible when they glitter in sunshine and occur only at very low temperatures and stable air masses. | Canada National Climate Archive 2015 |
| Ice crystals | Any one of a number of macroscopic crystalline forms of ice including hexagonal columns and platelets, dendritic crystals, ice needles and their combinations. | WMO METEOTERM accessed 2016 |
| Ice crystals | A barely visible crystalline form of ice that has the shape of needles, columns or plates. Ice crystals are so small that they seem to be suspended in air. Ice crystals occur at very low temperatures in a stable atmosphere. | NOAA National Weather Service Glossary 2009 |
| Ice day | Day on which the maximum temperature is less than 0 degrees C (or, by convention, less than or equal to 0 degrees C). | WMO METEOTERM accessed 2016 |
| Ice day | In climatology, a day on which the maximum air temperature in a thermometer shelter does not rise above 0C (32F), and ice on the surface of water does not thaw. This term is not used in the United States, but is used in the United Kingdom, throughout most of Europe, and probably in many other parts of the world. | AMS - glossary of meteorology |
| Ice desert | Any polar area permanently covered by ice and snow, with no vegetation other than occasional red snow or green snow. | AMS - glossary of meteorology |
| Ice discharge | Mass flux or volumetric flux of ice through a glacier cross section or 'gate'. The gate can be anywhere on the glacier, but is often at or close to the terminus. If the terminus is a calving front, ice discharge is usually in discrete pieces that, when discharged into a body of water, become icebergs, and the ice discharge is equivalent to the calving flux plus the flux due to advance (positive) or retreat (negative) of the calving front. Avalanching from the glacier margin, for example from the margin of a hanging glacier, may constitute ice discharge; see also dry calving. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice divide | The boundary separating opposing flow directions of ice on a glacier or ice sheet. | NSIDC accessed 2016 |
| Ice drift | Displacement of ice floes and other ice features resulting from the impact of wind and currentsincluding tidal currents and of forces transferred through the ice cover from other regions. The drift direction and velocity of a specific ice feature or ice cover area depends at any specific moment on themagnitude of the external forces, on the feature | Bushuyev 2004 |
| Ice drift | Movement of ice fields or floes in lakes and reservoirs, caused by wind or currents. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice drift | Movement of ice fields or floes in water bodies caused by wind or currents. | AMS - glossary of meteorology |
| Ice edge | The boundary at any given time between open water and sea, river or lake ice of any kind, whether drifting or fast; may be termed compacted when it is clear-cut, or open when it forms the indefinite edge of an area of dispersed ice. | NSIDC accessed 2016 |
| Ice edge | Sea ice terminology, which describes the differentiation at any given time between open water, and sea, lake or river ice whether fast or drifting. | Environment and Climate Change Canada 2014 |
| Ice edge | The demarcation at any given time between the open sea and sea ice of any kind, whether fast or drifting. It may be termed compacted or diffuse. | WMO Sea Ice Nomenclature 2017 |
| Ice edge | The demarcation between the open sea and sea ice of any kind, whether fast (fast ice edge) or drifting. The drift ice edge may be termed compacted or diffuse. | Bushuyev 2004 |
| Ice edge | The demarcation between open water and sea ice. | AMS - glossary of meteorology |
| Ice edge | The boundary at any given time between open water and sea, river or lake ice of any kind, whether drifting or fast. An ice edge may be termed compacted when it is clear-cut, or open when it forms the indefinite edge of an area of dispersed ice. | Illustrated Glossary of Snow and Ice |
| Ice equivalent | A unit, in full the 'metre [of] ice equivalent', that is an extension of the SI for describing glacier mass in specific units as the thickness (in 'm ice eq.') Of an equal mass having the density of ice. Ice equivalents can be converted to kg m-2 by multiplying by the density of ice, and to water equivalents (m w. E.) By multiplying by the density of ice and dividing by the density of water (with sufficient accuracy, 1000 kg m-3). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice extent | The total area covered by some amount of ice, including open water between ice floes; ice extent is typically reported in square kilometers. | NSIDC accessed 2016 |
| Ice fall | An area of crevassed ice on a glacier. Caused when the base of the glacier flows over steep topography. | PhysicalGeography.net |
| Ice feathers | A type of hoarfrost that is formed on the windward side of terrestrial objects and on aircraft flying from cold to warm air layers. Ice feathers are made up of single, columnar ice crystals, some of which grow out from others at large angles and thus build up a delicate spatial array of tiny crystals. (Also called frost feathers.) | AMS - glossary of meteorology |
| Ice field | An area of floating ice of any size, which is greater than 10 km across. The characteristics, position and sizes of fields are described as separate zones. | Bushuyev 2004 |
| Ice field | A continuous accumulation of snow and glacier ice that completely fills a mountain basin or covers a low-relief mountain plateau to a substantial depth. When the thickness become great enough, tongues of ice overflow the basins or plateaus as Valley Glaciers. | Molnia USGS 2004 |
| Ice field | Area of pack ice consisting of floes of any size that are greater than 5.5 n mi (10 km) across. | WMO Sea Ice Nomenclature 2017 |
| Ice field | Sea ice terminology that describes an area of floating ice, consisting of floes greater than 10 km across. | Environment and Climate Change Canada 2014 |
| Ice field | A large, level area of ice, either of sea ice ("more than five miles across") or an ice cap or highland ice. | AMS - glossary of meteorology |
| Ice field | Large level area of glacial ice found covering a large expanse of land. Similar in size to an ice cap but does not have a dome-shape. | PhysicalGeography.net |
| Ice floe | A cohesive sheet of ice floating in the water; the sea ice cover is made up of conglomerates of floes; ice floes are not unique to sea ice, as they also occur in rivers and lakes. | NSIDC accessed 2016 |
| Ice flow | The motion of ice driven by gravitational forces (see glacier flow) or, for sea ice, wind and water currents. | AMS - glossary of meteorology |
| Ice flowers | 1.Delicate tufts of hoarfrost that occasionally form in great abundance on an ice or snow surface (surface hoar); it also forms as a type of crevasse hoar or window frost. 2.Formations of ice crystals on the surface of a quiet, slowly freezing body of water. | AMS - glossary of meteorology |
| Ice fog | A type of fog composed of suspended particles of ice or ice crystals 20 to 100 microns resulting from the freezing of tiny supercooled water droplets. Ice fog occurs in clear, calm, stable air when temperatures are -30 | Canada National Climate Archive 2015 |
| Ice fog | Suspension of numerous minute ice particles in the air, reducing the visibility at the Earth's surface. | WMO METEOTERM accessed 2016 |
| Ice fog | A suspension of numerous minute ice crystals in the air, reducing visibility at the earth's surface; the crystals often glitter in the sunshine; ice fog produces optical phenomena such as luminous pillars and small haloes. | NSIDC accessed 2016 |
| Ice fog | (Also called ice-crystal fog, frozen fog, frost fog, frost flakes, air hoar, rime fog, pogonip.) A type of fog, composed of suspended particles of ice; partly ice crystals 20 to 100 micron in diameter, but chiefly (especially when dense) ice particles about 12 | NOAA National Weather Service Glossary 2009 |
| Ice fog | A type of fog, composed of suspended particles of ice, partly ice crystals 20 to 100 m in diameter, but chiefly, especially when dense, droxtals 12-20 m in diameter. It occurs at very low temperatures, and usually in clear, calm weather in high latitudes. The sun is usually visible and may cause halo phenomena. Ice fog is rare at temperatures warmer than -30C, and increases in frequency with decreasing temperature until it is almost always present at air temperatures of -45C in the vicinity of a source of water vapor. Such sources are the open water of fast-flowing streams or of the sea, herds of animals, volcanoes, and especially products of combustion for heating or propulsion. At temperatures warmer than -30C, these sources can cause steam fog of liquid water droplets, which may turn into ice fog when cooled ( see frost smoke). (Also called ice-crystal fog, frozen fog, frost fog, frost flakes, air hoar, rime fog, pogonip.) | AMS - glossary of meteorology |
| Ice fog | A fog that is composed of small suspended ice crystals. Common in Arctic locations when temperatures are below -30 Celsius and a abundant supply of water vapor exists. | PhysicalGeography.net |
| Ice fog | A suspension of numerous minute ice crystals in the air, reducing visibility at the earth's surface. The crystals often glitter in the sunshine. Ice fog produces optical phenomena such as luminous pillars and small haloes. | Illustrated Glossary of Snow and Ice |
| Ice foot | Sea ice firmly frozen to the shore at the high-tide line and unaffected by tide. This type of fast ice is formed by the freezing of seawater during ebb tide and of spray. It is separated from the floating sea ice by a tide crack; in many areas it offers a fairly level, continuous route for surface travel. | AMS - glossary of meteorology |
| Ice forecast | Statement of expected ice conditions for a specified period and for a specified locality. (TR) | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice forecast | Describes the predicted position of ice boundaries and expected ice phenomena (ice concentration, distribution, stage of development, thickness and direction of drift, number and size of icebergs) for a specified period and for a specified locality, based on forecast meteorological and oceanographic conditions and the regional ice climatology. An ice forecast is often issued to cover the period between the current ice analysis and the next scheduled ice analysis. | AMS - glossary of meteorology |
| Ice formation | Generation of ice from snow or frozen water. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice formation on aircraft | Ice formation can occur on aircraft either on the ground or in flight. Ice accretion in flight may constitute a danger by affecting the aerodynamic characteristics, engine performance, or in other ways. There are four types of airframe icing: 1) rime: a light, white opaque deposit that forms generally at temperatures well below 0C in clouds of low water content, consisting of small supercooled water droplets; 2) clear ice or glaze: a coating of clear ice that forms in clouds of high water content consisting of large (greater than 40 m in diameter) supercooled water droplets in the form of drizzle or rainfall on aircraft with a temperature near or below 0C; 3) mixed ice or cloudy ice: a rough, cloudy deposit that occurs in clouds containing a large range of drop sizes or a mix of ice crystals, cloud droplets, and snowflakes; and 4) hoarfrost: a white crystalline coating of ice that forms in clear air by deposition of water vapor when an aircraft surface is colder than the frost point of the air; this can occur when an aircraft moves rapidly (usually in descent) from very cold air into a region with warm and relatively moist air. | AMS - glossary of meteorology |
| Ice fracturing | Destruction of the ice cover on rivers before break-up, due to the impact of flood waves or ice breaking away from the banks. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice fragment | A general name of any relatively flat piece of sea or river ice with a size from fractions of meter up to several kilometers across. | Bushuyev 2004 |
| Ice free | No sea ice present. Some ice of land origin may occur. | WMO Sea Ice Nomenclature 2017 |
| Ice free | No ice is present. If ice of any kind is present this term shall not be used. | Bushuyev 2004 |
| Ice free | Sea ice terminology, meaning 'no ice present.' If ice of any kind is present, this term will not be used. | Environment and Climate Change Canada 2014 |
| Ice fringe | A very narrow ice piedmont, extending less than about 1 km inland from the sea. | NSIDC accessed 2016 |
| Ice fringe | Very narrow ice piedmont, extending less than about 1 km inland from the sea. | UK Antarctic Place-names Committee accessed 2016 |
| Ice fringe | A very narrow ice piedmont, extending less than about 1 km inland from the sea. | Illustrated Glossary of Snow and Ice |
| Ice front | The vertical cliff forming the seaward face of an ice shelf or other floating glacier, varying in height from 2 to 50 meters (2.2 to 55 yards) above sea level. | NSIDC accessed 2016 |
| Ice front | Sea ice terminology. Describes the vertical cliff that forms the seaward face of an ice shelf or other floating glacier. It varies in height from 2 m to 50 m or more above sea level. | Environment and Climate Change Canada 2014 |
| Ice front | The vertical cliff forming the seaward face of an ice shelf or other floating glacier varying in height from 6 to 165 ft (2-50 m) or more above sea level. | WMO Sea Ice Nomenclature 2017 |
| Ice front | Vertical cliff forming the seaward face of an ice shelf or other floating glacier and, because of its variable position, dated on maps and charts. | UK Antarctic Place-names Committee accessed 2016 |
| Ice front | The seaward facing, clifflike edge of an ice shelf (so called by the British Antarctic Place Names Committee). | AMS - glossary of meteorology |
| Ice front | The vertical cliff forming the seaward face of an ice shelf or other floating glacier, varying in height from 2 to 50 m above sea level (cf. Ice wall). | Illustrated Glossary of Snow and Ice |
| Ice gland | A column of ice in the granular snow at the top of a glacier. | NSIDC accessed 2016 |
| Ice gorge | The gorge or opening left in a jam after it has broken. | NOAA Glossary of Hydrologic Terms |
| Ice gorge | In hydrologic terms, the gorge or opening left in a jam after it has broken. | NOAA National Weather Service Glossary 2009 |
| Ice island | A form of tabular berg found in the Arctic Ocean, with a thickness of 30 - 50 meters (33 to 55 yards) and an area from a few thousand square meters to 500 square kilometers (123,550 acres); ice islands often have an undulating surface, which gives them a ribbed appearance from the air. | NSIDC accessed 2016 |
| Ice island | A large piece of floating ice about 16 ft (5 m) above sea level, which has broken away from an Arctic ice shelf, having a thickness of 100 to 165 ft (30-50 m) and an area of from a few thousand square yards (meters) to 200 sq mi (500 sq kin) or more, and usually characterized by a regularly undulating surface that gives it a ribbed appearance from the air. | WMO Sea Ice Nomenclature 2017 |
| Ice island | A large piece of floating ice protruding about 5 m above sea-level, which has broken away from an Arctic ice shelf, having a thickness of 15-30 m and an area of from a few thousand square meters to 500 km2 or more, and usually characterized by a regularly undulating surface which gives it a ribbed appearance from the air. [Note: Antarctic use is slightly different and refers to a grounded part of a floating ice sheet which rises significantly higher than its surroundings, eg Butler Island. There are also more substantial features, eg the Lyddan Ice Rise.] | Bushuyev 2004 |
| Ice island | Sea ice terminology. Describes a large piece of floating ice protruding about 5 metres above sea level, which has broken away from an Arctic ice shelf. Ice islands have a thickness of 30 m to 50 m, and an area of a few thousand square metres up to 500 sq. Km or more. They are usually characterized by a regularly rolling surface giving a ribbed appearance from the air. | Environment and Climate Change Canada 2014 |
| Ice island | A form of tabular iceberg found in the Arctic Ocean, with a thickness of 30-50 m and from a few thousand square meters to 500 km^2 in area. Ice islands often have an undulated surface, which gives them a ribbed appearance from the air. | AMS - glossary of meteorology |
| Ice island | A form of tabular berg found in the Arctic Ocean, with a thickness of 30 to 50 m and from a few thousand square m to 500 square km in area. Ice islands often have an undulating surface, which gives them a ribbed appearance from the air. | Illustrated Glossary of Snow and Ice |
| Ice island fragment | Sea ice terminology, describing a piece of an ice island that has broken away from the main mass. | Environment and Climate Change Canada 2014 |
| Ice jam | Blockage of a waterway by the accumulation of ice. | WMO METEOTERM accessed 2016 |
| Ice jam | A stationary accumulation that restricts or blocks streamflow. | NOAA Glossary of Hydrologic Terms |
| Ice jam | An accumulation of broken river or sea ice caught in a narrow channel. | NSIDC accessed 2016 |
| Ice jam | An accumulation of broken river ice or sea ice caught in a narrow channel. | WMO Sea Ice Nomenclature 2017 |
| Ice jam | In hydrologic terms, a stationary accumulation that restricts or blocks streamflow. | NOAA National Weather Service Glossary 2009 |
| Ice jam | Sea ice terminology that describes an accumulation of broken river ice or sea ice which is not moving, due to a physical restriction and its resistance to pressure. | Environment and Climate Change Canada 2014 |
| Ice jam | (1) Accumulation of shuga including ice cakes, below ice cover. (2) Broken ice in a river which causes a narrowing of the river channel, a rise in water level and local floods. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice jam | 1.An accumulation of broken river ice caught in a narrow channel. Ice jams during freeze-up are quite porous, whereas breakup jams may comprise solid flows, frequently producing local floods during a spring breakup. 2.Fields of lake or sea ice thawed loose from the shores in early spring and blown against the shore, sometimes exerting great pressures. | AMS - glossary of meteorology |
| Ice jam | The accumulation of ice at a specific location along a stream channel. Can cause the reduction of stream flow down stream of the obstruction and flooding upstream. | PhysicalGeography.net |
| Ice jam | An accumulation of broken river or sea ice caught in a narrow channel. | Illustrated Glossary of Snow and Ice |
| Ice keel | From the point of view of the submariner, a downward-projecting ridge on the underside of the ice canopy; the counterpart of a ridge; ice keels may extend as much as 50 meters (55 yards) below sea level. | NSIDC accessed 2016 |
| Ice keel | From the point of view of the submariner, a downward-projecting ridge on the underside of the ice canopy-the counterpart of a ridge. Ice keels may extend as much as 165 ft (50 m) below sea level. | WMO Sea Ice Nomenclature 2017 |
| Ice keel | Sea ice terminology which describes a downward-projecting ridge on the underside of the ice canopy; the submerged counterpart of a ridge. Ice keels may extend to as much as 50 metres below the surface. | Environment and Climate Change Canada 2014 |
| Ice keel | The submerged counterpart of an ice ridge. | AMS - glossary of meteorology |
| Ice keel | From the point of view of the submariner, a downward-projecting ridge on the underside of the ice canopy; the counterpart of a ridge. Ice keels may extend as much as 50 m below sea level. | Illustrated Glossary of Snow and Ice |
| Ice layer | An ice crust that has been covered by new snow. When exposed at a glacier front or in crevasses, the ice layers viewed in cross section are termed ice bands. | AMS - glossary of meteorology |
| Ice laying | Period of time from freeze-up to ice break-up. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice lens | A dominantly horizontal, lens-shaped body of ice of any dimension. | NSIDC accessed 2016 |
| Ice lens | A dominantly horizontal, lens-shaped body of ice of any dimension | Van Everdingen International Permafrost Association 2005 |
| Ice lense | Horizontal accumulation of permanently frozen ground ice. | PhysicalGeography.net |
| Ice limit | The average position of the ice edge in any given month or period based on observations over a number of years. | NSIDC accessed 2016 |
| Ice limit | Climatological term referring to the extreme minimum or extreme maximum extent of the ice edge in any given month or period based on observations over a number of years. Term should be preceded by minimum or maximum. | WMO Sea Ice Nomenclature 2017 |
| Ice limit | Climatological term referring to the mean, median, extreme minimum or extreme maximum extent of the ice edge in any given month or period based on observations over a number of years. Term should be preceded by the word mean, median, minimum or maximum. | Bushuyev 2004 |
| Ice limit | Sea ice terminology. A climatology term that refers to the extreme minimum or extreme maximum extent of the ice edge in any given month or period, based on observations over a number of years. This term should always be preceded by minimum or maximum. | Environment and Climate Change Canada 2014 |
| Ice limit | The climatological position of the extreme minimum or maximum of sea ice extent. | AMS - glossary of meteorology |
| Ice limit | The average position of the ice edge in any given month or period based on observations over a number of years. | Illustrated Glossary of Snow and Ice |
| Ice mass | A synonym of ice body. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice massif | A concentration of sea ice covering hundreds of square miles (kilometers) that is found in the same region every summer. | WMO Sea Ice Nomenclature 2017 |
| Ice massif | A variable accumulation of close or very close ice covering hundreds of square kilometers which is found in the same region every summer. | Bushuyev 2004 |
| Ice massif | Sea ice terminology that describes a variable accumulation of pack or very close pack, covering hundreds of square kilometres and found in the same region every summer. | Environment and Climate Change Canada 2014 |
| Ice matrix | Excess ice that acts as cementation of the soil particles, typically within coarser permafrost sediments, such as in colluvial slopes or Rock Glaciers. | Trombotto et al. 2014 |
| Ice mixing ratio | The ratio of the mass of ice per unit mass of dry air in a sample containing cloud ice and/or frozen precipitation. (Also called ice water mixing ratio.) | AMS - glossary of meteorology |
| Ice multiplication | A process from which more ice particles are produced from existing ice crystals in clouds. Sometimes known as ice enhancement. The process is inferred from the observation that ice particle concentration often exceeds that of ice nuclei, sometimes by several orders of magnitude. Currently the following mechanisms are thought to be responsible for the ice multiplication phenomenon: 1) mechanical fracturing of ice crystals during evaporation; 2) shattering or partial fragmentation of large drops during freezing; and 3) ice splinter formation during the riming of ice particles (Hallett-Mossop process). | AMS - glossary of meteorology |
| Ice needle | A long, thin ice crystal, axis coincident with the c axis of ice and with the cross section perpendicular to its long dimension being, at least in part, hexagonal. Ice needles grow in a narrow range of temperature near -4C and also at much lower temperatures, below -25 to -50C depending on ice supersaturation. | AMS - glossary of meteorology |
| Ice needles | Ice crystals with a long, slender, prism-like shape, forming at a temperature between -4 and -6C. | WMO METEOTERM accessed 2016 |
| Ice nuclei counter | Any of several devices for counting atmospheric particles that serve as heterogeneous ice nuclei that are suited by composition to catalyze the formation of ice crystals in the atmosphere. The devices operate on varied principles, include means to cool and moisturize the air within a chamber or over a nucleus-collection filter, and are intended to measure the number concentration of ice nuclei that form ice crystals as a function of temperatures that would occur in subzero tropospheric clouds (thus, 0 to near -40C). The product is the nucleation activity temperature spectrum. Some, but by no means all, types of ice nuclei counters are designed to attempt to replicate supersaturations that occur where ice crystals form in natural tropospheric clouds. (Abbreviated IN counter.) | AMS - glossary of meteorology |
| Ice nucleus | Nucleus which sets up the formation of ice crystals in the atmosphere (freezing or sublimation nucleus). | WMO METEOTERM accessed 2016 |
| Ice nucleus | Any particle that serves as a nucleus in the formation of ice crystals in the atmosphere. | NOAA National Weather Service Glossary 2009 |
| Ice nucleus | Any particle that serves as a nucleus leading to the formation of ice crystals without regard to the particular physical processes involved in the nucleation. The process is referred to as heterogeneous nucleation, as opposed to homogeneous nucleation, which depends on the formation of an ice particle large enough to grow by random motion of water molecules alone. Four processes are generally distinguished: 1) deposition (sorption; previously called sublimation), where the ice phase forms directly from water vapor; 2) condensation freezing, where the ice phase forms in a supercooled solution following growth and dilution of a cloud condensation nucleus; 3) contact freezing, where a supercooled droplet nucleates following contact of an ice nucleating aerosol; 4) immersion freezing, where the nucleating particle is completely immersed in the supercooled liquid, which nucleates with sufficient cooling. Because of this multiplicity of nucleation mechanisms it is often difficult to deduce the processes active in a given cloud. Artificially generated aerosols such as silver iodide show activity by all four mechanisms, but at different rates. For natural ice nucleating aerosols, activities in all modes do not generally occur. Observations strongly suggest that, whatever their physico-chemical nature, most natural nuclei act through a freezing process rather than by deposition. | AMS - glossary of meteorology |
| Ice occurrence | Beginning of the formation of ice on a water body. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice of land origin | Ice formed on land or in an ice shelf, found floating in water. The concept includes ice that is stranded or grounded. | WMO Sea Ice Nomenclature 2017 |
| Ice of land origin | Ice formed on land or in an ice shelf, found floating in water. | Bushuyev 2004 |
| Ice patch | An accumulation of floating ice less than 10 km across in ice-free water or among ice in smaller concentration. | Bushuyev 2004 |
| Ice patch | An area of pack ice less than 6 n mi (10 kin) across. | WMO Sea Ice Nomenclature 2017 |
| Ice patch | Sea ice terminology, meaning an area of ice which is less than 10 km across. | Environment and Climate Change Canada 2014 |
| Ice patrol ship | A research ship which performs ice surveys in polar regions. | NSIDC accessed 2016 |
| Ice pellet | Precipitation of small balls or pieces of ice (hailstones) with a diameter ranging from 5 to 50 millimeters (0.2 to 2.0 inches), or sometimes more, falling either separately or agglomerated into irregular lumps; when the diameter is less that about 5 millimeters (0.2 inch), the balls are called ice pellets. | NSIDC accessed 2016 |
| Ice pellet | For definition see Hail. | Illustrated Glossary of Snow and Ice |
| Ice pellets | Precipitation of transparent or translucent pellets of ice, which are spherical or irregular shaped, having a diameter of 5 mm or less. They are classified into two types hard grains of ice consisting of frozen rain drops or largely melted and refrozen snowflakes; pellets of snow encased in a thin layer of ice which have formed from the freezing of droplets intercepted by pellets or water resulting from the partial melting of pellets. Ice pellets usually bounce when hitting hard ground and make a sound on impact. They can fall as continuous precipitation or in showers. | Canada National Climate Archive 2015 |
| Ice pellets | (abbrev. IP) Same as Sleet; defined as pellets of ice composed of frozen or mostly frozen raindrops or refrozen partially melted snowflakes. These pellets of ice usually bounce after hitting the ground or other hard surfaces. A Winter Storm Warning is issued for sleet or a combination of sleet and snow based on total accumulation which is locally defined by area. | NOAA National Weather Service Glossary 2009 |
| Ice pellets | Tiny particles of ice that are formed when supercooled raindrops freeze before reaching the ground. | Environment and Climate Change Canada 2014 |
| Ice pellets | Precipitation of transparent particles of ice which are spherical or irregular, rarely conical, and which have a diameter of 5 mm or less. | WMO METEOTERM accessed 2016 |
| Ice pellets | A type of precipitation consisting of transparent or translucent pellets of ice, less than 5 mm in diameter. They may be spherical, irregular, or (rarely) conical in shape. Ice pellets usually bounce when hitting hard ground and make a sound upon impact. Now internationally recognized, ice pellets includes two basically different types of precipitation, known in the United States as 1) sleet and 2) small hail. Thus a two-part definition is given: 1) sleet or grains of ice, generally transparent, globular, solid grains of ice that have formed from the freezing of raindrops or the refreezing of largely melted snowflakes when falling through a below-freezing layer of air near the earth's surface; 2) small hail, generally translucent particles, consisting of snow pellets encased in a thin layer of ice. The ice layer may form either by the accretion of droplets upon the snow pellet or by the melting and refreezing of the surface of the snow pellet. | AMS - glossary of meteorology |
| Ice pellets | A type of precipitation. Ice pellets or sleet are transparent or translucent spheres of frozen water that fall from clouds. Ice pellets have a diameter less than 5 millimeters. To form, this type of precipitation requires an environment where raindrops develop in an atmosphere where air temperature is above freezing. These raindrops then fall into a lower layer of air with freezing temperatures. In this lower layer of cold air, the raindrops freeze into small ice pellets. Like freezing rain, an air temperature inversion is required for development of ice pellets. | PhysicalGeography.net |
| Ice piedmont | Ice covering a costal strip of low-lying land backed by mountains; the surface of an ice piedmont slopes gently seawards and may be anything from 1 to 50 kilometers (0.6 to 31 miles) wide, fringing long stretches of coastline with ice cliffs; ice piedmonts frequently merge into ice shelves; a very narrow ice piedmont may be called an ice fringe. | NSIDC accessed 2016 |
| Ice piedmont | An expanse of glacier ice covering a lowland, nourished by two or more upland tributary glaciers. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice piedmont | A glacier covering a coastal strip of low-lying land backed by mountains, and sloping gently seaward over a distance up to 30km or more to terminate in ice cliffs or to merge with an ice shelf, cf. ice fringe. | UK Antarctic Place-names Committee accessed 2016 |
| Ice piedmont | Ice covering a coastal strip of low-lying land backed by mountains. The surface of an ice piedmont slopes gently seawards and may be anything from 1 to 50 km wide, fringing long stretches of coastline with ice cliffs. Ice piedmonts frequently merge into ice shelves. A very narrow ice piedmont may be called an ice fringe (cf. Piedmont glacier). | Illustrated Glossary of Snow and Ice |
| Ice plain | Part of an ice stream extending upglacier from the grounding line and having a surface slope so small as to suggest that it is not far from the transition to being afloat. See flotation. The upglacier limit of the ice plain may be marked by a measurable break of surface slope, or may be indistinct. Ice plains are documented from several of the ice streams of Antarctica. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice plain | An area of slightly grounded ice in the mouth of some ice streams. Typically an area of very low basal stress. | AMS - glossary of meteorology |
| Ice point | Tm or Tf. The narrowly correct name of what in everyday usage is called the melting point or freezing point of water. See pressure-melting point. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice point | The true freezing point of water; the temperature at which a mixture of air-saturated pure water and pure ice exist in equilibrium at a pressure of one standard atmosphere. | WMO METEOTERM accessed 2016 |
| Ice point | The temperature at which a mixture of air-saturated pure water and pure ice may exist in equilibrium at a pressure of one standard atmosphere. The ice point is often used as one fiducial point (0C or 32F) in establishing a thermometric scale because it is reproduced relatively easily under laboratory conditions. The ice point is frequently called the freezing point, but the latter term should be reserved for the much broader reference to the solidification of any kind of liquid under various conditions. | AMS - glossary of meteorology |
| Ice pole | The approximate center of the most consolidated portion of the arctic pack ice, near 83 or 84N and 160W. This term was falling into disuse until its reintroduction with reference to antarctic International Geophysical Year (IGY) activity. (Also called pole of inaccessibility.) | AMS - glossary of meteorology |
| Ice port | An embayment in an ice front, often of a temporary nature, where ships can moor alongside and unload directly onto the ice shelf. | WMO Sea Ice Nomenclature 2017 |
| Ice prisms | A fall of unbranched ice crystals, in the form of needles, columns, or plates, often so tiny that they seem to be suspended in the air; these are visible mainly when they glitter in the sunshine (diamond dust); they may then produce a luminous pillar or other halo phenomena; this hydrometeor, which is frequent in polar regions, occurs at very low temperatures and in stable air masses. | NSIDC accessed 2016 |
| Ice prisms | Unbranched prismatic ice crystals, in the form of needles, columns or plates, often so tiny that they seem to be suspended in the air. These crystals may fall from a cloud or from a cloudless sky. | WMO METEOTERM accessed 2016 |
| Ice prisms | Ice crystals having well defined crystalline facets, usually on both basal planes and on prism planes. | AMS - glossary of meteorology |
| Ice prisms | A fall of unbranched ice crystals, in the form of needles, columns or plates, often so tiny that they seem to be suspended in the air. These crystals may fall from a cloud or from a cloudless sky. They are visible mainly when they glitter in the sunshine (diamond dust); they may then produce a luminous pillar or other halo phenomena. This hydrometeor, which is frequent in polar regions, occurs at very low temperatures and in stable air masses. | Illustrated Glossary of Snow and Ice |
| Ice push | Compression of an ice cover particularly at the front of a moving section of ice cover. | NOAA Glossary of Hydrologic Terms |
| Ice push | In hydrologic terms, compression of an ice cover particularly at the front of a moving section of ice cover. | NOAA National Weather Service Glossary 2009 |
| Ice quake | A shaking of ice caused by crevasse formation or jerky motion. | NSIDC accessed 2016 |
| Ice quake | See cryoseism. | GCW |
| Ice raft | Part of an ice stream raised slightly higher, and flowing slightly more slowly, than surrounding ice. The attributes that define the ice raft suggest that basal sliding is relatively slow at its bed, and therefore that it might represent a persistent 'sticky spot'. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice raft | A discrete block of slow-moving land ice that has been incorporated en masse into either an ice stream or an ice shelf. | AMS - glossary of meteorology |
| Ice rafting | The transportation of glacier sediment away from the ice margin by icebergs. Sediment transported by floating ice and deposited in the ocean is called glacial-marine sediment. Deposited in lakes, it is called glacial-lacustrine sediment. | Molnia USGS 2004 |
| Ice reef | Ridge formed by external pressure on an ice cover. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice regime | Sequence of regularly recurring processes of formation, development, and decay of ice cover on a water body. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice regime phase | The state or condition of the ice on a river, lake, or other body of water, caused by the thermodynamics of weather conditions. | AMS - glossary of meteorology |
| Ice rind | A brittle, shiny crust of floating ice, formed on a quiet surface by direct freezing or from grease ice, usually in water of low salinity; thickness less than 5 centimeters (2 inches); easily broken by wind or swell, commonly breaking into rectangular pieces. | NSIDC accessed 2016 |
| Ice rind | A brittle shiny crust of ice formed on a calm surface by direct freezing, or from grease ice, usually in water of low salinity. Thickness to about 5 cm. Easily broken by wind or swell, commonly breaking in rectangular pieces. | Bushuyev 2004 |
| Ice rind | A brittle shiny crust of ice formed on a quiet surface by direct freezing or from grease ice, usually in water of low salinity. Thickness to about 1 in (5 cm). Easily broken by wind or swell, commonly breaking in rectangular pieces. | WMO Sea Ice Nomenclature 2017 |
| Ice rind | Sea ice terminology. Describes a brittle, shiny crust of ice formed on a quiet surface by direct freezing, or from grease ice, usually in water of low salinity; with a thickness of about 5 centimetres. Easily broken by wind or swell, it commonly breaks into rectangular pieces. | Environment and Climate Change Canada 2014 |
| Ice rind | Floating ice, less than 5 centimetres thick, which forms on a calm freshwater surface. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice rind | A thin but hard layer of sea ice, river ice, or lake ice. Apparently this term is used in at least two ways: 1) for a new encrustation upon old ice; and 2) for a single layer of ice usually found in bays and fjords where freshwater freezes on top of slightly colder seawater. (Also called ice crust.) | AMS - glossary of meteorology |
| Ice rind | A brittle, shiny crust of floating ice, formed on a quiet surface by direct freezing or from grease ice, usually in water of low salinity. Thickness less than 5 cm. Easily broken by wind or swell, commonly breaking in rectangular pieces. | Illustrated Glossary of Snow and Ice |
| Ice rise | A mass of ice resting on rock and surrounded either by an ice shelf, or partly by an ice shelf and partly by sea; no rock is exposed and there may be none above sea level; ice rises often have a dome-shaped surface; the largest known is about 100 kilometers (62 miles) across. | NSIDC accessed 2016 |
| Ice rise | An area of grounded ice surrounded or almost surrounded by shelf ice or the ice of a floating tongue. Currently the largest ice rise, with an area of 44 000 km2, is Berkner Island in the Ronne-Filchner Ice Shelf. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice rise | Mass of ice, often dome shaped, resting on rock and surrounded either by an ice shelf, or partly by an ice shelf and partly by sea; no rock is exposed and there may be none above sea-level. For some features, properly ice rises, the term island has become established through usage. | UK Antarctic Place-names Committee accessed 2016 |
| Ice rise | A usually dome-shaped mass of ice resting on rock and surrounded either by an ice shelf, or partly by an ice shelf and partly by the sea. No rock is exposed. | AMS - glossary of meteorology |
| Ice rise | A mass of ice resting on rock and surrounded either by an ice shelf, or partly by an ice shelf and partly by sea. No rock is exposed and there may be none above sea level. Ice rises often have a dome-shaped surface. The largest known is about 100 km across. | Illustrated Glossary of Snow and Ice |
| Ice rumple | A small ice rise, generally of irregular outline, or a group of small ice rises. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice rumples | Locally grounded area of ice shelf which is over-ridden by an ice sheet and distinguished by crevassing together with a rise in the surface, cf. ice rise. | UK Antarctic Place-names Committee accessed 2016 |
| Ice run | Flow of ice in a river. An ice run may be light or heavy, and may consist of frazil, anchor, slush, or sheet ice. | NOAA Glossary of Hydrologic Terms |
| Ice run | In hydrologic terms, flow of ice in a river. An ice run may be light or heavy, and may consist of frazil, anchor, slush, or sheet ice. | NOAA National Weather Service Glossary 2009 |
| Ice run | Movement of ice or slush ice with the current of a stream. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice run | Movement of ice or slush ice with the current of a stream, particularly in the initial stage in the spring or summer breakup of river ice. | AMS - glossary of meteorology |
| Ice saints | Name given by popular tradition, in a large part of Europe, to certain Saints (Mamertus, Pancras, etc.) whose feast days, in the first fortnight of May, are said to be often accompanied by a temporary lowering of temperature and sometimes by late frosts. | WMO METEOTERM accessed 2016 |
| Ice Saints | St. Mamertus, St. Pancras, and St. Savertius or St. Gervais, whose feast-days fall on 11, 12, and 13 May, respectively. These days are associated with May frosts in the folklore of a large part of Europe. | AMS - glossary of meteorology |
| Ice segregation | The formation of discrete layers or lenses of segregated ice in freezing mineral or organic soils, as a result of the migration (and subsequent freezing) of pore water. | NSIDC accessed 2016 |
| Ice segregation | The formation of discrete layers or lenses of segregated ice in freezing mineral or organic soils, as a result of the migration (and subsequent freezing) of pore water | Van Everdingen International Permafrost Association 2005 |
| Ice segregation | The formation of discrete layers or lenses of Segregated Ice in freezing mineral or organic soils, as a result of the migration (and subsequent freezing) of pore water. | Trombotto et al. 2014 |
| Ice sheet | A dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres) (e.g., the Greenland and Antarctic ice sheets). | NSIDC accessed 2016 |
| Ice sheet | An ice body that covers an area of continental size, generally defined as covering 50 000 km2 or more. Currently there are only two ice sheets, the Greenland Ice Sheet and the Antarctic Ice Sheet. The latter is sometimes subdivided into the East Antarctic Ice Sheet and the West Antarctic Ice Sheet. See ice cap. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice sheet | A thick, subcontinental to continental-scale accumulation of glacier ice and perennial snow that spreads from a center of accumulation, typically in all directions. Also called a Continental Glacier. | Molnia USGS 2004 |
| Ice sheet | A mass of land ice of continental size that is sufficiently thick to cover most of the underlying bed, so that its shape is mainly determined by its dynamics (the flow of the ice as it deforms internally and/or slides at its base). An ice sheet flows outward from a high central ice plateau with a small average surface slope. The margins usually slope more steeply, and most ice is discharged through fast flowing ice streams or outlet glaciers, in some cases into the sea or into ice shelves floating on the sea. There are only two ice sheets in the modern world, one on Greenland and one on Antarctica. During glacial periods there were others. | IPCC WGII AR5 2014 |
| Ice sheet | Mass of ice and snow of considerable thickness, and often large area, either resting on rock or floating as an ice shelf, cf. ice cap. | UK Antarctic Place-names Committee accessed 2016 |
| Ice sheet | Mass of ice and snow of considerable thickness extending over a large area of land and water. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice sheet | A mass of Ice and Snow of considerable thickness and large area. Ice Sheets may be resting on rock or floating. Ice Sheets of less than about 50,000 square km resting on rock are called Ice Caps. | Trombotto et al. 2014 |
| Ice sheet | A mass of ice and snow of considerable thickness, defined as covering an area of more than 50,000 square kilometres. | Swisseduc - Photo glossary of glaciological terms |
| Ice sheet | A dome-shaped glacier covering an area greater than 50,000 square kilometers. Greenland and Antarctica are considered ice sheets. During the glacial advances of the Pleistocene ice sheets covered large areas of North America, Europe, and Asia. Larger than an ice cap. | PhysicalGeography.net |
| Ice sheet | A mass of ice and snow of considerable thickness and large area. Ice sheets may be resting on rock (see Inland ice sheet) or floating (see Ice shelf). Ice sheets of less than about 50,000 square km resting on rock are called ice caps. | Illustrated Glossary of Snow and Ice |
| Ice shelf | The floating terminus of a glacier, typically formed when a terrestrial glacier flow into a deep water basin, such as in Antarctica and the Canadian Arctic. | Molnia USGS 2004 |
| Ice shelf | Portion of an ice sheet that spreads out over water. | NSIDC accessed 2016 |
| Ice shelf | A floating ice sheet of considerable thickness showing 6 to 165 ft (2-50 m) or more above sea level, attached to the coast. Usually of great horizontal extent and with a level or gently undulating surface. Nourished by annual snow accumulation and also by the seaward extension of land glaciers. Limited areas may be aground. The seaward edge is termed an ice front. | WMO Sea Ice Nomenclature 2017 |
| Ice shelf | A floating ice sheet of considerable thickness showing 2-50 m or more above sea-level, attached to the coast or a glacier. Usually of great horizontal extent and with a level or gently undulating surface. Nourished by annual snow accumulation at the surface and often also by the seaward extension of land glaciers. Limited areas may be aground. The seaward edge is termed an ice front. | Bushuyev 2004 |
| Ice shelf | A thick and extensive ice body attached to a coast and floating on the sea, gaining mass by flow from grounded glacier ice. See floating tongue, shelf ice. Ice shelves are much thicker than sea ice. Currently, nearly all are located in Antarctica. The mass balance of an ice shelf may have significant components of both gain and loss at the base. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice shelf | Sea ice terminology. Describes a floating ice sheet of considerable thickness that is visible 2 metres or more above sea level, and is attached to the coast. They usually have great horizontal extension, and a level or gently rolling surface. Ice shelf growth occurs with annual snow accumulation, and also by the extension of land glaciers over see. Limited areas of the ice shelf may be attached to land. The edge facing the sea is termed as ice front. | Environment and Climate Change Canada 2014 |
| Ice shelf | A floating slab of ice of considerable thickness extending from the coast (usually of great horizontal extent with a very gently sloping surface), often filling embayments in the coastline of an ice sheet. Nearly all ice shelves are in Antarctica, where most of the ice discharged into the ocean flows via ice shelves. | IPCC WGII AR5 2014 |
| Ice shelf | Floating ice sheet of considerable thickness attached to a coast, and nourished by the accumulation of snow and often by the seaward extension of land glaciers. Limited areas may be aground as ice rises. The seaward edge is termed an ice front. | UK Antarctic Place-names Committee accessed 2016 |
| Ice shelf | A large slab of ice floating on the sea, but remaining attached to and largely fed by land-derived ice. | Swisseduc - Photo glossary of glaciological terms |
| Ice shelf | A thick ice formation with a fairly level surface, formed along a polar coast and in shallow bays and inlets, where it is fastened to the shore and often reaches bottom. An ice shelf may grow hundreds of miles out to sea. It is usually an extension of land ice, and the seaward edge floats freely in deep water. The calving of an ice shelf forms tabular icebergs and ice islands. (Also called shelf ice; formerly barrier.) | AMS - glossary of meteorology |
| Ice shelf | Large flat layer of ice that extends from the edge of the Antarctic ice cap into the Antarctic Ocean. Source of icebergs. | PhysicalGeography.net |
| Ice shelf | A floating ice sheet of considerable thickness attached to a coast. Ice shelves are usually of great horizontal extent and have a level or gently undulating surface. They are nourished by the accumulation of snow and often by the seaward extension of land glaciers. Limited areas may be aground. The seaward edge is termed an ice front (q.v.). | Illustrated Glossary of Snow and Ice |
| Ice shelf | Floating ice masses; Attached to the coast; Seaward extension of terrestrial glaciers beyond the grounding line; Nourished by snow accumulation and bottom freezing in addition to influx of glacier ice; The floating part is not effected by the dynamics of the nourishing glaciers ; Floating ice sheet of considerable thickness attached to a coast nourished by glacier(s); snow accumulation on its surface or bottom freezing; Generic development of an Ice shelf starts with the confluence of several floating glaciers. Therefore this classification combination should first be taken into account, before classifying an ice mass as Ice Shelf. | Illustrated GLIMS Glacier Classification Manual |
| Ice shelf nourishing | Glaciers which are tributaries of an ice shelf. Approximate grounding line may be detectable. This class has been introduced due to the necessity for classifying glaciers which are tributaries of an ice shelf. | Illustrated GLIMS Glacier Classification Manual |
| Ice ship | A pinnacle of ice, shaped like a triangular sail, typically several metres high, formed as a result of differential ablation under strong solar radiation, mainly in low, but sometimes high-arid latitudes. | Swisseduc - Photo glossary of glaciological terms |
| Ice shove | On-shore ice push caused by wind, and currents, changes in temperature, etcetera. | NOAA Glossary of Hydrologic Terms |
| Ice shove | In hydrologic terms, on-shore ice push caused by wind, and currents, changes in temperature, etcetera. | NOAA National Weather Service Glossary 2009 |
| Ice skylight | From the point of view of the submariner, thin places in the ice canopy, usually less than 1 meter (3.3 feet) thick and appearing from below as relatively light, translucent patches in dark surroundings; the under-surface of an ice skylight is normally flat; ice skylights are called large if big enough for a submarine to attempt to surface through them (120 meters, 131 yards), or small if not. | NSIDC accessed 2016 |
| Ice skylight | From the point of view of the submariner, thin places in the ice canopy, usually less than 1 m thick and appearing from below as relatively light translucent patches in dark surroundings. The under-surface of an ice skylight is normally flat. Ice skylights are called large if big enough for a submarine to attempt to surface through them (120 m) or small if not. | Illustrated Glossary of Snow and Ice |
| Ice storm | An ice storm is used to describe occasions when damaging accumulations of ice are expected during freezing rain situations. Significant accumulations of ice pull down trees and utility lines resulting in loss of power and communication. These accumulations of ice make walking and driving extremely dangerous. Significant ice accumulations are usually accumulations of | NOAA National Weather Service Glossary 2009 |
| Ice storm | A storm characterized by a fall of freezing liquid precipitation. The attendant formation of glaze on terrestrial objects creates many hazards. (Also called silver storm.) | AMS - glossary of meteorology |
| Ice storm syn. glaze storm | Intense formation of ice on objects by the freezing, on impact, of rain or drizzle. | WMO METEOTERM accessed 2016 |
| Ice stream | (1) a current of ice in an ice sheet or ice cap that flows faster than the surrounding ice (2) sometimes refers to the confluent sections of a branched-valley glacier (3) obsolete synonym of valley glaciers. | NSIDC accessed 2016 |
| Ice stream | A part of an ice sheet or ice cap with strongly enhanced flow, often separated from surrounding ice by strongly sheared, crevassed margins. 'Pure' ice streams are bounded by ice on either side and lack significant non-glacial topographic control, while 'topographic' ice streams are constrained by the topography. An ice stream of the latter type is similar to an outlet glacier, but outlet glaciers do not necessarily have strongly enhanced flow velocity. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice stream | Part of an island ice sheet in which the ice flows more rapidly and not necessarily in the same direction as the surrounding ice. The margins are sometimes clearly marked by a change in direction of the surface slope but may be indistinct. | WMO Sea Ice Nomenclature 2017 |
| Ice stream | Sea ice terminology. Describes the part of an inland ice sheet in which the ice flows more rapidly and not necessarily in the same direction as the surrounding ice. | Environment and Climate Change Canada 2014 |
| Ice stream | A linear or curvilinear part of an ice sheet, often a few kilometres to a few tens of kilometres wide and tens to hundreds of kilometres long, in which the ice flows much faster than main body of the surrounding ice sheet. The margins are sometimes defined clearly by the presence of a shear zone marked by surface crevasses. | UK Antarctic Place-names Committee accessed 2016 |
| Ice stream | A stream of ice with strongly enhanced flow that is part of an ice sheet. It is often separated from surrounding ice by strongly sheared, crevassed margins. See also Outlet glacier. | IPCC WGI AR5 2013 |
| Ice stream | Part of an ice sheet or ice cap in which the ice flows more rapidly, and not necessarily in the same direction as the surrounding ice. Zones of strongly sheared, crevassed ice often define the margins (cf. shear zone). | Swisseduc - Photo glossary of glaciological terms |
| Ice stream | A fast-moving section of an ice sheet contained within the ice sheet. Motion of an ice stream is dominated by basal sliding. | AMS - glossary of meteorology |
| Ice stream | Part of an ice sheet in which the ice flows more rapidly and not necessarily in the same direction as the surrounding ice. The margins are sometimes clearly marked by a change in direction of the surface slope, but may be indistinct. | Illustrated Glossary of Snow and Ice |
| Ice stream | Part of an Ice sheet; Ice flow of higher velocity than surrounding ice masses; Unrestricted by topographic features, which protrude out of the ice mass; The Primary Classification should be extended by the class 'Ice stream' because they play an important role in the drainage of the Antarctic ice sheet. Although variable in time and space, they are well defined glaciological features and are of high importance for draining the continental ice sheets. | Illustrated GLIMS Glacier Classification Manual |
| Ice structure | The arrangement of water molecules in an ice crystal. Under normal atmospheric temperatures and pressures between 0 and -100C, water molecules arrange themselves into an hexagonal crystalline structure called ice-Ih. When viewed along the principal c axis these molecules form spatial hexagonal rings lying above each other, each water molecule surrounded by four others, in a near tetrahedral arrangement. | AMS - glossary of meteorology |
| Ice survey | Measurement of the thickness and extent of ice and the underlying slush. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ice tongue | Synonymous with glacier tongue, which is the preferred term. | UK Antarctic Place-names Committee accessed 2016 |
| Ice tongue | See glacier tongue: The long slender part of a valley glacier that is subject to net ablation. | Swisseduc - Photo glossary of glaciological terms |
| Ice tongue | Any narrow extension of a glacier or ice shelf, such as a projection floating in the sea or an outlet glacier of an ice cap. | AMS - glossary of meteorology |
| Ice twitch | Downstream movement of a small section of an ice cover. Ice twitches occur suddenly and often appear successively. | NOAA Glossary of Hydrologic Terms |
| Ice twitch | In hydrologic terms, downstream movement of a small section of an ice cover. Ice twitches occur suddenly and often appear successively. | NOAA National Weather Service Glossary 2009 |
| Ice under pressure | Ice in which deformation processes are actively occurring and hence a potential impediment or danger to shipping. | WMO Sea Ice Nomenclature 2017 |
| Ice under pressure | Sea ice terminology describing ice in which the deformation processes are actively occurring. This form of ice is also a potential impediment or danger to shipping. | Environment and Climate Change Canada 2014 |
| Ice vein | An ice-filled crack or fissure in the ground. | NSIDC accessed 2016 |
| Ice vein | An ice-filled crack or fissure in the ground | Van Everdingen International Permafrost Association 2005 |
| Ice vein | An Ice-filled crack or fissure in the ground. | Trombotto et al. 2014 |
| Ice wall | An ice cliff forming the seaward margin of an inland ice sheet, ice piedmont or ice rise; the rock basement may be at or below sea level. | NSIDC accessed 2016 |
| Ice wall | An ice cliff forming the seaward margin of a glacier that is not afloat. An ice wall is aground, the rock basement being at or below sea level. | WMO Sea Ice Nomenclature 2017 |
| Ice wall | Sea ice terminology that describes an ice cliff forming at the seaward margin of a glacier which is aground. | Environment and Climate Change Canada 2014 |
| Ice wall | A steep rocky slope almost completely draped with glacier ice, including hanging glaciers and ice aprons (q.v.). | Swisseduc - Photo glossary of glaciological terms |
| Ice wall | An ice cliff forming the seaward margin of an inland ice sheet, ice piedmont or ice rise. The rock basement may be at or below sea level (cf. Ice front). | Illustrated Glossary of Snow and Ice |
| Ice wedge | Narrow ice mass that is 3 to 4 meters (10 to 13 feet) wide at the ground surface, and extends as much as 10 meters (33 feet) down; a decrease in temperature during the winter leads to ice wedge cracks in the ground around ice wedges; during the summer, these cracks accumulate melt-water and sediment, forming pseudomorphs. | NSIDC accessed 2016 |
| Ice wedge | A massive, generally wedge-shaped body with its apex pointing downward, composed of foliated or vertically banded, commonly white, ice | Van Everdingen International Permafrost Association 2005 |
| Ice wedge | A massive, generally wedge-shaped body with its apex pointing downward, composed of foliated or vertically banded, commonly white Ice. The size of Ice Wedges varies from less than 10 cm to more than 3 m in width at the top, commonly tapering to a feather edge at a depth of 1 to more than 10 m. Ice Wedges are formed in thermal contraction cracks (Figura 33) in which hoar frost forms and into which water from melting Snow penetrates in the spring. Repeated annual contraction cracking of the Ice in the wedge, followed by freezing of water in the crack, gradually increases the width (and possibly the depth) of the wedge and causes vertical banding of the Ice mass. The surface expression of Ice Wedges is generally a network of Polygons. Ice Wedges growing as a result of repeated winter cracking are called Active Ice Wedges. Inactive Ice Wedges can be stable and remain for many centuries without changing. Ice Wedges are more common in arctic environments than mountains due to differences in soil properties, topography and availability of water. | Trombotto et al. 2014 |
| Ice wedge | Wedge-shaped, ice body composed of vertically oriented ground ice that extends into the top of a permafrost layer. These features are approximately 2 to 3 meters wide at their top and extend into the soil about 8 to 10 meters. Form in cracks that develop in the soil during winter because of thermal contraction. In the spring, these cracks fill with liquid water from melting snow which subsequently re-freezes. The freezing process causes the water to expand in volume increasing the size and depth of the crack. The now large crack fills with more liquid water and again it freezes causing the crack to enlarge.This process continues for many cycles until the ice wedge reaches its maximum size. | PhysicalGeography.net |
| Ice wedge polygon | A Polygon outlined by Ice Wedges underlying its boundaries. | Trombotto et al. 2014 |
| Ice worm | An oligochaete worm that lives on temperate glaciers or perennial snow; there are several species that range in color from yellowish-brown to reddish-brown or black; they are usually less than 1 millimeter (0.04 inch) in diameter and average about 3 millimeters (0.1 inch) long; some eat red algae. | NSIDC accessed 2016 |
| Ice-accretion indicator | An instrument used to detect the occurrence of freezing precipitation. It usually consists of a strip of sheet aluminum about 4 cm (1.5 in.) wide and is exposed horizontally, faceup, in the free air about 1 m above the ground. | AMS - glossary of meteorology |
| Ice-albedo feedback | A climate feedback involving changes in the Earth's surface albedo. Snow and ice have an albedo much higher (up to ~0.8) than the average planetary albedo (~0.3). With increasing temperatures, it is anticipated that snow and ice extent will decrease, the Earth's overall albedo will decrease and more solar radiation will be absorbed, warming the Earth further. | IPCC WGI AR5 2013 |
| Ice-bearing permafrost | Permafrost that contains ice. | NSIDC accessed 2016 |
| Ice-bearing permafrost | Permafrost that contains ice | Van Everdingen International Permafrost Association 2005 |
| Ice-bearing permafrost | Permafrost that contains Ground Ice without specifying how much. | Trombotto et al. 2014 |
| Ice-bonded permafrost | Ice-bearing permafrost in which the soil particles are cemented together by ice. | NSIDC accessed 2016 |
| Ice-bonded permafrost | Ice-bearing permafrost in which the soil particles are cemented together by ice | Van Everdingen International Permafrost Association 2005 |
| Ice-bound | Sea ice terminology. A harbour, inlet, etc. Is said to be ice-bound when ships cannot navigate within it due to the ice. In some cases, navigation is possible with the assistance of an icebreaker. | Environment and Climate Change Canada 2014 |
| Ice-bulb temperature | Same as the wet-bulb temperature when the latter is below 0C and the water on the thermometer is frozen. Note that in dry conditions the wet bulb of a psychrometer may freeze when the air temperature is appreciably above the freezing point. | AMS - glossary of meteorology |
| Ice-cemented glacier | A rock glacier that has interstitial ice a meter or so below the surface. | NSIDC accessed 2016 |
| Ice-core stratigraphy | The determination of layering, usually identifiable as Annual or seasonal, in an ice core by visual, chemical, or isotopic methods; more loosely, the result of such determination. After correction for thinning due to ice flow, the resulting layer thicknesses are measures of climatic mass balance. If there is no ablation, they are measures of accumulation. While some information can be obtained from cores even when the ice is not cold, ice-core stratigraphy is usually done on cores through cold ice, such as in Greenland or Antarctica. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice-cored glacier | A rock glacier that has a buried core of ice. | NSIDC accessed 2016 |
| Ice-cored moraine | A moraine ridge consisting of a drape of sediment overlying a mass of stagnant ice. | Molnia USGS 2004 |
| Ice-cored topography | Topography that is due almost solely to differences in the amount of excess ice underlying its surface. | NSIDC accessed 2016 |
| Ice-cored topography | Topography that is due almost solely to differences in the amount of excess ice underlying its surface | Van Everdingen International Permafrost Association 2005 |
| Ice-crystal cloud | A cloud consisting entirely of ice crystals (such as cirrus); to be distinguished in this sense from water clouds and mixed clouds. Ice-crystal clouds have a diffuse and fibrous appearance, quite different from that typical of water droplet clouds, resulting from growth in much weaker updrafts and different fall speeds of a wider size particle spectrum. | AMS - glossary of meteorology |
| Ice-crystal haze | A type of very light ice fog composed only of ice crystals (no droxtals), and at times observable to altitudes as great as 7000 m. It is usually associated with precipitation of ice crystals. Observed from the ground, ice-crystal haze may be dense enough to hinder observation of celestial bodies, sometimes even the sun. Looking down from the air, however, the ground is usually visible and the horizon only blurred. For very sparse ice-crystal haze during daytime, sunlight reflecting from crystal faces produces sparkling in the air; hence the name diamond dust for these crystals. | AMS - glossary of meteorology |
| Ice-dammed lake | A temporary lake, dammed by a glacier or where two glaciers merge. Prone to seasonal catastrophic drainage. | Swisseduc - Photo glossary of glaciological terms |
| Ice-dammed lake | A lake that exists because its water is restricted from flowing by an ice dam. Sometimes these lakes form because an advancing glacier had blocked a valley. | Molnia USGS 2004 |
| Ice-fall | Closed ice cover over a steep mountain side; Entirely crevassed with many seracs; Break above a cliff, with reconstitution to a cohering ice mass below (WGMS, 1970); A glacier with a considerable drop in the longitudinal profile at one point causing heavily broken surface (WGMS, 1977) | Illustrated GLIMS Glacier Classification Manual |
| Ice-field | Approximately horizontal, ice covered area; Ice covering does not overwhelm surrounding topography; Occur in topographical depressions or plateaus; No dome like shape (in contrast to Ice cap); Smaller than 50.000km^2 (approx. 220 x 220 km) ; Ice masses of sheet or blanket type of a thickness not sufficient to obscure the sub-surface topography; In some cases no need to classify in "Frontal characteristic" (the frontal characteristic is described by the outreaching glaciers); Might also be used to classify low lying areas where the ice divides and flow directions are not clearly detectable "transectional glaciers") | Illustrated GLIMS Glacier Classification Manual |
| Ice-marginal lake | A lake that is located adjacent to the terminus of a glacier. Typically, these lakes form in bedrock basins scoured by the glacier. They enlarge as the glacier retreats. Sometimes they are dammed by an End or Recessional Moraine. | Molnia USGS 2004 |
| Ice-nucleation temperature | The temperature at which ice first forms during freezing of a soil/water system that does not initially contain ice. | NSIDC accessed 2016 |
| Ice-nucleation temperature | The temperature at which ice first forms during freezing of a soil/water system that does not initially contain ice | Van Everdingen International Permafrost Association 2005 |
| Ice-penetrating radar | Ground-penetrating radar when it is used to penetrate ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ice-rich permafrost | Permafrost containing excess ice. | NSIDC accessed 2016 |
| Ice-rich permafrost | Permafrost containing excess ice | Van Everdingen International Permafrost Association 2005 |
| Ice-rich permafrost | Permanetly frozen ground containing Excess Ice. | Trombotto et al. 2014 |
| Ice-wedge cast | A filling of sediment in the space formerly occupied by an ice wedge. | NSIDC accessed 2016 |
| Ice-wedge cast | A filling of sediment in the space formerly occupied by an ice wedge | Van Everdingen International Permafrost Association 2005 |
| Ice-wedge polygon | A polygon outlined by ice wedges underlying its boundaries. | NSIDC accessed 2016 |
| Ice-wedge polygon | A polygon outlined by ice wedges underlying its boundaries | Van Everdingen International Permafrost Association 2005 |
| Iceberg | A piece of ice that has broken off from the end of a glacier that terminates in water. | NSIDC accessed 2016 |
| Iceberg | A block of ice that has broken or calved from the face of a glacier and is floating in a body of marine of fresh water. Alaskan icebergs rarely exceed 500 feet in maximum dimension. In order of increasing size, the following names are used: Brash Ice, Growler, Bergy Bit. | Molnia USGS 2004 |
| Iceberg | A massive piece of ice of greatly varying shape, more than 5m above sea-level, which has broken away from a glacier (or an ice shelf), and which may be afloat or aground. Icebergs may be described as tabular, dome-shaped, sloping, pinnacled, weathered or glacier bergs (an irregularly shaped iceberg). Icebergs are not sea ice. They originate from the ice mass of the Antarctic continent that has accumulated over many thousands of years. When they melt they add fresh water to the ocean. | ASPECT 2012 |
| Iceberg | A massive piece of ice of greatly varying shape, more than 16 ft (5 m) above sea level, which has broken away from a glacier, and which may be afloat or aground. Icebergs may be described as tabular, dome-shaped, sloping, pinnacled, weathered, or glacier bergs. | WMO Sea Ice Nomenclature 2017 |
| Iceberg | A massive piece of ice of varying shape, protruding more than 5 m above sea-level, which has broken away from a glacier or an ice shelf, and which may be afloat or aground. Icebergs by their external look may be subdivided into tabular, dome-shaped, sloping and rounded bergs. | Bushuyev 2004 |
| Iceberg | A piece of a glacier which has broken off and is floating in the sea. | NOAA National Weather Service Glossary 2009 |
| Iceberg | Sea ice terminology. A large, massive piece of floating or stranded glacier ice of any shape detached (calved) from the front of a glacier into a body of water. An iceberg extends more than 5 m above sea level and has the greater part of its mass (4/5 to 8/9) below sea level. | Environment and Climate Change Canada 2014 |
| Iceberg | Large mass of floating or stranded ice, more than 5 metres above the water surface, which has broken away either from a glacier or from an ice-shelf formation. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Iceberg | A piece of ice of the order of tens of metres to many kilometres across that has been shed by a glacier terminating in the sea or a lake. | Swisseduc - Photo glossary of glaciological terms |
| Iceberg | A large mass of floating or stranded ice that has broken away from a glacier; usually more than 5 m above sea level. The unmodified term "iceberg" usually refers to the irregular masses of ice formed by the calving of glaciers along an orographically rough coast, whereas tabular icebergs and ice islands are calved from an ice shelf, and floebergs are formed from sea ice. In decreasing size, they are classified as: ice island (few thousand square meters to 500 km^2 in area); tabular iceberg; iceberg; bergy bit (less than 5 m above sea level, between 1 and 200 m^2 in area); and growler (less than 1 m above sea level, about 20 m^2 in area). | AMS - glossary of meteorology |
| Iceberg | A mass of ice found floating in the ocean or a lake. Often icebergs form when ice calves from land-based glaciers into the water body. Icebergs can be dangerous to shipping in high and mid-latitude regions of the ocean because 90 percent of their mass lies below the ocean surface. | PhysicalGeography.net |
| Iceberg | Large mass of floating or stranded ice of greatly varying shape, more than 5 m above sea level, which has broken away from a glacier. | Illustrated Glossary of Snow and Ice |
| Iceberg limit | Sea ice terminology, meaning the limit at any given time between ice of land origin and the open sea or sea ice. | Environment and Climate Change Canada 2014 |
| Iceberg tongue | A major accumulation of icebergs projecting from the coast, held in place by grounding and joined together by fast ice. | NSIDC accessed 2016 |
| Iceberg tongue | A major accumulation of icebergs projecting from the coast, held in place by grounding and joined together by fast ice. | WMO Sea Ice Nomenclature 2017 |
| Iceberg tongue | A major accumulation of icebergs, bergy bits and growlers projecting from the coast, held in place by grounding or joined together by fast ice. | Bushuyev 2004 |
| Iceberg tongue | Sea ice terminology describing a major accumulation of icebergs that are projecting toward the coast, held in place by grounding and joined together by fast ice. | Environment and Climate Change Canada 2014 |
| Iceberg tongue | A major accumulation of icebergs projecting from the coast, held in place by grounding and joined together by fast ice. | Illustrated Glossary of Snow and Ice |
| Icebound | A harbour, inlet, etc, is said to be icebound when navigation by ships is prevented due to ice, except possibly with the assistance of an icebreaker. | NSIDC accessed 2016 |
| Icebound | A harbour, inlet, etc., is said to be icebound when navigation by ships is prevented due to ice, except possibly with the assistance of an icebreaker. | Illustrated Glossary of Snow and Ice |
| Iced firn | Firn that has become permeated by meltwater and then refrozen; a late stage in the formation of land ice from snow. | AMS - glossary of meteorology |
| Icefall | Heavily crevassed area on a glacier where the descent is steep. | UK Antarctic Place-names Committee accessed 2016 |
| Icefall | Part of a glacier with rapid flow and a chaotic crevassed surface; occurs where the glacier bed steepenes or narrows. | NSIDC accessed 2016 |
| Icefall | Part of a glacier where the ice flows over a bed with a very steep gradient, typically at a higher rate than both above and below. As a result the surface is fractured and heavily crevassed. In a river system, this would be a waterfall. | Molnia USGS 2004 |
| Icefall | A steep reach of a glacier where the ice becomes heavily crevassed, commonly when flowing over a bedrock step. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Icefall | A steep, heavily crevassed, section of a glacier where it flows over a step in the bedrock. | Swisseduc - Photo glossary of glaciological terms |
| Icefall | That portion of a glacier where a sudden steepening of descent causes a chaotic breaking up of the ice. | AMS - glossary of meteorology |
| Icefall | A heavily crevassed area in a glacier at a region of steep descent. | Illustrated Glossary of Snow and Ice |
| Icefalls | Icefalls are somewhat analogous to waterfalls in rivers. The flow of the ice down a steep gradient often results in crevasses and seracs. | Molnia USGS 2004 |
| Icefield | A mass of glacier ice; similar to an ice cap, and usually smaller and lacking a dome-like shape; somewhat controlled by terrain. | NSIDC accessed 2016 |
| Icefield | A large ice body that covers mountainous terrain but is not thick enough to obscure all of the subsurface topography, its flow therefore not being predominantly radial as is that of an ice cap. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Icefoot | A narrow fringe of ice attached to the coast, unmoved by tides and remaining after the fast ice has broken free. | NSIDC accessed 2016 |
| Icefoot | A narrow fringe of ice attached to the coast, unmoved by tides and remaining after the fast ice has moved away. | WMO Sea Ice Nomenclature 2017 |
| Icefoot | Sea ice terminology describing a narrow fringe of ice attached to the coast, unmoved by tides and remaining after the fast ice has moved away. | Environment and Climate Change Canada 2014 |
| Icefoot | A narrow fringe of ice attached to the coast, unmoved by tides and remaining after the fast ice has broken free. | Illustrated Glossary of Snow and Ice |
| Icelandic low | 1. The low pressure center located near Iceland (mainly between Iceland and southern Greenland) on mean charts of sea level pressure. It is a principal center of action in the atmospheric circulation of the Northern Hemisphere. It is most intense during winter, having a January central pressure below 996 mb. In summer, it not only weakens but also tends to split into two centers, one near Davis Strait and the other west of Iceland. Like its Pacific counterpart, the Aleutian low, its daily position and intensity vary greatly so that it is best regarded as a region where migratory lows tend to slow up and deepen. 2. Any low, on a synoptic chart, centered near Iceland. | AMS - glossary of meteorology |
| Icelandic low | Subpolar low pressure system found near Iceland. Most developed during the winter season. This large-scale pressure system spawns mid-latitude cyclones. | PhysicalGeography.net |
| Iceport | Embayment (usually of variable position and extent) in an ice front, where ships can moor alongside and discharge on the ice shelf. | UK Antarctic Place-names Committee accessed 2016 |
| Iceport | An embayment in an ice front, often of temporary nature, where ships can moor alongside and unload directly into the ice shelf. | NSIDC accessed 2016 |
| Iceport | Sea ice terminology describing a bay of ice, often of a temporary nature, where ships can moor alongside and unload directly onto the ice itself. | Environment and Climate Change Canada 2014 |
| Iceport | An embayment in an ice front, often of a temporary nature, where ships can moor alongside and unload directly onto the ice shelf. | Illustrated Glossary of Snow and Ice |
| Icicle | Hanging spike of clear ice formed by the freezing of dripping water. | NSIDC accessed 2016 |
| Icicle | Ice in the shape of a narrow cone, hanging point downward from a roof, fence, cliffside, etc. An icicle is formed when above-freezing water, for example, snowmelt or groundwater, runs or drips into subfreezing air. The water freezes as it drips or runs, forming a narrow cone pointed downward and growing in both length and width, widest at its top. Most icicles are found hanging from the edges of heated, snow-topped roofs, with any water that has not frozen in its downward traverse forming ice on the surfaces below. | AMS - glossary of meteorology |
| Icicle | Hanging spike of clear ice formed by the freezing of dripping water. | Illustrated Glossary of Snow and Ice |
| Iciness | A qualitative term describing the quantity of ice in frozen ground. | NSIDC accessed 2016 |
| Iciness | A qualitative term describing the quantity of ice in frozen ground | Van Everdingen International Permafrost Association 2005 |
| Icing | A sheetlike mass of layered ice formed on the ground surface, or on river or lake ice, by freezing of successive flows of water that may seep from the ground, flow from a spring or emerge from below river or lake ice through fractures. | NSIDC accessed 2016 |
| Icing | A coating of ice on a solid object. | NOAA National Weather Service Glossary 2009 |
| Icing | Any deposit or coating of ice on an object caused by the impact of liquid hydrometeors, usually supercooled. | WMO METEOTERM accessed 2016 |
| Icing | A sheetlike mass of layered ice formed on the ground surface, or on river or lake ice, by freezing of successive flows of water that may seep from the ground, flow from a spring or emerge from below river or lake ice through fractures | Van Everdingen International Permafrost Association 2005 |
| Icing | A sheetlike mass of layered ice formed on the ground surface, or on river or lake ice, by freezing of successive flows of water that may seep from the ground, flow from a spring or emerge from below river or lake ice through fractures. Icings, also known as glaciation, may also occur in non-permafrost areas. In North America the term 'icing' is gradually replacing a variety of terms used in the past. Aufeis (German), flood ice, flood-plain icing, ice field, naled (Russian) and overflow ice usually indicated icings formed on river ice and floodplains. Chrystocrene (or crystocrene), ground icing, groundwater icing and spring icing usually indicated icings formed by freezing of ground-water discharge. Use of the term 'glacier' to describe icings, is inappropriate and should be avoided. | Trombotto et al. 2014 |
| Icing | 1. In general, any deposit or coating of ice on an object, caused by the impingement and freezing of liquid (usually supercooled) hydrometeors; to be distinguished from hoarfrost in that the latter results from the deposition of water vapor. The two basic types of icing are rime and glaze. See aircraft icing, carburetor icing. 2. A mass or sheet of ice formed during the winter by successive freezing of sheets of water that may seep from the ground, from a river, or from a spring. [Also known as flood icing, flooding ice, aufeis (German), naled (Russian).] | AMS - glossary of meteorology |
| Icing | The accumulation of a deposit of ice on exposed objects, e.g. aircraft, ships, aerials, instruments. Icing may be produced by the deposition of water vapour or by the freezing on impact of droplets in the air (e.g. supercooled fog, cloud droplets, supercooled drizzle and rain, or, in the case of ships, sea spray or breaking waves). | Illustrated Glossary of Snow and Ice |
| Icing blister | A seasonal frost mound consisting only of ice and formed at least in part through lifting of one or more layers of an icing by injected water. | NSIDC accessed 2016 |
| Icing blister | A seasonal frost mound consisting of ice only and formed at least in part through lifting of one or more layers of an icing by injected water | Van Everdingen International Permafrost Association 2005 |
| Icing glade | An area kept clear of trees and shrubs by the annual occurrence of icings. | NSIDC accessed 2016 |
| Icing glade | An area kept clear of trees and shrubs by the annual occurrence of icings | Van Everdingen International Permafrost Association 2005 |
| Icing index | Index which characterizes the probable icing intensity for specific meteorological and flight conditions. | WMO METEOTERM accessed 2016 |
| Icing intensity | Rate at which ice accretion occurs, expressed in units of depth per unit time. | WMO METEOTERM accessed 2016 |
| Icing intensity | Rate at which ice accretion occurs, expressed in units of depth per unit time. | AMS - glossary of meteorology |
| Icing level | Lowest height above mean sea-level at which an aircraft in flight may encounter icing. | WMO METEOTERM accessed 2016 |
| Icing level | Lowest height above sea level at which an aircraft in flight may encounter icing. | AMS - glossary of meteorology |
| Icing mound | A seasonal frost mound consisting exclusively of thinly layered ice, formed by freezing of successive flows of water issuing from the ground or from below river ice. | NSIDC accessed 2016 |
| Icing mound | A seasonal frost mound consisting exclusively of thinly layered ice, formed by freezing of successive flows of water issuing from the ground or from below river ice | Van Everdingen International Permafrost Association 2005 |
| Icing-rate meter | An instrument for the measurement of the rate of ice accretion on an unheated body, for example, rotating cylinders or discs, stationary airfoils, vibrating rods, and electrical- impedance devices. | AMS - glossary of meteorology |
| Inactive ice wedge | An ice wedge that is no longer growing. | NSIDC accessed 2016 |
| Inactive ice wedge | An ice wedge that is no longer growing | Van Everdingen International Permafrost Association 2005 |
| Inactive rock glacier | A mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of past, but not present, movement. | NSIDC accessed 2016 |
| Inactive rock glacier | A mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of past, but not present, movement | Van Everdingen International Permafrost Association 2005 |
| Inactive rock glacier | A mass of rock fragments and finer material, on a slope, that contains either an Ice core or interstitial Ice, and shows evidence of past, but not present, movement. Rock Glaciers are said to be inactive when their main body ceases to move, and they show no evidence of very recent movement. The Active Layer of an Inactive Rock Glacier is likely to be thicker than that of an Active Rock Glacier at the same elevation band. Inactivity is usually caused by a warming climate causing a decrease in Ground Ice Content. | Trombotto et al. 2014 |
| Indigenous peoples | Indigenous peoples and nations are those that, having a historical continuity with pre-invasion and pre-colonial societies that developed on their territories, consider themselves distinct from other sectors of the societies now prevailing on those territories, or parts of them. They form at present principally non-dominant sectors of society and are often determined to preserve, develop, and transmit to future generations their ancestral territories, and their ethnic identity, as the basis of their continued existence as peoples, in accordance with their own cultural patterns, social institutions, and common law system. | IPCC WGII AR5 2014 |
| Induction icing | The formation of ice in the air intake channels of jet engines. | AMS - glossary of meteorology |
| Infiltration | The entry of a liquid such as water into a permeable solid such as snow or firn, and, more loosely, the percolation of the liquid through the void spaces of the solid. In general, two forces govern infiltration gravity and capillary tension. The latter allows the solid to draw in the liquid and is determined by adhesive molecular forces, which can be substantial in materials with very small pores. The rate of infiltration of a liquid into a permeable solid is determined by the porosity and liquid content of the solid and by its hydraulic conductivity. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Infiltration ice | In Russian-language usage, ice derived from the refreezing of meltwater that has saturated the void spaces in snow or firn. See congelation, recrystallization, superimposed ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Infiltration zone | In the Russian-language literature, part of the lower percolation zone where meltwater is abundant in the snow and firn, but the firn is either a survival from previous years of more positive mass balance or is advected by the glacier flow from higher elevations. See zone. The infiltration zone is sometimes also referred to as the 'firn-ice zone'. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Infiltration-congelation zone | In the Russian-language literature, a synonym of superimposed ice zone. See zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Infiltration-recrystallization zone | A term in Russian-language usage referring to the lower percolation zone, where enough meltwater is produced at the surface to percolate out of the snow and into the firn. See zone. In the 'cold infiltration-recrystallization zone', generally at higher elevation and sometimes called the 'cold firn zone', the meltwater refreezes in the firn because the temperature is below the freezing point. This refreezing is the dominant mechanism for the formation of glacier ice. In the 'warm infiltration-recrystallization zone', generally at lower elevation and sometimes called the 'warm firn zone', the temperature is at or near the freezing point and refreezing makes a lesser contribution to the formation of ice. The runoff limit may lie within the warm firn zone, or within the cold firn zone where slopes are steep. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Inland ice | A translation, seen infrequently in earlier English-language literature, of 'inlandsis', an originally Danish word which is the word for ice sheet in several European languages. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Inland ice | 1. An older reference to the Greenland Ice Sheet. 2. Same as land ice, particularly the more interior portions of an ice sheet. | AMS - glossary of meteorology |
| Inland ice sheet | An ice sheet of considerable thickness and an area of more than about 50,000 square kilometers (12.4 million acres), resting on rock; inland ice sheets near sea level may merge into ice shelves. | NSIDC accessed 2016 |
| Inland ice sheet | An ice sheet of considerable thickness and more than about 50,000 square km in area, resting on rock. Inland ice sheets near sea level may merge into ice shelves. | Illustrated Glossary of Snow and Ice |
| Inlet | Small indentation in the coastline usually tapering towards its head, cf, creek, but also applied to an arm of a bay or to a coastal embayment on the landward side of an ice shelf. | UK Antarctic Place-names Committee accessed 2016 |
| InSar | An acronym for interferometric synthetic aperture radar, an instrument (and by extension a method) for microwave remote sensing of the topography, velocity field and other characteristics of a surface. A synthetic aperture radar (SAR) consists of a side-looking radar system that takes advantage of the forward motion of the radar platform to synthesize a very long antenna, enabling a much higher ground resolution than in ordinary radar altimetry. Each SAR acquisition contains information on the amplitude and phase of the radiation reflected from the target and received at the antenna. Interferometric SAR requires the calculation of differences in phase between two co-registered SAR images obtained with slightly different viewing geometries, either at the same time from two antennae, or at two different times from one antenna. These phase differences yield fringe patterns (interferograms) that are an expression of both surface topography and surface motion. If the surface is not in motion, or the time between images is sufficiently short, phase differences can be converted to surface elevations with knowledge of the attitude and orbital position of the interferometer; more specifically, the baseline length, or distance between the two orbital positions, must be known. Using insar to detect motion of the surface requires imagery from two different epochs (repeat pass interferometry).In this case topographic effects are removed using an independently derived digital elevation model. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Interfacial water | Water that forms transition layers at mineral/water and mineral/water/ice interfaces in frozen ground. | NSIDC accessed 2016 |
| Interfacial water | Interfacial water forms transition layers at mineral/water and mineral/water/ice interfaces in frozen ground | Van Everdingen International Permafrost Association 2005 |
| Interferometer | An instrument that relies on the interference of waves, particularly electromagnetic waves, from a common source such as a radar to measure the length or displacement of a target with an ambiguity that is an integer multiple of the wavelength. See insar. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Interferometry | Measurement of the interference of waves, particularly electromagnetic waves, from a common source such as a radar, with the aim of obtaining information about the topography, velocity field and other characteristics of the glacier surface. See insar. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Interglacial | A period of warm climate during the Pleistocene (and earlier glacial epochs) during which continental glaciers retreated to minimum extent. Interglacials have been of approximately 10 000 years duration, spaced at approximately 100 000-year intervals over the last 1 000 000 years. The last 10 000 years, or postglacial, is generally considered to be an interglacial. | AMS - glossary of meteorology |
| Interglacial | Period of time during an ice age when glaciers retreated because of milder temperatures. | PhysicalGeography.net |
| Interglacial phase | Period characterized by a relatively mild climate within an ice age. | WMO METEOTERM accessed 2016 |
| Interglacial phase | Generally, an interval of geologic time that was marked by a major poleward retreat of ice. This may be applied to an entire interval between ice ages or (rarely) to the individual "stages" that make up an interglacial period. | AMS - glossary of meteorology |
| Interglacials or interglaciations | The warm periods between ice age glaciations. Often defined as the periods at which sea levels were close to present sea level. For the Last Interglacial (LIG) this occurred between about 129 and 116 ka (thousand years) before present (defined as 1950) although the warm period started in some areas a few thousand years earlier. In terms of the oxygen isotope record interglaciations are defined as the interval between the midpoint of the preceding termination and the onset of the next glaciation. The present interglaciation, the Holocene, started at 11.65 ka before present although globally sea levels did not approach their present position until about 7 ka before present. | IPCC WGI AR5 2013 |
| Intermediate discontinuous permafrost | (1) (North American usage) permafrost underlying 35 - 65% of the area of exposed land surface (2) (Russian usage) permafrost underlying 40 - 60% of the area of exposed land surface. | NSIDC accessed 2016 |
| Intermediate discontinuous permafrost | 1. (North-American usage) <B>Permafrost underlying 35 to 65 percent of the area of exposed land surface; 2. (Russian usage) Permafrost underlying 40 to 60 percent of the area of exposed land surface | Van Everdingen International Permafrost Association 2005 |
| Intermediate water | As a general term, any water mass found at intermediate depth in the ocean. Antarctic Intermediate Water is the most important of these, followed by Subarctic Intermediate Water and Arctic Intermediate Water. Other water masses identified as intermediate water are Atlantic Intermediate Water in Baffin Bay, also called Polar Atlantic Water, identified by a temperature maximum at a depth of about 500 m resulting from inflow from the West Greenland Current; Arctic Intermediate Water in Baffin Bay, identified by a temperature minimum at a depth between 50 and 200 m resulting from inflow of arctic water from the north; and Levantine Intermediate Water in the Eurafrican Mediterranean Sea, identified by a salinity maximum at a depth between 150 and 400 m and formed when cold winter winds, descending on the region between Rhodes and Cyprus and on the northern and central Adriatic Sea, result in the cooling and sinking of surface water. | AMS - glossary of meteorology |
| Internal ablation | Loss of mass from a glacier by melting of ice or firn between the summer surface and the bed. See mass-balance units. Internal ablation can occur due to strain heating of temperate ice as the ice deforms. However, the largest heat sources for internal ablation are likely to be the potential energy released by downward motion of the ice and of meltwater. The magnitude of the former is equivalent to a few mm w. E. A-1, and of the latter, which occurs mainly in conduits transferring water from the glacier surface to the bed, to up to a few tens of mm w. E. A-1. (These rates are expressed over the extent of a typical valley glacier.) | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Internal accumulation | Refreezing of water within a glacier, between the summer surface and the bed, which goes undetected by measurements of surface mass balance. See mass-balance units, zone. Accumulation beneath the summer surface is the refreezing of surface meltwater (or freezing of rain) that is in transit and otherwise would have left the glacier as runoff. In the case of meltwater, it may be regarded as redistributing mass within the glacier. This may require careful accounting in the calculation of mass balance. Internal accumulation proceeds by the freezing of water that percolates early in the ablation season into firn that is still cold, heating the firn in the process, or by the freezing of retained pore water during the accumulation season, also releasing latent heat and thus slowing the downward advance of the winter cold wave. The term is reserved for refreezing beneath the summer surface, that is, within the firn or the ice. Meltwater that refreezes within the snow does not constitute internal accumulation since it is accounted for by end-of-season density measurements as part of conventional mass-balance measurements. Internal accumulation may be small in magnitude, and negligible on temperate glaciers, but if not accounted for it constitutes a bias towards overestimation of mass loss. In remote-sensing studies, it is not always possible to detect the summer surface. In addition models of the surface mass balance do not always distinguish between internal accumulation and refreezing within the snow. To avoid confusion, it is advisable to use 'internal accumulation' only in the sense given above and to use the more inclusive 'refreezing' only for 'internal accumulation plus refreezing within the snow'. Refreezing within the snow should be described as such explicitly. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Internal deformation | The component of glacier flow that is the result of the deformation of glacier ice under the influence of accumulated snow and firn, and of gravity. | Swisseduc - Photo glossary of glaciological terms |
| Internal ice stress | A measure of the compactness, or strength of the ice; plays an important role in the deformation of the ice and formation of features such as ridges and leads. | NSIDC accessed 2016 |
| Internal mass balance | The change in the mass of the glacier due to internal accumulation and internal ablation over a stated period. See mass-balance units, climatic mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| International Geophysical Year - IGY | Period (1 July 1957 - 31 December 1958), fixed by the International Union of Geodesy and Geophysics, during which an extensive programme of geophysical observations was carried out over a worldwide network of stations. | WMO METEOTERM accessed 2016 |
| International Polar Year - IPY | Period in 1882-83 or 1932-33, fixed by international agreement, during which an extensive programme of geophysical observations was carried out at various stations temporarily established, especially in polar regions. | WMO METEOTERM accessed 2016 |
| Interrupted glacier | Glacier flow is interrupted by very steep cliff(s); No dynamic connection; Reconstruct below the cliff; Glacier that breaks off over a cliff and reconstitutes below. (WGMS, 1977); The entire catchment area of the glacier has to be looked at in order to identify if a glacier is interrupted or not! | Illustrated GLIMS Glacier Classification Manual |
| Interrupted glacier | A glacier consisting of two or more parts between which mass transfer or 'flow' to the lower part is by avalanching. Whether to regard the parts as separate entities is a matter of convenience. See regenerated glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Interstitial ice | Ice formed in narrow spaces between small rocks and sediment in soil. | NSIDC accessed 2016 |
| Intra-permafrost water | Water occurring in unfrozen zones (Taliks and Cryopegs) within Permafrost. It includes water in open, lateral and transient Taliks and in basal, isolated and marine Cryopegs. | Trombotto et al. 2014 |
| Intrapermafrost water | Water occurring in unfrozen zones (taliks and cryopegs) within permafrost. | NSIDC accessed 2016 |
| Intrapermafrost water | Water occurring in unfrozen zones (taliks and cryopegs) within permafrost | Van Everdingen International Permafrost Association 2005 |
| Intrusive ice | Ice formed from water injected into soils or rocks. | NSIDC accessed 2016 |
| Intrusive ice | Ice formed from water injected into soils or rocks | Van Everdingen International Permafrost Association 2005 |
| Intrusive ice | Ice formed from water injected into soils or rocks. | Trombotto et al. 2014 |
| Irregular crystal | A snow particle, sometimes covered with rime, without visible crystalline facets; sometimes used as a last category for snow identification. (Sometimes called amorphous snow.) | AMS - glossary of meteorology |
| Island(s) | Piece of land of less than continental size completely surrounded by water at least at mean high-water spring tide, or by ice shelf, cf. ice rise. A very small island may be termed a rock or a skerry. | UK Antarctic Place-names Committee accessed 2016 |
| Isoband cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form subhorizontal layers of similar thickness. | NSIDC accessed 2016 |
| Isoband cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form subhorizontal layers of similar thickness | Van Everdingen International Permafrost Association 2005 |
| Isochasm | A line connecting points on the earth's surface at which the aurora is observed with equal frequency. (Also called isaurore.) | AMS - glossary of meteorology |
| Isochion | Line on a map joining points of equal altitude of the snowline. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Isolated cryopeg | A body of unfrozen ground, that is perennially cryotic (T 0 degrees Celsius) and entirely surrounded by perennially frozen ground. | NSIDC accessed 2016 |
| Isolated cryopeg | A body of unfrozen ground, that is perennially cryotic (T < 0°C) and entirely surrounded by perennially frozen ground | Van Everdingen International Permafrost Association 2005 |
| Isolated patches of permafrost | Permafrost underlying less than 10% of the exposed land surface. | NSIDC accessed 2016 |
| Isolated patches of permafrost | Permafrost underlying less than 10 percent of the exposed land surface | Van Everdingen International Permafrost Association 2005 |
| Isolated patches of permafrost | Permafrost underlying less than 10% of the exposed land surface. Individual areas of Permafrost are of limited areal extent, widely separated, and are completely surrounded by Unfrozen Ground. | Trombotto et al. 2014 |
| Isolated talik | A layer or body of unfrozen ground entirely surrounded by perennially frozen ground. | NSIDC accessed 2016 |
| Isolated talik | A layer or body of unfrozen ground entirely surrounded by perennially frozen ground | Van Everdingen International Permafrost Association 2005 |
| Isonival | Line connecting points of equal snow depth. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Isonival | Refers to a line of equal water equivalent of snow or equal snow depth. (Also called isochion.) | AMS - glossary of meteorology |
| Isostasy | The balance between changes within the Earth's crust and mantle, where material is displaced in response to an increase (isostatic depression) or decrease (isostatic rebound) in mass at any point on the Earth's surface above. Such changes are frequently caused by advances or retreats of glaciers. | Molnia USGS 2004 |
| Isostatic adjustment | The movement of the solid part of the earth until it is in balance; also called isostatic compensation. The prime example of isostatic adjustment is the continents "floating" on the denser parts of the crust. | AMS - glossary of meteorology |
| Isostatic depression | Large scale sinking of the crust into the asthenosphere because of an increase in weight on the crustal surface. Common in areas of continental glaciation where the crust was depressed by the weight of the ice. | PhysicalGeography.net |
| Isostatic or Isostasy | Isostasy refers to the response of the earth to changes in surface load. It includes the deformational and gravitational response. This response is elastic on short time scales, as in the earth-ocean response to recent changes in mountain glaciation, or viscoelastic on longer time scales, as in the response to the last deglaciation following the Last Glacial Maximum. See also Glacial Isostatic Adjustment (GIA). | IPCC WGI AR5 2013 |
| Isostatic rebound | The upward movement of the Earth's crust following isostatic depression. | PhysicalGeography.net |
| J?kulhlaup | (from the Icelandic). A sudden and often catastrophic outburst of water from a glacier during a volcanic eruption. The term is also used to describe when an ice-dammed lake bursts or an internal water pocket escapes, resulting in flooding. | Swisseduc - Photo glossary of glaciological terms |
| Jammed brash barrier | Sea ice terminology. Describes a strip or narrow belt of new, young or brash ice usually 100 m to 5000 m across, formed at the edge of either floating or fast ice, or at the shore. Heavily compacted, mostly due to wind action, a jammed brash barrier may extend 2 m to 20 m below the surface. | Environment and Climate Change Canada 2014 |
| January thaw | A period of mild weather popularly supposed to recur each year in late January. | NOAA National Weather Service Glossary 2009 |
| January thaw | In the United States, a period of mild weather popularly supposed to recur each year, in later January; most pronounced in the Northeast and, to a lesser extent, the Midwest. The daily temperature averages at Boston, computed for the years 1873 to 1952, show a well- marked peak on 20-23 January; the same peak occurs in the daily temperatures of Washington, D.C., and New York City. Statistical tests show a high probability that it is a real singularity. The January thaw is associated with the frequent occurrence on the above-mentioned dates of southerly winds on the back side of an anticyclone off the southeastern United States. | AMS - glossary of meteorology |
| Jet stream | Relatively strong winds concentrated within a narrow stream in the atmosphere. While this term may be applied to any such stream regardless of direction (including vertical), it is coming more and more to mean only a quasi-horizontal jet stream of maximum winds embedded in the midlatitude westerlies, and concentrated in the high troposphere. The question of the maintenance of the jet stream is a cardinal problem of theoretical meteorology. Two such jet streams are sometimes distinguished. The predominant one, the polar-front jet stream, is associated with the polar front of middle and upper-middle latitudes. Very loosely, it may be said to extend around the hemisphere, but, like the polar front, it is discontinuous and varies greatly from day to day. A subtropical jet stream is found, at some longitudes, between 20 and 30 latitude and is strongest off the Asian coast. Currently, in the analysis of upper-level charts, a jet stream is indicated wherever it is reliably determined that the wind speed equals or exceeds 50 knots. | AMS - glossary of meteorology |
| Jokulhlaup | An Icelandic term meaning glacier dammed lake outburst flood. | NOAA Glossary of Hydrologic Terms |
| Jokulhlaup | (1) a large outburst flood that usually occurs when a glacially dammed lake drains catastrophically (2) any catastrophic release of water from a glacier. | NSIDC accessed 2016 |
| Jokulhlaup | In hydrologic terms, an Icelandic term meaning glacier dammed lake outburst flood. | NOAA National Weather Service Glossary 2009 |
| Jokulhlaup | Jokulhlaup's (an Icelandic term pronounced Yo-kul-hloips) are sudden outbursts of water released by a glacier. The water may be released from glacier cavities, sub-glacial lakes, and from glacier-dammed lakes in side valleys. Also known as 'glacial outburst floods'. A glacier outburst flood resulting from the failure of a glacier-ice-dam, glacier-sediment-dam, or from the melting of glacier ice by a volcanic eruption. | Molnia USGS 2004 |
| Jokulhlaup | A glacier outburst flood resulting from the failure of a glacier-ice-dam, glacier-sediment-dam, or from the melting of glacier ice by a volcanic eruption (Icelandic). | Molnia USGS 2004 |
| Kame | A sand and gravel deposit formed by running water on stagnant or moving-glacier ice. Crevasse fills or crevasse ridges form within crevasses. Kames form on flat or inclined ice, in holes, or in cracks. A kame terrace forms between the glacier and the adjacent land surface. Shapes include hills, mounds, knobs, hummocks, or ridges. | Molnia USGS 2004 |
| Kame | A steep conical hill composed of glaciofluvial sediments. This feature develops when glacial crevasses and depressions in stagnant glacial ice are filled with sand and gravel deposits from sediment loaded meltwater. | PhysicalGeography.net |
| Kame terrace | Valley-side terrace or bench formed by the deposition of fluvial or lake sediment along the margin of a glacier. The terrace is left stranded on the hillside after the glacier has receded. | Swisseduc - Photo glossary of glaciological terms |
| Kame terrace | A long flat ridge composed of glaciofluvial sediment. This feature forms along the margin of a valley glacier where the glacial ice meets the valley's slope. Sediment is deposited by laterally flowing meltwater streams. | PhysicalGeography.net |
| Katabatic wind | Downslope wind caused by greater air density on the slope than at some distance, horizontally from it. The wind is associated with surface cooling of the slope. | Australian Bureau of Meteorology 2016 |
| Katabatic wind | 1. Most widely used in mountain meteorology to denote a downslope flow driven by cooling at the slope surface during periods of light larger-scale winds; the nocturnal component of the along-slope wind systems. The surface cools a vertical column of the atmosphere starting at the slope surface and reaching perhaps 10-100 m deep. This column is colder than the column at equivalent levels over the valley or plain, resulting in a hydrostatic pressure excess over the slope relative to over the valley or plain. The horizontal pressure gradient, maximized at the slope surface, drives an acceleration directed away from the slope, or downslope. Although the pressure-gradient forcing is at its maximum at the slope, surface friction causes the peak in the katabatic wind speeds to occur above the surface, usually by a few meters to a few tens of meters. The depth of the downslope flow layer on simple slopes has been found to be 0.05 times the vertical drop from the top of the slope. Surface-wind speeds in mountain-valley katabatic flows are often 3-4 m/s, but on long slopes, they have been found to exceed 8 m/s. Slopes occur on many scales, and consequently katabatic flows also occur on many scales. At local scales katabatic winds are a component of mountain-valley wind systems. At scales ranging from the slopes of individual hills and mountains to the slopes of mountain ranges and massifs, katabatic flows represent the nocturnal component of mountain-plains wind systems. Besides diurnal-cycle effects, surface cooling can also result from cold surfaces such as ice and snow cover. Katabatic flows over such surfaces have been studied as glacier winds in valleys and as large-scale slope flows in Antarctica and Greenland. The large- scale katabatic wind blowing down the ice dome of the Antarctic continent has sometimes reached 50 m/s on the periphery of the continent. The persistence of the surface forcing and the great extent of the slopes on these great landmasses means that the flows are subject to Coriolis deflection, and thus they are not pure katabatic flows. 2. Occasionally used in a more general sense to describe cold air flowing down a slope or incline on any of a variety of scales, including phenomena such as the bora, in addition to thermally forced flows as described above. From its etymology, the term means simply "going down" or "descending," and thus could refer to any descending flow; some authors have further generalized it to include downslope flows such as the foehn or chinook even though they do not represent a flow of cold air. This concept has given rise to the expression katafront, which indicates flow down a sloped cold-frontal surface. | AMS - glossary of meteorology |
| Katabatic wind | Any wind blowing down the slope of a mountain. | PhysicalGeography.net |
| Keel | The part of a ridge below the ocean surface; wind, ocean currents, and other forces can push sea ice into piles that rise and form small mountains below the level sea ice surface. | NSIDC accessed 2016 |
| Kernel ice | In aircraft icing, an extreme form of rime ice, that is, very irregular, opaque, and of low density. Kernel ice forms at temperatures of -15C and lower. | AMS - glossary of meteorology |
| Kettle | A depression that forms in an outwash plain or other glacial deposit by the melting of an in-situ block of glacier ice that was separated from the retreating glacier-margin and subsequently buried by glacier sedimentation. As the buried ice melts, the depression enlarges. | Molnia USGS 2004 |
| Kettle | (or kettlehole) A self-contained bowl-shaped depression within an area covered by glacial stream deposits, often containing a pond. A kettle forms from the burial of a mass of glacier ice by glacial or stream sediment, followed by its subsequent melting. | Swisseduc - Photo glossary of glaciological terms |
| Kettle hole | Depression found in glacial deposits. Created when a piece of ice from a retreating glacier becomes embedded in soft glacial till or glacial drift deposits. Many are filled with water to form a small lake or pond. | PhysicalGeography.net |
| Kettle moraine | An area of glaciofluvial influenced moraine deposits pitted with kames and kettle holes. | PhysicalGeography.net |
| Killing freeze | The occurrence of air temperature below 0C (32F) that kills annual vegetation without formation of frost crystals on surfaces. | AMS - glossary of meteorology |
| Killing frost | A frost severe enough to destroy annual plants and new growth on trees (in the spring), or to end the growing season (in the fall). | Environment and Climate Change Canada 2014 |
| Kinematic method | Any method of determining the mass balance that involves measurement or calculation of glacier flow, including the flux-divergence method, the kinematic-equation method and methods in which the mass balance is determined as the sum of the discharge through a cross section and the surface mass balance of the region upglacier from the cross section. Information about density is needed to convert the volumetric fluxes obtained by kinematic methods to mass fluxes. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Kinematic waves | Refers to a wave of ice moving downglacier propagated by its increased thickness. The wave of ice may move at two to six times the velocity of surrounding thinner ice. | Molnia USGS 2004 |
| Kinematic-equation method | A method of determining the spatial distribution of the mass balance by solving the equation of the kinematic boundary condition at the surface for the ice-equivalent mass-balance rate bb as a function of the rate of change hh of the ice-equivalent thickness, the spatial gradient of the thickness h (usually approximated by the inclination of the surface), and the velocity at the surface uub hu b hu huhh V hu Vhuh hhhhu h H , where subscripts H and V denote horizontal and vertical vector components respectively of uu. It is assumed that the basal ice velocity is zero, for example because the ice is frozen to the bed. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Kinetic growth | Grain growth at high temperature gradients, i.e., when excess water vapour density is above a critical value (see also equilibrium growth). Water vapour diffuses from grains showing higher to those having lower water vapour density, i.e., the so called hand-to-hand mechanism. This process results in the sublimation and deposition or recrystallization of ice as well as changes in crystal size and shape. These changes usually result in a decrease of the specific surface area of snow. Examples of kinetic growth shapes are faceted crystals (FC) and depth hoar (DH)that form within the snowpack, or surface hoar (SH) that grows on the snow surface. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Kinetic-growth metamorphism | Snow metamorphism that builds angular facets on crystals and makes cup and scroll shaped crystals. | NSIDC accessed 2016 |
| Knoll | Small hill or relatively low mountain or nunatak. | UK Antarctic Place-names Committee accessed 2016 |
| Kossava | A cold, very squally wind, descending from the east or southeast in the region of the Danube "Iron Gate" through the Carpathians, continuing westward over Belgrade, thence spreading northward to the Rumanian and Hungarian borderlands and southward as far as Nish. In winter it brings temperatures down to below -29C and it is cool even in summer, when it is also dusty. It usually occurs with a depression over the Adriatic and high pressure over southern Russia, a frequent situation in winter. It is usually explained as a jet-effect wind through the Iron Gate, giving speeds well above the gradient wind, but J. K ttner (1940) regards it rather as a katabatic wind intermediate between foehn and bora. The kossava has a marked diurnal variation, with its maximum occurring between 5am and 10am. (Also spelled kosava, koschawa.) | AMS - glossary of meteorology |
| Kurum | A general term for all types of coarse clastic formations on slopes of 2-3 to 40 degrees, moving downslope mainly due to creep. | Van Everdingen International Permafrost Association 2005 |
| Labrador Sea Water | The last water mass to contribute to the formation of North Atlantic Deep Water before it enters the southward path of the ocean conveyor belt. It occupies the central Labrador Sea with temperatures of 3.0-3.6C, salinities of 34.86-34.96 psu, and consistently high oxygen content. | AMS - glossary of meteorology |
| Lahar | A lahar is a mudflow or debris flow originating on a volcano. Lahars (also called debris flows or mudflows) are mixtures of water, rock, sand, and mud that rush down valleys leading away from a volcano. They can travel over 50 miles downstream, commonly reaching speeds between 20 and 40 miles per hour. Sometimes they contain so much rock debris (60-90% by weight) that they look like fast-moving rivers of wet concrete. Close to the volcano they have the strength to rip huge boulders, trees, and houses from the ground and carry them downvalley. Further downstream they simply entomb everything in mud. Historically, lahars have been one of the most deadly volcanic hazards. Lahars can form in a variety of ways, either during an eruption or when a volcano is quiet. Some examples include the following: (1) rapid release of water from the breakout of a summit crater lake; (2) generation of water by melting snow and ice, especially when a pyroclastic flow erodes a glacier; (3) flooding following intense rainfall; and (4) transformation of a volcanic landslide into a lahar as it travels downstream. | Molnia USGS 2004 |
| Lake effect snow | Snow showers that are created when cold, dry air passes over a large warmer lake, such as one of the Great Lakes, and picks up moisture and heat. | NOAA National Weather Service Glossary 2009 |
| Lake effect snow | Localized, convective snow bands that occur in the lee of lakes when relatively cold airflows over warm water. In the United States this phenomenon is most noted along the south and east shores of the Great Lakes during arctic cold-air outbreaks. | AMS - glossary of meteorology |
| Lake effect snowstorm | Snowstorm occurring on the shore of a lake or downwind from a lake, arising as a result of the modification of the air during its passage over the water. | WMO METEOTERM accessed 2016 |
| Lake effect storm | A fall or winter storm that produces heavy but localized precipitation as a result of temperature differences between the air over snow-covered ground and the air over the open waters of a lake. | NOAA National Weather Service Glossary 2009 |
| Lake ice | Floating ice formed in lakes. | NSIDC accessed 2016 |
| Lake ice | Ice formed on a lake, regardless of observed location. | WMO Sea Ice Nomenclature 2017 |
| Lake ice | Sea ice terminology describing ice formed on a lake, regardless of where it ends up. | Environment and Climate Change Canada 2014 |
| Lake ice | Floating ice formed in lakes. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Lake ice | Ice formed on the surface of a lake. | AMS - glossary of meteorology |
| Lake ice | Floating ice formed in lakes. | Illustrated Glossary of Snow and Ice |
| Lake talik | A layer or body of unfrozen ground occupying a depression in the permafrost table beneath a lake. | NSIDC accessed 2016 |
| Lake talik | A layer or body of unfrozen ground occupying a depression in the permafrost table beneath a lake | Van Everdingen International Permafrost Association 2005 |
| Lake-effect snowstorm | Snowstorm occurring near or downwind from the shore of a lake resulting from the warming (destabilization) and moistening of relatively cold air during passage over a warm body of water. | AMS - glossary of meteorology |
| Lake-terminating glacier | A glacier the terminus of which stands or floats in a lake. See calving, tidewater glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Lambing storm | A slight fall of snow in the spring in England. (Also called lamb-blasts, lamb-showers, lamb storm.) | AMS - glossary of meteorology |
| Land ice | Any part of the earth's seasonal or perennial ice cover that has formed over land as the result, principally, of the freezing of precipitation; opposed to sea ice formed by the freezing of seawater. Thus, an iceberg or tabular iceberg is land ice as well as its parent glacier, ice sheet, or ice shelf. The two major concentrations of land ice are the ice sheets of Greenland and Antarctica. Glaciers and ice caps are the other important forms. | AMS - glossary of meteorology |
| Large ice field | An ice field over 12 n mi (20 kin) across. | WMO Sea Ice Nomenclature 2017 |
| Large ice field | Sea ice terminology describing an ice field that is over 20 kilometres across. | Environment and Climate Change Canada 2014 |
| Large iceberg | Sea ice terminology that describes a piece of glacier ice extending 46 m to 75 m above sea level, and with a length of 121 m to 200 m. | Environment and Climate Change Canada 2014 |
| Laser altimeter | An instrument for altimetry, and in mass-balance studies for the measurement of elevation change by repeated altimetry, that uses pulses of laser radiation, for example at 532 nm (green) or 1024 nm (near infrared) wavelengths. There are both profiling and scanning laser altimeters. A profiling system is nadir-pointing, while a scanning system uses a rotating mirror, or a series of sensors arrayed in a parallel (push broom) configuration, to obtain a swath rather than a linear profile of measurements. The Ice, Cloud and land Elevation Satellite (icesat, 20032010) measured surface elevations with approximately 70 m footprint and 170 m along-track spacing. Adjacent tracks are separated by a few to a few tens of kilometres, the lesser separations being found at the polar extremities of the orbit. Sources of error include sensor saturation, atmospheric scattering effects, and inaccurate knowledge of the laser pointing angles. Aircraft altimeters have footprints of 1 m or smaller and along-track spacing on the order of 1 to 3 m, and are less affected by atmospheric and pointing errors. Laser altimeters are unable to obtain measurements through clouds. Laser is an acronym standing for light amplification by stimulated emission of radiation. A related term, lidar (light detection and ranging), applies more generally to the measurement of scattered light from distant targets. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Laser altimetry | The measurement of surface elevation (altitude) with a laser altimeter. Particularly when used to measure elevation change, laser altimetry has become a leading source of data for the measurement of mass balance by the geodetic method. If, for logistical or financial reasons, it is not possible to survey the whole glacier by airborne laser altimetry, it is necessary to extrapolate to obtain a glacier-wide geodetic mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Last glacial | The most recent time (15 000 to 80 000 years ago) during which continental glaciers covered subpolar regions and existed at elevations as much as 1000 m lower than today; corresponding to periods in which oxygen isotopes from marine sediment cores indicate that global sea level was 50-150 m lower and global temperature 5-10C lower than today. | AMS - glossary of meteorology |
| Last Glacial Maximum (LGM) | The period during the last ice age when the glaciers and ice sheets reached their maximum extent, approximately 21 ka ago. This period has been widely studied because the radiative forcings and boundary conditions are relatively well known. | IPCC WGII AR5 2014 |
| Last interglacial | The most recent time (115 000 to 125 000 years ago) during which global temperatures were as high as or higher than in the postglacial, when continental glaciers were limited to the Arctic and Antarctic, and sea levels were near current positions. | AMS - glossary of meteorology |
| Latent heat | The amount of heat required to melt all the Ice (or freeze all the pore water) in a unit mass of soil or rock. | Trombotto et al. 2014 |
| Latent heat | The specific enthalpy difference between two phases of a substance at the same temperature. The latent heat of vaporization is the water vapor specific enthalpy minus the liquid water specific enthalpy. When the temperature of a system of dry air and water vapor is lowered to the dewpoint and water vapor condenses, the enthalpy released by the vapor heats the air-vapor-liquid system, reducing or eliminating the rate of temperature reduction. Similarly, when liquid water evaporates, the system must provide enthalpy to the vapor by cooling. The latent heat of fusion is the specific enthalpy of water minus that of ice and the latent heat of sublimation is the specific enthalpy of water vapor minus that of ice. The latent heats of vaporization, fusion, and sublimation of water at 0C are, respectively, L_v = 2.501 * 10^6 J/kg L_f = 3.337 * 10^5 J/kg L_s = 2.834 * 10^6 J/kg It is common to see an expression like "release of latent heat." In other thermodynamic terms in this glossary, such expressions are avoided in favor of others using enthalpy and temperature, which are measurable quantities. | AMS - glossary of meteorology |
| Latent heat (of fusion) | The amount of heat required to melt all the ice (or freeze all the pore water) in a unit mass of soil or rock | Van Everdingen International Permafrost Association 2005 |
| Latent heat of sublimation | Amount of heat absorbed (or released) when a unit mass of ice changes into water vapour (or vice-versa). | UNESCO-WMO International Glossary of Hydrology 2012 |
| Latent heat polynya | A polynya that forms from strong winds in a persistent direction that push the ice away from a barrier (the coast, fast ice, a grounded iceberg, or an ice shelf). | NSIDC accessed 2016 |
| Lateral moraine | A ridge-shaped moraine deposited at the side of a glacier and composed of material eroded from the valley walls by the moving glacier. | NSIDC accessed 2016 |
| Lateral moraine | Lateral moraines are piles of loose unsorted rocks along the side margins of the glacier. The rocks may be pushed there by the moving ice or dumped from the glacier's rounded surface. As glaciers melt, their remaining load of rocks is distributed in several ways. Rocks may be dropped in place by the melting ice; they may be rolled to the ice margins, or they may be deposited by meltwater streams. Collectively, these deposits are called 'glacial drift'. 'Till' refers to the debris deposited directly by the glacier. Rock debris rolls off the glacier edges and builds piles of loose unconsolidated rocks called 'glacier moraine'. 'Lateral moraines' form along the side of a glacier and curl into a 'terminal moraine' at the glacier's downvalley end. Drift and moraines are valuable to geologists because they outline the boundaries of past glaciations. | Molnia USGS 2004 |
| Lateral moraine | A sediment ridge, located on a glacier's surface adjacent to the valley walls, extending down glacier to the terminus. It forms by the accumulation of rock material falling onto the glacier from the valley wall, rather than by water deposition. | Molnia USGS 2004 |
| Lateral moraine | Debris deposited along the side of a glacier, comprising both rockfall debris from above and debris ground up by ice-marginal processes. | Swisseduc - Photo glossary of glaciological terms |
| Lateral moraine | Moraine that is found along the sides of a glacier. Commonly found on glaciers that occupy a valley. | PhysicalGeography.net |
| Lateral talik | A layer or body of unfrozen ground, overlain and underlain by perennially frozen ground. | NSIDC accessed 2016 |
| Lateral talik | A layer or body of unfrozen ground, overlain and underlain by perennially frozen ground | Van Everdingen International Permafrost Association 2005 |
| Latitudinal limit of permafrost | The southernmost (northernmost) latitude at which permafrost occurs in a lowland region in the northern (southern) hemisphere. | NSIDC accessed 2016 |
| Latitudinal limit of permafrost | The southernmost (northernmost) latitude at which permafrost occurs in a lowland region in the northern (southern) hemisphere | Van Everdingen International Permafrost Association 2005 |
| Latitudinal zonation of permafrost | The subdivision of a permafrost region into permafrost zones, based on the percentage of the area that is underlain by permafrost. | NSIDC accessed 2016 |
| Latitudinal zonation of permafrost | The subdivision of a permafrost region into permafrost zones, based on the percentage of the area that is underlain by permafrost | Van Everdingen International Permafrost Association 2005 |
| Layer thickness | Snow layer thickness L (measured in centimetres or fractions thereof) is an essential parameter when characterising the current state of a snowpack. Layer thickness is usually measured vertically. If the measurement is taken perpendicular, i.e., slope normal, layer thickness should be denoted by Lp. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Layered cryostructure | The cryostructure of frozen silt or loam in which ice layers alternate with mineral layers that have a massive cryostructure. | NSIDC accessed 2016 |
| Layered cryostructure | The cryostructure of frozen silt or loam in which ice layers alternate with mineral layers that have a massive cryostructure | Van Everdingen International Permafrost Association 2005 |
| Lead | Long, linear areas of open water that range from a few meters to over a kilometer in width, and tens of kilometers long; they develop as ice diverges, or pulls apart. | NSIDC accessed 2016 |
| Lead | Any fracture or passage-way through sea ice which is navigable by surface vessels. A more general description of a lead is an area of open water or new ice between ice floes, although the term is generally applied to linear features. If the open area is very large it may be called a polynya. A lead between the shore and the pack ice is called a coastal lead or shore lead, and a lead between the fast ice and the pack ice is called a flaw lead. | ASPECT 2012 |
| Lead | A more than 50 m wide rectilinear or wedge-shaped crack from several kilometers to several hundreds of kilometers in length. At below freezing temperatures, new, nilas and young ice forms at the surface of leads. | Bushuyev 2004 |
| Lead | Any fracture or passageway through sea ice that is navigable by surface vessels. | WMO Sea Ice Nomenclature 2017 |
| Lead | Sea ice terminology describing any fracture or passageway through ice, which is navigable by surface vessels. | Environment and Climate Change Canada 2014 |
| Lead | A long fracture or separation between ice floes wide enough to be navigated by a ship. A lead may be covered by thin ice. | AMS - glossary of meteorology |
| Lead | A navigable passage through floating ice. From the point of view of the submariner, a recently frozen lead is an ice skylight. | Illustrated Glossary of Snow and Ice |
| Lead shore | A lead that forms between drift ice and the coast. | NSIDC accessed 2016 |
| Lee | Side of a slope that is opposite to the direction of flow of ice, wind, or water. Opposite of stoss. | PhysicalGeography.net |
| Lens ice | Ground ice occurring as ice lenses. | NSIDC accessed 2016 |
| Lens ice | Ground ice occurring as ice lenses | Van Everdingen International Permafrost Association 2005 |
| Lens-type cryostructure | The cryostructure of frozen silt or loam containing numerous ice lenses. | NSIDC accessed 2016 |
| Lens-type cryostructure | The cryostructure of frozen silt or loam containing numerous ice lenses | Van Everdingen International Permafrost Association 2005 |
| Level ice | Floating ice with a flat surface which has never been hummocked. | NSIDC accessed 2016 |
| Level ice | Sea ice that is unaffected by deformation. | WMO Sea Ice Nomenclature 2017 |
| Level ice | Sea ice which has not been affected by deformation. | Bushuyev 2004 |
| Level ice | Sea ice terminology describing ice that is unaffected by deformation. | Environment and Climate Change Canada 2014 |
| Level ice | Ice that has not been deformed. | AMS - glossary of meteorology |
| Level ice | Floating ice with a flat surface which has never been hummocked. | Illustrated Glossary of Snow and Ice |
| Lidar | Light detection and ranging. See laser altimeter. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Life zone | A thermal belt, either of latitude or altitude, in which the plant and animal life is of a distinctive type. The limits of each life zone are mainly fixed by minimum temperatures. The major life zones are boreal, temperate, subtropical, and tropical in both Northern and Southern Hemispheres, with tropical being equatorial. Within each thermal life zone, moisture gradients provide further subdivisions into a number of biogeographical provinces. Latitudinal and altitudinal life zones are not strictly equivalent. | AMS - glossary of meteorology |
| Light freeze | The occurrence of air temperature below 0C (32F) that kills some, but not all, annual vegetation. This often occurs in the 0 to -1C (32-30F) range. | AMS - glossary of meteorology |
| Light frost | A thin and more or less patchy deposit of hoarfrost on surface objects and vegetation. This term is used, inappropriately, for a light freeze. | AMS - glossary of meteorology |
| Light nilas | Nilas that is more than 2 in (5 cm) in thickness and rather lighter in color than dark nilas. | WMO Sea Ice Nomenclature 2017 |
| Light nilas | Nilas which is more than 5 cm in thickness and rather lighter in colour than dark nilas. | Bushuyev 2004 |
| Light nilas | Sea ice terminology describing a nilas which is more than 5 cm in thickness and lighter in colour than dark nilas. | Environment and Climate Change Canada 2014 |
| Limit of all known ice | Sea ice terminology that describes the limit at any given time between icebergs and/or sea ice infested waters, and ice-free waters. | Environment and Climate Change Canada 2014 |
| Line of ridges | A thick ice ridge on fast ice, including stamukhas, which in places may attach it to the bottom. | Bushuyev 2004 |
| Liquid water content | Liquid water content LWC is defined as the amount of water within the snow that is in the liquid phase. This parameter is synonymous with the free-water content of a snow sample. Liquid water in snow originates from either melt, rain, or a combination of the two. Measurements of liquid water content or wetness are expressed as either a volume or mass fraction. Both can be reported as a percent (%), which usually requires a separate measurement of density. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Liquid water equivalent | Same as Water Equivalent; the liquid content of solid precipitation that has accumulated on the ground (snow depth). The accumulation may consist of snow, ice formed by freezing precipitation, freezing liquid precipitation, or ice formed by the refreezing of melted snow. | NOAA National Weather Service Glossary 2009 |
| Little ice age | A period of cooling that occurred from the 16th through the early 19th century, and was marked by expanding glaciers in Europe, North America, and Asia | NSIDC accessed 2016 |
| Little ice age | (1) The period from about 1430 to 1850 AD which was characterized in Europe and North America by a markedly colder climate than the present. (2) A period during which there is a renewal of glacial growth after previous shrinkage or disappearance during the preceding milder megathermal phase. | WMO METEOTERM accessed 2016 |
| Little Ice Age | The period of time that led to expansion of valley and cirque glaciers world-wide, with their maximum extents being attained in about 1700-1850 AD in many temperate regions, and around 1900 in Arctic regions. | Swisseduc - Photo glossary of glaciological terms |
| Little ice age | A period between approximately A.D. 1550 (or perhaps as early as 1300) and 1850 in which mountain glaciers advanced in many parts of the world. The precise timing of the advances and retreats varied from region to region. Temperatures were not uniformly colder throughout this period, but rather showed marked variations on decadal timescales. | AMS - glossary of meteorology |
| Little ice age | Time period from 1550 to 1850 AD. During this period, global temperatures were at their coldest since the beginning of the Holocene. | PhysicalGeography.net |
| Little Ice Age (LIA) | A period of greater glacier mass and extent, relative to the preceding and following periods, with increased glacier thickness and extension to lower altitudes. In different regions of the Earth, in both hemispheres, the Little Ice Age began and ended at different times, beginning as early as about AD 1300 and ending as late as about AD 1900, with one or more glacier advances distinguishable during that period. In many regions the LIA maximum glacier extent was also the maximum extent of the entire Holocene (the past 10 000 years). Gain of mass usually resulted from both enhanced accumulation and reduced ablation. See trimline. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Little Ice Age (LIA) | An interval during the last millennium characterized by a number of extensive expansions of mountain glaciers and moderate retreats in between them, both in the Northern and Southern Hemispheres. The timing of glacial advances differs between regions and the LIA is, therefore, not clearly defined in time. Most definitions lie in the period 1400 CE and 1900 CE. Currently available reconstructions of average Northern Hemisphere temperature indicate that the coolest periods at the hemispheric scale may have occurred from 1450 to 1850 CE. | IPCC WGI AR5 2013 |
| Little Ice Age (Neoglaciation) | The most recent interval of temperate glacier expansion and advance on Earth. It began ~650 years ago and continued into the 20th century in many locations. Temperate glaciers in North America, South America, Africa, Europe, and Asia were affected. | Molnia USGS 2004 |
| Living glacier | A glacier experiencing glacier flow. Expansion or retreat is determined by the balance between mass accretion and mass depletion processes. | AMS - glossary of meteorology |
| Lobe | A tongue-like extension of some material. For example, the ice lobe of an alpine glacier. | PhysicalGeography.net |
| Lobed | Initial stage of tongue formation (occurs on both micro and macro scales); In many cases part of an ice sheet, cap, field; Large or small scale radial ice margin; Is not an outlet or a valley glacier; If it terminates into sea, use class 'calving and lobed'; Part of an ice sheet or ice cap, disqualified as an outlet glacier (WGMS 1970, 1998); Tongue like form of an icefield or ice cap. (WGMS 1977) | Illustrated GLIMS Glacier Classification Manual |
| Loess | Deposits of silt laid down by aeolian processes over extensive areas of the mid-latitudes during glacial and postglacial times. | PhysicalGeography.net |
| Lolly ice | Saltwater frazil, a heavy concentration of which is called sludge. | AMS - glossary of meteorology |
| Lombarde | An easterly wind (from Lombardy) that predominates along the French-Italian frontier. It comes from the High Alps. In winter it is violent and forms snowdrifts in the mountain valleys. In the plains it is gentle and very dry. It is associated with an anticyclone over France and central Europe, or with high pressure to the southeast of Europe and low pressure to the northwest along with falling pressure over western France. | AMS - glossary of meteorology |
| Long-term strength | The failure strength of a material after a long period of creep deformation. | NSIDC accessed 2016 |
| Long-term strength | The failure strength of a material after a long period of creep deformation | Van Everdingen International Permafrost Association 2005 |
| Longitudinal crevasse | A crevasse oriented more or less parallel to the long axis of a glacier. Longitudinal crevasses typically open on a valley glacierwhen the glacier becomes wider. | Swisseduc - Photo glossary of glaciological terms |
| Looped moraine | Curving, folded or teardrop-shaped medial moraine resulting from a surge of a tributary glacier. | Swisseduc - Photo glossary of glaciological terms |
| Low-center polygon | An ice-wedge polygon in which thawing of ice-rich permafrost has left the central area in a relatively depressed position. | NSIDC accessed 2016 |
| Low-centre polygon | An ice-wedge polygon in which thawing of ice-rich permafrost has left the central area in a relatively depressed position | Van Everdingen International Permafrost Association 2005 |
| Luminous pillars | White or sometimes reddish vertical streaks of light extending from above and below the sun; they are caused by light reflected off the mirror-like surfaces of ice; most commonly seen at sunrise and sunset. | NSIDC accessed 2016 |
| Macro-scale polygons | Closed, multi-sided, roughly equidimensional, patterned ground features, typically 15 to 30 meters (16 to 33 yards) across; commonly resulting from thermal contraction cracking of the ground. | NSIDC accessed 2016 |
| Macro-scale polygons | Macro-scale polygons are closed, multi-sided, roughly equidimensional patterned-ground features, typically 15 to 30 m across, commonly resulting from thermal contraction cracking of the ground | Van Everdingen International Permafrost Association 2005 |
| Malvinas current | A jetlike northward looping excursion of the Antarctic Circumpolar Current east of southern Argentina; also known as the Falkland Current. Somewhere between 33 and 38S it meets the Brazil Current and turns eastward, forming an intense temperature and salinity front. | AMS - glossary of meteorology |
| Marginal crevasse | A crevasse near the side of a glacier formed as the glacier moves past stationary valley walls; usually oriented about 45 degrees up-glacier from the side wall. | NSIDC accessed 2016 |
| Marginal ice zone | A part of the seasonal ice zone that varies in width (100 to 200 kilometers, 62 to 124 miles) that extends from the ice edge into the ice pack, where waves and swells affect the ice; often characterized by highly variable ice conditions; in general, it is wider in the Antarctic than the Arctic. | NSIDC accessed 2016 |
| Marginal ice zone (MIZ) | The marginal ice zone (MIZ) is not a very well defined term and it is useful for an author to be specific about its meaning when using it. Probably the most accepted definition is that of Wadhams (1986) who describes it as 'that part of the ice cover which is close enough to the open ocean boundary to be affected by its presence'. This definition is open to interpretation, but is generally applied to that region of the pack which is significantly affected by ocean swell. In the Antarctic this region may extend hundreds of kilometres from the ice edge, and in some regions right to the coast. The MIZ is an area of enhanced ice drift, deformation and divergence. | ASPECT 2012 |
| Marine cryopeg | A layer or body of unfrozen ground, that is perennially cryotic (T 0 degrees Celsius), forming part of the coastal or subsea permafrost. | NSIDC accessed 2016 |
| Marine cryopeg | A layer or body of unfrozen ground, that is perennially cryotic (T < 0°C), forming part of coastal or subsea permafrost | Van Everdingen International Permafrost Association 2005 |
| Marine ice | Ice formed by the freezing of sea water at the base of an ice shelf. The formation of marine ice can contribute substantially to ice-shelf mass balance (see basal accumulation), and marine ice can be a substantial component of the ice shelf itself. See also accreted ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Marine-based ice sheet | An ice sheet containing a substantial region that rests on a bed lying below sea level and whose perimeter is in contact with the ocean. The best known example is the West Antarctic ice sheet. | IPCC WGI AR5 2013 |
| Maritime polar air mass (mP) | Air mass that forms over extensive ocean areas of the middle to high latitudes. Around North America, these air mass system form over the Atlantic and Pacific oceans at the middle latitudes. Maritime Polar air masses are mild and humid in summer and cool and humid in winter. In the Northern Hemisphere, maritime polar air masses are normally unstable during the winter. In the summer, atmospheric stability depends on the position of the air mass relative to a continent. Around North America, Maritime Polar air masses found over the Atlantic are stable in summer, while Pacific systems tend to be unstable. | PhysicalGeography.net |
| Maritime tundra | Tundra found along many subarctic coastal belts, usually with a high proportion of arctic plants and animals far south of their normal limit. | AMS - glossary of meteorology |
| Marker horizon | A distinctive, datable layer in ice, firn or snow; see isochrone. Ice-core stratigraphy relies on an uninterrupted series of Annual marker horizons. Volcanic eruptions and nuclear tests (see bomb horizon) yield marker horizons which allow the measurement of average accumulation rates. Marker horizons with relative dielectric constants that contrast strongly enough allow the mapping of accumulation with ground-penetrating radar. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mascon | The mass of a thin layer of uniform thickness added to or subtracted from a reference model of the solid and liquid Earth over a specified region, particularly a glacierized region, during a specified period. See GRACE, gravimetric method. Mascon is an abbreviation by geodesists of 'mass concentration', coined originally to stand for a large positive gravitational anomaly. In modern usage the mascon itself is a number representing the mass of the layer as a surface density (kg m-2), although the word is often used loosely to refer to the 'mascon region', that is, the region over which the mass is added or subtracted. The 'mascon parameters' are sets of coefficients describing the difference of gravitational potential that arises due to the mascon. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass balance | The difference between accumulation and ablation on a glacier; usually calculated on an annual basis. | NSIDC accessed 2016 |
| Mass balance | Mass balance describes the net gain or loss of snow and ice through a given year. It is usually expressed in terms of water gain or loss. | Molnia USGS 2004 |
| Mass balance | A measure of the change in mass of a glacier at a certain point for a specific period of time. The balance between accumulation and ablation. Also called Mass Budget. | Molnia USGS 2004 |
| Mass balance | The change in the mass of a glacier, or part of the glacier, over a stated span of time; the term mass budget is a synonym. See mass-balance units for recommended units. The span of time is often a year or a season. A seasonal mass balance is nearly always either a winter balance or a summer balance, although other kinds of season are appropriate in some climates, such as those of the tropics. The definition of year depends on the method adopted for measurement of the balance. See time system. The reference in the definition to a glacier means that a particular volume of space is being studied. A properly delineated glacier has no mass transfer of ice across its boundary other than as ice discharge. However, the mass balance is often quoted for volumes other than that of the whole glacier, for example a column through the glacier, the part of the glacier upglacier or downglacier from the grounding line, or a band defined by two contours of surface elevation. It is necessary in such cases to make clear that the study volume is something other than the whole glacier, and also to make clear which components of the mass balance are being reported. The quantity reported may be the climatic mass balance or the climatic-basal mass balance, but will often be the surface mass balance. In all cases the need for a defined study volume is fundamental because without it the principle of conservation of mass cannot be invoked. The study volume may change over the study period. The surface and bed elevations may change, and the areal extent is unlikely to be the same at the end of the period as it was at the beginning. Whether these changes are significant will depend not just on their magnitude and the accuracy with which they can be determined but on the purpose of the investigation. See conventional balance, reference-surface balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass balance | (1) In a hydrosystem, equivalence between the total mass of water entering the system and that leaving the system. (2) The necessary condition in a chemical reaction for mass conservation of each element regardless of the component in which the element participates. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Mass balance | (or mass budget) A year-by-year measure of the state of health of a glacier, reflecting the balance between accumulation and ablation. A glacier with a positive mass balance in a particular year gained more mass through accumulation than was lost through ablation; the reverse is true for negative mass balance. | Swisseduc - Photo glossary of glaciological terms |
| Mass balance | Usually, a model that employs the limitation that the system observed maintains a constant mass, that is, total mass divergence for the entire system is zero, but may be nonzero within the system. | AMS - glossary of meteorology |
| Mass balance | The relative balance between the input and output of material within a system. | PhysicalGeography.net |
| Mass balance/budget (of glaciers or ice sheets) | The balance between the mass input to the ice body (accumulation) and the mass loss (ablation and iceberg calving) over a stated period of time, which is often a year or a season. Point mass balance refers to the mass balance at a particular location on the glacier or ice sheet. Surface mass balance is the difference between surface accumulation and surface ablation. The input and output terms for mass balance are: Accumulation All processes that add to the mass of a glacier. The main contribution to accumulation is snowfall. Accumulation also includes deposition of hoar, freezing rain, other types of solid precipitation, gain of wind-blown snow, and avalanching. Ablation Surface processes that reduce the mass of a glacier. The main contributor to ablation is melting with runoff but on some glaciers sublimation, loss of wind-blown snow and avalanching are also significant processes of ablation. Discharge/outflow Mass loss by iceberg calving or ice discharge across the grounding line of a floating ice shelf. Although often treated as an ablation term, in this report iceberg calving and discharge is considered separately from surface ablation. | IPCC WGI AR5 2013 |
| Mass budget | A synonym of mass balance. Mass budget is a more correct term than mass balance, but is used less often. While water balance and energy balance refer to equations in which the change in storage is only one of the terms, common glaciological usage equates mass balance with the change in storage (in other words, with the mass imbalance). It is unlikely that this usage will change. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass conservation | See conservation of mass. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass flux | 1 The horizontal rate of flow of mass through a plane normal to the direction of the horizontal velocity vector. Depending on the context, the flux may be through an element of area at a given position in the vertical plane, through a unit of width extending from the glacier bed to the surface, or through an entire glacier cross section. 2 The vertical rate of flow of mass at the glacier surface or bed. In sense 2, the flux at the surface is equal to the sum of surface accumulation and surface ablation, or in other words to the surface mass balance. Equivalently the flux at the bed is equal to the basal mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass turnover | The renewal of the mass of a glacier by mass-balance processes. Mass turnover is measured most usefully by the mass-turnover time, which is the mass of the glacier divided by the mass-balance amplitude, with the latter expressed as an Annual rate. Mass-turnover times range from several decades for glacierets to tens of thousands of years for ice sheets. See response time. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass wasting | Downslope movement of soil or rock on, or near, the earth's surface under the influence of gravity | Van Everdingen International Permafrost Association 2005 |
| Mass-balance amplitude | One half of the difference between winter mass balance and summer mass balance, (Bw Bs)/2. Summer mass balance is generally negative because ablation dominates in the summer season. A more general definition, (Ca Aa)/2 or one half of the Annual exchange, could be offered in terms of Annual accumulation and Annual ablation, but these quantities are so seldom measured that a calculation from seasonal balances is more practicable. The balance amplitude tends to be large in maritime climates, in which accumulation is large, and small in continental climates, in which accumulation is small. In consequence the mean balance amplitude is well correlated with the interannual variability of Annual mass balance, and, when it can be estimated from climatological information, has been used as an estimator of the magnitude of the Annual mass balance itself. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass-balance gradient | The rate of change of mass balance with altitude, that is, the derivative db/dz of the mass-balance profile b (z). If mass balance varies linearly with altitude, the mass-balance gradient will be constant with z; if not, the gradient will vary with z. The mass-balance gradient at the equilibrium-line altitude is called the activity index. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass-balance index | The rate of change db/dx of mass balance with horizontal distance from the upper end of a flowline. The term has also been used informally for a variety of measures of the mass balance.64 | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass-balance profile | The variation b (z) of mass balance with altitude. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass-balance rate | The change of mass per unit of time as the interval of mass change approaches zero, obtained in practice by dividing the mass balance by the duration over which it is measured or modelled. See mass-balance units. The qualifiers 'instantaneous' and 'average' can be used to distinguish between the rate in the mathematical sense and the rate as obtained in practice. For example, the average mass-balance rate | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass-balance ratio | The ratio of the mass-balance gradient in the ablation zone to the mass-balance gradient in the accumulation zone, each of these gradients being assumed constant and that in the accumulation zone also being assumed non-zero. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass-balance sensitivity | The change in mass balance due to a change in a climatic variable such as air temperature or precipitation. Sensitivities to temperature and precipitation are often expressed as changes in response to a 1 K warming or a 10% precipitation increase, resulting in a negative sensitivity to temperature and a positive sensitivity to precipitation. Sensitivities are generally derived from mass-balance modelling, that is, from the difference in mass balance between model runs with and without climate perturbation, but they have also been estimated from mass-balance and climate observations. Mass balance does not vary linearly with the climate in general. That is, d: B/d: T and d: B/d: P are not constant, but they may be assumed constant as a good approximation for small changes of the climatic variable. The 'dynamic' mass-balance sensitivity changes as the extent and area-altitude distribution of the glacier or glacierized region evolve. In contrast, the 'static' sensitivity neglects these geometric changes, although it may still vary with, for example, components of the surface energy balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass-balance units | The dimension of mass balance is [M] (mass). The dimension of the mass-balance rate is [M T-1] (mass per unit time). When the mass balance is presented per unit area, it is called specific mass balance and its dimension becomes [M L-2], while the dimension of the mass-balance rate becomes [M L-2 T-1]. When water-equivalent units are adopted (see below), the dimension becomes [L3] or [L3T-1], the corresponding specific units being [L] or [L T-1]. The unit for expressing mass or change of mass numerically is the kilogram (kg). When more convenient the petagram (Pg) or gigatonne (Gt; 1 Gt = 1 Pg = 1012 kg) can be substituted. When mass balance is expressed per unit area, its unit is kg m-2. The unit kg m-2 is usually replaced by the millimetre water equivalent, mm w. E. This substitution is convenient because 1 kg of liquid water, of density 1000 kg m-3, has a vertical extent of exactly 1 mm when distributed uniformly over a horizontal area of 1 m2. The units kg m-2 and mm w. E. Are therefore numerically identical. More formally, the metre water equivalent (m w. E.) Is an extension of the SI that is obtained by dividing a particular mass per unit area by the density of water, w: 1 m w. E. = 1000 kg m-2 / w: Because of the risk of confusion with the metre ice equivalent, or with ordinary lengths, it is important that the qualifier 'w. E.' Not be omitted. Mass balances can also be stated in m3 w. E. (1 m3 w. E. = 1 m w. E. Distributed uniformly over 1 m2) or km3 w. E. Note that 1 km3 w. E. Is numerically identical with 1 Gt. For the mass-balance rate, appropriate units are kg a-1 or kg m-2 a-1 (or m3 w. E. A-1 or mm w. E. A-1) when the time span is an integer multiple of 1 year. Over shorter intervals the unit of time should be the second or the day. Mass units (kg or m3 w. E.) Are useful for hydrological and oceanographic purposes, while specific mass units (kg m-2, mm w. E., m w. E.) Are needed when comparing the mass balances of different glaciers and for studying glacier-climate relations. To convert, with sufficient accuracy for many purposes, to the frequently needed sea-level equivalent (SLE), mass balance in kg m-2 is first converted to kg by multiplying by the area of the glacier, and then divided by the product of w and the area of the ocean (362.5 1012 m2). The sign of SLE is opposite to that of glacier mass balance, a loss from the ice being deemed to be an equivalent gain for the ocean. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mass-balance year | The time span, equal or approximately equal in duration to one calendar year, to which the Annual mass balance in any time system refers. In the stratigraphic system the Annual mass balance is the change of mass during the period between formation of two successive minima in the sequence of Annual cycles of mass growth and decline. These minima are usually reached at different times in successive years, and the duration of the mass-balance year may therefore vary irregularly and substantially in duration from year to year. Point mass balances can be determined unambiguously in the stratigraphic system, but glacier-wide determinations require the assumption that the diachronous character of the summer surface can be neglected. In the fixed-date system the first day of the mass-balance year is always on the same calendar date, which is typically chosen to coincide with the start of the local hydrological year, for example 1 October in the mid-latitudes of the Northern Hemisphere or 1 April in the mid-latitudes of the Northern Hemisphere, or sometimes with the average date of minimum Annual mass. The mass-balance year is 365 (or 366) days long. In the floating-date system the mass-balance year is defined by the calendar dates of the two successive surveys, which may vary from year to year and may or may not be 365 (or 366) days apart. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Massif | A compact portion of a mountain range, containing one or more summits. | NOAA National Weather Service Glossary 2009 |
| Massif | Compact group of mountain heights, which may be partly or almost entirely ice-covered. | UK Antarctic Place-names Committee accessed 2016 |
| Massive cryostructure | The cryostructure of frozen sand in which all mineral particles are bonded together with ice. | NSIDC accessed 2016 |
| Massive cryostructure | The cryostructure of frozen sand in which all mineral particles are bonded together with ice | Van Everdingen International Permafrost Association 2005 |
| Massive ice | A comprehensive term used to describe large masses of ground ice, including ice wedges, pingo ice, buried ice and large ice lenses. | NSIDC accessed 2016 |
| Massive ice | A comprehensive term used to describe large masses of ground ice, including ice wedges, pingo ice, buried ice and large ice lenses | Van Everdingen International Permafrost Association 2005 |
| Massive ice | A comprehensive term used to describe large masses of Ground Ice, including Ice Wedges, Buried Ice and large Ice lenses. | Trombotto et al. 2014 |
| Massive-agglomerate cryostructure | The cryostructure of frozen silt or loam in which ice veins form an irregular three-dimensional network. | NSIDC accessed 2016 |
| Massive-agglomerate cryostructure | The cryostructure of frozen silt or loam in which ice veins form an irregular three-dimensional network | Van Everdingen International Permafrost Association 2005 |
| Massive-porous cryostructure | The cryostructure of frozen sand and gravel in which all mineral particles are bonded together with ice, but larger pore spaces are not completely filled with ice. | NSIDC accessed 2016 |
| Massive-porous cryostructure | The cryostructure of frozen sand and gravel in which all mineral particles are bonded together with ice, but larger pore spaces are not completely filled with ice | Van Everdingen International Permafrost Association 2005 |
| Maximum ice extent | The largest sea ice extent during a given year; maximum ice extent marks the end of the growth period for sea ice, and the start of the melt season | NSIDC accessed 2016 |
| Maximum iceberg limit | Sea ice terminology, describing the maximum limit of icebergs, based on observations over a period of years. | Environment and Climate Change Canada 2014 |
| Mean annual ground temperature (MAGT) | Mean annual temperature of the ground at a particular depth. | NSIDC accessed 2016 |
| Mean annual ground temperature (MAGT) | Mean annual temperature of the ground at a particular depth | Van Everdingen International Permafrost Association 2005 |
| Mean annual ground temperature (MAGT) | Mean annual temperature of the ground at a particular depth. The mean annual temperature of the ground usually increases with depth below the surface. The Mean Annual Ground Temperature at the Depth of Zero Annual Amplitude is often used to assess the thermal regime of the ground at various locations. | Trombotto et al. 2014 |
| Mean annual ground-surface temperature (MAGST) | Mean annual temperature of the surface of the ground. | NSIDC accessed 2016 |
| Mean annual ground-surface temperature (MAGST) | Mean annual temperature of the surface of the ground | Van Everdingen International Permafrost Association 2005 |
| Mean annual ground-surface temperature (MAGST) | Mean annual temperature of the surface of the ground. Permafrost exists if the Mean Annual Ground-Surface Temperature is perennially below 0C. Although the mean annual surface temperature may be below 0C, the surface temperature will fluctuate during the year, causing a layer of ground immediately beneath the surface to thaw in the summer and freeze in the winter (the Active Layer). | Trombotto et al. 2014 |
| Mean annual temperature | The average temperature for the entire year at any given location. | NOAA National Weather Service Glossary 2009 |
| Mean areal precipitation | (abbrev. MAP) The average rainfall over a given area, generally expressed as an average depth over the area. | NOAA National Weather Service Glossary 2009 |
| Mean ice edge | Average position of the ice edge in any given month or period based on observations over a number of years. Other terms that may be used are mean maximum ice edge and mean minimum ice edge. | WMO Sea Ice Nomenclature 2017 |
| Mean ice edge | Sea ice terminology that describes the average position of an ice edge in any given month or period, based on observations over a number of years. Other terms which may be used are mean maximum ice edge, and mean minimum ice edge. | Environment and Climate Change Canada 2014 |
| Mean iceberg limit | Sea ice terminology. Describes the average position of the limit of icebergs at any given time, based on observations over a number of years. | Environment and Climate Change Canada 2014 |
| Mechanical properties of frozen ground | The properties of frozen ground governing its deformability and strength | Van Everdingen International Permafrost Association 2005 |
| Mechanical strength | The failure strength of a material under given loading conditions | Van Everdingen International Permafrost Association 2005 |
| Medial moraine | A ridge-shaped moraine in the middle of a glacier originating from a rock outcrop, nunatak, or the converging lateral moraines of two or more ice streams. | NSIDC accessed 2016 |
| Medial moraine | A sediment ridge, located on a glacier's exposed ice surface, away from its valley walls, extending down glacier to the terminus. It forms by the joining of two lateral moraines when two glaciers merge. | Molnia USGS 2004 |
| Medial moraine | Deposit of material found down the center of a glacier. Created when two glacier and their lateral moraines merge. | PhysicalGeography.net |
| Medial moraines | Medial moraines form where two mountain glaciers bearing lateral moraines unite. They appear as dark streaks of rock along the glacier centerline. | Molnia USGS 2004 |
| Medial moraines | Distinct ridge of debris occurring on the surface of a glacier where two streams of ice merge. | Swisseduc - Photo glossary of glaciological terms |
| Median ice edge | Sea ice terminology describing the position of the ice edge, where its frequency of occurrence is 50 per cent. | Environment and Climate Change Canada 2014 |
| Median iceberg limit | Sea ice terminology describing the position where the historical or statistical frequency of occurrence of the iceberg limit is 50 per cent. | Environment and Climate Change Canada 2014 |
| Medium first-year ice | First-year ice 25 to 50 in (70-120 cm) thick. | WMO Sea Ice Nomenclature 2017 |
| Medium first-year ice | First-year ice 70-120 cm thick. | Bushuyev 2004 |
| Medium first-year ice | Sea ice terminology meaning ice that is 70 cm to 120 cm thick. | Environment and Climate Change Canada 2014 |
| Medium ice field | An ice field 8 to 10 mi (15-20 km) across. | WMO Sea Ice Nomenclature 2017 |
| Medium ice field | Sea ice terminology meaning an ice field that is 15 km to 20 km across. | Environment and Climate Change Canada 2014 |
| Medium iceberg | Sea ice terminology meaning a piece of glacier ice extending 16 m to 45 m above sea level, and with a length of 61 m to 120 metres. | Environment and Climate Change Canada 2014 |
| Medium lake ice | Sea ice terminology meaning ice that is 15 to 30 cm thick. | Environment and Climate Change Canada 2014 |
| Megadunes | Unlike snow dunes that are piles of drifted snow, antarctic megadunes are long, undulating waves in the surface of the ice sheet that are 2 to 4 meters (6.5 to 13 feet) high and 2 to 5 kilometers (1 to 3 miles) apart; they are slightly rounded at their crests and are so subtle that a person on the ground cannot see the pattern. | NSIDC accessed 2016 |
| Melt | (1) To undergo fusion, or (when used transitively) to cause to undergo fusion. See latent heat of fusion. (2) The liquid produced by the process of fusion (see meltwater). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Melt extent | The spatial extent (dimension [L2]) of melting on the surface of the glacier. The melt extent can be measured by microwave remote sensing of the brightness temperature with a passive-microwave sensor, or equivalent analysis of radar or scatterometer imagery. The spatial resolution of passive-microwave radiometers and scatterometers being low at present (several km or coarser), the method is mainly exploited on ice sheets and large ice caps. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Melt pond | A pond of liquid water (mostly from melted snow) on the surface of sea ice, usually occurring in the spring. Melt ponds are common in the Arctic but less so in the Antarctic. | AMS - glossary of meteorology |
| Melt ponds | Pools of melted snow and ice on the sea ice surface created during the summer melt. | NSIDC accessed 2016 |
| Melting | The process by which a solid changes phase into a liquid; a synonym of fusion. See ablation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Melting | The physical process of a solid becoming a liquid. For water, this process requires approximately 80 calories of heat energy for each gram converted. | PhysicalGeography.net |
| Melting index | A measure, with dimension [L2 T] and units such as km2 d, of the spatiotemporal extent of surface melting. The melting index, usually obtained by remote sensing, is the integral over a defined region and time span of the time-varying melt extent, and is approximated in practice as a regional sum of products at local scale (such as that of the pixels of a passive-microwave sensor) of the melt extent and the duration of melting. The accuracy of the duration is principally determined by the frequency of imaging, which tends to be high at high latitudes because most orbital sensors are in polar orbits. The melting index is a valuable proxy indicator in the absence of more direct measures of melting. The melting index is sometimes called the melt index or the surface-melt index, and is formulated in slightly different ways by different authors. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Melting layer | The altitude interval throughout which ice-phase precipitation melts as it descends. The top of the melting layer is the melting level. The melting layer may be several hundred meters deep, reflecting the time it takes for all the hydrometeors to undergo the transition from solid to liquid phase. The temperature of the melting layer is typically 0C or slightly warmer. | AMS - glossary of meteorology |
| Melting level | The altitude at which ice crystals and snowflakes begin to melt as they descend through the atmosphere. In cloud physics and in radar meteorology, this is the accepted term for the 0C constant-temperature surface ( see bright band). It is physically more apt than the corresponding operational term, freezing level, for melting of pure ice must begin very near 0C, but freezing of liquid water can occur over a broad range of temperatures (between 0 and -40C; see supercooling). | AMS - glossary of meteorology |
| Melting point | The temperature at which a solid liquefies (see freezing point). The melting point of ice is 273.15 K at 1013.25 hpa. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Melting point | The temperature, Tm = 273.15 K = 0 | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Melting point | The temperature at which a solid substance undergoes fusion, that is, melts, changes from solid to liquid form. The melting point of a substance should be considered a property of its crystalline form only. At the melting point the liquid and solid forms of a substance exist in equilibrium. All substances of crystalline nature have their characteristic melting points. For very pure substances the temperature range over which the process of fusion occurs is very small. The melting point of a pure crystalline solid is a function of pressure; it increases with increasing pressure for most substances. However, in the case of ice (and a few other substances) the melting point decreases with increasing pressure (see regelation). Under a pressure of one standard atmosphere, the melting point of pure ice is the same as the ice point, that is, 0C. | AMS - glossary of meteorology |
| Meltwater | The liquid resulting from melting of ice, firn or snow. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Meltwater | Water produced from the melting of snow and/or glacial ice. | PhysicalGeography.net |
| Meltwater conduit | A channel within, underneath, on top of, or near the side of a glacier that drains meltwater out of the glacier; usually kept open by the frictional heating of flowing water that melts the ice walls of the conduit. | NSIDC accessed 2016 |
| Meltwater discharge | See article Meltwater discharge under Discharge. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Meltwater discharge | The rate of flow through a cross section, usually a stream cross section, of water produced by melting of glacier ice, firn or snow that is removed from the glacier in surface, englacial or subglacial flows. See runoff. The measured discharge may include a contribution from rainfall on the glacier, and typically includes contributions from unglacierized parts of the drainage basin. Meltwater discharge is always reported as volume per unit time. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Meltwater runoff | The component of runoff (in sense 2) produced by melting of glacier ice, firn or snow that is removed in surface, englacial or subglacial flows. Meltwater runoff is not the same as surface ablation by melting, because surface meltwater may refreeze in the glacier (see refreezing, internal accumulation), and part of the meltwater runoff may originate from basal ablation or internal ablation. Nor is it usually the same as the total runoff, which is likely to include contributions from unglacierized parts of the drainage basin, and may include a contribution from rainfall on the glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Metamorphosis of snow | The modification of snow grains to a less angular, more rounded form accompanied by a gradual increase in density. Metamorphic processes include sublimation, evaporation, and vapor diffusion. | AMS - glossary of meteorology |
| Micro-scale polygon | Closed, multi-sided, roughly equidimensional, patterned ground features, less than 2 meters (6.6 feet) in diameter; usually caused by desiccation cracking of fine-grained soil materials. | NSIDC accessed 2016 |
| Micro-scale polygon | Micro-scale polygons are closed, multi-sided, roughly equidimensional patterned-ground features, less than 2 m in diameter, usually caused by desiccation cracking of fine-grained soil materials | Van Everdingen International Permafrost Association 2005 |
| Microstructure | The thermal, mechanical, and electromagnetic – including optical – properties of snow depend heavily on the configuration of the ice and air spaces. The microstructure of snow is complex, since the size, shape, and number of structural elements vary widely in natural snowpacks. Although snow is commonly disaggregated into ice particles for recording grain shape and size, this process destroys the microstructure and changes the properties we are attempting to measure. As a result, snow characterization solely by shape and size is incomplete. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Microwave remote sensing | Remote sensing with an Active-microwave sensor or a passive-microwave sensor. At frequencies between about 1 ghz and 40 ghz, microwaves are capable of penetrating clouds, and orbiting sensors can measure surface properties in all atmospheric conditions. Corrections must be made for scattering resulting from atmospheric and ionospheric variations. At frequencies below a few ghz, the depth of penetration beneath the glacier surface becomes great enough to permit Active-microwave imaging or profiling of the subsurface from the surface or from aircraft. The terms microwave and radar are often used interchangeably. This is mainly because the boundary between the lower-frequency radio and higher-frequency microwave regions of the electromagnetic spectrum is fixed differently, between 0.3 and 300 ghz (wavelengths of 1 m to 1 mm), by different authorities. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mid-range altitude | The average of the minimum altitude and maximum altitude of the glacier. The mid-range altitude is of interest in itself as a measure of the vertical location of the glacier, but has also been shown to be (to within the accuracy of measurements) an unbiased estimator of the Balanced-budget ELA. See glaciation level. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Milky ice | A form of aircraft icing intermediate in all respects between clear ice and rime ice. It forms in the temperature range between -4 and -15C. | AMS - glossary of meteorology |
| Minerogenic palsa | A palsa in which the frozen core extends below the peat into underlying mineral material. | NSIDC accessed 2016 |
| Minerogenic palsa | A palsa in which the frozen core extends below the peat into underlying mineral material | Van Everdingen International Permafrost Association 2005 |
| Minimum iceberg limit | Sea ice terminology that describes the minimum limit of icebergs based on observations over a period of years. | Environment and Climate Change Canada 2014 |
| Mires | Also known as tundra mires, generally described as an area of wet, soggy, muddy ground., and often feature a layer of peat over permafrost. | NSIDC accessed 2016 |
| Mist | Very small to microscopic-sized water droplets that are suspended in the atmosphere, usually in association with precipitation, and causing obstruction to visibility from one-half (1/2) to five (5) nautical miles, inclusive. | Environment and Climate Change Canada 2014 |
| Mixed precipitation | Precipitation consisting of a mixture of rain and wet snow; it usually occurs when the temperature of the air layer near the ground is slightly above freezing; the British term for this mixture is sleet (which has a different meaning in the United States). | NSIDC accessed 2016 |
| Moisture content | Synonymous with liquid water content. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Mollition | The act or process of thawing the active layer (mollisol). | AMS - glossary of meteorology |
| Monolith | Pillar like rock peak or nunatak | UK Antarctic Place-names Committee accessed 2016 |
| Moraine | A mound, ridge, or other distinct accumulation of glacial till. | NSIDC accessed 2016 |
| Moraine | A general term for unstratified and unsorted deposits of sediment that form through the direct action of, or contact with, glacier ice. Many different varieties are recognized on the basis of their position with respect to a glacier. | Molnia USGS 2004 |
| Moraine | Ridges or deposits of rock debris transported by a glacier. | UK Antarctic Place-names Committee accessed 2016 |
| Moraine | Mounds, ridges or deposits of rock debris transported by a Glacier (glacial till). Common forms are: ground Moraine formed under a Glacier; lateral Moraine, along the sides; medial Moraine, down the centre; and end Moraine, deposited at the foot. Moraines are left after a Glacier has receded, providing evidence of its former extent. Moraines can have frozen cores and exist in Permafrost environments. On steep slopes such Moraines can show signs of Creep. | Trombotto et al. 2014 |
| Moraine | Ridges or deposits of rock debris transported by a glacier. Moraines are left after a glacier has receded, providing evidence of its former extent. Common forms are ground moraine, formed under a glacier; lateral moraine, along the sides; medial moraine, down the center; and end moraine, deposited at the terminus. | AMS - glossary of meteorology |
| Moraine | A hill of glacial till deposited directly by a glacier. | PhysicalGeography.net |
| Moraine | Ridges or deposits of rock debris transported by a glacier. Common forms are: ground moraine, formed under a glacier; lateral moraine, along the sides; medial moraine, down the centre; and end moraine, deposited at the foot. Moraines are left after a glacier has receded, providing evidence of its former extent. | Illustrated Glossary of Snow and Ice |
| Moraine code 1 (in contact with present day glacier) | No moraines: no moraines; Terminal moraines : Sometimes problematic to identify in satellite imagery due to the lack of distinction between terminal moraine and debris surface coverage of a glacier; Lateral and/or medial moraine: Sometimes problematic for detection by means of remote sensing techniques due to the lack of distinction between lateral moraine and debris surface coverage of a glacier; Push moraine: Push moraines are difficult to identify unambiguously by remote sensing techniques, because in satellite images they are often not distinguishable from 'normal' terminal moraines; Debris, uncertain if morainic: Debris, uncertain if morainic; Moraines, type uncertain or not listed: Moraines, type uncertain or not listed; | Illustrated GLIMS Glacier Classification Manual |
| Moraine code 2 (moraines farther downstream) | No moraines: no moraines; Terminal moraines : terminal moraines; Lateral and/or medial moraine: Lateral and/or medial moraine; Push moraine: Push moraines are difficult to identify unambiguously by remote sensing techniques, because in satellite images they are often not distinguishable from 'normal' terminal moraines. The only way to identify push moraines is by ground observations; Debris, uncertain if morainic: Debris, uncertain if morainic; Moraines, type uncertain or not listed: Moraines, type uncertain or not listed; | Illustrated GLIMS Glacier Classification Manual |
| Moraine shoal | Glacial moraine that has formed a shallow place in water. | NSIDC accessed 2016 |
| Moraine-dammed lake | A lake formed as a glacier recedes from its terminal moraine, the moraine acting as an unstable dam (see glacial lake outburst flood). | Swisseduc - Photo glossary of glaciological terms |
| Morphological classification | A classification based on the shape of the individual grains or particles. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Morphology | A study of the structure, form, or shape of meteorological phenomena, such as clouds or ice crystals; includes the classification of these phenomena. | AMS - glossary of meteorology |
| Moulin | A nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses; also called a pothole. | NSIDC accessed 2016 |
| Moulin | A deep shaft, nearly vertical and of roughly circular cross section, formed when surface meltwater enlarges a crack in the ice by transferring kinetic and thermal energy to its walls. Moulins connect to the englacial drainage network, facilitating transfer of surface meltwater to the bed. The meltwater resulting from enlargement of the moulin is an instance of internal ablation. Moulins may play a significant role in supplying lubricant to the bed. The word is French for mill, referring to the swirling motion of the water as it descends the shaft. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Moulin | (from the French) A water-worn pothole formed where a surface meltstream exploits a weakness in the ice. Many moulins are cylindrical, several metres across, and extend down to the glacier bed, often in a series of steps. | Swisseduc - Photo glossary of glaciological terms |
| Moulin (glacier mill) | A narrow, tubular chute or crevasse through which water enters a glacier from the surface. Occasionally, the lower end of a moulin may be exposed in the face of a glacier or at the edge of a stagnant block of ice. | Molnia USGS 2004 |
| Mount | Synonymous with mountain and preceding the specific part of a name. | UK Antarctic Place-names Committee accessed 2016 |
| Mount Rose snow sampler | A snow water content sampler consisting of a hollow tube of steel or duralumin and having an internal diameter of 1.485 in. so that each inch of water in the sample weighs one ounce. This sampler is used almost exclusively in sampling deep snow in the mountains of the western United States. Its design includes a cutting lip for penetrating ice layers in the snow, longitudinal slots for cleaning after a measurement, and accessory wrenches for assembling and driving. The tube is made in short sections with threaded couplings so that it can be disassembled for transportation. | AMS - glossary of meteorology |
| Mountain | Natural elevation rising to a relatively great height. Mountain, hill and knoll are terms indicating various degrees of height in descending order, varying with the general configuration of the vicinity. The term mountains may be used for a grouping within a range. | UK Antarctic Place-names Committee accessed 2016 |
| Mountain apron glacier | A small glacier of irregular outline, elongate along slope, in mountainous terrain. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mountain glacier | A glacier that is confined by surrounding mountain terrain; also called an alpine glacier. | NSIDC accessed 2016 |
| Mountain glacier | (1) A glacier that is confined by surrounding mountain terrain, also called an alpine glacier. (2) A glacier in mountainous terrain that is a cirque glacier, a niche glacier, a crater glacier, or a mountain apron glacier. See also valley glacier. Sense 2 is that in which the term is used in the World Glacier Inventory, but the more general sense 1 is also widely used. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Mountain glacier | Glaciers adhering to mountain sides, and fitting in no other primary classification pattern; e.g. Cirque-, Niche-, Crater- Glaciers as well as Groups, Aprons and hanging glaciers and glaciated flanks; Cirque, niche or crater type, hanging glacier; includes ice apron and groups of small units (WGMS 1970); Any shape; sometimes similar to a valley glacier, but much smaller; frequently located in cirque or niche. (WGMS 1977); Cirque, niche or crater type, hanging glacier; includes ice apron and groups of small units (WGMS 1998); Must be distinguished from valley glaciers where no valley has yet developed (often difficult to estimate from above ground) | Illustrated GLIMS Glacier Classification Manual |
| Mountain permafrost | Permafrost existing at high altitudes in high, middle, and low latitudes. | NSIDC accessed 2016 |
| Mountain permafrost | Permafrost existing at high altitudes in high, middle, and low latitudes | Van Everdingen International Permafrost Association 2005 |
| Mountain permafrost | Permafrost existing in mountainous areas in high, middle, and low latitudes. Mountain Permafrost may show some degree of altitudinal zonation. Plateau Permafrost is a subdivision of Mountain Permafrost but use of this term is not recommended. | Trombotto et al. 2014 |
| Mud circle | A type of nonsorted circle developed in fine-grained materials. | NSIDC accessed 2016 |
| Mud circle | A type of nonsorted circle developed in fine-grained materials. | Van Everdingen International Permafrost Association 2005 |
| Multi-year ice | Sea ice that has survived more than two summer melt seasons. Such ice is typically 3 m or more thick, is less saline, and has smoother hummocks and ridges than does younger ice. Undeformed multiyear ice is distinguished by its undular surface (remnants of drained or refrozen melt ponds). Multiyear ridges are distinct from first-year ridges in that they are typically smaller, more rounded, nearly solid ice and are therefore a serious impediment to surface ships. | AMS - glossary of meteorology |
| Multi-year ice | Old ice up to 3m or more thick which has survived at least two summers' melt. Hummocks (hillocks of broken ice that have been forced up by pressure) even smoother than in second-year ice, and the ice is almost salt-free. Colour, where bare, is usually blue. Melt pattern consists of large interconnecting irregular puddles and a well-developed drainage system. Multi-year ice is less common in the Antarctic than the Arctic, and is usually confined to the western Weddell Sea and isolated embayments at other locations around the coast. Ocean currents and the atmospheric circulation result in a net divergence of sea ice around the continent, causing most of the ice to melt in the summer as it drifts into warmer waters, or as the upper ocean heats up as the open water areas within the pack absorb solar radiation. The Weddell Sea accounts for about 80% of the multi-year ice in the Antarctic. The clockwise circulating current known as the Weddell Gyre is responsible for trapping sea ice along the eastern side of the Antarctic Peninsula, allowing it to survive for more than one year. Eventually the current transports the ice further north where it dissipates into the ocean and melts. Melt patterns on multi-year ice are a feature most commonly observed in the Arctic. The ablation season of Antarctic sea ice is rarely associated with the presence of melt water on the surface of the ice. | ASPECT 2012 |
| Multi-year ice | Old ice up to 3 m or more thick that has survived at least two summers' melt. Hummocks are even smoother than in second-year ice and attain a look of mounds and hills. The surface of multiyear ice fields in places not subject to deformations is also hillocky due to non-uniform multiple melting. The ice is almost salt-free. Its color, where bare, is usually blue. As a result of melting, round puddles appear at its surface in summer and a well-developed drainage system is formed. | Bushuyev 2004 |
| Multi-year ice | Sea ice terminology that describes old ice which has survived at least two summer's worth of melt. Hummocks are smoother on multi-year ice than on second-year ice, and the ice is almost salt-free. Where bare, this ice is usually blue in colour. The melt pattern consists of large, interconnecting, irregular puddles and a well developed drainage system. | Environment and Climate Change Canada 2014 |
| Multi-year ice | Old ice up to 10 ft (3 m) or more thick that has survived at least two summers' melt. Hummocks even smoother than in second-year ice, and the ice is almost salt free. The color, where snow free, is usually blue. The melt pattern consists of large interconnecting irregular puddles and a well developed drainage system. | WMO Sea Ice Nomenclature 2017 |
| Multiple retrogressive slide | A type of mass movement associated with shear failure in unfrozen sediments underlying permafrost, leading to detachment of blocks of frozen ground that move downslope. | NSIDC accessed 2016 |
| Multiple retrogressive slide | A type of mass movement associated with shear failure in unfrozen sediments underlying permafrost, leading to detachment of blocks of frozen ground that move downslope | Van Everdingen International Permafrost Association 2005 |
| Multiyear ice | Ice that has survived at least one melt season; it is typically 2 to 4 meters (6.6 to 13.1 feet) thick and thickens as more ice grows on its underside. | NSIDC accessed 2016 |
| Muskeg | In the northern United States and Canada: a swamp or bog in an undrained or poorly drained area of alluvium or glacial till. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Muskeg | A swamp or bog occurring in depressions in poorly drained alluvial or glacial terrain in northern Canada or the United States. The depression usually accumulates a saturated, highly compressible mixture of mineral particles and decaying vegetal matter, topped by a hummocky surface of sphagnum moss, and incapable of supporting heavy loads or traffic. In the colder and wetter parts of Alaska, these accumulations spread widely over low-amplitude terrain and are not confined to depressions. | AMS - glossary of meteorology |
| Muskeg | Poorly drained marshes or swamps found overlying permafrost. | PhysicalGeography.net |
| N v | 1. Same as firn. 2. Same as accumulation area. | AMS - glossary of meteorology |
| N-factor | The ratio of the surface freezing or thawing index to the air freezing or thawing index. | NSIDC accessed 2016 |
| N-factor | The ratio of the surface freezing or thawing index to the air freezing or thawing index | Van Everdingen International Permafrost Association 2005 |
| N-factor | The ratio of the surface freezing or Thawing Index to the air freezing or Thawing Index. The difference between air and surface temperatures at any specific time and location is greatly influenced by climatic, surface and subsurface conditions (e.g. latitude, cloud cover, time of day or year, relative humidity, wind speed, type of surface and thermal properties of the ground). Freezing Index: n_f = I_sf/I_af where I_sf = ground surface freezing index; I_af = air freezing index Thawing Index: n_f = I_sf/I_at where I_st = ground surface thawing index; I_at = air thawing index | Trombotto et al. 2014 |
| Near-surface permafrost | A term frequently used in climate model applications to refer to permafrost at depths close to the ground surface (typically down to 3.5 m). In modelling studies, near-surface permafrost is usually diagnosed from 20 or 30 year climate averages, which is different from the conventional definition of permafrost. Disappearance of near-surface permafrost in a location does not preclude the longer-term persistence of permafrost at greater depth. See also Active layer, Frozen ground and Thermokarst. | IPCC WGI AR5 2013 |
| Needle | Needle-like peak or off-shore rock. | UK Antarctic Place-names Committee accessed 2016 |
| Needle ice | Thin, elongated ice crystals that form perpendicular to the ground surface. | NSIDC accessed 2016 |
| Needle ice | Thin, elongated ice crystals that form perpendicular to the ground surface | Van Everdingen International Permafrost Association 2005 |
| Needle ice | Thin, elongated ice crystals that form perpendicular to the ground surface. Single crystals are rarer. The optimum ground temperature range between 0C and -5C, with a temperature gradient between 0.3 and 0.5C/cm. | Trombotto et al. 2014 |
| Needle ice | 1.Same as candle ice. 2.Same as frazil. | AMS - glossary of meteorology |
| Needle ice | A form of periglacial ground ice that consists of groups ice slivers at or immediately below the ground surface. Needle ice is about a few centimeters long. | PhysicalGeography.net |
| Negative mill | A geyser; a fountain that develops when water from a conduit is forced up to the surface of a glacier. | NSIDC accessed 2016 |
| Neoglacial | A period of general expansion of glaciers variously defined as spanning from approximately 3000 to 2000 years ago or covering the last 4000-5000 years. | AMS - glossary of meteorology |
| Neoglaciation | Neoglaciation refers to the advances made by mountain glaciers since the great Pleistocene ice age. In the Cascades the advances have occurred since 6,600 years before present. | Molnia USGS 2004 |
| Net ablation | The sum, if negative, of accumulation and ablation over any time period; if the sum is positive then net ablation is zero. In the ablation zone the net ablation is equal to the mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Net accumulation | See article Net accumulation under Mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Net accumulation | The sum, if positive, of accumulation and ablation over any time period; if the sum is negative then net accumulation is zero. In the accumulation zone the net accumulation is equal to the mass balance. The term appears often in ice-core studies, where the layer thickness is related to the mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Net balance | The mass balance at the end of the balance year. It represents the annual addition or loss of mass at a point on a glacier. | AMS - glossary of meteorology |
| Net balance (of glacier) | Difference between accumulation and ablation of a glacier, usually expressed in terms of volume of water equivalent per unit area. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Net budget | The difference between accumulation and ablation; usually expressed in terms of volumes of water equivalent per unit area. | Illustrated Glossary of Snow and Ice |
| Net mass balance | According to Anonymous (1969), the sum of accumulation and ablation over the mass-balance year in the stratigraphic system. In common usage, 'net balance' has a number of meanings inconsistent with that of Anonymous (1969; Appendix A). It is used for the balance over approximately one year, regardless of the time system (see fixed-date system, floating-date system), and for balances over other periods than the mass-balance year. In these usages 'net' has its plain-language meaning, referring to the change of mass after all deductions (here ablation) have been made. To resolve this ambiguity, it is recommended that the original definition of 'net mass balance' be retired, and that i) Annual mass balance be used instead for the mass balance over a mass-balance year in any time system; and ii) explicit information about the time system be given as metadata whenever it is relevant (as it is for all measurements by the glaciological method). The adjective 'net' thus becomes a plain-language word, and in many cases becomes redundant because the meaning of 'balance' includes the meaning of 'net'. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Nevada | A cold wind descending from a mountain glacier (glacier wind) or snowfield, for example, in the higher valleys of Ecuador. | AMS - glossary of meteorology |
| Neve | Young, granular snow that has been partially melted, refrozen and compacted; neve that survives a full season is called firn; firn becomes glacial ice; (2) also refers to the accumulation zone of a glacier. | NSIDC accessed 2016 |
| Neve | (1) A more or less extensive and persistent surface of snow, generally at high altitude. Synonymous with snowfield. (2) Synonymous with firn. Used less frequently in this sense now than formerly. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Neve | (1) A synonym of firn, of French origin, now little used. (2) A little-used synonym of snowfield, or sometimes of accumulation zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Neve | Partially melted and compacted snow that has a density of at least 500 kilograms per cubic meter. | PhysicalGeography.net |
| New ice | A general category of ice that consists of frazil, grease ice, slush, and shuga. | NSIDC accessed 2016 |
| New ice | A general term for recently formed ice that includes frazil ice, grease ice, slush, and shuga. Theses types of ice are composed of ice crystals that are only weakly frozen together (if at all) and have a definite form only while they are afloat. | WMO Sea Ice Nomenclature 2017 |
| New ice | A general term for recently formed ice which includes frazil ice, grease ice, slush and shuga. | ASPECT 2012 |
| New ice | A general term for recently formed ice which includes frazil ice, grease ice, slush and shuga. These types of ice are composed of ice crystals which are only weakly frozen together (if at all) and have a definite form only while they are afloat. | Bushuyev 2004 |
| New ice | Sea ice terminology. This is a general term for recently formed ice which includes frazil ice, grease ice, slush, and shuga. These types of ice are composed of ice crystals which are only weakly frozen together (if at all) and have a definite form only while they are afloat. | Environment and Climate Change Canada 2014 |
| New ice | Recently formed floating ice composed of ice crystals weakly frozen together. | UNESCO-WMO International Glossary of Hydrology 2012 |
| New ice | A general term for floating ice recently formed. It includes frazil ice, grease ice, slush, shuga, ice rind, nilas and pancake ice. | Illustrated Glossary of Snow and Ice |
| New lake ice | Sea ice terminology describing recently formed ice, which is less than 5 cm thick. | Environment and Climate Change Canada 2014 |
| New ridge | Ridge newly formed with sharp peaks and slope of sides usually 40 degrees. Fragments are visible from the air at low altitude. | WMO Sea Ice Nomenclature 2017 |
| New ridge | Sea ice terminology that describes a ridge with sharp peaks and sides that has a slope of 40 degrees or more. | Environment and Climate Change Canada 2014 |
| New snow | A recent snow deposit in which the original form of the ice crystals can be recognized. | NSIDC accessed 2016 |
| New snow | Recently fallen snow in which the original form of the ice crystals can be recognized. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| New snow | Recent snow deposit in which the original form of the ice crystals can be recognized. | UNESCO-WMO International Glossary of Hydrology 2012 |
| New snow | 1. Recently fallen snow in which the original form of the snow crystals is recognizable. 2. The amount of snow fallen within the previous 24 hours. | AMS - glossary of meteorology |
| New snow | A recent snow deposit in which the original form of the ice crystals can be recognized (cf. Powder snow). | Illustrated Glossary of Snow and Ice |
| Niche | Small glaciers in v shaped couloirs or depressions; Adhering a mountain slope; Genetically less developed in form than cirque glacier; Small glacier in V-shaped gully or depression on a mountain slope; generally more common than the genetically further developed cirque glacier (WGMS 1970, 1998); Small glacier in V-shaped gully or depression on a mountain slope (WGMS 1977) | Illustrated GLIMS Glacier Classification Manual |
| Niche glacier | Very small glacier that occupies gullies and hollows on north-facing slopes (northern hemisphere) ; may develop into cirque glacier if conditions are favorable. | NSIDC accessed 2016 |
| Niche glacier | A small glacier in a gully or depression, elongate downslope. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Nilas | A thin sheet of smooth, level ice less than 10 centimeters (4 inches) thick; appear darkest when thin. | NSIDC accessed 2016 |
| Nilas | A thin elastic crust of ice, easily bending on waves and swell and under pressure, thrusting in apattern of interlocking 'fingers' (finger rafting). Has a matt surface and is up to 10 cm in thickness. May be subdivided into dark nilas and light nilas. | Bushuyev 2004 |
| Nilas | A thin, elastic crust of ice bending easily on waves and swell. Nilas has a matte surface and is up to 4 in (- 10 cm) thick. Under pressure it thrusts into a pattern of inter- locking fingers (see FINGER-RAFTED ICE). May be subdivided into dark nilas and light nilas. | WMO Sea Ice Nomenclature 2017 |
| Nilas | Sea ice terminology. Describes a thin, elastic crust of gray-colored ice that is formed on a calm sea, and is easily bent by waves and thrust into a pattern of interlocking fingers (known as finger rafting). Nilas has a matte surface, is up to 10 cm in thickness, and may be subdivided into dark nilas and light nilas. | Environment and Climate Change Canada 2014 |
| Nilas | A thin elastic crust of ice up to 10 cm thick that, under pressure, may deform by finger rafting. | AMS - glossary of meteorology |
| Nilas | A thin elastic crust offloating ice, easily bending on waves and swell and rafting under pressure. It has a matt surface and is up to 10 cm thick. When under about 5 cm in thickness it is very dark in colour; when more than 5 cm, rather lighter. | Illustrated Glossary of Snow and Ice |
| Nilas ice | A thin elastic crust of ice, easily bending on waves and swell and under pressure, thrusting in a pattern of interlocking 'fingers' (finger rafting). Has a matt surface and is up to 10cm in thickness. May be subdivided into dark nilas and light nilas. Dark nilas is 5cm thick and very dark in colour. Light nilas is 5-10cm thick and reflects proportionately more light than dark nilas, depending on its thickness. | ASPECT 2012 |
| Nip | Ice is said to nip when it forcibly presses against a ship which is beset; a vessel so caught, though undamaged, is said to have been nipped. | NSIDC accessed 2016 |
| Nip | Ice is said to nip when it forcibly presses against a ship. A vessel so caught, though undamaged, is said to have been nipped. | WMO Sea Ice Nomenclature 2017 |
| Nip | Ice is said to nip when it forcibly presses against a ship. A ship so caught, though undamaged, is said to have been nipped. | Bushuyev 2004 |
| Nip | Sea ice terminology. Ice is said to nip when it forcibly presses against a ship. When a vessel is caught in this way, though undamaged, it is said to have been 'nipped.' | Environment and Climate Change Canada 2014 |
| Nip | Ice is said to nip when it forcibly presses against a ship which is beset. A vessel so caught, though undamaged, is said to have been nipped. | Illustrated Glossary of Snow and Ice |
| Nival | Characterized by snow or a snowy environment. | AMS - glossary of meteorology |
| Nivation | Nivation is a collective name for the different processes that occur under a Snow Patch. The primary processes are Mass Wasting and the freeze and thaw cycle, in which fallen Snow gets compacted into Firn. Nivation includes various sub-processes related to Snow Patches which may be immobile or semi-permanent. These sub-processes include erosion, weathering, and meltwater flow from beneath the Snow Patch. | Trombotto et al. 2014 |
| Nivation | Process where snow patches initiate erosion through physical weathering, meltwater flow, and gelifluction. | PhysicalGeography.net |
| Nivation hollow | Ground depression found in periglacial areas that is created by nivation. | PhysicalGeography.net |
| Noctilucent clouds | Thin silvery-blue cirrus-like clouds frequently seen during summer twilight conditions at high latitudes (above 50 deg) in both hemispheres. They are the highest visible clouds in the atmosphere, occurring in the upper mesosphere at heights of about 85 km, and are closely related to the polar mesospheric clouds seen in satellite observations at similar altitudes over the summer polar cap. Noctilucent clouds are now known to consist of tiny ice particles with dimensions of the order of tens of nanometers, growing in the extreme cold of the summer polar mesopause region. The condensation nuclei on which the particles grow are thought to be either smoke and dust particles of meteoric origin or large hydrated positive ions. Strong upwelling of air from below, associated with a pole-to-pole meridional circulation in the upper mesosphere, is responsible for both the extreme cold and the upward flux of water vapor. Although water-vapor mixing ratios are very low (less than 10 parts per million by volume) in the region, the temperatures are also low enough to produce a high degree of supersaturation at times. Anomalously strong radar echoes from the region, known as polar summer mesospheric echoes, are also associated with the clouds. (Rarely called luminous clouds.) | AMS - glossary of meteorology |
| Noctilucent clouds | High altitude clouds composed of ice crystals that appear to glow silver or bright blue shortly after sunset. | PhysicalGeography.net |
| Noncryotic ground | Soil or rock at temperatures above 0 degrees Celsius. | NSIDC accessed 2016 |
| Noncryotic ground | Soil or rock at temperatures above 0°C | Van Everdingen International Permafrost Association 2005 |
| Nonsorted circle | A patterned ground form that is equidimensional in several directions, with a dominantly circular outline which lacks a border of stones. | NSIDC accessed 2016 |
| Nonsorted circle | A nonsorted circle is a patterned ground form that is equidimensional in several directions, with a dominantly circular outline which lacks a border of stones | Van Everdingen International Permafrost Association 2005 |
| Nonsorted net | A patterned ground with cells that are equidimensional in several directions, neither dominantly circular nor polygonal, and lacking borders of stones. | NSIDC accessed 2016 |
| Nonsorted net | A nonsorted net is a type of patterned ground with cells that are equidimensional in several directions, neither dominantly circular nor polygonal, and lacking borders of stones | Van Everdingen International Permafrost Association 2005 |
| Nonsorted polygon | A patterned ground form that is equidimensional in several directions, with a dominantly polygonal outline which lacks a border of stones. | NSIDC accessed 2016 |
| Nonsorted polygon | A nonsorted polygon is a patterned ground form that is equidimensional in several directions, with a dominantly polygonal outline which lacks a border of stones | Van Everdingen International Permafrost Association 2005 |
| Nonsorted step | A patterned ground feature with a step-like form and a downslope border of vegetation embanking an area of relatively bare ground upslope. | NSIDC accessed 2016 |
| Nonsorted step | A nonsorted step is a patterned ground feature with a step-like form and a downslope border of vegetation embanking an area of relatively bare ground upslope | Van Everdingen International Permafrost Association 2005 |
| Nonsorted stripe | Form patterned ground with a striped and nonsorted appearance, due to parallel strips of vegetation-covered ground and intervening strips of relatively bare ground, oriented down the steepest available slope. | NSIDC accessed 2016 |
| Nonsorted stripe | Nonsorted stripes form patterned ground with a striped and nonsorted appearance, due to parallel strips of vegetation-covered ground and intervening strips of relatively bare ground, oriented down the steepest available slope | Van Everdingen International Permafrost Association 2005 |
| Nordenskj?ld line | The line connecting all places at which the mean temperature (C) of the warmest month is equal to 9 - 0.1k, where k is the mean temperature of the coldest month. (In degrees Fahrenheit the relationship becomes 51.4 - 0.1k.) This line fits the arctic tree line better than any other purely climatic isopleth hitherto tried. | AMS - glossary of meteorology |
| Normal | The long-term average value of a climate element for a certain area, averaged over a 30-year period. Elements can include temperature, precipitation, hours of sunshine, etc. | Environment and Climate Change Canada 2014 |
| Normal or miscellaneous | The entire width of the tongue terminates on dry ground; Irregular or single lobe frontal line | Illustrated GLIMS Glacier Classification Manual |
| North foehn | A northerly foehn wind blowing down the Italian side of the Alps. The northern slopes are normally cooler than the southern slopes, and the dynamic warming is often insufficient to overcome the difference of temperature. Hence a warm dry northerly wind of foehnlike character occurs less frequently than the south foehn. | AMS - glossary of meteorology |
| North pole | Surface location defined by the intersection of the polar axis with Earth's surface in the Northern Hemisphere. This location has a latitude of 90 North. | PhysicalGeography.net |
| Northern Annular Mode (NAM) | A winter fluctuation in the amplitude of a pattern characterized by low surface pressure in the Arctic and strong mid-latitude westerlies. The NAM has links with the northern polar vortex into the stratosphere. Its pattern has a bias to the North Atlantic and its index has a large correlation with the North Atlantic Oscillation index. | IPCC WGI AR5 2013 |
| Norwegian Sea Deep Water | One of the water masses, with a temperature of -0.95C, that contributes to the formation of Arctic Bottom Water. | AMS - glossary of meteorology |
| Nova Zemlya | This phenomenon owes its name to an event in 1596 when explorers (in search of the northeast passage) wintering on the island of Nova Zemlya saw a distorted image of the sun two weeks before astronomical calculation would have had it rise. Since that time, the term has been used generically for any such observation of an image of the sun when the actual sun was substantially below the horizon. In the original case, the angular difference between the image and the object was 5. This is explained by the ducting of the sunlight between the surface and a lifted inversion. | AMS - glossary of meteorology |
| Nubbins | Protuberances within the ground that result from the heaving of ground particles due to the presence of needle ice. | Trombotto et al. 2014 |
| Nucleation | Action of special particles, termed "nuclei", in the passage from the vapour phase of a substance to the liquid or solid phase, or from the liquid to the solid phase. | WMO METEOTERM accessed 2016 |
| Nucleation | The process of initiation of a new phase in a supercooled (for liquid) or supersaturated (for solution or vapor) environment; the initiation of a phase change of a substance to a lower thermodynamic energy state (vapor to liquid condensation, vapor to solid deposition, liquid to solid freezing). In nature, heterogeneous nucleation is the more common where such a change takes place on small particles of different composition and structure. Homogeneous nucleation occurs when the change of state centers upon embryos that exist in the same initial state as the changing substance. In this case, the nucleation system contains only one component, and it is termed homogeneous nucleation. In meteorology, particularly in cloud physics, a number of types of nucleation are of interest. The process by which cloud condensation nuclei initiate the phase change from vapor to liquid is important in all cloud formation problems. The physical nature of freezing nuclei that may be responsible for the conversion of drops of supercooled water into ice crystals is critically important in precipitation theory, as is the clarification of the role of homogeneous nucleation near -40C. Thermodynamically, all nucleation processes involve free energy decrease associated with the bulk phase change and the free energy increase associated with the creation of new interfaces between phases. | AMS - glossary of meteorology |
| Nucleus | In physical meteorology, a particle of any nature upon which molecules of water or ice accumulate as a result of a phase change to a more condensed state. | WMO METEOTERM accessed 2016 |
| Nucleus | The positively charged core of an atom about which its electrons orbit. 1. Almost all the mass of an atom resides in its nucleus, the diameter of which is about 10^4 times smaller than that of the atom. The nucleus of an (electrically neutral) atom is made up of protons, equal in number to its electrons, and neutrons bound together by nuclear forces. 2. In physical meteorology, a particle of any nature that initiates a phase transition in an environment supersaturated or supercooled with respect to a phase with lower chemical (Gibbs) potential, for example, a solid or liquid particle or gas/vapor bubble in a supercooled/supersaturated environment. | AMS - glossary of meteorology |
| Nunatak | A rocky crag or small mountain projecting from and surrounded by a glacier or ice sheet. | NSIDC accessed 2016 |
| Nunatak | A mountain peak or ridge that pokes through the surface of an Ice Field or a Glacier. It may separate adjacent Valley Glaciers (Greenlandic). | Molnia USGS 2004 |
| Nunatak | A mountain, or any exposed ground, projecting from and surrounded by glacier ice. The word is a 19th-century borrowing from the Greenlandic language. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Nunatak | Small mountain, rocky crag, or outcrop projecting from a glacier, ice shelf or snowfield. | UK Antarctic Place-names Committee accessed 2016 |
| Nunatak | (from the Inuit) An island of bedrock or mountain projecting above the surface of an ice sheet or highland icefield. | Swisseduc - Photo glossary of glaciological terms |
| Nunatak | A rocky crag or small mountain projecting from and surrounded by a glacier or ice sheet. | Illustrated Glossary of Snow and Ice |
| Nye channel | (named after a British physicist) A channel cut into bedrock by subglacial meltwater under high pressure. Usually less than 1 m wide. Commonly deeper than it is wide. | Swisseduc - Photo glossary of glaciological terms |
| Ogive | Arcuate bands or waves, convex downglacier, that develop in an icefall. Alternating light and dark bands are called banded ogives or Forbes bands. Each pair of bands, that is, one crest (light) and one trough (dark), represents a year's movement through the icefall. It can be shown that, to yield visible banding, ice must flow through the icefall in a time shorter than the duration of the ablation season or accumulation season. James Forbes was the first to describe ogives, in 1843. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Ogive | An arcuate, convex, down-glacier-pointing band or undulation that forms on the surface of a glacier at the base of an icefall. Two types of ogives occur: wave ogives, which are undulations of varying height and band ogives, which are alternating light- and dark-colored bands. | Molnia USGS 2004 |
| Ogive | 1. A band or wave on the surface of a valley glacier, stretching from side to side and arched in the direction of flow. 2. The graph of a cumulative frequency distribution. | AMS - glossary of meteorology |
| Ogive | Band or wave on the surface of a valley glacier, stretching from side to side and arched in the direction of flow. | Illustrated Glossary of Snow and Ice |
| Ogives | Alternate bands of light and dark ice seen on a glacier surface. | NSIDC accessed 2016 |
| Ogives | Ogives are arc-shaped features occasionally found across the glacier surface below icefalls. They may be ridges and swales in the ice or bands of darker or lighter ice. One theory of their formation suggests that the ice is stretched and sometimes dirtied when exposed in the icefall during the high velocities of summer; it is compressed during the winter so that bands of different ice thickness form. | Molnia USGS 2004 |
| Ogives | Arcuate bands or waves, with their apices pointing down-glacier, that develop in an icefall. Alternating light and dark bands are called band ogives or Forbes bands. Each pair of bands, or one wave and trough, is believed to represent a year's movement through the icefall. | Swisseduc - Photo glossary of glaciological terms |
| Old ice | Sea ice more than 2-years-old, up to 3 meters (10 feet) or more thick; hummocks on old ice are even smoother than in second-year ice, and the ice is almost salt-free; when old ice is bare of snow, it is blue and lacks the greenish tint of second-year ice. | NSIDC accessed 2016 |
| Old ice | Sea ice that has survived at least one summer's melt. Most topographic features on old ice are smoother than those on first-year ice. May be subdivided into second-year ice and multiyear ice. | WMO Sea Ice Nomenclature 2017 |
| Old ice | Sea ice which has survived at least one summer's melt; typical thickness up to 3m or more. It is subdivided into residual first-year ice, second-year ice and multi-year ice. | Bushuyev 2004 |
| Old ice | Sea ice terminology describing sea ice which has survived at least one summer's melt. The surface of old ice is generally smoother than first-year ice. Old ice may be subdivided into second-year ice and multi-year ice. | Environment and Climate Change Canada 2014 |
| Old ice | Sea ice more than two years old, up to 3 m or more thick. Hummocks on old ice are even smoother than in second-year ice, and the ice is almost salt-free. When old ice is bare of snow, it is blue and lacks the greenish tint of second-year ice. | Illustrated Glossary of Snow and Ice |
| Old snow | Deposited snow whose transformation into firn is so far advanced that the original form of the ice crystals can no longer be recognized. | NSIDC accessed 2016 |
| Old snow | Deposited snow whose transformation into firn is so far advanced that the original form of the ice crystals can no longer be recognized. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Old snow | Deposited snow in which the original crystalline forms are no longer recognizable, such as firn, spring snow. | AMS - glossary of meteorology |
| Old snow | Deposited snow whose transformation intofirn is so far advanced that the original form of the ice crystals can no longer be recognized (cf. Firn). | Illustrated Glossary of Snow and Ice |
| Onshore permafrost | Permafrost occurring beneath exposed land surfaces. | NSIDC accessed 2016 |
| Onshore permafrost | Permafrost occurring beneath exposed land surfaces | Van Everdingen International Permafrost Association 2005 |
| Open drift | Sea ice terminology which describes floating ice in which the concentration is 4/10 to 6/10, with many leads and polynyas. Floes are generally not in contact with one another in open drift. | Environment and Climate Change Canada 2014 |
| Open lead | A lead that connects two open bodies of water; ships can traverse between them through this lead; it also refers to a lead where open water is found, or a lead that has not completely frozen. | NSIDC accessed 2016 |
| Open pack ice | Composed of floes seldom in contact and with many leads; ice cover 4/10ths to 6/10ths. | NSIDC accessed 2016 |
| Open pack ice | Floating ice in which the ice concentration is 4/10 to 6/10, with many fractures, and floes that are generally not in contact with one another. | Bushuyev 2004 |
| Open pack ice | Pack ice in which the ice concentration is four-tenths to six-tenths, with many leads and polynyas, and the floes are generally not in contact with one another. | WMO Sea Ice Nomenclature 2017 |
| Open pack ice | Composed of floes seldom in contact and with many leads. Ice cover 4/10ths to 6/10ths. | Illustrated Glossary of Snow and Ice |
| Open talik | A body of unfrozen ground that penetrates the permafrost completely, connecting suprapermafrost and subpermafrost water. | NSIDC accessed 2016 |
| Open talik | A body of unfrozen ground that penetrates the permafrost completely, connecting suprapermafrost and subpermafrost water | Van Everdingen International Permafrost Association 2005 |
| Open talik | Is a form of localized unfrozen ground (talik) in an area of permafrost. It is open to the ground surface but enclosed to permafrost below and at its sides. | PhysicalGeography.net |
| Open water | A large area of freely navigable water in which floes may be present in concentration under 1/10th; if there is no sea ice present, the area may be termed open water, even though icebergs are present. | NSIDC accessed 2016 |
| Open water | A large area of freely navigable water in which sea ice is present in concen- trations less than one-tenth. When no sea ice is present, the area should be termed ice free, even though icebergs occur. | WMO Sea Ice Nomenclature 2017 |
| Open water | A large area of freely navigable water in which sea ice is present in concentrations less than 1/10 and ice of land origin is absent. | Bushuyev 2004 |
| Open water | Sea ice terminology describing a large area of freely navigable water in which ice is present, with a concentration less than 1/10. In open water no ice of land origin is present. | Environment and Climate Change Canada 2014 |
| Open water | A large area of freely navigable water in which floes may be present in concentrations under 1/10th. If there is no sea ice present the area may be termed open water, even though icebergs are present. | Illustrated Glossary of Snow and Ice |
| Open-cavity ice | Ice formed in an open cavity or crack in the ground by reverse sublimation of water vapour. | NSIDC accessed 2016 |
| Open-cavity ice | Ice formed in an open cavity or crack in the ground by reverse sublimation of water vapour | Van Everdingen International Permafrost Association 2005 |
| Open-system freezing | Freezing that occurs under conditions that allow gain or loss of water by the system. | NSIDC accessed 2016 |
| Open-system freezing | Freezing that occurs under conditions that allow gain or loss of water by the system | Van Everdingen International Permafrost Association 2005 |
| Open-system pingo | A pingo formed by doming of frozen ground; caused by groundwater that moves downslope through taliks and onto the pingo surface, where it freezes. | NSIDC accessed 2016 |
| Open-system pingo | A pingo formed by doming of frozen ground due to freezing of injected water supplied by groundwater moving downslope through taliks to the site of the pingo, where it moves towards the surface | Van Everdingen International Permafrost Association 2005 |
| Optical-equivalent grain size | Classical grain size E may not always be the physically relevant size to describe, e.g., the grain size determined from standard field techniques may not adequately represent the electromagnetic properties of snow. For this purpose, a so called optical-equivalent grain size, OGS, can be defined. Optical-equivalent grain size is related to the specific surface area and therefore to the microstructure of snow. Although OGS depends on the wavelength of the electromagnetic waves of interest, the concept is equally applicable from the visible throughout to the microwave range. It is therefore particularly useful for remote sensing applications. To a first approximation, OGS can be estimated from the branch width of dendrites, the thickness of either thin plates or dendrites, the diameter of needles, or the shell thickness of hollow crystals. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Orbiculic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles form circular to ellipsoidal patterns. | NSIDC accessed 2016 |
| Orbiculic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles form circular to ellipsoidal patterns | Van Everdingen International Permafrost Association 2005 |
| Organic cryosol | An organic soil having a surface layer containing more than 17% organic carbon by weight, with permafrost within 1 meter (3.3 feet) below the surface. | NSIDC accessed 2016 |
| Organic cryosol | An organic soil having a surface layer containing more than 17% organic carbon by weight, with permafrost within 1 m below the surface. | Van Everdingen International Permafrost Association 2005 |
| Oriented lake | One of a group of lakes possessing a common, preferred, long-axis orientation. | NSIDC accessed 2016 |
| Oriented lake | One of a group of lakes possessing a common, preferred, long-axis orientation | Van Everdingen International Permafrost Association 2005 |
| Orogenesis | The process of mountain building through tectonic forces of compression and volcanism. | PhysicalGeography.net |
| Orogenic belt | A major range of mountains on the continents. | PhysicalGeography.net |
| Orographic precipitation | Precipitation caused or enhanced by one of the mechanisms of orographic lifting of moist air. Examples of precipitation caused by mountains include rainfall from orographic stratus produced by forced lifting and precipitation from orographic cumuli caused by daytime heating of mountain slopes. Many of the classic examples of locations having excessive annual precipitation are located on the windward slopes of mountains facing a steady wind from a warm ocean. As another example, wintertime orographic stratus (cap clouds) often produce the major water supply for populated semiarid regions such as the mountainous western United States, and as a result these cloud systems have been a target of precipitation enhancement, cloud-seeding projects intended to produce snowpack augmentation. Orographic precipitation is not always limited to the ascending ground, but may extend for some distance windward of the base of the barrier (upwind effect), and for a short distance to the lee of the barrier (spillover). The lee side with respect to prevailing moist flow is often characterized as the dry rain shadow. | AMS - glossary of meteorology |
| Orographic precipitation | Is precipitation that forms when air is forced to rise because of the physical presence of elevated land. As the parcel rises it cools as a result of adiabatic expansion at a rate of approximately 10 Celsius per 1,000 meters until saturation. The large amounts of precipitation along the west coast of Canada are due mainly to this process. | PhysicalGeography.net |
| Orographic snowline | See snowline. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Orographic snowline | The imaginary line formed by the generalized lower limit of perennial snowpatches on the terrain surface between glaciers at the end of the ablation season. The orographic snowline is so called (originally by Ratzel in 1886) because its altitude is predominantly defined by local topography and exposure. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Orographic snowline | The freezing level for precipitation formed by orographic lifting; the elevation above which rain or drizzle turns to snow. | AMS - glossary of meteorology |
| Outburst flood | See Jokulhlaup. | NOAA Glossary of Hydrologic Terms |
| Outburst flood | Any catastrophic flooding from a glacier; may originate from trapped water in cavities inside a glacier or at the margins of glaciers or from lakes that are dammed by flowing glaciers. | NSIDC accessed 2016 |
| Outcrop | Area of exposed rock surrounded by a glacier or snowfield. | UK Antarctic Place-names Committee accessed 2016 |
| Outlet glacier | A valley glacier which drains an inland ice sheet or ice cap and flows through a gap in peripheral mountains. | NSIDC accessed 2016 |
| Outlet glacier | A glacier, usually of valley-glacier form, that drains an ice sheet, icefield or ice cap. In the accumulation zone the glacier outline may not be well defined because of the subdued relief. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Outlet glacier | A glacier, usually between rock walls, that is part of, and drains an ice sheet. See also Ice stream. | IPCC WGI AR5 2013 |
| Outlet glacier | A valley glacier, occupying a trough, emanating from an ice sheet or ice cap. | Swisseduc - Photo glossary of glaciological terms |
| Outlet glacier | A valley glacier that drains an ice sheet or ice cap and flows through a gap in peripheral mountains. | AMS - glossary of meteorology |
| Outlet glacier | A valley glacier which drains an inland ice sheet or ice cap and flows through a gap in peripheral mountains. | Illustrated Glossary of Snow and Ice |
| Outlet glacier | Flows down from an ice sheet, ice field or ice cap beyond its margins; No clearly defined catchment area; Usually follows local topographic depressions; Drains an ice sheet, ice field or ice cap, usually of valley glacier form; the catchment area may not be clearly delineated; The source ice sheet, ice field or ice cap has the function of a "parent ice mass" in GLIMS | Illustrated GLIMS Glacier Classification Manual |
| Outline | See glacier outline. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Outwash | Glaciofluvial sediments deposited by meltwater streams at the edge of a glacier. | PhysicalGeography.net |
| Outwash plain | A broad, low-slope angle alluvial plain composed of glacially eroded, sorted sediment (termed outwash), that has been transported by meltwater. The alluvial plain begins at the foot of a glacier and may extend for miles. Typically, the sediment becomes finer grained with increasing distance from the glacier terminus. | Molnia USGS 2004 |
| Outwash plain | (ground view) A relatively flat spread of debris deposited by meltwater streams emanating from a glacier (cf. Sandur). | Swisseduc - Photo glossary of glaciological terms |
| Outwash plain | A flat or gentle sloping surface of glaciofluvial sediments deposited by meltwater streams at the edge of a glacier. Usually found in close spatial association with moraines. | PhysicalGeography.net |
| Overland flow | The flow of rainwater or snowmelt over the land surface toward stream channels. After it enters a watercourse it becomes runoff. | NOAA Glossary of Hydrologic Terms |
| Ozone hole | A characteristic severe depletion of stratospheric ozone that occurs each spring over the Antarctic continent. The depletion is caused by the catalytic destruction of ozone by chlorine, released from fluorocarbons and activated by the presence of polar stratospheric cloud particles in the extreme cold of the Antarctic stratosphere. | AMS - glossary of meteorology |
| Ozone hole | Is a sharp seasonal decrease in stratospheric ozone concentration that occurs over Antarctica in the spring. First detected in the late 1970s, the ozone hole continues to appear as a result of complex chemical reaction in the atmosphere that involves CFCs. | PhysicalGeography.net |
| P-forms | (or plastically moulded forms) Smooth rounded forms of various types cut into bedrock by the combined erosive power of ice, meltwater and subglacial sediment under high pressure. | Swisseduc - Photo glossary of glaciological terms |
| Pack ice | Ice that is not attached to the shoreline and drifts in response to winds, currents, and other forces; some prefer the generic term drift ice, and reserve pack ice to mean drift ice that is closely packed. | NSIDC accessed 2016 |
| Pack ice | Term used in a wide sense to include any area of sea ice, other than fast ice, no matter what form it takes or how it is disposed. The pack can be described as very open (with an ice concentration of 1/10 to 3/10), open (4/10 to 6/10, with many leads and polynyas and the floes generally not in contact with one another), close (7/10 to 8/10, composed of floes mostly in contact), very close (9/10 to less than 10/10), and compact (10/10, with no water visible, called consolidated pack ice if the floes are frozen together). | ASPECT 2012 |
| Pack ice | Any ice at the sea surface except for fast ice and stamukhas regardless of its age, form, origin and other characteristics that has a possibility of movement (drift) under the action of winds, currents and tides. As a result of the dynamic processes (drift, divergence, convergance), the total and partial concentrations of drifting ice constantly change. | Bushuyev 2004 |
| Pack ice | Term used in a wide sense to include any area of sea ice, other than fast ice, no matter what form it takes or how it is disposed. | WMO Sea Ice Nomenclature 2017 |
| Pack ice | A general term for the frozen state of the sea, and embracing a wide range of sea ice terms. | Swisseduc - Photo glossary of glaciological terms |
| Pack ice | All sea ice other than fast ice; thus, sea ice that is capable of substantial motion and deformation. (Also called ice pack.) | AMS - glossary of meteorology |
| Pack ice | Any area of sea, river or lake ice other than fast ice, no matter what form it takes or how it is disposed. Pack ice cover may be reported in tenths, or may be described as very open pack ice ( 1/10th to 3/10ths), open pack ice (4/10ths to 6/10ths), close pack ice (7/10ths to 9/10ths), and very close pack ice (practically 10/10ths, with little if any water visible). | Illustrated Glossary of Snow and Ice |
| Palaeoclimate | Climate during periods prior to the development of measuring instruments, including historic and geologic time, for which only proxy climate records are available. | EU Climate-ADAPT |
| Palaeoclimate | Climate for periods prior to the development of measuring instruments, including historic and geologic time, for which only proxy climate records are available. (Or geological climate.) | AMS - glossary of meteorology |
| Paleoclimate | Climatic conditions in the geological past reconstructed from a direct or indirect data source. | PhysicalGeography.net |
| Paleoclimatic sequence | The sequence of climatic changes in geologic time. It shows a succession of oscillations between warm periods and ice ages, but superimposed on this are numerous shorter oscillations. The tendency to regard the whole of a geologic period, lasting for 20 million years and more, as having a single type of climate is a great oversimplification, as is shown by the succession of glacial and interglacial periods in the Quaternary. Even the warm periods are known to have been made up of successions of climates of different degrees of warmth; but until much more information is available, it will not be possible to set out in detail the sequence of changes of the earlier paleoclimates. | AMS - glossary of meteorology |
| Paleoclimatology | Study of paleoclimates. | WMO METEOTERM accessed 2016 |
| Paleoclimatology | The study of past climates throughout geologic and historic time (paleoclimates), and the causes of their variations. | AMS - glossary of meteorology |
| Paleoclimatology | Scientific study of the Earth's climate during the past. | PhysicalGeography.net |
| Paleocrystic ice | Old sea ice, generally considered to be at least ten years old; it is nearly always a form of pressure ice and is often found in floebergs and in the pack ice of the central Arctic Ocean. | AMS - glossary of meteorology |
| Paleopermafrost | Soil, rock or organics that had been subjected to temperatures below 0C for several consecutive years in the past. Often, micro-indicators of paleopermafrost are visible on geological profiles, such as ice wedge shapes, soil particle sorting or paleo-cryoturbation. Paleopermafrost is identified using micro-morphological indicators, such as vesicular or lamellar structures, structures of compacted silt deposits and transport, preferential orientation of certain grain sizes, structural plane banded, laminar micro-frost weathering, carbonation and hydrolysis of Fe. Signs of paleopermafrost are important indicators for the reproducing paleo-climatic conditions since it indicates possible variations in the 0C isotherm, and indirectly provides information on paleo-temperatures and when the mean annual soil temperatures increased above freezing. This phenomenon can be observed Patagonia and the Andes. | Trombotto et al. 2014 |
| Palsa | A peaty permafrost mound possessing a core of alternating layers of segregated ice and peat or mineral soil material. | NSIDC accessed 2016 |
| Palsa | A peaty permafrost mound possessing a core of alternating layers of segregated ice and peat or mineral soil material | Van Everdingen International Permafrost Association 2005 |
| Palsa | A mound of peat that develops as the result of the formation of a number ice lenses beneath the ground surface. Typical size is 1 to 7 meters high, 10 to 30 meters wide, and 15 to 150 meters long. Found in the high latitudes. Similar to a pingo. | PhysicalGeography.net |
| Palsa bog | A poorly-drained lowland underlain by organic-rich sediments, which contains perennially frozen peat bodies (peat plateaux) and, occasionally, palsas. | NSIDC accessed 2016 |
| Palsa bog | A poorly-drained lowland underlain by organic-rich sediments, which contains perennially frozen peat bodies (peat plateaux) and occasionally palsas. | Van Everdingen International Permafrost Association 2005 |
| Pancake ice | Circular flat pieces of ice with a raised rim; the shape and rim are due to repeated collisions. | NOAA Glossary of Hydrologic Terms |
| Pancake ice | Pieces of new ice approximately circular, up to 10 centimeters (4 inches) thick and 0.03 to 3 meters (0.1 to 9.8 feet) in diameter, with raised edges that form from rubbing against each other; formed from the freezing together of grease ice, slush or shuga, or the reaking up of ice rind or nilas. | NSIDC accessed 2016 |
| Pancake ice | Predominantly circular pieces of ice from 30cm3m in diameter, and up to 10cm in thickness (unrafted), with raised rims due to the pieces striking against one another. It may be formed on a slight swell from grease ice, shuga or slush or as the result of the breaking of ice rind, nilas or, under severe conditions of swell or waves, of grey ice. A common process of sea ice development in the Antarctic is 'the pancake cycle'. The pancakes start with a diameter of tens of centimetres, but through wind and wave action they aggregate with loose frazil crystals to increase in diameter, and raft with other pancakes to increase in thickness. In this manner the pancakes can rapidly grow to a few metres in diameter and up to 1 m thick. Eventually the pancakes can freeze together into larger floes or a consolidated ice cover. | ASPECT 2012 |
| Pancake ice | In hydrologic terms, circular flat pieces of ice with a raised rim; the shape and rim are due to repeated collisions. | NOAA National Weather Service Glossary 2009 |
| Pancake ice | Predominantly circular pieces of ice from 1 to 10 ft (30 cm-3 m) in diameter and up to about 4 in (- 10 cm) in thickness, with raised rims due to the pieces striking against one another. It may be formed on a slight swell from grease ice, shuga, or slush, or as a result of the breaking of ice rind, nilas, or, under severe conditions of swell or waves, of gray ice. Sometimes pancake ice forms at some depth, at an interface between water bodies of different physical characteristics, from where it floats to the surface; it may cover wide areas of water rapidly. | WMO Sea Ice Nomenclature 2017 |
| Pancake ice | Predominantly circular plates of ice from 30 cm to 3 m in diameter, and up to about 10 cm in thickness, with raised rims due to the pieces striking against one another. It may be formed on a slight swell from grease ice, shuga or slush or as a result of the breaking of ice rind, nilas or, under heavy swell, of grey ice. | Bushuyev 2004 |
| Pancake ice | Sea ice terminology. Describes (predominantly) circular pieces of ice that are 30 cm to 3 m in diameter and up to 10 cm in thickness, which have raised rims due to the pieces striking against one another. Pancake ice may form on a slight swell from grease ice, shuga or slush, or as a result of the breaking of ice rind, nilas or, under severe conditions of swell or waves, from grey ice. | Environment and Climate Change Canada 2014 |
| Pancake ice | Pieces of newly-formed ice, usually approximately circular and with raised rims due to pieces striking against each other. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Pancake ice | Roughly circular accumulations of frazil ice, usually less than about 3 m in diameter, with raised rims caused by collisions. This form of ice is common in the Antarctic. Pancake ice may develop from grease ice or shuga. | AMS - glossary of meteorology |
| Pancake ice | Pieces of new ice usually approximately circular, about 30 cm to 3 m across, and with raised rims due to the pieces striking against each other. Formed from the freezing together of grease ice, slush or shuga, or the breaking up of ice rind or nilas. | Illustrated Glossary of Snow and Ice |
| Paraglacial environment | Non-glacial Earth surface processes, sediment Accumulations, landforms, land systems and landscapes that are directly conditioned by glaciation and deglaciation. | Trombotto et al. 2014 |
| Paraperiglacial environment | Environment, often also partly-included in the Periglacial Environment, which is dominated by seasonal freezing, but does not contain Permafrost, or perennial Ground Ice. For example, sorted ground can develop in this environment where the processes are driven by Frost Weathering. | Trombotto et al. 2014 |
| Partially-bonded permafrost | Ice-bearing permafrost in which some of the soil particles are not held together by ice. | NSIDC accessed 2016 |
| Partially-bonded permafrost | Ice-bearing permafrost in which some of the soil particles are not held together by ice | Van Everdingen International Permafrost Association 2005 |
| Particle | The smallest characteristic subunit of snow microstructure recognizable with a hand lens (8-10x magnification); a particle can consist of one or more crystals of ice (see also grain). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Pass | Relatively low area that provides easy passage through hills or mountains, or a comparatively narrow channel. | UK Antarctic Place-names Committee accessed 2016 |
| Passage | Navigable channel between two seas or oceans, or between reefs or islands. | UK Antarctic Place-names Committee accessed 2016 |
| Passive construction methods in permafrost | Special design and construction methods used for engineering works in permafrost areas where preservation of the frozen condition is feasible | Van Everdingen International Permafrost Association 2005 |
| Passive permafrost | Permanently frozen ground (permafrost) that, under present climatic conditions, will not refreeze if thawed; opposed to active permafrost. (Also called fossil permafrost.) | AMS - glossary of meteorology |
| Passive single-phase thermal pile | A foundation pile provided with a single-phase natural convection cooling system to remove heat from the ground | Van Everdingen International Permafrost Association 2005 |
| Passive two-phase thermal pile | A foundation pile provided with a two-phase natural convection cooling system to remove heat from the ground | Van Everdingen International Permafrost Association 2005 |
| Passive-microwave sensor | A radiometer sensing the emission of radiation at microwave frequencies from a medium. Frequencies from about 5 ghz up to 37 ghz are used in the study of quantities related to mass balance with passive-microwave sensors. The intensity of emission depends on the temperature of the medium and its emissivity. See brightness temperature. Microwave radiometers in orbit have resolutions of a few to a few tens of kilometres, so that they are best suited to monitoring of extensive ice and snow covers. All are in polar, sun-synchronous orbits, and offer daily near-global coverage. At high latitudes, coverage is available at least twice daily, that is, from an ascending (south to north) pass, typically in the afternoon or evening, and a descending (north to south) pass, typically in the morning. SMMR, the Scanning Multi-channel Microwave Radiometer, operated from 1978 to 1987. SSM/I, the Special Sensor Microwave Imager, was first launched in 1987 and has operated on several different satellites since. AMSR-E, the Advanced Microwave Scanning Radiometer for the Earth Observing System, has operated since 2002. In snow hydrology, passive-microwave radiometers are operational tools for the estimation of snow water equivalent ('SWE'). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Patch | A collection of pack ice, less than 10 kilometers (6.2 miles) across, whose limits can be seen from the masthead. | NSIDC accessed 2016 |
| Patch | A collection of pack ice, less than 10 km across, whose limits can be seen from the masthead. | Illustrated Glossary of Snow and Ice |
| Paternoster lakes | A linear series of mountain valley lakes that are formed from glacial erosion. They form behind glacial moraines or in glacially carved out rock basins. The name of this feature is related to the series of lakes looking like a string of beads. | PhysicalGeography.net |
| Patterned ground | A general term for any ground surface exhibiting a discernibly ordered, more or less symmetrical, morphological pattern of ground and, where present, vegetation. | NSIDC accessed 2016 |
| Patterned ground | A general term for any ground surface exhibiting a discernibly ordered, more or less symmetrical, morphological pattern of ground and, where present, vegetation | Van Everdingen International Permafrost Association 2005 |
| Patterned ground | A general term for any ground surface exhibiting a discernibly ordered, more or less symmetrical, morphological pattern of ground and, where present, vegetation. Some Patterned Ground features are not confined to Permafrost regions but they are best developed in regions of present or past intensive Frost Action. A descriptive classification of Patterned Ground includes such features as non-sorted and sorted circles, nets, Polygons, steps and stripes, and Solifluction Features. In Permafrost regions, the most ubiquitous macro-form is the Ice-wedge Polygon, and a common micro-form is the nonsorted circle. | Trombotto et al. 2014 |
| Patterned ground | A general term for any ground surface exhibiting a discernibly ordered, more- or-less symmetrical, morphological pattern of ground and, when present, vegetation. | AMS - glossary of meteorology |
| Patterned ground | Term used to describe a number of surface features found in periglacial environments. These features can resemble circles, polygons, nets, steps, and stripes. The development of some of these shapes is thought to be the result of freeze-thaw action. | PhysicalGeography.net |
| Peak | A hill or mountain with a comparatively sharp summit. | UK Antarctic Place-names Committee accessed 2016 |
| Peat | A deposit consisting of decayed or partially decayed humified plant remains. | NSIDC accessed 2016 |
| Peat | A deposit consisting of decayed or partially decayed humified plant remains | Van Everdingen International Permafrost Association 2005 |
| Peat bog / peatland | Peat is a deposit consisting of decayed or partially decayed humified plant remains. Peat plateaus are generally flat-topped expanses of peat, elevated above the general surface of a peatland, and containing segregated ice that may or may not extend downward into the underlying mineral soil. Some controversy exists as to whether peat plateaus and palsas are morphological variations of the same features, or genetically different. Layers or lenses of segregated ice occur especially in the mineral soil but they are thinner and less extensive in peat plateaus than in palsas. Flat-topped, somewhat raised peatlands without an icy core occur in non-permafrost environments but are not peat plateaus. | Trombotto et al. 2014 |
| Peat hummock | A hummock consisting of peat. | NSIDC accessed 2016 |
| Peat hummock | A hummock consisting of peat | Van Everdingen International Permafrost Association 2005 |
| Peat plateau | A generally flat-topped expanse of peat, elevated above the general surface of a peatland, and containing segregated ice that may or may not extend downward into the underlying mineral soil. | NSIDC accessed 2016 |
| Peat plateau | A generally flat-topped expanse of peat, elevated above the general surface of a peatland, and containing segregated ice that may or may not extend downward into the underlying mineral soil | Van Everdingen International Permafrost Association 2005 |
| Peatland | Peat-covered terrain. | NSIDC accessed 2016 |
| Peatland | Peat-covered terrain | Van Everdingen International Permafrost Association 2005 |
| Pendular regime | (of water) The condition of low liquid water content where a continuous air space as well as discontinuous volumes of water coexist in a snowpack, i.e., air-ice, water-ice, and air- liquid interfaces are all found. Grain-to-grain bonds give strength. The volume fraction of free water does not exceed 8%, i.e., the wetness index is 3 (see also funicular regime). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Penetrability of snow surface | Penetrability P is the depth that an object penetrates into the snow from the surface. It can be used as a rough measure of the amount of snow available for transport by aeolian processes or the ability of a snowpack to support a certain load. The depth of penetration of some suitable object, such as a ramsonde element, a foot, or a ski, is measured in centimetres. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Penitent | A spike or pillar of compacted snow, firn, or glacier ice caused by differential melting and evaporation. It is the extreme relief of sun cups found most often at high altitudes in low latitude regions; the resulting spikes resemble repentant souls. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Penitent ice | A spike or pillar of compacted snow, firn, or glacier ice caused by differential melting and evaporation. Necessary for this formation are 1) air temperature near freezing; 2) dewpoint much below freezing; and 3) strong insolation. Consequently, penitent ice is most developed on low-latitude mountains, especially the Chilean Andes, but has been found in polar regions. Penitents are oriented individually toward the noonday sun, and usually occur in east-west lines. The term is derived from the Spanish nieve penitente (penitent snow), which is still widely used throughout the literature. | AMS - glossary of meteorology |
| Penitent ice syn. penitent snow | A field of columnar shapes of compacted snow or glacier ice formed by sublimation and/or melting. | WMO METEOTERM accessed 2016 |
| Penitente | A spike-like irregularity of the glacier surface, significantly taller than wide and on occasion reaching heights as great as a few metres. Penitentes are an extreme form of the metre-scale roughness which must be accounted for in all ablation measurements using stakes. They are usually found together in large numbers when low temperature and intense solar radiation favour ablation by sublimation and the consequent amplification of small surface irregularities. The word is Spanish and is generally not Anglicized; the final e is retained (and pronounced). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Penitents | The extreme relief of ablation hollows found most often at high altitudes in the tropics; the resulting spikes of snow resemble repentant souls. | NSIDC accessed 2016 |
| Percolation | The movement of water, under hydrostatic pressure, through the interstices of a rock or soil, except the movement through large openings such as caves. | NOAA Glossary of Hydrologic Terms |
| Percolation | Flow of a liquid through an unsaturated porous medium such as snow under the action of gravity. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Percolation | In hydrologic terms, the movement of water, under hydrostatic pressure, through the interstices of a rock or soil, except the movement through large openings such as caves. | NOAA National Weather Service Glossary 2009 |
| Percolation | The movement of a liquid such as water through the void spaces of a permeable solid such as snow or firn, the rate of movement being governed by the porosity and liquid content of the solid, the geometric attributes of the pores, including their diameter and tortuosity, and the response of the pore walls to wetting. See infiltration. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Percolation | Downward motion of water through the soil or a snow layer. | WMO METEOTERM accessed 2016 |
| Percolation deep | In irrigation or farming practice, the amount of water that passes below the root zone of the crop or vegetation. | NOAA Glossary of Hydrologic Terms |
| Percolation path | The course followed by water moving or percolating through any other permeable material, or under a dam which rests upon a permeable foundation. | NOAA Glossary of Hydrologic Terms |
| Percolation path | In hydrologic terms, the course followed by water moving or percolating through any other permeable material, or under a dam which rests upon a permeable foundation. | NOAA National Weather Service Glossary 2009 |
| Percolation rate | The rate, usually expressed as a velocity, at which water moves through saturated granular material. The term is also applied to quantity per unit of time of such movement, and has been used erroneously to designate Infiltration Rate or Infiltration Capacity. | NOAA Glossary of Hydrologic Terms |
| Percolation zone | The part of the glacier where water from surface melting or rainfall percolates into the subsurface; see percolation, zone. In the upper percolation zone, above the wet-snow line, water percolates only into the snow. In the lower percolation zone, also called the wet-snow zone, water percolates into the firn below the summer surface. The lower percolation zone contains the slush zone. If, having percolated, the water refreezes, it warms its surroundings by releasing latent heat. If it refreezes in the firn, the result is internal accumulation. If it refreezes as a layer immediately above the summer surface, it forms superimposed ice. If this superimposed ice becomes exposed by continued surface ablation, the resulting superimposed ice zone is conventionally regarded as distinct from the percolation zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Pereletok | A layer of frozen ground which forms as part of the seasonally frozen ground (in areas free of permafrost or with a lowered permafrost table); remains frozen throughout one or several summers, and then thaws. | NSIDC accessed 2016 |
| Pereletok | A layer of frozen ground which forms as part of the seasonally frozen ground (in areas free of permafrost or with a lowered permafrost table), remains frozen throughout one or several summers, and then thaws | Van Everdingen International Permafrost Association 2005 |
| Perennial | Persisting for an indefinite time longer than one year. Perennial refers to the persistence of an object rather than, for example, to the duration of a measurement. See multi-Annual. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Perennial | Persisting for an indefinite time longer than one year, e.g., perennial snow (see also seasonal snow). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Perennial snow | Snow that persists on the ground year after year. | NSIDC accessed 2016 |
| Perfectly plastic solid | A solid that does not deform until it reaches a critical value of stress, after which it will yield infinitely. Some glaciologists say that ice is a perfectly plastic substance. That is, brittle and capable of cracking like a solid, yet deformable and capable of flowing at other stresses. | Molnia USGS 2004 |
| Pergelation | The act or process of forming permafrost (pergelisol). | AMS - glossary of meteorology |
| Periglacial | The conditions, processes and landforms associated with cold, nonglacial environments. | NSIDC accessed 2016 |
| Periglacial | The conditions, processes and landforms associated with cold, nonglacial environments | Van Everdingen International Permafrost Association 2005 |
| Periglacial | The conditions, processes and landforms associated with cold, non-glacial environments. The term was originally used to describe the climatic and geomorphic conditions of areas peripheral to Pleistocene Ice Sheets and Glaciers. Modern usage refers, however, to a wider range of cold climatic conditions regardless of their proximity to a Glacier, either in space or time. Many, but not all, Periglacial Environments possess Permafrost; all are dominated by Frost Action processes. | Trombotto et al. 2014 |
| Periglacial | Of, or pertaining to, the outer perimeter of a glacier, particularly to the fringe areas surrounding the great continental glaciers of the geologic ice ages. Thus, "periglacial weathering" is said to have produced certain characteristic land forms. | AMS - glossary of meteorology |
| Periglacial | Landforms created by processes associated with intense freeze-thaw action in an area high latitude areas or near an alpine or continental glacier. | PhysicalGeography.net |
| Periglacial climate | Climate characteristic of regions immediately on the periphery of an ice-cap or continental glacier. | WMO METEOTERM accessed 2016 |
| Periglacial climate | The climate characteristic of the regions immediately bordering the outer perimeter of an ice cap or continental glacier. The principal climatic feature is the high frequency of very cold and dry winds off the ice area. These regions have been thought to create ideal conditions for the maintenance of a belt of intense cyclonic activity. | AMS - glossary of meteorology |
| Periglacial environment - Andean definition | The environment, which is cold and cryogenic, but not Glaciated, above of the tree line if existent. There is no clear physical limit to the glacial environment and its boundary is diffuse. However, the limit to the non-Periglacial Environment is clearly marked by the following indicators: occurrence of Permafrost in depth, including permanently frozen soil and possibly presence of Ground Ice preserved under natural conditions for long periods of time. This constitutes the decisive element whereby an environment is called Periglacial or cryogenic environment dominated by cycles of freezing and thawing affecting rocks and the top of the soil; and presence of Solifluction / Gelifluction and other cryogenic processes (Frost Weathering, sorting, Cryoturbation, etc.) that lead to the so-called Periglacial geomorphology, such as the formation of small scale sorted ground or Rock Glaciers on a mesoscale. For some authors of the northern hemisphere the presence of Permafrost is not a prerequisite for the Periglacial Environment, however, it is for the cryo-scientists working in the Andes. | Trombotto et al. 2014 |
| Periglacial environment - Northern Hemisphere definition | The Periglacial Environment is defined as those areas in which Frost Action and / or Permafrost related processes dominate. Note: In the early definition of the Periglacial Environment two criteria were regarded as diagnostic of the Periglacial Environment: i) there is ground freezing and thawing, and ii) presence of perennially Frozen Ground. Today, Permafrost is considered to not being the only diagnostic criterion because Permafrost is a thermal concept, whereas Periglacial is a geomorphological definition that is concerned with landforms and processes that are not controlled by temperature alone. | Trombotto et al. 2014 |
| Periglacial phenomena | Landforms and soil characteristics produced by periglacial processes. | NSIDC accessed 2016 |
| Periglacial phenomena | Landforms and soil characteristics produced by periglacial processes | Van Everdingen International Permafrost Association 2005 |
| Periglacial processes | Processes associated with frost action in cold, nonglacial environments. | NSIDC accessed 2016 |
| Periglacial processes | Processes associated with frost action in cold, nonglacial environments | Van Everdingen International Permafrost Association 2005 |
| Periglacial processes | Processes associated with Frost Action in cold, non-glacial environments. Periglacial Processes include frost jacking, Frost Sorting, frost wedging, Cryoturbation, and the development of Cryotextures, Cryostructures and Cryogenic fabrics in soils. | Trombotto et al. 2014 |
| Permacrete | An artificial mixture of frozen soil materials cemented by pore ice, which forms a concrete-like construction material used in cold regions. | NSIDC accessed 2016 |
| Permacrete | An artificial mixture of frozen soil materials cemented by pore ice, which forms a concrete-like construction material used in cold regions | Van Everdingen International Permafrost Association 2005 |
| Permafrost | Layer of soil or rock, at some depth beneath the surface, in which the temperature has been continuously below 0 | NSIDC accessed 2016 |
| Permafrost | A layer of soil at varying depths below the surface in which the temperature has remained below freezing continuously from a few to several thousands of years. | NOAA National Weather Service Glossary 2009 |
| Permafrost | Ground (soil or rock and included ice and organic material) that remains at or below 0C for at least two consecutive years. | IPCC WGII AR5 2014 |
| Permafrost | Layer of soil or rock in which the temperature has been continuously below 0 degrees Celsius for at least some years. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Permafrost | Ground (soil or rock and included ice and organic material) that remains at or below 0°C for at least two consecutive years | Van Everdingen International Permafrost Association 2005 |
| Permafrost | Ground (soil or rock and included Ice and organic material) that remains at or below 0C for at least two consecutive years. Permafrost is synonymous with perennially Cryotic Ground: it is defined on the basis of temperature. It is not necessarily frozen, because the Freezing Point of the included water may be depressed several degrees below 0C; moisture in the form of water or Ice may or may not be present. In other words, whereas all perennially Frozen Ground is Permafrost, not all Permafrost is perennially frozen. Permafrost should not be regarded as permanent, because natural or man-made changes in the climate or terrain may cause the temperature of the ground to rise above 0C. The following classification may be used for Permafrost distribution models: Very High Likelihood (> 90% underlain by Permafrost): Most of this area is expected to be underlain by Permafrost. _ High Likelihood (70-90% underlain by Permafrost): Large parts of this area are expected to be underlain by Permafrost. Locally Permafrost Thicknesses of >50 m are expected depending on the topographic conditions. _ Medium Likelihood (40-70% underlain by Permafrost): Depending on the local surface characteristics and topography Permafrost is expected. Large bodies of Permafrost as well as areas with only isolated patches are possible. However, no thick (> 20m) and Continuous Permafrost layers are expected. _ Low Likelihood (10-40% underlain by Permafrost): Little Permafrost is expected in these areas. However, patches of Permafrost are possible due to local microclimatic conditions. _ Very Low Likelihood (1-10% underlain by Permafrost): Generally, no Permafrost is expected in these areas. However, sporadic exceptions are possible due to local microclimatic conditions. _ Extremely Low Likelihood (<1% underlain by Permafrost): No Permafrost is expected within these areas. However, cold caves, local Dead Ice or relict Ground Ice cannot be completely ruled out even in these areas depending on local microclimate and paleoglacial conditions. | Trombotto et al. 2014 |
| Permafrost | 1. A layer of soil or bedrock at a variable depth beneath the surface of the earth in which the temperature has been below freezing continuously from a few to several thousands of years. (Also called perennially frozen ground, pergelisol, permanently frozen ground.) Permafrost exists where the summer heating fails to descend to the base of the layer of frozen ground. A continuous stratum of permafrost is found where the annual mean temperature is below about -5C (23F). 2. As limited in application by P. F. Svetsov, soil that is known to have been frozen for at least a century. | AMS - glossary of meteorology |
| Permafrost | Zone of permanently frozen water found in high latitude soils and sediments. Five types of permafrost have been recognized: continuous permafrost, discontinuous permafrost, sporadic permafrost, alpine permafrost, and subsea permafrost. | PhysicalGeography.net |
| Permafrost aggradation | A naturally or artificially caused increase in the thickness and/or areal extent of permafrost. | NSIDC accessed 2016 |
| Permafrost aggradation | A naturally or artificially caused increase in the thickness and/or areal extent of permafrost | Van Everdingen International Permafrost Association 2005 |
| Permafrost aggradation | A naturally or artificially caused increase in the thickness and/or areal extent of Permafrost. Permafrost Aggradation may be caused by climatic cooling or by changes in terrain conditions, including vegetation succession, infilling of lake basins in areas underlain by Permafrost, drainage of lake in Permafrost terrain and a decrease in Snow Cover and thus the insulating agent. It may be expressed as a thinning of the Active Layer and/or a thickening of the Permafrost. | Trombotto et al. 2014 |
| Permafrost base | The lower boundary surface of permafrost, above which temperatures are perennially below 0 degrees Celsius (cryotic) and below which temperatures are perennially above 0 degrees Celsius (noncryotic). | NSIDC accessed 2016 |
| Permafrost base | The lower boundary surface of permafrost, above which temperatures are perennially below 0°C (cryotic) and below which temperatures are perennially above 0°C (noncryotic) | Van Everdingen International Permafrost Association 2005 |
| Permafrost base | The lower boundary surface of Permafrost, above which temperatures are perennially below 0C (cryotic) and below which temperature are perennially above 0C (non-cryotic). | Trombotto et al. 2014 |
| Permafrost boundary | (1) the geographical boundary between the continuous anddiscontinuous permafrost zones(2) the margin of a discrete body of permafrost. | NSIDC accessed 2016 |
| Permafrost boundary | 1. The geographical boundary between the continuous and discontinuous permafrost zones; 2. The margin of a discrete body of permafrost. | Van Everdingen International Permafrost Association 2005 |
| Permafrost boundary | 1. The geographical boundary between the Continuous and Discontinuous Permafrost zones in Arctic and Antarctic environments; 2. the boundary between the existence of mountain permafrost and no permafost in mountainous environments; or 3. the margin of a discrete body of Permafrost. | Trombotto et al. 2014 |
| Permafrost degradation | A naturally or artificially caused decrease in the thickness and/or areal extent of permafrost. | NSIDC accessed 2016 |
| Permafrost degradation | A naturally or artificially caused decrease in the thickness and/or areal extent of permafrost | Van Everdingen International Permafrost Association 2005 |
| Permafrost degradation | A naturally or artificially caused decrease in the thickness and/or areal extent of Permafrost. Permafrost Degradation may be caused by climatic warming or by changes in terrain conditions, such as disturbance or removal of an insulating vegetation layer by fire, or by flooding, or by human activity. It may be expressed as a thickening of the Active Layer, a lowering of the Permafrost Table, a rising of the Permafrost Base, or a reduction in the areal extent or the complete disappearance of Permafrost. | Trombotto et al. 2014 |
| Permafrost extent | The total geographic area containing some amount of permafrost; typically reported in square kilometers. | NSIDC accessed 2016 |
| Permafrost island | An isolated area of permafrost. | AMS - glossary of meteorology |
| Permafrost limit | Outermost (latitudinal) or lowest (altitudinal) limit of the occurrence of permafrost. | NSIDC accessed 2016 |
| Permafrost limit | Outermost (latitudinal) or lowest (altitudinal) limit of the occurrence of permafrost | Van Everdingen International Permafrost Association 2005 |
| Permafrost region | A region in which the temperature of some or all of the ground below the seasonally freezing and thawing layer remains continuously at or below 0 degrees Celsius for at least two consecutive years. | NSIDC accessed 2016 |
| Permafrost region | A region in which the temperature of some or all of the ground below the seasonally freezing and thawing layer remains continuously at or below 0°C for at least two consecutive years | Van Everdingen International Permafrost Association 2005 |
| Permafrost syn. pergelisol | Layer of soil or rock, at some depth beneath the surface, in which the temperature has been continuously below 0 degrees C for at least some years. It exists where summer heating fails to reach the base of the layer of frozen ground. | WMO METEOTERM accessed 2016 |
| Permafrost table | The upper boundary surface of permafrost. | NSIDC accessed 2016 |
| Permafrost table | The upper boundary surface of permafrost | Van Everdingen International Permafrost Association 2005 |
| Permafrost table | The upper boundary surface of Permafrost. | Trombotto et al. 2014 |
| Permafrost table | (Also called pergelisol table.) The more or less irregular surface in the ground that marks the upper limit of the permafrost; not to be confused with frost table. | AMS - glossary of meteorology |
| Permafrost thickness | The vertical distance between the permafrost table and the permafrost base. | NSIDC accessed 2016 |
| Permafrost thickness | The vertical distance between the permafrost table and the permafrost base | Van Everdingen International Permafrost Association 2005 |
| Permafrost thickness | The vertical distance between the Permafrost Table and the Permafrost Base. | Trombotto et al. 2014 |
| Permafrost zone | A major subdivision of a permafrost region. | NSIDC accessed 2016 |
| Permafrost zone | A major subdivision of a permafrost region | Van Everdingen International Permafrost Association 2005 |
| Permanent ice zone | A region that is covered with sea ice year-round; most of the sea ice in the permanent ice zone is multiyear ice, but younger ice and open water may still be present; the permanent ice zone is what remains in summer after all melting has occurred (often called the summer minimum extent). | NSIDC accessed 2016 |
| Permeability | Varying capacity with which water sinks into the ground under the force of gravity. It thus expresses the rate of percolation. | WMO METEOTERM accessed 2016 |
| Perpetual frost climate | Climate of the ice-cap regions; the temperatures are sufficiently low that ablation does not exceed the annual accumulation of snow and ice. | WMO METEOTERM accessed 2016 |
| Perpetual frost climate | In general, the climate of the ice cap regions of the world; thus, it requires temperatures sufficiently cold so that the annual accumulation of snow and ice is never exceeded by ablation. The perpetual frost climate is one of the polar climates in W. K?ppen's climatic classification and is characterized by a warmest-month mean temperature of less than 0C (32F). It is designated by letter code EF and is equivalent to the frost climate of C. W. Thornthwaite's classifications and to Nordenskj?ld's (1928) high arctic climate. (Also called frost climate, ice-cap climate.) | AMS - glossary of meteorology |
| Phase change | Reorganization of a substance at the atomic or molecular level resulting in a change of the physical state of matter. For example, a change from solid to liquid to a gas. | PhysicalGeography.net |
| Piedmont | Occurs in unconstrained topographic areas (lowland); Expanding glacial fronts; Radial frontal shape; If it terminates into sea, use class calving and piedmont; Icefield formed on a lowland by lateral expansion of one or coalescence of several glaciers | Illustrated GLIMS Glacier Classification Manual |
| Piedmont glacier | Large ice lobe spread out over surrounding terrain, associated with the terminus of a large mountain valley glacier. | NSIDC accessed 2016 |
| Piedmont glacier | A fan or lobe-shaped glacier, located at the front of a mountain range. It forms when one or more valley glaciers flow from a confined valley onto a plain where it expands. The 30-mile wide Malaspina is the largest in Alaska. | Molnia USGS 2004 |
| Piedmont glacier | A glacier the lower tongue of which is fan-shaped and significantly wider than the upper tongue. The lateral expansion of a piedmont glacier is markedly greater than that of an expanded-foot glacier. In some classifications piedmont glaciers are distinguished from expanded-foot glaciers by requiring that a piedmont glacier have two or more coalescing tributaries. See the related but not synonymous ice piedmont. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Piedmont glacier | A glacier that spreads out as a wide lobe as it leaves a narrow mountain valley to enter a wider valley or a plain. | Swisseduc - Photo glossary of glaciological terms |
| Piedmont glacier | The lobe-shaped, expanded, terminal part of a valley glacier spread out over broad lowlands at the base of mountains. | AMS - glossary of meteorology |
| Piedmont glacier | A large glacier formed from the merger of several alpine glaciers. | PhysicalGeography.net |
| Piedmont glacier | The lobe-shaped, expanded, terminal part of a valley glacier spread out over broad lowlands at the base of mountains (cf. Ice piedmont). | Illustrated Glossary of Snow and Ice |
| Pillar | Synonymous with pinnacle for an off-shore rock. | UK Antarctic Place-names Committee accessed 2016 |
| Pingo | An eskimo term for a perennial frost mound consisting of a core of massive ice with soil and vegetation cover; the size can range from a few meters to tens of meters, in both diameter and height; can be found in continuous and discontinuous permafrost zones. | NSIDC accessed 2016 |
| Pingo | A large frost mound of more than one-year duration. | NOAA National Weather Service Glossary 2009 |
| Pingo | A perennial frost mound consisting of a core of massive ice, produced primarily by injection of water, and covered with soil and vegetation | Van Everdingen International Permafrost Association 2005 |
| Pingo | A perennial Frost Mound consisting of a core of Massive Ice, produced primarily by injection of water, and covered with soil and vegetation. | Trombotto et al. 2014 |
| Pingo | A large frost mound of more than one year's duration. While this Eskimo term is used in several related senses, the above meaning is becoming increasingly accepted. | AMS - glossary of meteorology |
| Pingo | A large conical mound that contains an ice core. This feature can be up to 60 to 70 meters in height. Form in regions of permafrost. Common in the Mackenzie Delta region of Canada. Also see the related palsa. | PhysicalGeography.net |
| Pingo ice | Massive ice forming the core of a pingo. | NSIDC accessed 2016 |
| Pingo ice | Massive ice forming the core of a pingo | Van Everdingen International Permafrost Association 2005 |
| Pingo remnant | A collapsed pingo. | NSIDC accessed 2016 |
| Pingo remnant | A collapsed pingo | Van Everdingen International Permafrost Association 2005 |
| Pingo scar | A pingo remnant in a contemporary non-permafrost environment. | NSIDC accessed 2016 |
| Pingo scar | A pingo remnant in a contemporary non-permafrost environment | Van Everdingen International Permafrost Association 2005 |
| Pinnacle | A rock rising shear from the sea bottom, or slender peak or rock on land. | UK Antarctic Place-names Committee accessed 2016 |
| Pinnacled iceberg | Sea ice terminology that describes an iceberg that has a central spire or pyramid. This pyramid can have one or more spires. | Environment and Climate Change Canada 2014 |
| Pit pond | A depression in an outwash plain by the melting of a block of ice floated to its depositional site by meltwater and subsequently buried by sediment. As it melts, a depression in the surface of the outwash plain develops. | Molnia USGS 2004 |
| Pitted topography | Landscape characterized by numerous kettle holes on a glacial outwash plain. | PhysicalGeography.net |
| Plain | Level, mainly ice-free area which may be at low or high elevation, cf. plateau. | UK Antarctic Place-names Committee accessed 2016 |
| Plane-dendritic crystal | An ice crystal exhibiting an elaborately branched (dendritic) structure of hexagonal symmetry, with its much larger dimension lying perpendicular to the principal (c axis) of the crystal. (Or plane dendrite; sometimes called stellar crystal.) Such crystals usually form by vapor deposition at atmospheric temperatures between about -14 and -18C. In sufficient concentration they readily aggregate to snowflakes by interlocking of their branches. | AMS - glossary of meteorology |
| Planetary permafrost | Permafrost occurring on other planetary bodies (planets, moons, asteroids). | NSIDC accessed 2016 |
| Planetary permafrost | Permafrost occurring on other planetary bodies (planets, moons, asteroids) | Van Everdingen International Permafrost Association 2005 |
| Plastic frozen ground | Fine-grained soil in which only a portion of the pore water has turned into ice. | NSIDC accessed 2016 |
| Plastic frozen ground | Fine-grained soil in which only a portion of the pore water has turned into ice | Van Everdingen International Permafrost Association 2005 |
| Plate crystal | An ice crystal usually having an aspect ratio greater than 2 and as much as 100 and with hexagonal symmetry, although trigonal (threefold) and occasionally other symmetries occur. As such crystals fall through the clouds in which they form, they may encounter conditions causing them to develop dendritic extensions, that is, become plane-dendritic crystals. (Or platelet.) | AMS - glossary of meteorology |
| Plateau | More or less extensive ice-covered area of relatively high and uniform elevation, which may include one or more domes and be limited by mountain walls or not so limited, cf. plain, snowfield. | UK Antarctic Place-names Committee accessed 2016 |
| Pleistocene | The epoch of geologic time, informally called the 'The Great Ice Age' or the 'Glacial Epoch', that began ~1.8 million years ago and ended ~8,000 years ago (see the CVO's Geologic Time Scale). During this interval continental glaciers repeatedly formed and covered significant parts of the Earth's surface. Together, the Holocene and Pleistocene epochs comprise the Quaternary Period. | Molnia USGS 2004 |
| Pleistocene climate | The climate of the Pleistocene division of geological time (roughly the last two million years). | WMO METEOTERM accessed 2016 |
| Pleistocene climate | The climate from about 2 500 000 to 10 000 years ago, differing from earlier (Pliocene) climate in being generally colder and with greater extremes of glacial (cold) to interglacial (warm) climate. Characterized in the last 875 000 years by repeated glacials, each lasting approximately 110 000 years, punctuated by interglacials lasting 10 000 to 15 000 years. Before that, the predominant periodicity was 41 000 years rather than 110 000 years. The distribution of continents and oceans has been relatively stable during the Pleistocene, but the oscillation between glacials and interglacials has been characterized by major changes in atmospheric concentrations of optically active gases such as carbon dioxide and methane (higher in interglacials), and global changes in sea level (lower in glacials) associated with changes in the volume of ice on land (lower in interglacials). Changes in the amount, and the seasonal and latitudinal distribution, of insolation resulting from the evolving characteristics of the earth's orbit around the sun play a major role as the pacemaker of these changes. | AMS - glossary of meteorology |
| Pleistocene epoch | The period from 2 500 000 to 10 000 years ago, during which continental glaciers periodically expanded to cover subpolar regions in both hemispheres. | AMS - glossary of meteorology |
| Pleistocene epoch | Period of time from about 2 million years ago to 10,000 years ago. During this period areas of land at higher and middle latitudes where covered with glacial ice. | PhysicalGeography.net |
| Pleistocene glaciation | The periodic expansion of continental ice sheets to cover much of Canada and northeastern Asia during the interval 2 500 000-10 000 years ago. | AMS - glossary of meteorology |
| Pliocene climatic optimum | The period from about 3.2 to 2.5 million years ago during which polar temperature was 5-10C warmer than today, the Antarctic and Arctic ice caps nearly melted, and sea level was 35 m higher. | AMS - glossary of meteorology |
| Plucking | The mechanical removal of pieces of rock from a bedrock face that is in contact with glacier ice. Blocks are quarried and prepared for removal by the freezing and thawing of water in cracks, joints, and fractures. The resulting pieces are frozen into the glacier ice and transported. | Molnia USGS 2004 |
| Plucking | Erosive process of particle detachment by moving glacial ice. In this process, basal ice freezes in rock surface cracks. As the main body of the glacial ice moves material around the ice in the cracks is pulled and plucked out. Also called quarrying. | PhysicalGeography.net |
| Pogonip | Same as ice fog; a Native American word applied particularly to ice fogs occurring in the mountain valleys of the western United States. | AMS - glossary of meteorology |
| Point | Sharp and often comparatively low piece of land jutting out from the coast or forming a turning point in the coastline, but usually applied to a less prominent or less navigationally significant feature than a cape. The term may also be applied to a rock feature at a little distance from a low ice-covered coast. | UK Antarctic Place-names Committee accessed 2016 |
| Point mass balance | Mass balance at a particular location on the glacier, for example at an ablation stake or a snow pit. The point referred to is at the top of a vertical column through the glacier. Most measurements of point mass balance are actually measurements of surface mass balance. That is, they exclude the internal mass balance and basal mass balance, which are either assumed to be negligible or corrected for later, and the flux divergence of the column. In the absence of an overriding reason for a different notation, point balances are indicated by lower-case letters, for example bw for the winter balance, while glacier-wide balances are denoted by upper-case letters, for example Bw. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Point mass balance | See article Point mass balance under Mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Poisson's ratio | The absolute value of the ratio between linear strain changes, perpendicular to and in the direction of a given uniaxial stress change, respectively | Van Everdingen International Permafrost Association 2005 |
| Polar air | Mass of air which has laid over high latitudes for several days and which, therefore, has become fairly cold, at least in the lower levels. | WMO METEOTERM accessed 2016 |
| Polar air | A type of air mass with characteristics developed over high latitudes, especially within the subpolar highs. Continental polar air (cP) has low surface temperature, low moisture content, and, especially in its source regions, great stability in the lower layers. It is shallow in comparison with arctic air. Maritime polar air (mP) initially possesses similar properties to those of continental polar air, but in passing over warmer water it becomes unstable with a higher moisture content. | AMS - glossary of meteorology |
| Polar air depression | A weak low pressure system that forms in a polar air mass. | AMS - glossary of meteorology |
| Polar amplification | In climate modeling studies, the tendency for simulated temperature changes to be larger at high latitudes, as in the case of the warming induced by increased greenhouse gases. | AMS - glossary of meteorology |
| Polar anticyclone | 1. Same as arctic high. 2. Same as subpolar high. | AMS - glossary of meteorology |
| Polar blackout | Failure of radio communication caused by polar cap absorption. | WMO METEOTERM accessed 2016 |
| Polar cap absorption | Effect on radio waves in high latitudes, caused by a sudden increase in the electron concentration in the D layer of the ionosphere. The effect is produced by the influx of high energy solar protons; it begins a few hours after a solar flare is observed and may in exceptional cases persist for a few days. | WMO METEOTERM accessed 2016 |
| Polar cap absorption events | Episodes of intense absorption of HF and VHF radio waves over the polar caps caused by excess ionization resulting from an influx of solar energetic particles into the upper atmosphere. PCA events have a pronounced diurnal variation, being much more intense during daytime than at night, and typically last for two to three days. (Abbreviated PCA events.) | AMS - glossary of meteorology |
| Polar cell | Direct, weak, meridional circulation approximately between the pole and 60? latitude. There is a sinking motion near the poles, weak easterlies at low levels, a rising motion near latitude 60? and a poleward flow aloft. | WMO METEOTERM accessed 2016 |
| Polar cell | A weak meridional circulation in the high-latitude troposphere characterized by ascending motion in the subpolar latitudes (50-70), descending motion over the pole, poleward motion aloft, and equatorward motion near the surface. As a residual of many transient weather systems, the polar cell is barely detectable in means with respect to time of latitude-height cross sections. | AMS - glossary of meteorology |
| Polar cell | Three-dimensional atmospheric circulation cell located at roughly 60 to 90 North and South of the equator. Vertical air flow in the Polar cell consists of rising air at the polar font and descending air at the polar vortex. | PhysicalGeography.net |
| Polar climate | A climatic zone located in the polar latitudes marked by conditions too harsh to support vegetation. (Also called frost climate, snow climate.) | AMS - glossary of meteorology |
| Polar continental air | A continental air mass that develops over or near the polar region. | AMS - glossary of meteorology |
| Polar easterlies | Diffuse belt of low-level easterly winds located on the poleward side of the subpolar low-pressure belt. | WMO METEOTERM accessed 2016 |
| Polar easterlies | The rather shallow, irregular, and diffuse easterly winds located poleward of the subpolar low pressure belt. In the mean in the Northern Hemisphere, these easterlies exist to an appreciable extent only north of the Aleutian low and the Icelandic low. | AMS - glossary of meteorology |
| Polar easterlies | Winds that originate at the polar highs and blow to the subpolar lows in a east to west direction. | PhysicalGeography.net |
| Polar front | A semipermanent, semicontinuous front that separates tropical air masses from polar air masses. | NOAA National Weather Service Glossary 2009 |
| Polar front | Quasi-permanent front of great extent, in middle latitudes, which separates polar air from tropical air. | WMO METEOTERM accessed 2016 |
| Polar front | 1. According to the polar-front theory, the semipermanent, semicontinuous front separating air masses of tropical and polar origin. This is the major front in terms of air mass contrast and susceptibility to cyclonic disturbance. Compare arctic front. 2. In oceanography, see Antarctic Polar Front, Arctic Polar Front. | AMS - glossary of meteorology |
| Polar front | Weather front located typically in the mid-latitudes that separates arctic and polar air masses from tropical air masses. Along the polar front we get the development of the mid-latitude cyclone. Above the polar front exists the polar jet stream. | PhysicalGeography.net |
| Polar front theory | Theory of the Bergen school (1918) which describes the formation and evolution of extratropical depressions in terms of the interaction between polar and tropical air masses and the characteristics of the surface of discontinuity which separates them. | WMO METEOTERM accessed 2016 |
| Polar frontal zone | In the Southern Hemisphere, the region of low salinity water between the Antarctic Polar Front and the subantarctic front. | AMS - glossary of meteorology |
| Polar glacier | A glacier entirely below freezing, except possibly for a thin layer of melt near the surface during summer or near the bed; polar glaciers are found only in polar regions of the globe or at high altitudes. | NSIDC accessed 2016 |
| Polar glacier | An obsolete term, due to Ahlmann (1935), originally in the form 'high-polar glacier', describing a glacier with an accumulation zone in which there is little or no melting and the temperature is below the freezing point to depths of at least 200 m. See cold glacier, polythermal glacier for rough equivalents in modern terminology. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Polar glacier | A glacier with a thermal or temperature regime in which ice temperatures always remain below the freezing point. | Molnia USGS 2004 |
| Polar glacier | In Ahlmann's glacier classification, a glacier with an accumulation area covered by firn and with subsurface temperatures below freezing throughout the year. The two subtypes are the high polar glacier and the subpolar glacier. | AMS - glossary of meteorology |
| Polar high | 1. Same as arctic high. 2. Same as subpolar high. | AMS - glossary of meteorology |
| Polar high | Surface area of atmospheric high pressure located at about 90 North and South latitude. These high pressure systems produced by vertically descending air currents from the polar vortex. | PhysicalGeography.net |
| Polar ice | 1. The thickest form of sea ice, one to several years old (perhaps paleocrystic), and sometimes more than 3 m (10 ft) thick. 2. The pack ice of the central Arctic Ocean. (Also called polar-cap ice.) | AMS - glossary of meteorology |
| Polar ice cap | A high-latitude region covered in ice; not a true ice cap, which are less than 50,000 square kilometers (12.4 million acres) and are always over land; more like an ice sheet; also called polar ice sheet. | NSIDC accessed 2016 |
| Polar invasion | A vigorous thrust of polar air behind a polar front. | AMS - glossary of meteorology |
| Polar invasion syn. polar outbreak | A movement of a polar air mass into middle latitudes. | WMO METEOTERM accessed 2016 |
| Polar jet stream | Relatively fast uniform winds concentrated within the upper atmosphere in a narrow band. The polar jet stream exists in the mid-latitudes at an altitude of approximately 10 kilometers. This jet stream flows from west to east at speeds between 110 to 185 kilometers per hour. Also see jet stream and subtropical jet stream. | PhysicalGeography.net |
| Polar low | Small, shallow depression which forms mainly in winter over some high-latitude seas within a polar or arctic air mass. Its motion is approximately the same as the air stream in which it is embedded. | WMO METEOTERM accessed 2016 |
| Polar low | A small but intense cyclone that forms in cold polar air advected over warmer water. These vortices often form in the subpolar North Pacific and subpolar North Atlantic equatorward of the sea ice margin. Horizontal scales range from several tens to several hundreds of kilometers. Because of strong winds and intense precipitation, these cyclones are sometimes referred to as "arctic hurricanes." | AMS - glossary of meteorology |
| Polar maritime air | A maritime air mass that develops over or near the polar region. | AMS - glossary of meteorology |
| Polar mesospheric clouds | Cirrus-like clouds seen from spacecraft over the polar regions during summer in both hemispheres. (Abbreviated PMC.) They occur near the mesopause, at heights of roughly 85 km, and are closely related to noctilucent clouds. | AMS - glossary of meteorology |
| Polar mesospheric summer echoes | Anomalously strong radar echoes received from the mesopause region during summer at high latitudes. (Abbreviated PMSE.) They are loosely associated with the occurrence of noctilucent clouds and polar mesospheric clouds. | AMS - glossary of meteorology |
| Polar night jet | Westerly jet stream of maximum intensity near the stratopause, in the middle and subpolar latitudes of the winter hemisphere, caused by prolonged radiative cooling of the air in high latitudes during this season. | WMO METEOTERM accessed 2016 |
| Polar night jet stream | A core of strong westerly winds that develop during autumn and winter in the upper stratosphere and mesosphere near the boundary of the polar night. Radiative cooling in the polar night appears to maintain the required baroclinicity. | AMS - glossary of meteorology |
| Polar outbreak | The movement of a cold air mass from its source region; almost invariably applied to a vigorous equatorward thrust of cold polar air, a rapid equatorward movement of the polar front. (Or cold-air outbreak.) | AMS - glossary of meteorology |
| Polar stratospheric clouds | Clouds are cirrus or altocumulus lenticularis, and show very strong irisation similar to that of mother-of-pearl, especially when the sun is several degrees below the horizon. They occur at heights about 20-30 km above the earth. These clouds are rarely seen, and it would appear that they can be observed only in certain regions. They have been observed mainly over Antarctica due to the lower temperatures present there in the circumpolar vortex. They also form over Scotland and Scandinavia in winter during periods with an intense, broad, deep, and homogeneous westerly to northwesterly flow of air over northern Europe; they are also observed in Alaska. Less frequent sightings have been reported at lower latitudes. The simultaneous occurrence of various colors of the spectrum in more or less irregular patterns strongly suggests diffraction by spherical particles. The exact physical constitution of cloud particles has been determined by aircraft (e.g., the NASA ER2 aircraft) penetration showing the presence of nitric acid hydrates (in particular nitric acid tri-hydrate, type I) with the addition of water ice at temperatures a few degrees lower (type II). Nuclei for clouds are thought to be sulfuric acid aerosol, possibly of volcanic origin. The clouds form in regions where dynamic lifting or radiational cooling lowers the air to temperatures below saturation for these different constituents (about 95C). PSC are thought to play a major role in the formation of the "ozone hole" because they absorb odd nitrogen from the atmosphere, which allows the catalytic destruction of ozone to occur. Nacreous clouds appear stationary and, by day, often resemble pale cirrus. At sunset, all the colors of the spectrum appear; as the sky darkens after sunset, they increase in brilliance. As the sun drops lower and lower below the horizon and the clouds are lighted by last rays, the various colors are replaced by a general coloration that is first orange and then becomes pink, contrasting vividly with the darkening sky. The clouds next become gray and the colors of the spectrum reappear but very weakly, then fade out rapidly. Later, up until about two hours after sunset, the nacreous clouds can still be distinguished standing out against the starry sky as tenuous and gray clouds. They can even be observed all night if there is moonlight. Before dawn, the same series of aspects appear, but in reverse order. (Abbreviated PSC; also called nacreous clouds, mother-of-pearl clouds; rarely, luminous clouds.) | AMS - glossary of meteorology |
| Polar stratospheric clouds | High altitude clouds found in the stratosphere where the temperature is less than -85 Celsius. Commonly found over Antarctica. Have a role in the creation of the ozone hole over Antarctica. | PhysicalGeography.net |
| Polar trough | In tropical meteorology, a wave trough in the circumpolar westerlies having sufficient amplitude to reach the Tropics in the upper air. At the surface it is manifest as a trough in the tropical easterlies, but at moderate elevations it is characterized by westerly winds. It moves generally from west to east, accompanied by considerable cloudiness. Cumulus congestus and cumulonimbus clouds are usually found in and around the trough lines. Early- and late-season (June and October) hurricanes of the western Caribbean frequently form in polar troughs. | AMS - glossary of meteorology |
| Polar vortex | High pressure system located in the upper atmosphere at the polar regions. In this system, air in the upper troposphere moves into the vortex center and then descends to the Earth's surface to create the polar highs. | PhysicalGeography.net |
| Polar vortex | The term polar vortex is used to describe several different features in the atmosphere. It most commonly refers to a planetary-scale mid- to high-latitude circumpolar circulation. There are distinct tropospheric and stratospheric circumpolar vortices. The tropospheric polar vortex is usually defined by geopotential contours that lie within the core of the tropospheric westerlies.1 The tropospheric vortex edge is generally between 40? and 50? latitude (Fig. 1), and the vortex exists throughout the year but is strongest during winter when the air within the polar vortex is the coldest. The term 'polar vortex' is sometimes used in reference to smaller-scale (meso- to synoptic scale) vortices that usually occur within the tropospheric polar vortex in polar regions near the tropopause - for example, tropopause polar vortices. 2. The stratospheric polar vortex exists from spring to fall and usually extends from just above tropopause to the upper stratosphere (see Fig. 1). The stratospheric vortex generally increases in size from the lower stratosphere to the upper stratosphere where its edge is located around 50? latitude. The stratospheric vortex breaks down, and the circumpolar flow reverses, during summer. 3. Circumpolar vortices have also been observed on other planetary bodies (e.g., Mars, Venus, Saturn, and Titan). 4. | AMS - glossary of meteorology |
| Polar vortex syn. circumpolar vortex | The large-scale cyclonic circulation in the middle and upper troposphere centred generally in the polar regions. | WMO METEOTERM accessed 2016 |
| Polar wandering | The steady motion of the rotational axis relative to coordinates fixed in the earth. The pole moves at a rate of about 10 cm per year in the general direction of Philadelphia, Pennsylvania. Polar wander is believed to be due to the redistribution of matter within the earth. It is sometimes called "apparent polar wander" because it is difficult to separate from continental drift. | AMS - glossary of meteorology |
| Polar wind | Stream of plasma escaping (dispersing) from the terrestrial atmosphere above the regions of the geomagnetic poles and moving along the magnetospheric lines of force. | WMO METEOTERM accessed 2016 |
| Polar wind | The permanent outflow of ionization from the polar regions of the magnetosphere. | AMS - glossary of meteorology |
| Polar wind divide | A somewhat antiquated term for the very diffuse boundary of low pressure between the midlatitude westerlies and the polar easterlies. | AMS - glossary of meteorology |
| Pole | 1. A point in an electromagnetic field at which electric or magnetic field lines converge. See also dipole, magnetic dipole. 2. For any circle on the surface of a sphere, the point of intersection of the surface of the sphere and the normal line through the center of the circle. The North and South geographic poles are the poles of the equator or of any other latitude circle. 3. The origin of a system of polar coordinates. | AMS - glossary of meteorology |
| Pole of inaccessibility | The approximate center of the most consolidated portion of the arctic pack ice near 83S or 84N, and 160W. | AMS - glossary of meteorology |
| Polyarnik | Russian word for a person working for a long time at one of the polar observing stations. | NSIDC accessed 2016 |
| Polycrystal | A snowflake composed of many individual ice crystals. | NSIDC accessed 2016 |
| Polygon | Literally means many angled; polygons are closed, multi-sided, roughly equidimensional shapes, bounded by more or less straight sides; some of the sides may be irregular; in cryospheric science, it refers to patterned ground formations. | NSIDC accessed 2016 |
| Polygon | Polygons are closed, multi-sided, roughly equidimensional patterned-ground features, bounded by more or less straight sides; some of the sides may be irregular | Van Everdingen International Permafrost Association 2005 |
| Polygon | Polygons are closed, multi-sided, roughly equidimensional Patterned Ground features, bounded by more or less straight sides; some of the sides may be irregular. Macro-scale Polygons, typically 15 to 30 m across, result from thermal contraction cracking of the ground and form random or oriented Polygonal patterns. They occur in both mineral terrain and peatland. Ice Wedge Polygons are common in poorly drained areas and may be either high-centred or low-centred. | Trombotto et al. 2014 |
| Polygon trough | The narrow depression surrounding a high-centre polygon. | NSIDC accessed 2016 |
| Polygon trough | The narrow depression surrounding a high-centre polygon | Van Everdingen International Permafrost Association 2005 |
| Polygonal pattern | A pattern consisting of numerous multi-sided, roughly equidimensional figures bounded by more or less straight sides. | NSIDC accessed 2016 |
| Polygonal pattern | A pattern consisting of numerous multi-sided, roughly equidimensional figures bounded by more or less straight sides | Van Everdingen International Permafrost Association 2005 |
| Polygonal peat plateau | A peat plateau with ice-wedge polygons. | NSIDC accessed 2016 |
| Polygonal peat plateau | A peat plateau with ice-wedge polygons | Van Everdingen International Permafrost Association 2005 |
| Polyn'ya | A Russian term meaning an area of open water, possibly containing some thin ice, within the ice pack. A polyn'ya is distinguished from a lead by being a broad opening rather than a long, narrow fracture. (Also called ice clearing.) | AMS - glossary of meteorology |
| Polynya | Irregularly shaped areas of persistent open water that are sustained by winds or ocean heat; they often occur near coasts, fast ice, or ice shelves. | NSIDC accessed 2016 |
| Polynya | Any non-linear shaped opening enclosed in ice. Polynyas may contain brash ice and/or be covered with new ice, nilas or young ice; submariners refer to these as skylights. Sometimes the polynya is limited on one side by the coast and is called a shore polynya or by fast ice and is called a flaw polynya. If it recurs in the same position every year, it is called a recurring polynya. Polynyas range in size from relatively small to enormous. The largest polynya observed in the Antarctic was the Weddell Polynya of 1975-77, covering an area of 2x105km2. The two main categories of polynya are sensible heat and latent heat, depending on the mechanism responsible for maintaining their presence. Latent heat polynyas are maintained by persistent katabatic winds that drain off the continent. Newly formed ice is advected away by the wind, leaving the surface ice-free and open to more ice formation. In this manner latent heat polynyas can be major sources of new ice production. Coastal polynyas are primarily of this type. Sensible heat polynyas are maintained by upwelling warm water that supplies a sufficiently large oceanic heat flux to the base of the ice to reduce its thickness, or melt it completely. These polynyas are not responsible for large quantities of new ice production. A polynya may also form by a combination of the sensible and latent heat processes. | ASPECT 2012 |
| Polynya | A stable ice-free water space in or at the boundary of fast ice. Polynyas may contain very open broken and brash ice or be covered with new ice, nilas or young ice. A polynya is sometimes restricted by the shore from one side and is termed a shore polynya. If it is restricted by fast ice, then it is termed a flaw polynya. If it recurs in the same position every year, it is termed a recurring polynya. Polynyas can form in the pack, e.g. in the Weddell Sea. | Bushuyev 2004 |
| Polynya | Any nonlinear-shaped opening in the water but enclosed by ice. Sometimes the polynya is limited on one side by the coast and is called a shore polynya, or by fast ice and is called a flaw polynya. Some polynyi recur annually in the same position. | WMO Sea Ice Nomenclature 2017 |
| Polynya | Sea ice terminology. Describes any non-linear-shaped opening that is enclosed by ice. May contain brash ice and/or be covered with new ice, nilas or young ice. Submariners refer to polynya's as 'skylights.' | Environment and Climate Change Canada 2014 |
| Polynya | Any water area in pack ice or fast ice other than a lead, not large enough to be called open water. If a polynya is found in the same region every year, e.g. off the mouths of big rivers, it is called a recurring polynya. A temporary small clearing in pack ice which consists of small floes and brash in continuous local movement is called an unstable polynya; an opening which is flanked by large floes and therefore appears to be relatively stable is called a stable polynya. When frozen over, a polynya becomes an ice skylight from the point of view of the submariner. | Illustrated Glossary of Snow and Ice |
| Polythermal glacier | A glacier containing some cold ice and some temperate ice. Classically, as first described, a polythermal glacier has a basal layer of temperate ice overlain by a layer of cold ice (panel a in Figure 9), above which there may be a surface layer up to about 1015 m thick that warms to the melting point seasonally. See cold glacier, temperate glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Polythermal glacier | A thermally complex glacier with both warm and cold ice (q.v.). Typically, warm ice occurs where the ice is thickest as a result of geothermal heating, whilst the snout and margins of the glacier are frozen to the bed. | Swisseduc - Photo glossary of glaciological terms |
| Poorly-bonded permafrost | Ice-bearing permafrost in which few of the soil particles are held together by ice. | NSIDC accessed 2016 |
| Poorly-bonded permafrost | Ice-bearing permafrost in which few of the soil particles are held together by ice | Van Everdingen International Permafrost Association 2005 |
| Pore ice | Ice occurring in the pores of soils and rocks. | NSIDC accessed 2016 |
| Pore ice | Ice occurring in the pores of soils and rocks | Van Everdingen International Permafrost Association 2005 |
| Pore ice | Ice occurring in the pores of soils and rocks. Pore Ice does not include Segregated Ice. Upon melting, Pore Ice does not yield water in excess of the pore volume of the same soil when unfrozen. | Trombotto et al. 2014 |
| Pore ice | A form of periglacial ground ice that is found in the spaces that exist between particles of soil. | PhysicalGeography.net |
| Pore water | Water occurring in the pores of soils and rocks | Van Everdingen International Permafrost Association 2005 |
| Porosity | The fraction of any given volume not occupied by solid matter, and therefore available for occupation by fluids such as air and water. In snow and firn the porosity is nearly equal to 1 /i, where is the density of the dry snow or firn and i the density of ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Porosity | Porosity φ is a fundamental parameter of any porous medium. It is defined as the volume of
the pore space divided by the total volume. Porosity can be calculated from the snow density. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Positive degree-day | The name of a derived unit, the K d, equal in magnitude to a 1 K excess of temperature above the melting point (273.15 K, 0 C) | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Positive degree-day sum | The integral, in K d (kelvin days), of the excess of temperature T above the melting point Tm (273.15 K, 0 C) | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Positive feedback | A sequence of interactions that amplifies the response to an initial perturbation. The snow and ice albedo-temperature feedback is an example of a positive feedback. | AMS - glossary of meteorology |
| Pothole | A nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses; also called a moulin. | NSIDC accessed 2016 |
| Pothole | Verically sided, commonly cylindrical hollows cut into bedrock by turbulent water that is laden with debris. In a glacial context they may be several metres deep, formed by water under high pressure at the glacier bed. | Swisseduc - Photo glossary of glaciological terms |
| Poudrin | (Rare.) Same as ice crystal. | AMS - glossary of meteorology |
| Powder snow | A thin, dry snow surface which is composed of loose, fresh ice crystals. | NSIDC accessed 2016 |
| Powder snow | Dry snow surface which is composed of loose, fresh ice crystals. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Powder snow | A skiing term for a cover of dry snow that has not been compacted in any way. | AMS - glossary of meteorology |
| Powder snow | A thin, dry snow surface which is composed of loose, fresh ice crystals (cf. New snow). | Illustrated Glossary of Snow and Ice |
| Preactivation | The ability of an ice nucleating particle to act at a higher temperature or a lower supersaturation once it has activated an ice crystal that has subsequently evaporated, provided that critical conditions of temperature and undersaturation are not exceeded. | AMS - glossary of meteorology |
| Precipitation | Measurements are usually made four times daily at principal stations. At ordinary sites they are usually made once or twice per day. Rainfall, snowfall and precipitation amounts given in the tables represent the average accumulation for a given month or year. | Canada National Climate Archive 2015 |
| Precipitation | Liquid or solid products of the condensation of water vapour that fall from clouds or are deposited from the air onto the surface. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Precipitation | Hydrometeor consisting of a fall of an ensemble of particles. The forms of precipitation are: rain, drizzle, snow, snow grains, snow pellets, diamond dust, hail and ice pellets. | WMO METEOTERM accessed 2016 |
| Precipitation | Precipitation is the term given to rain, drizzle, dew, hail, snow and other forms of moisture from the atmosphere which reaches the ground. | Australian Bureau of Meteorology 2016 |
| Precipitation | (1) Liquid or solid products of the condensation or sublimation of water vapour falling from clouds or deposited from air on to the ground. (2) Amount of precipitation on a unit of horizontal surface per unit time. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Precipitation | 1. All liquid or solid phase aqueous particles that originate in the atmosphere and fall to the earth's surface. 2. The amount, usually expressed in millimeters or inches of liquid water depth, of the water substance that has fallen at a given point over a specified period of time. As this is usually measured in a fixed rain gauge, small amounts of dew, frost, rime, etc., may be included in the total. The more common term rainfall is also used in this total sense to include not only amounts of rain, but also the water equivalents of frozen precipitation. For obvious reasons, precipitation is the preferred general term. | AMS - glossary of meteorology |
| Precipitation | (1) Is any aqueous deposit, in liquid or solid form, that develops in a saturated atmosphere (relative humidity equals 100%) and falls to the ground generally from clouds. Most clouds, however, do not produce precipitation. In many clouds, water droplets and ice crystals are too small to overcome natural updrafts found in the atmosphere. As a result, the tiny water droplets and ice crystals remain suspended in the atmosphere as clouds. (2) The state of being precipitated from a solution. | PhysicalGeography.net |
| Precipitation gauge | A device which measures the amount of precipitation; principally a raingauge or snow-gauge. | WMO METEOTERM accessed 2016 |
| Precipitation intensity syn. rainfall intensity, rainfall rate | Amount of precipitation collected per unit time interval. | WMO METEOTERM accessed 2016 |
| Precipitation station syn. rainfall station | Station at which only observations of precipitation are made. This may include observations of snow cover. | WMO METEOTERM accessed 2016 |
| Pressure ice | A general term for floating ice which has been squeezed together and in places forced upwards; includes rafted ice, telescoped ice, hummocked ice and ridge ice. | NSIDC accessed 2016 |
| Pressure ice | Floating sea, river, or lake ice that has been deformed, altered, or forced upward in pressure ridges by the lateral stresses of any combination of wind, water currents, tides, waves, and surf. | NOAA National Weather Service Glossary 2009 |
| Pressure ice | General term for floating ice which has been squeezed together and in places forced upwards. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Pressure ice | Sea ice (or river ice or lake ice) that has been deformed or altered by the lateral stresses of any combination of wind, water currents, tides, waves, and surf. This may include ice pressed against the shore, or one piece of ice upon another. Its two major forms are rafted ice and tented ice, which, individually or in combinations, may form pressure ridges or hummocked ice. | AMS - glossary of meteorology |
| Pressure ice | A general term for floating ice which has been squeezed together and in places forced upwards, when it can also be described as rafted ice, hummocked ice or ridge. | Illustrated Glossary of Snow and Ice |
| Pressure melting | Melting that occurs in ice at temperatures colder than normal melting temperature because of added pressure. | NSIDC accessed 2016 |
| Pressure melting | The melting of ice due to applied pressure. The melting point of pure ice is lowered 0.0072 K per atmosphere of applied pressure. Pressure melting is responsible for regelation. | AMS - glossary of meteorology |
| Pressure melting point | Temperature at which minerals deep within the Earth and ice below the surface of a glacier are caused to melt because of the introduction of pressure. | PhysicalGeography.net |
| Pressure ridge | Process that occurs when wind, ocean currents, and other forces push sea ice around into piles that rise and form small mountains above the level sea ice surface; ridges are initially thin and transparent with very sharp edges from blocks of ice piling up; also see keels. | NSIDC accessed 2016 |
| Pressure ridge | 1. See ridge. 2. A ridge of ice, up to 35 m (100 ft) high and sometimes several kilometers long, in pressure ice. | AMS - glossary of meteorology |
| Pressure-melting | Lowering the melting point of ice by applying pressure. | NSIDC accessed 2016 |
| Pressure-melting | Lowering the melting point of ice by applying pressure | Van Everdingen International Permafrost Association 2005 |
| Pressure-melting point | The temperature at which ice and water are in thermodynamic equilibrium at a given pressure. The pressure-melting temperature is 273.15 K when the pressure is 101 325 Pa, changing, when the water is saturated with air, at 9.8 108 K Pa-1 or, in ice of density 900 kg m-3, about 0.86 103K m-1. This means, for example, that beneath 4000 m of such ice the pressure-melting temperature is 269.75 K3 K m-1. For pure water and ice the corresponding rates are 7.4 108 K Pa-1 and about 0.65 10Factors other than pressure can alter the melting point; see temperate ice. The pair (273.15 K, 101 325 Pa) is known in thermodynamics as the ice point. The specified pressure is the sea-level pressure of the standard atmosphere defined by the International Civil Aeronautical Organization (1993). See also triple point. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Proglacial | Pertaining to an object in physical contact with, or close to, the glacier margin. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Proglacial environment | Is an environment that is located close to the Ice front of a Glacier, Ice Cap or Ice Sheet. | Trombotto et al. 2014 |
| Proglacial lake | A lake developed immediately in front of the glacier, commonly bordered by the mounds of unconsolidated deposits that characterise the terminal zone of a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Promontory | Similar to a headland, but of larger extent, that may be above open sea, above an ice piedmont or above an ice shelf. | UK Antarctic Place-names Committee accessed 2016 |
| Protalus rampart | A Protalus Rampart is a ridge or ramp of debris that develops along the lower margin of a perennial Snow Patch. Early studies assumed that they were formed simply through the Accumulation of rock fall debris. Two views on the origin of Protalus Rampart compete. The first suggests that they are part of a linear developmental continuum of Rock Glaciers, thus thought to be due to Permafrost Creep. The second view suggests that Protalus Ramparts are not part of a developmental continuum of Rock Glaciers. Although very common in the central Andes, there are few studies devoted to these landforms (Trombotto, 2000). Note: This type of landform, when larger than 0.01 km2 and showing downslope movements, it could already be considered as a Rock Glacier. | Trombotto et al. 2014 |
| Proxy | A proxy climate indicator is a record that is interpreted, using physical and biophysical principles, to represent some combination of climate-related variations back in time. Climate-related data derived in this way are referred to as proxy data. Examples of proxies include pollen analysis, tree ring records, speleothems, characteristics of corals, and various data derived from marine sediments and ice cores. Proxy data can be calibrated to provide quantitative climate information. | IPCC WGII AR5 2014 |
| Puddle | (1) The act of compacting earth, soil clay, etc., by mixing them with water and rolling or tamping the mixture. (2) A compact mass of earth, soil, clay, or a mixture of material, which has been compacted through the addition of water, rolling and tamping. This makes the material less permeable. (3) A small pool of water, usually a few inches in depth and from several inches to several feet in it greatest dimension. | NOAA Glossary of Hydrologic Terms |
| Puddle | An accumulation of melt water on an ice surface, mainly due to melting snow, but in later stages also to the melting of ice; the initial stage consists of patches of slush. | NSIDC accessed 2016 |
| Puddle | An accumulation melt-water on ice, mainly due to melting snow, but in the more advanced stages also to the melting of ice. The initial stage consists of patches of melted snow. | Bushuyev 2004 |
| Puddle | An accumulation on ice of meltwater, mainly due to melting snow, but in the more advanced stages, also to the melting of ice. Initial stage consists of patches of melted snow. | WMO Sea Ice Nomenclature 2017 |
| Puddle | In hydrologic terms, (1) The act of compacting earth, soil clay, etc., by mixing them with water and rolling or tamping the mixture. (2) A compact mass of earth, soil, clay, or a mixture of material, which has been compacted through the addition of water, rolling and tamping. This makes the material less permeable. (3) A small pool of water, usually a few inches in depth and from several inches to several feet in it greatest dimension. | NOAA National Weather Service Glossary 2009 |
| Puddle | Sea ice terminology that describes an accumulation of water on ice, mainly due to melting snow. However, in the more advanced stages puddles can also be due to the melting of ice. | Environment and Climate Change Canada 2014 |
| Puddle | Accumulation of meltwater on ice, mainly due to melting snow and, at a later stage, the melting of ice. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Puddle | An accumulation of melt water on an ice surface, mainly due to melting snow, but in later stages also to the melting of ice. The initial stage consists of patches of slush. | Illustrated Glossary of Snow and Ice |
| Purga | In Russia, a severe storm, similar to the blizzard and buran, that rages in the tundra regions of northern Siberia in winter. (Also spelled poorga.) | AMS - glossary of meteorology |
| Push moraine | Moraine built out ahead of an advancing glacier. | NSIDC accessed 2016 |
| Push moraine | A ridge or pile of unstratified glacial sediment that is formed in front of the ice margin by the terminus of an advancing glacier, bulldozing sediment in its path. | Molnia USGS 2004 |
| Push moraine | A complex landform ranging from a few metres to tens of metres in height comprising assorted debris that has been pushed up by a glacier during an advance. Push moraines are best developed in front of polythermal glaciers. | Swisseduc - Photo glossary of glaciological terms |
| Quality of snow | The amount of ice in a snow sample expressed as a percent of the weight of the sample. | NOAA National Weather Service Glossary 2009 |
| Quality of snow | The amount of ice in a snow sample expressed as a percent of the weight of the sample. | AMS - glossary of meteorology |
| Quartz microtexture of the periglacial environment | Micro textural characteristics of the quartz grains (sand size) that exist in sediments found in the Periglacial Environment. Their characteristics are related to cryogenic processes like frost weathering, sorting, cryoturbation and friction intergranular movements due to freezing and thawing cycles in sedimentary deposits. The main characteristics are: grains with a high degree of roughness, angular, conchoidal fractures, chatter marks, straight and curved lines, and graduated arches. There are also micro phenomena in terms of deposition and dilution. | Trombotto et al. 2014 |
| Quaternary climate | The climate of the last 2 500 000 years, including the alternating glacial-interglacial climate of the Pleistocene and the comparatively warm climate of the Holocene or postglacial (the last 10 000 years). | AMS - glossary of meteorology |
| Quaternary period | The last two million years of geologic time, comprising the Pleistocene and Holocene glacial epochs. Estimates of the date of the beginning of the Quaternary vary between 2.5 and 1.6 million years ago. | AMS - glossary of meteorology |
| Quiescent phase | The period in which a surge-type glacier is slow-moving or stagnant. This period is typically decades long in contrast to the surge phase that may last only a few months or years. | Swisseduc - Photo glossary of glaciological terms |
| Radar | A method of, and by extension an instrument for, detecting and locating objects by sensing radiation transmitted by the instrument and reflected from the objects. See Active-microwave sensor. The depth to which a radio or microwave signal is likely to penetrate ice or snow before being absorbed or scattered depends on the frequency (or equivalently the wavelength). In the case of scattering, the penetration depth also depends on the size of any inhomogeneities in the ice; those smaller than the wavelength of the signal cause less scattering. In glaciology, the lower frequencies (about 2 to several hundred mhz) are the basis for ground-penetrating radar (see also radar method), while frequencies of 1 to 15 ghz, at which effective penetration depths can still reach some metres, are used in radar altimeters mounted on aircraft or satellites (see also insar, Shuttle Radar Topography Mission). Radar is an acronym standing for radio detection and ranging. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Radar altimeter | An instrument for altimetry that transmits and receives pulses of microwave radiation. Satellite radar altimeters (including ERS-1 and 2, Envisat and others) typically operate in the Ku band (13.5 ghz; 22 mm wavelength) and were designed primarily for oceanographic monitoring. Because of their relatively large footprint (several km), they are best suited for measuring elevationsof gently-sloping regions of the ice sheets. Steep or undulating terrain produces complex waveforms and difficulties in achieving accurate estimates of range (i. E. Distance). Surface and volume scattering also affect the radar pulse and create uncertainty in the effective depth of the reflecting horizon. Surface dielectric properties and roughness that cause scattering are time-varying and introduce errors in calculations of elevation change. Recent radar altimeters use synthetic aperture processing (see insar) that increases resolution and decreases slope errors relative to earlier radar altimeters. The Shuttle Radar Topography Mission (SRTM) used a C-band radar (5.6 ghz; 54 mm wavelength) and synthetic aperture processing to obtain an accurate map of surface elevations with near-global coverage. Cryosat-2, launched in April 2010, will also use insar to map glaciers and ice sheets. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Radiation fog | Fog caused by nocturnal radiational cooling of the Earth's surface, which in turn cools the adjacent air to a degree sufficient to cause condensation of the water vapour within the air. | WMO METEOTERM accessed 2016 |
| Radiation frost | Frost caused by nocturnal radiational cooling of the Earth's surface, usually under conditions of clear skies and little or no wind. Surface temperatures must fall to 0 degrees C or below. | WMO METEOTERM accessed 2016 |
| Radiation frost | Freezing conditions that typically occur on clear nights with little or no wind, when the outgoing is greater than the incoming radiation and cooling air temperature near the surface creates a stable temperature inversion near the ground. | AMS - glossary of meteorology |
| Radiation inversion | Temperature inversion produced by nocturnal radiational cooling of the Earth's surface, a snow or ice surface, or the upper part of a cloud layer, etc. | WMO METEOTERM accessed 2016 |
| Radiative cooling syn. radiational cooling | A decrease of temperature at the Earth's surface or within the atmosphere due to a negative radiation balance, i.e. when infrared emission from a particular volume or body is greater than solar and/or infrared absorption by that volume or body. | WMO METEOTERM accessed 2016 |
| Radioactive snow gauge | A device that automatically and continuously records the water equivalent of snow on a given surface as a function of time. A small sample of a radioactive salt is placed in the ground in a lead-shielded collimator that directs a beam of radioactive particles vertically upward. A Geiger-M ller counting system (located above the snow level) measures the amount of depletion of radiation caused by the presence of the snow. | AMS - glossary of meteorology |
| Radioisotope snow gage | A snow water equivalent gage based on the absorption of gamma radiation by snow; this gage can measure up to 55 inches water equivalent with a 2 to 5 percent error. | NOAA Glossary of Hydrologic Terms |
| Radius-dependent metamorphism | Snow metamorphism that occurs when there are large differences in convex and concave portions of a crystal. | NSIDC accessed 2016 |
| Rafted ice | Deformed sea ice in which one piece has overridden another; also called telescoped ice. | NSIDC accessed 2016 |
| Rafted ice | Sea ice terminology, describing a type of deformed ice, formed by one piece of ice overriding another. | Environment and Climate Change Canada 2014 |
| Rafted ice | Type of deformed ice formed by one piece of ice overriding another. | WMO Sea Ice Nomenclature 2017 |
| Rafted ice | Type of deformed ice formed by one piece of ice overriding another. When young ice under pressure is forced alternately over and under like thrusting fingers, the ice is termed finger rafted ice. | Bushuyev 2004 |
| Rafted ice | Two-layered or multilayered floating ice under pressure, resulting from one flow overriding another. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Rafted ice | Deformed sea ice in which one piece has overridden another. (Also called telescoped ice.) | AMS - glossary of meteorology |
| Rafted ice | A form of pressure ice in which one floe overrides another. | Illustrated Glossary of Snow and Ice |
| Rafting | A process by which currents or winds push around thin ice so they slide over each other; also called finger rafting. | NSIDC accessed 2016 |
| Rafting | Pressure process whereby one piece of ice overrides another. Most common in new and young ice (cf. Finger rafting). Finger rafting is a type of rafting whereby interlocking thrusts are formed, each floe thrusting 'fingers' alternately over and under each other. Common in nilas and grey ice. Rafting plays an important role in increasing ice thickness within the Antarctic pack. It is the dominant dynamic mechanism whereby floes reach between about 0.4 and 0.6m thick in the early stages of ice development. Beyond this thickness, converging floes are more likely to form ridges than to raft. | ASPECT 2012 |
| Rafting | Pressure processes whereby one piece of ice overrides another. Most common in new and young ice. | WMO Sea Ice Nomenclature 2017 |
| Rafting | Sea ice terminology describing the pressure process whereby one piece of ice overrides another. Most common in new and young ice. | Environment and Climate Change Canada 2014 |
| Rafting | Pressure process by which one floe overrides another; most commonly found in new and young ice. A type of rafting common in nilas whereby interlocking thrusts are formed - each floe thrusting "fingers" alternately over and under the other - is known as finger rafting. | Illustrated Glossary of Snow and Ice |
| Rain | Precipitation other than dew that falls from the air as liquid. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Rain | Precipitation of liquid water drops greater than 0.5 mm in diameter. In contrast to showers, it is steadier and normally falls from stratiform (layer) cloud. | Australian Bureau of Meteorology 2016 |
| Rain | Precipitation in the form of liquid water drops that have diameters greater than 0.5 mm, or, if widely scattered, the drops may be smaller. The only other form of liquid precipitation, drizzle, is to be distinguished from rain in that drizzle drops are generally less than 0.5 mm in diameter, are very much more numerous, and reduce visibility much more than does light rain. For observing purposes, the intensity of rainfall at any given time and place may be classified as 1) "light," the rate of fall varying between a trace and 0.25 cm (0.10 in.) per hour, the maximum rate of fall being no more than 0.025 cm (0.01 in.) in six minutes; 2) "moderate," from 0.26 to 0.76 cm (0.11 to 0.30 in.) per hour, the maximum rate of fall being no more than 0.076 cm (0.03 in.) in six minutes; 3) "heavy," over 0.76 cm (0.30 in.) per hour or more than 0.076 cm (0.03 in.) in six minutes. When rain gauge measurements are not readily available to determine the rainfall intensity, estimates may be made according to a descriptive system set forth in observing manuals. | AMS - glossary of meteorology |
| Rain | A form of precipitation. It is any liquid deposit that falls from clouds in the atmosphere to the ground surface. Rain normally has a diameter between than 0.5 and 5.0 millimeters. | PhysicalGeography.net |
| Rain and snow mixed | Precipitation consisting of a mixture of rain and wet snow. It usually occurs when the temperature of the air layer near the ground is slightly above freezing. The British term for this mixture is sleet (which has a different meaning in the United States). | AMS - glossary of meteorology |
| Rain crust | A type of snow crust formed by refreezing after surface snow crystals have been melted and wetted by liquid precipitation. This type of crust is composed of individual ice particles such as firn. Rain may also help to form film crust or ice crust. | AMS - glossary of meteorology |
| Rainfall | The amount of rain that falls during a stated period. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Rainfall | The total liquid product of precipitation or condensation from the atmosphere, as received and measured in a rain gauge. | Australian Bureau of Meteorology 2016 |
| Rainfall/snowfall/precipitation | Rain, drizzle, freezing rain, freezing drizzle and hail are usually measured using the standard Canadian rain gauge, a cylindrical container 40 cm high and 11.3 cm in diameter. The precipitation is funneled into a plastic graduate that serves as the measuring device. Snowfall is the measured depth of newly fallen snow, measured using a snow ruler. Measurements are made at several points which appear representative of the immediate area, and then averaged. 'Precipitation' in Canadian Climate Normals tables is the water equivalent of all types of precipitation. | Canada National Climate Archive 2015 |
| Raingauge | Instrument for measuring the depth of water from precipitation supposedly distributed over a horizontal impervious surface and not subject to evaporation. | WMO METEOTERM accessed 2016 |
| Raingauge shield | Protective attachment around the funnel of a raingauge to eliminate the influence of wind eddies on the catch. | WMO METEOTERM accessed 2016 |
| Raingauge shield | A device that surrounds a rain gauge and acts to maintain horizontal flow in the vicinity of the funnel so that the catch will not be influenced by eddies generated near the gauge. (Also called wind shield.) Types in use include the Alter shield, Nipher shield, and Wild fence. | AMS - glossary of meteorology |
| Ram | A horizontal underwater projection of ice from an ice front, ice wall, iceberg or floe. | NSIDC accessed 2016 |
| Ram | An underwater ice projection from an ice wall, ice front, iceberg, or floe. Its formation is usually due to a more intensive melting and erosion of the unsubmerged part. | WMO Sea Ice Nomenclature 2017 |
| Ram | An underwater ice projection from an ice wall, ice front, iceberg or floe. Its formation is usually due to a more intensive melting and erosion of the unsubmerged part. | Bushuyev 2004 |
| Ram | Sea ice terminology. Describes an underwater protruding piece of ice that has come from an ice wall, ice front, iceberg or floe. Its formation is usually due to a more intensive melting and erosion of the un-submerged part. | Environment and Climate Change Canada 2014 |
| Ram | A horizontal underwater projection of ice from an ice front, ice wall, iceberg or floe. | Illustrated Glossary of Snow and Ice |
| Ram penetrometer | A cone-tipped metal rod designed to be driven downward into deposited snow. The measured amount of force required to drive the rod a given distance is an indication of the ram resistance of the snow (see snow hardness). (Swiss rammsondecone tip angle 60 | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Ram penetrometer | A cone-tipped metal rod designed to be driven downward into deposited snow or firn. The measured amount of force required to drive the rod a given distance is an indication of the physical properties of the snow or firn. (Also called ramsonde.) | AMS - glossary of meteorology |
| Rammsonde | A device for measuring the penetration hardness (also called the ram resistance) of snow or firn, a quantity formerly believed to be a reliable guide to the density, and still commonly used in assessments of the risk of snow avalanches. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Rammsonde | British term for ram penetrometer. | AMS - glossary of meteorology |
| Randkluft | A fissure that separates a moving glacier from its headwall rock; like a bergschrund. | NSIDC accessed 2016 |
| Range | (1) The distance to a target such as a glacier surface from an Active sensor such as a sonic ranger or a radar. (2) The cross-track coordinate in the coordinate frame of an airborne or orbiting radar. See azimuth. (3) Of an Active sensor, to measure the distance to, that is, to 'range to', a target. Senses 2 and 3 have evolved from sense 1, which originated in gunnery but has become common in several branches of remote sensing. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Range | Row of mountains, or groups of mountains broken by glaciers, extending over a considerable distance. | UK Antarctic Place-names Committee accessed 2016 |
| Rapid dynamical change (of glaciers or ice sheets) | Changes in glacier or ice sheet mass controlled by changes in flow speed and discharge rather than by accumulation or ablation. This can result in a rate of mass change larger than that due to any imbalance between accumulation and ablation. Rapid dynamical change may be initiated by a climatic trigger, such as incursion of warm ocean water beneath an ice shelf, or thinning of a grounded tidewater terminus, which may lead to reactions within the glacier system, that may result in rapid ice loss. See also Mass balance/budget (of glaciers or ice sheets). | IPCC WGI AR5 2013 |
| Raw | Colloquially descriptive of uncomfortably cold weather, usually meaning cold and damp, but sometimes cold and windy. | AMS - glossary of meteorology |
| Reaction time | The time required for a change in forcing of mass balance to result in an observable response of the geometry, particularly the length, of the glacier. The reaction time is not a physical property of the glacier. Estimates of the reaction time depend on, among other things, the precision of observation and the extent to which the glacier is out of equilibrium. See response time. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Rear snowmelt boundary | Boundary between melting seasonal snow cover and snowless land surface. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Recessional moraine | Ridge of debris representing a stationary or minor readvance phase during otherwise general retreat. | Swisseduc - Photo glossary of glaciological terms |
| Recessional moraine | Moraine that is created during a pause in the retreat of a glacier. Also called a stadial moraine. | PhysicalGeography.net |
| Recessional moraine | A ridge of glacial sediment that forms when the terminus of a retreating glacier remains at or near a single location for a period of time sufficient for a cross-valley accumulation to form. | Molnia USGS 2004 |
| Reconstituted glacier | A glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier then re-adhering; also called reconstructed glacier, regenerated glacier, or glacier remainie. | NSIDC accessed 2016 |
| Reconstituted glacier | A glacier formed below the terminus of a hanging glacier by the accumulation, and reconstitution by pressure melting (regelation), of ice blocks that have fallen and/or avalanched from the terminus of the hanging glacier. Also called Glacier Remani | Molnia USGS 2004 |
| Reconstructed glacier | A synonym of regenerated glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Recording albedometer | An instrument that chronicles the ratio of the radiation reflected by a surface to the radiation incident upon it. | AMS - glossary of meteorology |
| Recrystallization | (1) The metamorphosis, without melting but not necessarily without advection in the vapour phase, of an assemblage of grains of snow and old crystals of ice to a new assemblage of crystals of ice, generally resulting in changes of mean crystal size and orientation (fabric) and, of most significance for mass-balance purposes, an increase of density. See congelation, infiltration ice, glacier. (2) The formation of a new assemblage of crystals from an old assemblage. Sense 1 is the meaning of the term in studies of the densification of snow, while sense 2 is its everyday meaning. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Recrystallization zone | In the Russian-language literature, where it is sometimes also referred to as the 'snow zone', a synonym of dry-snow zone. See zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Recrystallization-regelation zone | In the Russian-language literature, where it is sometimes also referred to as the 'snow-firn zone', a term for the upper percolation zone. See zone. In this context the Russian word 'regelatsiya' refers to refreezing, not to regelation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Recrystallize | To crystallize again, i.e., to form into new crystals. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Recurring polynya | Irregularly shaped areas of persistent open water that are sustained by winds or ocean heat; they often occur near coasts, fast ice, or ice shelves. | NSIDC accessed 2016 |
| Recurring polynya | A polynya that recurs in the same position every year. | WMO Sea Ice Nomenclature 2017 |
| Recurring polynya | Sea ice terminology for a polynya which recurs in the same position every year. | Environment and Climate Change Canada 2014 |
| Red algae | Algae common on temperate glaciers and perennial snow; its red color sometimes prompts people to call it watermelon snow. | NSIDC accessed 2016 |
| Red snow | A snow surface of reddish color due to the presence within it of certain microscopic algae (cryoplankton) or particles of red dust. | AMS - glossary of meteorology |
| Redistribution | Redistribution of previously deposited snow that was eroded and transported by the wind. Redistribution features such as snowdrifts are usually formed from densely packed and friable snow (see surface features). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Reference glacier | In the monitoring strategy of the Global Terrestrial Network for Glaciers, a glacier with a long-term, continuous, continuing programme of mass-balance observations. See tier, benchmark glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Reference-surface balance | The glacier-wide mass balance that would have been observed if the glacier surface topography had not changed since a reference date. The time-invariant surface is called the 'reference surface', and is defined at some convenient time within a mass-balance programme, often at the start. The reference-surface balance is obtained when point measurements are extrapolated from their actual altitude to the altitude of the reference surface at the same horizontal position, and then extrapolated over the reference area. The reference surface is likely to differ from the actual surface in both area and area-altitude distribution. Differences in area and area-altitude distribution feed back on the magnitude of glacier response to climate. The reference-surface balance does not incorporate any of these feedback effects and is therefore more closely correlated to variations in climate than is the conventional balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Reflectivity | Ratio of the energy reflected by a given surface to that incident upon it. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Refreezing | The freezing of meltwater generated at the glacier surface, or of rain, that percolates to some depth at which the temperature is below the freezing point. Refreezing below the summer surface represents internal accumulation. Percolating water may also refreeze at the base of snow overlying impermeable glacier ice, in which case it is called superimposed ice. See zone. The release of latent heat heats the layer within which the water freezes. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Refuge | Hut containing emergency rations, etc., for temporary occupation by field personnel or for the use of parties in distress. | UK Antarctic Place-names Committee accessed 2016 |
| Regelation | Motion of an object through ice by melting and freezing that is caused by pressure differences; this process allows a glacier to slide past small obstacles on its bed. | NSIDC accessed 2016 |
| Regelation | Process by which ice melts when subjected to pressure and refreezes when pressure is removed. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Regelation | The freezing of meltwater due to a change in pressure alone. The term is often used for 'pressure melting and regelation'. Regelation happens because the pressure-melting point of ice varies inversely with pressure. Water in equilibrium with ice will freeze, releasing the latent heat of fusion, 333.5 k: J kg-1, if there is a decrease of pressure, as on the downglacier face of a bump in the bed of a temperate glacier. Ice in equilibrium with water will melt if there is an increase of pressure, as on the upglacier face of the bump. However, the latent heat of fusion must be supplied for this change of phase. A natural source is the latent heat released by regelation on the downglacier face. If pressure melting and regelation are unequal, there will be a contribution to basal ablation or basal accumulation. Smaller bumps are more favourable to pressure melting and regelation than larger ones. The Russian word 'regelatsiya' refers to refreezing rather than to regelation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Regelation | Regelation is the phenomenon of melting under pressure and freezing again when the pressure is reduced. A Glacier can exert a sufficient amount of pressure on its lower surface to lower the melting point of its ice. The melting of the Ice at the glacier's base allows it to move from a higher elevation to a lower elevation. Liquid water may flow from the base of a Glacier at lower elevations when the temperature of the air is above the freezing point of water. | Trombotto et al. 2014 |
| Regelation | A twofold process in which a localized region on the surface of a piece of ice melts when pressure is applied to that region (pressure melting) and then refreezes when pressure is reduced. Regelation was discovered by Faraday, who found that two pieces of ice at 0C would freeze together if pressed against each other and then released. Regelation occurs only for substances, such as ice, that have the property of expanding upon freezing, for the melting points of those substances decrease with increasing external pressure. The melting point of pure ice decreases with pressure at the rate of 0.0072C per atmosphere. Since this rate is very small, regelation only occurs at ice temperatures of 0C or very slightly less. The fact that snowballs can be packed well at near 0C but not at much colder temperatures is a consequence of regelation. | AMS - glossary of meteorology |
| Regelation ice | Ice which is formed from meltwater and basal debris as a result of changes of pressure beneath a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Regenerated (or rejuvenated) glacier | A glacier which develops from ice-avalanche material beneath a rock cliff. | Swisseduc - Photo glossary of glaciological terms |
| Regenerated glacier | A glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier then re-adhering; also called reconstituted or reconstructed glacier, or glacier remainie. | NSIDC accessed 2016 |
| Regenerated glacier | The lower part of an interrupted glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Regional snowline | See article Regional snowline under Snowline. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Regional snowline | The mean orographic snowline on a regional scale; climatic snowline is a synonym. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Relative density | While density is mass per unit volume given in kilograms per cubic metre, relative density or specific gravity is the ratio of the mass of a given volume of a substance to the mass of an equal volume of water at a temperature of 4 | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Relative dielectric constant | The ratio r of the electric displacement (electric flux per unit area) at any point in a dielectric (that is, non-conducting) medium to the displacement that an identical electric field would produce in a vacuum, measured at the same point. The relative dielectric constant, which is not in fact a constant and is more properly called the relative permittivity, is a complex number. Its imaginary part, r , is sensitive to attenuation of microwaves by absorption and other phenomena; it is sometimes called the dielectric loss. Ice, however, is generally assumed to be a low-loss medium, and its dielectric loss is approximated as r= 0. The real part of r, denoted r, depends on frequency and temperature, and more subtly on variations in crystalline fabric and the presence of impurities. It determines the geometry of wave propagation, including refraction at and reflection from interfaces between layers within the medium. See ground-penetrating radar. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Relative humidity with respect to ice | The ratio of the vapor pressure to the saturation vapor pressure with respect to ice. | AMS - glossary of meteorology |
| Relative permittivity | The relative permittivity of a soil is the ratio of the permittivity of the soil to the permittivity of a vacuum | Van Everdingen International Permafrost Association 2005 |
| Relict active layer | A layer of ground, now perennially frozen, lying immediately below the modern active layer; its thickness indicates the greater annual depth of thaw that occurred during a previous period. | NSIDC accessed 2016 |
| Relict active layer | A layer of ground, now perennially frozen, lying immediately below the modern active layer. Its thickness indicates the greater annual depth of thaw that occurred during a previous period | Van Everdingen International Permafrost Association 2005 |
| Relict active layer | A layer of ground, now perennially frozen lying immediately below the modern Active Layer. Its thickness indicates the greater annual Depth of Thaw that occurred during a previous period. | Trombotto et al. 2014 |
| Relict ice | Ice formed in, and remaining from, the geologically recent past. | NSIDC accessed 2016 |
| Relict ice | Ice formed in, and remaining from, the geologically recent past | Van Everdingen International Permafrost Association 2005 |
| Relict ice | Ice formed in, and remaining from, the geologically recent (typically the late Quaternary or early Holocene) past. | Trombotto et al. 2014 |
| Relict permafrost | Permafrost existing in areas where permafrost can not form under present climatic conditions; reflects past climatic conditions that were colder. | NSIDC accessed 2016 |
| Relict permafrost | Permafrost existing in areas where permafrost can not form under present climatic conditions | Van Everdingen International Permafrost Association 2005 |
| Relict permafrost | Permafrost existing in areas where Permafrost cannot form under present climatic conditions. Relict Permafrost (including Relict Ice) formed when the mean annual surface temperature was lower than at present; it is in disequilibrium with the present mean annual surface temperature. This Permafrost persists in places where it could not form today. Relict Ice and associated landforms are a sign of degrading Permafrost. | Trombotto et al. 2014 |
| Relict rock glacier | A mass of rock fragments and finer material, on a slope, that shows evidence of past movement, but does no longer contain any Ground Ice. | Trombotto et al. 2014 |
| Remnant | An isolated melting mass of glacier ice, that has become detached from its source and the remainder of the glacier. Some remnants cover many square miles. | Molnia USGS 2004 |
| Remnant | Disconnected from accumulation area; Inactive; An inactive, usually small ice mass left by a receding glacier | Illustrated GLIMS Glacier Classification Manual |
| Residual first-year ice | First-year ice that has survived the summers melt and is now in the new cycle of growth. It is 30 to 180 cm thick depending on the region where it was in summer. After 1 January (in the Southern hemisphere after 1 July), this ice is called second-year ice. | Bushuyev 2004 |
| Residual stress | The effective stress generated in a thawing soil if no volume change is permitted during thaw | Van Everdingen International Permafrost Association 2005 |
| Residual thaw layer | A layer of thawed ground between the seasonally frozen ground and the permafrost table. | NSIDC accessed 2016 |
| Residual thaw layer | A layer of thawed ground between the seasonally frozen ground and the permafrost table | Van Everdingen International Permafrost Association 2005 |
| Response time | The e-folding time scale for the transition of a glacier, following a step change in mass balance, from one steady state to another. Response times have been formulated for various attributes of the glacier such as volume and length. They can be confused easily with the mass-turnover time; the reaction time; and the growth time. The volumetric response time is the most commonly seen formulation. Here the glacier changes from an initial volume V1 to a later volume V2, and the response time is the time needed for the volume to change by (V2 V1) (1 e-1), where e = 2.71828... Is the base of natural logarithms. The response time is much shorter than the time required to attain volume V2. Indeed, in this formulation the time to attain volume V2 is infinite. The change between state 1 and state 2 is assumed to be 'small'. The response time for volume is somewhat shorter than that for length, that is, for the length to change by (L2 L1) (1 e-1). The response time is an idealization. The essence of the idea is that the glacier 'remembers' its earlier steady state because it adjusts its size and shape by flow. The volume response time is often estimated with an expression due to J | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Resublimation | The process by which a vapour changes phase directly into a solid; deposition and desublimation are synonyms. See latent heat of sublimation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Reticulate cryostructure | The cryostructure in which horizontal and vertical ice veins form a three-dimensional, rectangular or square lattice. | NSIDC accessed 2016 |
| Reticulate cryostructure | The cryostructure in which horizontal and vertical ice veins form a three-dimensional, rectangular or square lattice | Van Everdingen International Permafrost Association 2005 |
| Reticulate ice | A network of horizontal and vertical ice veins forming a three-dimensional, often rectangular or square lattice. | NSIDC accessed 2016 |
| Reticulate ice | A network of horizontal and vertical ice veins forming a three-dimensional, often rectangular or square lattice | Van Everdingen International Permafrost Association 2005 |
| Reticulate-blocky cryostructure | The cryostructure in which horizontal and vertical ice veins form a three-dimensional, irregular rectangular lattice. | NSIDC accessed 2016 |
| Reticulate-blocky cryostructure | The cryostructure in which horizontal and vertical ice veins form a three-dimensional, irregular rectangular lattice | Van Everdingen International Permafrost Association 2005 |
| Retreat | When a mountain glacier's terminus doesn't extend as far downvalley as it previously did; occurs when ablation surpasses accumulation. | NSIDC accessed 2016 |
| Retreat | A decrease in the length of a glacier compared to a previous point in time. As ice in a glacier is always moving forward, its terminus retreats when more ice is lost at the terminus to melting and/or calving than reaches the terminus. During retreat, ice in a glacier does not move back up the valley. | Molnia USGS 2004 |
| Retreat | Decrease of the length of a flowline, measured from a fixed point. In practice, when the retreat is of a land-terminating glacier terminus, the fixed point is usually downglacier from the terminus, that is, on the glacier forefield. The quantity reported is most often the amount of retreat rather than the length itself. Advance is the opposite of retreat, that is, advance of the terminus. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Retreating glacier | A glacier whose terminus is increasingly retreating upvalley compared to its previous position due to a higher level of ablation compared to accumulation. | NSIDC accessed 2016 |
| Retrogressive thaw slump | A slope failure resulting from thawing of ice-rich permafrost. | NSIDC accessed 2016 |
| Retrogressive thaw slump | A slope failure resulting from thawing of ice-rich permafrost | Van Everdingen International Permafrost Association 2005 |
| Returning polar maritime air | Air that has originated over subpolar oceans and is returning poleward after an equatorward excursion around an anticyclone. | AMS - glossary of meteorology |
| Ridge | A line or wall of broken ice forced up by pressure. May be fresh or weathered. | NOAA Glossary of Hydrologic Terms |
| Ridge | (1) An elongated area of relatively high atmospheric pressure; the opposite of trough. or (2) In hydrologic terms, a line or wall of broken ice forced up by pressure. May be fresh or weathered. | NOAA National Weather Service Glossary 2009 |
| Ridge | A comparatively rectilinear conglomeration of ice fragments formed by pressure at the contact line between ice floes, usually along earlier existing cracks and leads or at the boundary between ice floes of different age. In this case, isostatically unbalanced hummocks usually form on the older ice surface. Ice ridges can also form as a result of direct fracturing of ice fields of thick and even first-year and multiyear ice at very strong pressures. The underwater portion of a ridge is termed an ice keel. | Bushuyev 2004 |
| Ridge | A line or wall of broken ice forced up by pressure; it may be fresh or weathered. The submerged volume of broken ice under a ridge, forced downwards by pressure, is termed an ice keel. | WMO Sea Ice Nomenclature 2017 |
| Ridge | Long narrow hill or mountain top, or spur leading to a summit. | UK Antarctic Place-names Committee accessed 2016 |
| Ridge | 1. In meteorology, an elongated area of relatively high atmospheric pressure, almost always associated with and most clearly identified as an area of maximum anticyclonic curvature of wind flow. The locus of this maximum curvature is called the ridge line. Sometimes, particularly in discussions of atmospheric waves embedded in the westerlies, a ridge line is considered to be a line drawn through all points at which the anticyclonically curved isobars or contour lines are tangent to a latitude circle. The most common use of this term is to distinguish it from the closed circulation of a high (or anticyclone); but a ridge may include a high (and an upper-air ridge may be associated with a surface high) and a high may have one or more distinct ridges radiating from its center. The opposite of a ridge is a trough. (Sometimes called wedge.) 2. Also used as reference to other meteorological quantities such as equivalent potential temperature, temperature, and mixing ratio. That is, an elongated area of relatively high values of any particular field emanating from a maximum. 3. In oceanography, a linear accumulation of broken ice blocks projecting upward, formed by ice deformation, often at the edge of a floe. A ridge is distinguished from a hummock by being much longer than it is wide. The term ridge is often used to describe an entire ridged ice feature, in which case the portion above the water line is termed the sail and the portion below the water line is termed the keel. | AMS - glossary of meteorology |
| Ridge | A ridge or wall of broken floating ice forced up by pressure. May be fresh or weathered. A corresponding ridge may also occur on the underside of the ice canopy and is called an ice keel. | Illustrated Glossary of Snow and Ice |
| Ridge (ice) | Sea ice terminology describing a line or wall of broken ice forced up by pressure that may be fresh or weathered. Also see ice keel. | Environment and Climate Change Canada 2014 |
| Ridge ice | Ice piled haphazardly one piece over another in the form of ridges or walls. | NOAA Glossary of Hydrologic Terms |
| Ridge ice | Piled ice formed by ridging. | NSIDC accessed 2016 |
| Ridge ice | In hydrologic terms, ice piled haphazardly one piece over another in the form of ridges or walls. | NOAA National Weather Service Glossary 2009 |
| Ridged ice | Ice piled haphazardly one piece over another in the form of ridges or walls. Usually found in first-year ice. | WMO Sea Ice Nomenclature 2017 |
| Ridged ice | Sea ice terminology describing ice that is piled haphazardly, one piece over another in the form of ridges or walls. Usually found in first-year ice. | Environment and Climate Change Canada 2014 |
| Ridged ice belt | Fractured ice piled in the form of several parallel ridges formed at the external boundary of fast ice or on drift divides as a result of repeated pressure. | Bushuyev 2004 |
| Ridged ice zone | Sea ice terminology that describes an area of many ridges with similar characteristics. | Environment and Climate Change Canada 2014 |
| Ridged-ice zone | An area in which much ridged ice with similar characteristics has formed. | WMO Sea Ice Nomenclature 2017 |
| Ridging | Process that occurs when wind, ocean currents, and other forces push sea ice around into piles that rise and form small mountains above the level sea ice surface; ridges are initially thin and transparent with very sharp edges from blocks of ice piling up; also see keels. | NSIDC accessed 2016 |
| Ridging | The pressure process by which sea ice is forced into ridges. A ridge is a line or wall of broken ice forced up by pressure. May be fresh or weathered. The submerged volume of broken ice under a ridge, forced downwards by pressure, is termed an ice keel. In the Antarctic, ridges are commonly point features rather than the long linear features observed in the Arctic. A considerable percentage of ice mass is contained within ridged areas of the Antarctic pack. Data from eight voyages into the East Antarctic pack show that by incorporating the ridged ice, the mean thickness increases, on average, by 1.7 times the observed mean undeformed ice thickness. | ASPECT 2012 |
| Ridging | Sea ice terminology that describes the pressure process by which ice is forced into ridges. | Environment and Climate Change Canada 2014 |
| Ridging | The pressure process by which sea ice is forced into ridges. | WMO Sea Ice Nomenclature 2017 |
| Ridging | Compression mechanism by which ice cover becomes forced up in ridges. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ridging | Pressure process by which floating ice becomes forced up in ridges. | Illustrated Glossary of Snow and Ice |
| Riegel | (from the German) A rock barrier that extends across a glaciated valley, usually comprising harder rock than above and below, and commonly having a smooth up-valley facing slope and a rough down-valley facing slope. | Swisseduc - Photo glossary of glaciological terms |
| Rime | A white or milky and opaque granular deposit of ice formed by the rapid freezing of super-cooled water drops as they impinge upon an exposed object; it is denser and harder than hoarfrost, but lighter, softer, and less transparent than glaze. | NSIDC accessed 2016 |
| Rime | A solid surface deposit formed by the rapid freezing of supercooled water, distinguished from glaze by being less dense. See also hoar. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Rime | Deposit of ice generally formed by the freezing of supercooled fog or cloud droplets on objects the surface temperature of which is below or slightly above 0 degrees C. | WMO METEOTERM accessed 2016 |
| Rime | Deposit of ice composed of grains more or less separated by trapped air. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Rime | A white or milky and opaque granular deposit of ice formed by the rapid freezing of supercooled water drops as they impinge upon an exposed object. It is denser and harder than hoarfrost, but lighter, softer, and less transparent than glaze. Rime is composed essentially of discrete ice granules and has densities as low as 0.2-0.3 g cm-3. Glaze is generally continuous but with some air pockets and has much higher densities. Factors that favor rime formation are small drop size, slow accretion, a high degree of supercooling, and rapid dissipation of latent heat of fusion. The opposite effects favor glaze formation. Both rime and glaze occur when supercooled water drops strike an object at a temperature below freezing. Such formation on terrestrial objects constitutes an ice storm; on aircraft, it is called aircraft icing (where rime is known as rime ice). Either rime or glaze may form on snow crystals, droxtals, or other ice particles in the atmosphere. When such a deposit is wholly or chiefly of rime, snow pellets result; when most or all of the deposit is glaze, ordinary hail or ice pellets result. The alternating clear and opaque layers of some hailstones represent glaze and rime, deposited under varying conditions around the growing hailstone. | AMS - glossary of meteorology |
| Rime | Deposit of ice crystals that occurs when fog or super cooled water droplets comes in contact with an object with a temperature below freezing (0 Celsius). This deposit develops outward on the windward side of the object. | PhysicalGeography.net |
| Rime | A deposit of ice composed of grains more or less separated by trapped air, sometimes adorned with crystalline branches, produced by the rapid freezing of supercooled and very small water droplets. | Illustrated Glossary of Snow and Ice |
| Rime fog | 1. A supercooled fog that deposits rime on exposed objects. See fog deposit. 2. Same as ice fog. | AMS - glossary of meteorology |
| Rime ice | An opaque coating of tiny, white, granular ice particles caused by the rapid freezing of supercooled water droplets on impact with an object. See also clear ice. | NOAA National Weather Service Glossary 2009 |
| Rime ice | Same as rime, but especially applied to rime formation on aircraft. Flight through an extremely supercooled cloud (-10C or colder) is very conducive to rime icing. This type of ice weighs less than clear ice, but it may seriously distort airfoil shape and thereby diminish the lift. In aviation parlance, ice that has the ideal rime character may be called kernel ice, and that intermediate between rime and clear ice may be called milky ice. | AMS - glossary of meteorology |
| Rime rod | A simple, cooled cylindrical rod, usually of metal or glass, that is exposed to the airflow in a cloud to collect supercooled cloud droplets for chemical analysis. The collection efficiency of the rod, which is dependent on the size of the drops, can be calculated. | AMS - glossary of meteorology |
| Ripe | Descriptive of snow that is in a condition to discharge meltwater. Ripe snow usually has a coarse crystalline structure, a snow density near 0.5 kg m-3, and a temperature near 0C. | AMS - glossary of meteorology |
| Ripening of snow | The process by which a snow pack reaches a state where it can yield meltwater, including warming of the snowpack to 0C, wetting of the snow, and coarsening of the snow texture. | AMS - glossary of meteorology |
| Ripple | Small, undulating ridge and furrow (or crest and trough) formed by the action of the flow of water on the bed of a channel, or by the action of the wind on sand or snow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Ripple marks | Corrugation on a snow surface caused by wind (as on sand). | NSIDC accessed 2016 |
| Ripple marks | Corrugations on a snow surface caused by wind (as on sand). | Illustrated Glossary of Snow and Ice |
| River ice | Floating ice formed in rivers. | NSIDC accessed 2016 |
| River ice | Ice formed on a river, regardless of observed location. | WMO Sea Ice Nomenclature 2017 |
| River ice | Sea ice terminology that describes ice that is formed on a river, regardless of where it is observed. | Environment and Climate Change Canada 2014 |
| River ice | Floating ice formed in rivers. | Illustrated Glossary of Snow and Ice |
| River ice statement | A public product issued by the RFC containing narrative and numeric information on river ice conditions. | NOAA National Weather Service Glossary 2009 |
| River ice statement (RVI) | A public product issued by the RFC's containing narrative and numeric information on river ice conditions. | NOAA Glossary of Hydrologic Terms |
| River talik | A layer or body of unfrozen ground occupying a depression in the permafrost table beneath a river. | NSIDC accessed 2016 |
| River talik | A layer or body of unfrozen ground occupying a depression in the permafrost table beneath a river | Van Everdingen International Permafrost Association 2005 |
| River/lake ice | Ice formed on a river or on a lake and which may be exported to sea. River ice fields are depicted on radar images as similar to old fields. Fresh water ice differs significantly in its mechanical and electro-magnetic characteristics from sea ice of the same age. | Bushuyev 2004 |
| Roche moutonnee | A roche moutonnee is a small asymetrically-shaped hill formed by glacial erosion. The upper sides are rounded and smoothed and the lower sides are rough and broken due to quarrying by the glacier. Bedrock knobs are commonly polished on their upper side and are quarried and broken on the lower. These rounded knobs are formed in all sizes. Observers of the 1700s thought they resembled fashionable wavy wigs of their day and named the rouches moutonnees. | Molnia USGS 2004 |
| Roche moutonnee | An elongated, rounded, asymmetrical, bedrock knob produced by glacier erosion. It has a gentle slope on its up-glacier side and a steep- to vertical-face on the down-glacier side. | Molnia USGS 2004 |
| Roche moutonnee | A rocky hillock with a gently inclined, smooth up-valley facing slope resulting from glacial abrasion, and a steep, rough down-valley facing slope resulting from glacial plucking. | Swisseduc - Photo glossary of glaciological terms |
| Roche moutonnee | A feature of glacial erosion that resembles an asymmetrical rock mound. It is smooth and gently sloping on the side of ice advance. The lee-side of this feature is steep and jagged. | PhysicalGeography.net |
| Rock basin | A lake- or sea-filled bedrock depression carved out by a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Rock flour | Fine-grained, silt-size sediment formed by the mechanical erosion of bedrock at the base and sides of a glacier by moving ice. When it enters a stream, it turns the stream's color brown, gray, iridescent blue-green, or milky white. Also called Glacier Flour or Glacier Milk. | Molnia USGS 2004 |
| Rock flour | A fine powder of silt- and clay-sized particles that a glacier creates as its rock-laden ice scrapes over bedrock; usually flushed out in meltwater streams, causing water to look powdery gray; lakes and oceans that fill with glacier flour may develop a banded appearance. | NSIDC accessed 2016 |
| Rock flour | Fine-grained, silt-size sediment formed by the mechanical erosion of bedrock at the base and sides of a glacier by moving ice. When it enters a stream, it turns the stream's color brown, gray, iridescent blue-green, or milky white. Also called Glacier Flour or Glacier Milk. | Molnia USGS 2004 |
| Rock flour | Very finely ground rock fragments that form between the base of a glacier and the underlying bedrock surface. | PhysicalGeography.net |
| Rock glacier | A glacier-like landform that often heads in a cirque and consists of a valley-filling accumulation of angular rock blocks. Rock glaciers have little or no visible ice at the surface. Ice may fill the spaces between rock blocks. Some rock glaciers move, although very slowly. | Molnia USGS 2004 |
| Rock glacier | A glacier-like landform that often heads in a cirque and consists of a valley-filling accumulation of angular rock blocks. Rock glaciers have little or no visible ice at the surface. Ice may fill the spaces between rock blocks. Some rock glaciers move, although very slowly. | Molnia USGS 2004 |
| Rock glacier | Looks like a mountain glacier and has active flow; usually includes a poorly sorted mess of rocks and fine material; may include: (1) interstitial ice a meter or so below the surface ('ice-cemented'), (2) a buried core of ice ('ice-cored'), and/or (3) rock debris from avalanching snow and rock. | NSIDC accessed 2016 |
| Rock glacier | A mass of rock fragments and finer material in a matrix of ice, showing evidence of past or present flow. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Rock glacier | A mass of rock fragments and finer material, on a slope, that contains either interstitial ice or an ice core and shows evidence of past or present movement | Van Everdingen International Permafrost Association 2005 |
| Rock glacier | A mass of rock fragments and finer material, on a slope, that contains either interstitial Ice or an Ice core and shows evidence of past or present movement. It is a cryogenic landform, supersaturated with Ice that if active, moves down slope by the influence of gravity which produces Creep and deformation of the Mountain Permafrost. Rock Glaciers do not form where there is insufficient moisture to form the interstitial Ice that permits movement of the mass. Some are believed to have been formed, at least partly, by burial of Glacier Ice. Active Rock Glaciers possess steep fronts with slope angles greater than the angle of repose. Rock Glaciers are said to be inactive when the main body ceases to move. Most Rock Glaciers have transverse ridges and furrows on their surface. In general, Rock Glaciers present a lobate shape with surficial morphology similar to a lava flow. However, especially in the central Andes, the morphologies can be considerably complex with multiple basins contributing material and the superposition of two or more lobes. | Trombotto et al. 2014 |
| Rock glacier | Rock glaciers are not strictly glaciers, but a flow phenomen in permafrost. A mixture of rock debris interspersed with ice in cavities slowly moves downhill (typically much slower than a glacier). | Swisseduc - Photo glossary of glaciological terms |
| Rock glacier | Lava stream like debris mass containing interstitial ice; Movement is primarily due to debris mass under the influence of gravity, and not due to ice flow patterns; Not a debris covered glacier, but permafrost phenomenon; A glacier-shaped mass of angular rock in a cirque or valley either with interstitial ice, firn and snow or covering the remnants of a glacier, moving slowly downslope. (WGMS 1970); A glacier-shaped mass of angular rock in a cirque or valley either with interstitial ice, firn and snow or covering the remnants of a glacier, moving slowly downslope. If in doubt about the ice content, the frequently present surface; firn field should be classified as 'Glacieret and snowfield' (WGMS 1977); Lava stream like debris mass containing ice in several possible forms and moving slowly down slope (WGMS 1998); A debris covered glacier is not necessarily a rock glacier. To distinguish between rock glaciers and debris covered; glaciers the parameter group 'Debris coverage of tongue' is offered. | Illustrated GLIMS Glacier Classification Manual |
| Rockslide | Several landslides generated by the Great Alaskan Earthquake, Good Friday 1964, fell onto the surface of the so-named glacierin the Chugach Mountains, Alaska. | Molnia USGS 2004 |
| Rotor | Circulation of flow about a horizontal or nearly horizontal axis that is usually associated with flow over the lee side of a barrier, such as a mountain range. The rotation may extend to the ground, cause hazards to aircraft, and carry large amounts of dust aloft. | AMS - glossary of meteorology |
| Rotor cloud | A turbulent, altocumulus-type cloud formation found in the lee of some large mountain barriers, particularly in the Sierra Nevada near Bishop, California. (Sometimes called roll cloud.) The air in the cloud rotates around an axis parallel to the range. The term was first applied to clouds of this type in Europe, especially in the Riesengebirge and on Crossfell. Rotor clouds are often associated with lee wave (lenticular) clouds that may be present above. | AMS - glossary of meteorology |
| Rotten ice | Ice in an advanced stage of disintegration. | NOAA Glossary of Hydrologic Terms |
| Rotten ice | Floating ice which has become honeycombed in the course of melting, and which is in an advanced state of disintegration. | NSIDC accessed 2016 |
| Rotten ice | Sea ice that has become honeycombed and is in an advanced state of disintegration. | WMO Sea Ice Nomenclature 2017 |
| Rotten ice | Sea ice which has become honeycombed (laced) and which is in an advanced state of disintegration. | Bushuyev 2004 |
| Rotten ice | Sea ice terminology that describes ice which has become honeycombed and is in an advanced state of disintegration. | Environment and Climate Change Canada 2014 |
| Rotten ice | Floating ice which has become honeycombed in the course of melting and is in an advanced stage of disintegration. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Rotten ice | Any piece, body, or area of ice that is in the process of melting or disintegrating. It is characterized by honeycomb structure, weak bonding between crystals, or the presence of meltwater or seawater between grains. Rotten ice may appear transparent (and thus dark) when saturated with seawater and so may be easily confused with newly forming black ice. | AMS - glossary of meteorology |
| Rotten ice | Floating ice which has become honeycombed in the course of melting, and which is in an advanced state of disintegration. | Illustrated Glossary of Snow and Ice |
| Rough ice | First-year ice subjected to fracturing and hummocking at the stage of young ice, that has formed as a result of the freezing together of pancake ice or of fragments of fresh ridges that have collapsed into fractures after the end of compaction and the onset of ice divergance. The irregularities cover significant areas where snow accumulation increases and the heat conductivity and the tangential stress coefficient significantly change. During a radar sounding, segments of rough ice are depicted by increased brightness with ice ridges being indiscernible. As a result of further growth, the irregularities at the bottom surface of rough ice are usually completely smoothed by the end of winter and the ice thickness becomes approximately equal to that of ice of the same age of quiet growth. During the period of summer melting, all small irregularities at the surface of ice fields are smoothed; hence this type of relief is typical only of first-year ice. | Bushuyev 2004 |
| Rubber ice | Newly formed sea ice that is weak and elastic. | AMS - glossary of meteorology |
| Run-out distance | The distance an ice avalanche travels from its source. | Swisseduc - Photo glossary of glaciological terms |
| Runoff | (1) Discharge of water divided by the area of the drainage basin contributing water to the measurement cross section, expressed in specific units such as mm w. E. D-1 or kg m-2 s-1. (2) The flux of water leaving the glacier. Sense 2 is common in mass-balance studies, especially in studies of ice-sheet mass balance. See mass-balance units; it is useful to have one word for total flux and a different word for specific flux, so the distinction between discharge and runoff is to be encouraged. Runoff includes meltwater discharge but also water from other sources than melt, such as rainfall. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Runoff | That part of precipitation that does not evaporate and is not transpired, but flows through the ground or over the ground surface and returns to bodies of water. | IPCC WGII AR5 2014 |
| Runoff | The water, derived from precipitation, that ultimately reaches stream channels. | AMS - glossary of meteorology |
| Runoff limit | The altitude above which all rainfall and surface melt, if any, refreezes in the snow or firn, and below which part or all of it runs off the glacier. See zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Rush of snowmelt flood | The rate of change in time of discharge and water surface elevations during spring snowmelt. | AMS - glossary of meteorology |
| S | A jagged pinnacle or tower of glacier ice located on the surface of a glacier, formed as a glacier flows down an icefall or by the intersection of crevasses. Frequently, large areas of a glacier will be covered by s | Molnia USGS 2004 |
| S rac | (from the French) A tower of unstable ice that forms between crevasses, commonly in icefalls or other regions of accelerated glacier flow. | Swisseduc - Photo glossary of glaciological terms |
| Sail | The part of a ridge above sea level; like a sail on a sailboat, it catches wind and moves the ice. | NSIDC accessed 2016 |
| Saline permafrost | Permafrost in which part or all of the total water content is unfrozen because of freezing-point depression due to a high dissolved-solids content of the pore water. | NSIDC accessed 2016 |
| Saline permafrost | Permafrost in which part or all of the total water content is unfrozen because of freezing-point depression due to the dissolved-solids content of the pore water | Van Everdingen International Permafrost Association 2005 |
| Salinity | (1) a general property of aqueous solutions caused by the alkali, alkaline earth, and metal salts of strong acids (Cl, SO4 and NO3) that are not hydrolyzed (2) in soil science, the ratio of the weight of salt in a soil sample to the total weight of the sample. | NSIDC accessed 2016 |
| Salinity | 1. A general property of aqueous solutions caused by the alkali, alkaline earth, and metal salts of strong acids (Cl, SO<SUB>4</SUB> and NO<SUB>3</SUB>) that are not hydrolyzed; 2. In soil science, the ratio of the weight of salt in a soil sample to the total weight of the sample. | Van Everdingen International Permafrost Association 2005 |
| Saltation | Saltation is the mechanism by which snow particles are eroded from or deposited onto the snow surface and transported by the wind near to the surface. The process involves particles bouncing downstream and shattering new particles from the snow surface (King et al., 2008). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Sand snow | Snow that has fallen at very cold temperatures (of the order of -25C). A surface cover of this snow has the consistency of dust or light, dry sand. | AMS - glossary of meteorology |
| Sand wedge | A wedge-shaped body of sand produced by filling of a thermal contraction crack with sand either blown in from above or washed down the walls of the crack | Van Everdingen International Permafrost Association 2005 |
| Sand wedge | A form of ice wedge that contains accumulations of wind blown sand in long vertical layers. A form of periglacial ground ice. | PhysicalGeography.net |
| Sand-wedge polygon | A polygon outlined by sand wedges underlying its boundaries. | NSIDC accessed 2016 |
| Sand-wedge polygon | A polygon outlined by sand wedges underlying its boundaries | Van Everdingen International Permafrost Association 2005 |
| Sandur | (plur. Sandar; from the Icelandic) Extensive flat plain of sand and gravel with braided streams of glacial meltwater flowing across it. Sandar are usually not bounded by valley walls and commonly form in coastal areas. | Swisseduc - Photo glossary of glaciological terms |
| Sastruga | A single sastrugi ridge (in some English-language articles). | AMS - glossary of meteorology |
| Sastrugi | From Russian zastrugi, plural form of zastruga. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Sastrugi | Complex, fragile shapes of snow on top of sea ice that resemble sand dunes; they form parallel to the prevailing wind direction; sastrugi can also form on snow cover over land. | NSIDC accessed 2016 |
| Sastrugi | A variant spelling of zastrugi. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Sastrugi | Sea ice terminology. Describes sharp, irregular ridges formed on a snow surface by wind erosion and snow accumulation. On floating ice, the ridges are parallel to the direction of the wind that was present at the time they were formed. | Environment and Climate Change Canada 2014 |
| Sastrugi | Sharp, irregular ridges formed on a snow surface by wind erosion and deposition. On drift ice the ridges are parallel to the direction of the prevailing wind at the time they were formed. | WMO Sea Ice Nomenclature 2017 |
| Sastrugi | Sharp irregular ridges formed on a snow surface by wind erosion and deposition. The ridges are parallel to the direction of the prevailing wind. The Russian word (zastrugi) is a collective noun and lacks a singular form. An individual ridge in a field of sastrugi has been called a sastruga in some English-language articles. | AMS - glossary of meteorology |
| Sastrugi | Sharp, irregular ridges formed on a snow surface by wind erosion and deposition. The ridges are parallel to the direction of the prevailing wind. | Illustrated Glossary of Snow and Ice |
| Sastrugi syn. zastrugi | A series of long, frequently sharp, wave-like ridges of hard snow characteristic of windswept polar plains when the winds blow continually from one direction. Sastrugi are oriented perpendicular to the wind with a gentle slope to windward and a steep slope to leeward. | WMO METEOTERM accessed 2016 |
| Saturation | The condition in which vapor pressure is equal to the equilibrium vapor pressure over a plane surface of pure liquid water, or sometimes ice. | AMS - glossary of meteorology |
| Scatterometer | A radar designed to measure microwave backscattering, quantified as the scattering coefficient or normalized radar cross section 0, from natural media. Exposed glacier ice in the ablation zone lacks a distinctive mass-balance-related signature at microwave wavelengths. In the percolation zone, subsurface ice lenses are strong scatterers, but there is a sharp reduction in backscattering when meltwater appears at the surface. When wet, the surface becomes a more nearly specular (forward) reflector and appears radar-dark instead of radar-bright. In the dry-snow zone radar returns are unaffected by liquid water, which is absent, and the scattering coefficient contains information on snow grain size and possibly on the accumulation rate. Scatterometers have relatively poor spatial resolution (several to some tens of kilometres), which can be improved by temporal averaging, but they compensate by offering wide and frequent coverage. Seawinds, on the polar-orbiting quikscat satellite (1999-2009) has been a productive scatterometer. Intended for the measurement of ocean-surface wind speeds, it has also proved valuable for measuring the extent and duration of melting on ice caps and ice sheets. See also brightness temperature. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Scavenging by precipitation | Removal of pollutants from the air by either rain or snow. Rainout (or snowout), which is the in-cloud capture of particulates as condensation nuclei, is one form of scavenging. The other form is washout, the below-cloud capture of particulates and gaseous pollutants by falling raindrops. Large particles are most efficiently removed by washout. Small particles (especially those less than 1 'm in diameter) more easily follow the airstream flowing around raindrops and generally avoid capture by raindrops except in heavy rain events. | AMS - glossary of meteorology |
| Scour | (1) Refers to the erosive power of water. (2) Abrasive effects of rocks and sediments incorporated in the ice base of a glacier. | PhysicalGeography.net |
| Scree | Rock debris on the side of or at the foot of a hill or mountain, forming a steep stoney slope. The term may be applied to a mountain feature with such slopes. | UK Antarctic Place-names Committee accessed 2016 |
| Sea breeze | This is the breeze which blows from the sea or a large lake, to the land. The breeze is set off when the temperature of the land is higher than the temperature of the water. The land heats the air above, which rises, and it is then replaced by the cooler air from over the water. (Opposite to the land breeze). | Environment and Climate Change Canada 2014 |
| Sea fog | Fog which forms in the lower part of a relatively moist and warm air mass as it moves over a relatively cooler water surface. This process cools the water vapour to such an extent that it condenses into the suspended water droplets that create the fog. It reduces visibility to less than one-half (1/2) nautical miles. (See also advection fog). | Environment and Climate Change Canada 2014 |
| Sea ice | Any form of ice found at sea which has originated from the freezing of sea water. | NSIDC accessed 2016 |
| Sea ice | Any form of ice found at sea which has originated from the freezing of sea water (sea ice does NOT include superstructure icing). Ice formed from the freezing of the waters of the Great Lakes will be considered the same as sea ice. | NOAA National Weather Service Glossary 2009 |
| Sea ice | Any form of ice found at the freezing of sea water. | WMO Sea Ice Nomenclature 2017 |
| Sea ice | Ice formed at the sea surface by the freezing of sea water. Except where it forms ridges, sea ice is up to a few metres thick, in which respect it differs from shelf ice. See also marine ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Sea ice | Ice, which has originated from the freezing of seawater. It presents the main kind of floating ice encountered at sea. | Bushuyev 2004 |
| Sea ice | Sea ice terminology describing any form of ice found at sea, which has originated from the freezing of water. | Environment and Climate Change Canada 2014 |
| Sea ice | Ice found at the sea surface that has originated from the freezing of seawater. Sea ice may be discontinuous pieces (ice floes) moved on the ocean surface by wind and currents (pack ice), or a motionless sheet attached to the coast (land-fast ice). Sea ice concentration is the fraction of the ocean covered by ice. Sea ice less than one year old is called firstyear ice. Perennial ice is sea ice that survives at least one summer. It may be subdivided into second-year ice and multi-year ice, where multiyear ice has survived at least two summers. | IPCC WGI AR5 2013 |
| Sea ice | Ice that forms by the freezing of sea water. (Cf. ice shelves and icebergs which also float on the sea and are derived from glacier ice on land). | Swisseduc - Photo glossary of glaciological terms |
| Sea ice | 1. Specifically, ice formed by the freezing of seawater; as opposed, principally, to land ice. In brief, it forms first as lolly ice (frazil crystals), thickens into sludge, and coagulates into sheet ice, pancake ice, or into floes of various shapes and sizes. Thereafter, sea ice may develop into pack ice and/or become a form of pressure ice. 2. Generally, any ice floating in the sea. | AMS - glossary of meteorology |
| Sea ice | Any form of ice found at sea which has originated from the freezing of sea water. | Illustrated Glossary of Snow and Ice |
| Sea ice development stage | A phrase used to classify sea ice for operational purposes using the age of the ice as a proxy for its thickness. Specific terms such as new ice, nilas, young ice, and multiyear ice are used for each stage of sea ice development. | NSIDC accessed 2016 |
| Sea ice extent | See ice extent. | NSIDC accessed 2016 |
| Sea ice maximum extent | The day of the year when the sea ice covers the largest area of the Arctic or Antarctic. | NSIDC accessed 2016 |
| Sea ice minimum extent | The day of the year when the sea ice covers the smallest area of the Arctic or Antarctic | NSIDC accessed 2016 |
| Sea loch | The Scottish term for a fjord (q.v.). | Swisseduc - Photo glossary of glaciological terms |
| Sea smoke | Evaporation fog formed when water vapor is added to air which is much colder than the vapor's source; most commonly, when very cold air drifts across relatively warm water; also called steam fog. | NSIDC accessed 2016 |
| Sea smoke | A fog that forms when an outbreak of cold air settles over an expanse of open, relatively warmer water, reducing visibility to less than 1 kilometre. Also known as steam fog. (See also arctic sea smoke, and advection fog or sea fog) | Environment and Climate Change Canada 2014 |
| Sea smoke syn. antarctic sea smoke, arctic sea smoke | Evaporation fog produced above a surface of open water when the air is stable and relatively cold (for example, air which has moved over stretches of ice). | WMO METEOTERM accessed 2016 |
| Sea state | Overall state of agitation of a large expanse of ocean or sea due to the combined effects of wind-generated waves, swell waves, and surface currents. | Environment and Climate Change Canada 2014 |
| Sea state syn. state of sea | Local state of agitation of the sea due to the combined effects of wind and swell. | WMO METEOTERM accessed 2016 |
| Sea surface temperature | Temperature of the water film at the sea surface. | NSIDC accessed 2016 |
| Seasonal freezing index | The cumulative number of degree-days below 0 degrees Celsius, calculated as the arithmetic sum of all the negative and positive mean daily air temperatures (degrees Celsius) for a specific station during the time period between the highest point in the fall and the lowest point the next spring on the cumulative degree-day time curve. | NSIDC accessed 2016 |
| Seasonal freezing index | The cumulative number of degree-days below 0°C, calculated as the arithmetic sum of all the negative and positive mean daily air temperatures (°C) for a specific station during the time period between the highest point in the fall and the lowest point the next spring on the cumulative degree-day time curve | Van Everdingen International Permafrost Association 2005 |
| Seasonal frost | The occurrence of ground temperatures below 0 degrees Celsius for only part of the year; see also active layer. | NSIDC accessed 2016 |
| Seasonal frost | The occurrence of ground temperatures below 0°C for only part of the year | Van Everdingen International Permafrost Association 2005 |
| Seasonal frost | The occurrence of ground temperatures below 0C for only part of the year. | Trombotto et al. 2014 |
| Seasonal ice zone | An area of ocean that extends from the permanent ice zone to the boundary where winter sea ice extent is at a maximum; here, sea ice is present only part of the year; this zone primarily consists of first-year ice. | NSIDC accessed 2016 |
| Seasonal sensitivity characteristic (SSC) | A set of sensitivities, CT,k (in m w. E. K-1) and CP,k (in m w. E.), of Annual mass balance Ba to changes in monthly mean temperature Tk and normalized monthly precipitation Pk / Pref, k , where k = 1, ..., 12 is the month index and Pref, k, is the monthly precipitation averaged over a reference period. The SSC, which is estimated either from observations or from model calculations, was introduced by Oerlemans and Reichert (2000). It consists of two sets of 12 numbers each: bba a C C ;T k P k , T P P ( / k k ref, k ) Describing seasonal sensitivity with a resolution of 1 month is a matter of convenience. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Seasonal snow | (1) snow that accumulates during one season. (2) Snow that lasts for only one season. | NSIDC accessed 2016 |
| Seasonal snow | Snow that accumulates during one season and does not last for more than one year. See also perennial. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Seasonal thawing index | The cumulative number of degree-days above 0 degrees Celsius, calculated as the arithmetic sum of all the positive and negative mean daily air temperatures (degrees Celsius) for a specific station during the time period between the lowest point in the spring and the highest point the next fall on the cumulative degree-day time curve. | NSIDC accessed 2016 |
| Seasonal thawing index | The cumulative number of degree-days above 0°C, calculated as the arithmetic sum of all the positive and negative mean daily air temperatures (°C) for a specific station during the time period between the lowest point in the spring and the highest point the next fall on the cumulative degree-day time curve | Van Everdingen International Permafrost Association 2005 |
| Seasonally frozen ground | Ground that freezes and thaws annually. | NSIDC accessed 2016 |
| Seasonally frozen ground | Ground that freezes and thaws annually | Van Everdingen International Permafrost Association 2005 |
| Seasonally frozen layer (SFL) | The active layer in areas without permafrost. | NSIDC accessed 2016 |
| Seasonally frozen layer (SFL) | Active layer" in areas without permafrost" | Van Everdingen International Permafrost Association 2005 |
| Seasonally thawed ground | Ground that thaws and refreezes annually. | NSIDC accessed 2016 |
| Seasonally thawed ground | Ground that thaws and refreezes annually | Van Everdingen International Permafrost Association 2005 |
| Seasonally thawed layer (STL) | The active layer in permafrost areas. | NSIDC accessed 2016 |
| Seasonally thawed layer (STL) | The active layer in permafrost areas | Van Everdingen International Permafrost Association 2005 |
| Seasonally-active permafrost | The uppermost layer of the permafrost which undergoes seasonal phase changes due to the lowered thawing temperature and freezing-point depression of its pore water. | NSIDC accessed 2016 |
| Seasonally-active permafrost | The uppermost layer of the permafrost which undergoes seasonal phase changes due to the lowered thawing temperature and freezing-point depression of its pore water | Van Everdingen International Permafrost Association 2005 |
| Second-year ice | Sea ice which has not melted in the first summer of its existence; by the end of the second winter, it attains a thickness of 2 meters (6.6 feet) or more; it stands higher out of the water than first-year ice; summer melting has somewhat smoothed and rounded the hummocks, which accentuation of minor relief by differential melting may have caused others to develop; bare patches and puddles are usually greenish-blue. | NSIDC accessed 2016 |
| Second-year ice | Old ice which has survived only one summer's melt. Because it is thicker and less dense than first-year ice, it stands higher out of the water. In contrast to multi-year ice, summer melting produces a regular pattern of puddles. Bare patches and puddles are usually greenish-blue. The regular pattern of puddles produced during the melt season is only a feature of Arctic se ice. Melt water does not usually accumulate on the surface of Antarctic sea ice. Second-year ice is the most common form of old ice present in Antarctica. | ASPECT 2012 |
| Second-year ice | Old ice that has survived only one summer's melt. Because it is thicker and less dense than first-year ice, it stands higher out of the water. In contrast to multiyear ice, summer melting produces a regular pattern of numerous small puddles. Bare patches and puddles are usually greenish-blue. | WMO Sea Ice Nomenclature 2017 |
| Second-year ice | Old ice which has survived only one summer's melt; typical thickness up to 2.5 m and sometimes more. Because it is thicker than first-year ice, it stands higher out of the water. Ridged features as a result of melting during the preceding summer attain a smoothed rounded shape. In summer, numerous puddles of extended irregular shape form on its surface. Bare ice patches and puddles r usually greenish-blue. | Bushuyev 2004 |
| Second-year ice | Sea ice terminology. Describes old ice which has survived only one summer's melt. Thicker than first-year ice, it stands higher out of the water. In contrast to multi-year ice, summer melting of second-year ice produces a regular pattern of numerous small puddles. In this case, bare patches and puddles are usually greenish-blue. | Environment and Climate Change Canada 2014 |
| Second-year ice | Sea ice that has survived only one summer melt season. | AMS - glossary of meteorology |
| Second-year ice | Sea ice which has not melted in the first summer of its existence. By the end of the second winter it attains a thickness of 2 m and more. It stands higher out of the water than first-year ice. Summer melting has somewhat smoothed and rounded the hummocks, while accentuation of minor relief by differential melting may have caused others to develop. Bare patches and puddles are usually greenish-blue. | Illustrated Glossary of Snow and Ice |
| Secondary ice crystal | An ice crystal formed by a process other than homogeneous or heterogeneous nucleation, as by shatter of a drop freezing on accretion, or breakup of an ice particle on evaporation. | AMS - glossary of meteorology |
| Sedimentary ogives | Alternating bands of light and dark at the firn limit of a glacier; the light bands are usually young and lightest at the highest level up-glacier, becoming increasingly older and darker as they progress down-glacier. | NSIDC accessed 2016 |
| Sedimentary stratification | The annual layering that forms from the build-up of snow in the accumulation area of a glacier. It is preserved in firn and sometimes in glacier ice. | Swisseduc - Photo glossary of glaciological terms |
| Segregated ice | Ice in discrete layers or ice lenses, formed by ice segregation. | NSIDC accessed 2016 |
| Segregated ice | Ice in discrete layers or ice lenses, formed by ice segregation | Van Everdingen International Permafrost Association 2005 |
| Segregated ice | Ice in discrete layers or Ice lenses, formed by Ice Segregation. It can range in thickness from hairline to more than 10 m. It commonly occurs in alternating layers of Ice and soil. | Trombotto et al. 2014 |
| Segregated ice | A form of periglacial ground ice that consists of almost pure ice that often exists as an extensive horizontal layer. The ice layer grows because of the active migration of water from around the feature. These features are found just below the active layer. | PhysicalGeography.net |
| Segregation potential | The ratio of the rate of moisture migration to the temperature gradient in a frozen soil near the 0 degrees Celsius isotherm. | NSIDC accessed 2016 |
| Segregation potential | The ratio of the rate of moisture migration to the temperature gradient in a frozen soil near the 0°C isotherm | Van Everdingen International Permafrost Association 2005 |
| Semipermanent anticyclone | High pressure area largely predominate during a major portion of the year where an anticyclone appears on the mean monthly pressure charts. | NSIDC accessed 2016 |
| Sensible heat polynya | A polynya that forms from the upwelling of warm (above-freezing) ocean water from lower depths; these can form in mid-ocean areas, far from coasts or other barriers. | NSIDC accessed 2016 |
| Serac | An isolated block of ice that is formed where the glacier surface is fractured. | NSIDC accessed 2016 |
| Serac | A tower or block of glacier ice bounded by intersecting crevasses. The term is of French origin. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Serac | A large block of ice, generally taller than broad, formed by the fracturing of ice. Most commonly found within an icefall, at the edge of an ice cliff, or at the margins of fast- moving ice. | AMS - glossary of meteorology |
| Seracs | Seracs are the pinnacles of ice formed where the glacier surface is torn by sets of crevasses. | Molnia USGS 2004 |
| Settlement | The settlement of snow is the result of creep under the action of overburden pressure as well as of metamorphic processes going on within the snowpack. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Severe icing | The rate of ice accumulation on an aircraft is such that de-icing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary. | NOAA National Weather Service Glossary 2009 |
| Shale ice | Mass of thin and brittle plates of freshwater ice formed by breaking up of thin, skin ice into small pieces lumped together. | AMS - glossary of meteorology |
| Shear ridge | A ridge formed primarily by shear deformation, usually found along the boundary between fast ice and pack ice. | AMS - glossary of meteorology |
| Shear zone | A zone of severe deformation, especially where a fast-flowing ice stream (q.v.) moves past relatively slow-moving ice. The deformation is characterised especially by intense crevassing. | Swisseduc - Photo glossary of glaciological terms |
| Shearing | An area of pack ice is subject to shear when the ice motion varies significantly in the direction normal to the motion, subjecting the ice to rotational forces. These forces may result in phenomena similar to a flaw. | WMO Sea Ice Nomenclature 2017 |
| Shearing | Mutual displacement of ice floes resulting in their turn and deformation and formation of fractures. | Bushuyev 2004 |
| Shearing | Sea ice terminology. An area of floating ice is subject to shear when the ice motion varies significantly from its main direction, subjecting the ice to rotational forces. These forces may result in phenomena similar to a flaw. | Environment and Climate Change Canada 2014 |
| Sheet frost | A thick coating of rime formed on windows and other surfaces. | AMS - glossary of meteorology |
| Sheet ice | Ice formed by the freezing of liquid precipitation or the freezing of melted solid precipitation (see snow depth) | NOAA National Weather Service Glossary 2009 |
| Sheet ice | Ice formed in a smooth thin layer on a water surface by the coagulation of frazil through rapid freezing. | AMS - glossary of meteorology |
| Shelf ice | Ice forming part of an ice shelf, whether glacier ice, marine ice or ice originating from accumulation on the surface of the ice shelf. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Shell ice | Ice, on a body of water, that remains as an unbroken surface when the water level drops so that a cavity is formed between the water surface and the ice. (Also called cat ice.) | AMS - glossary of meteorology |
| Ship icing | The icing resulting from freezing spray on a ship's hull, decks and superstructure. | WMO METEOTERM accessed 2016 |
| Shoal | A place where the depth of water is shallow, especially where the seafloor is visible at low tide. | Environment and Climate Change Canada 2014 |
| Shore ice | An ice sheet in the form of a long border attached to the bank or shore; border ice. | NOAA Glossary of Hydrologic Terms |
| Shore ice | Basic form of fast ice: a compact ice cover attached to the shore and, in shallow waters, also grounded. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Shore ice | Compact sea ice that is attached to the shore or to anchoring points on the sea bed. It is a type of fast ice, and may sometimes be rafted ice or ice that has been beached by wind, tides, currents, or by ice pressure. | AMS - glossary of meteorology |
| Shore lead | A stretch of navigable water between pack ice and the shore. | NSIDC accessed 2016 |
| Shore lead | A lead between pack ice and the shore or between drift ice and an ice front. | Bushuyev 2004 |
| Shore lead | A lead between pack ice and the shore or between pack ice and an ice front. | WMO Sea Ice Nomenclature 2017 |
| Shore lead | Sea ice terminology meaning a lead between ice and the shore, or between ice and an ice front. | Environment and Climate Change Canada 2014 |
| Shore lead | A stretch of navigable water between pack ice and the shore (cf. Flaw lead). | Illustrated Glossary of Snow and Ice |
| Shore polynya | A polynya between pack ice and the coast, or between pack ice and an ice front. | WMO Sea Ice Nomenclature 2017 |
| Shore polynya | Sea ice terminology describing a polynya between ice and the coast, or between ice and an ice front. | Environment and Climate Change Canada 2014 |
| Short-term strength | The failure strength of a material under a short-term loading (e.g. Up to about 10 minutes in a uniaxial compression test). | NSIDC accessed 2016 |
| Short-term strength | The failure strength of a material under a short-term loading (e.g. up to about 10 minutes in a uniaxial compression test) | Van Everdingen International Permafrost Association 2005 |
| Shuga | A form of new ice, composed of spongy, white lumps a few cm across, that tend to form in rough seas; they resemble slushy snow balls. | NSIDC accessed 2016 |
| Shuga | An accumulation of spongy white ice lumps, a few centimeters across; they are formed from grease ice or slush and sometimes from anchor ice rising to the surface. | Bushuyev 2004 |
| Shuga | An accumulation of spongy white ice lumps, a few inches (centimeters) across; they are formed from grease ice or slush and sometimes from ice rising to the surface. | WMO Sea Ice Nomenclature 2017 |
| Shuga | Sea ice terminology meaning an accumulation of spongy white ice lumps that have a diameter of a few centimeters across. Shuga are formed from grease ice or slush, and sometimes from anchor ice rising to the surface. | Environment and Climate Change Canada 2014 |
| Shuga | Accumulation of spongy white ice lumps, a few centimetres across, formed from grease ice or slush, and sometimes from anchor ice rising to the surface. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Shuga | An accumulation of spongy, whitish chunks of ice a few centimeters across formed from grease ice or slush. It forms instead of pancake ice if the freezing takes place in seawater that is considerably agitated. | AMS - glossary of meteorology |
| Shuga | An accumulation of spongy white ice lumps, a few cm across, formed from grease ice or slush, and sometimes from anchor ice rising to the surface. | Illustrated Glossary of Snow and Ice |
| Shuga ice | An accumulation of spongy white lumps, a few centimetres across; they are formed from grease ice or slush and sometimes from anchor ice rising to the surface. With the interaction of surface winds and waves, shuga may line up along the wind direction and form characteristic ice bands. | ASPECT 2012 |
| Siberian high | An area of high pressure that forms over Siberia in winter and that is particularly apparent on mean charts of sea level pressure. Its center is near Lake Baikal, where the average sea level pressure exceeds 1030 mb from late November to early March. This anticyclone is enhanced by the surrounding mountains that prevent the cold air from flowing away readily. In the center of the anticyclone the normal clockwise circulation is replaced by katabatic winds down the river valleys, but to the east along the Pacific Coast there is a belt of very strong northerly winds. The offshore flow is known as the winter monsoon. In summer the Siberian high is replaced by a low pressure area. (Or Siberian anticyclone.) | AMS - glossary of meteorology |
| Siberian high | High pressure system that develops in winter over northern central Asia. | PhysicalGeography.net |
| Sikussak | Very old, thick sea ice that forms in fjords; it often resembles glacial ice, because snow can pile up on the ice over many years. | NSIDC accessed 2016 |
| Sikussak | Very old sea ice trapped in fjords. It resembles glacier ice because snowfall and snowdrifts contribute to its formation. | AMS - glossary of meteorology |
| Silt cappings | Concentration of silt in bands, zones or layers adhered to coarser grains. This is a cryogenic phenomenon caused by freeze-thaw cycles that are responsible for the downward silt movements. Some authors explain these conditions as fragipan formations. | Trombotto et al. 2014 |
| Silver frost | Colloquial expression for a deposit of glaze built up on trees, shrubs, and other exposed objects during a fall of freezing precipitation; the product of an ice storm. (Also called silver thaw.) | AMS - glossary of meteorology |
| Simple basin | Glacier is fed from one single basin; Catchment area is detectable; Defined and limited by underlying or surface topographic features; Develops a glacier tongue out of one basin; Single accumulation area; Does not need to be located in a valley (-> Mountain glacier) | Illustrated GLIMS Glacier Classification Manual |
| Single-phase thermosyphon | A passive heat transfer device, filled with either a liquid or a gas, installed to remove heat from the ground. | NSIDC accessed 2016 |
| Single-phase thermosyphon | A passive heat transfer device, filled with either a liquid or a gas, installed to remove heat from the ground | Van Everdingen International Permafrost Association 2005 |
| Sintering | The bonding together of ice crystals. | NSIDC accessed 2016 |
| Sintering | The process by which intergranular bonds form in a powder or porous material such as snow dry or wet, decreasing thereby the surface energy of the material. In dry snow, direct deposition of water vapour diffusing through the pore space is usually the dominant bond growth mechanism, but several other mechanisms may contribute depending on the prevailing conditions surface, volume, and grain boundary diffusion as well as plastic flow. Externally applied pressures, e.g., overburden by snow or ice, assist the sintering process by so-called pressure sintering. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Sintering | Sintering is the process whereby ice crystals adhere through the diffusion of water vapor from regions of positive curvature to regions of negative curvature, such as the boundary between the two crystals. | AMS - glossary of meteorology |
| Skavler | A Norwegian word generally equivalent to sastrugi. | AMS - glossary of meteorology |
| Skylight | From the point of view of the submariner, thin places in the ice canopy, usually less than 3 ft (1 m) thick and appearing from below as relatively light, translucent patches in dark surroundings. The undersurface of a skylight is normally flat. Skylights are called large if big enough for a submarine to attempt to surface through them, or small if not. | WMO Sea Ice Nomenclature 2017 |
| Skylight | Sea ice terminology. Describes the thin places in an ice canopy, usually less than 1 meter thick, that appear from below as light, translucent patches in dark surroundings. The under surface of skylights are normally flat. They are termed small or large; if they are big enough for a submarine to attempt to surface through them (120 meters wide or more) they qualify as large. | Environment and Climate Change Canada 2014 |
| Sleet | (1) (United States) frozen raindrops that bind on impact with the ground (2) (elsewhere) a mix of rain and snow, a mix of rain and hail, or melting snow. | NSIDC accessed 2016 |
| Sleet | (PL) - Sleet is defined as pellets of ice composed of frozen or mostly frozen raindrops or refrozen partially melted snowflakes. These pellets of ice usually bounce after hitting the ground or other hard surfaces. Heavy sleet is a relatively rare event defined as an accumulation of ice pellets covering the ground to a depth of ' or more. | NOAA National Weather Service Glossary 2009 |
| Sleet | Depending on the region, precipitation of rain and snow mixed, or rain and hail, or rain and ice pellets, or melting snow, or sudden and briel rainfall with wind and hail. | WMO METEOTERM accessed 2016 |
| Sleet | Generally refers to a mixture of rain and snow or falling snow that is melting into rain. | Australian Bureau of Meteorology 2016 |
| Sleet | Precipitation of mixed rain and snow, mixed rain and hail or snow melting as it falls. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Sleet | 1. See ice pellets. 2. In British terminology, and colloquially in some parts of the United States, precipitation in the form of a mixture of rain and snow. | AMS - glossary of meteorology |
| Sleet | See ice pellets. | PhysicalGeography.net |
| Sleet | Precipitation of snow and rain together, or of snow melting as it falls. | Illustrated Glossary of Snow and Ice |
| Slope angle | Slope angle Ψ is the acute angle measured from the horizontal to the plane of a slope. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Slope failure | Mass movement of earth material down a slope; includes landslides, mudslides, debris flows, avalanches, etc; speed of movement can be sudden and catastrophic or slow. | NSIDC accessed 2016 |
| Sludge | A dense accumulation of frazil (or lolly ice); an early stage in the freezing of a body of water. (Also called slush.) The sea surface becomes thick and soupy and sometimes greasy in appearance. Sludge depth seldom exceeds one foot. | AMS - glossary of meteorology |
| Sluff | A small downhill movement of snow. | AMS - glossary of meteorology |
| Slush | A mixture of snow and grease ice. | NSIDC accessed 2016 |
| Slush | Snow which is saturated and mixed with water on land or ice surfaces, or as a viscous floating mass in water after heavy snowfall. | ASPECT 2012 |
| Slush | Sea ice terminology describing snow which is saturated and mixed with water on land, on ice surfaces, or as a thick floating mass in water, after a heavy snowfall. | Environment and Climate Change Canada 2014 |
| Slush | Snow or firn mixed with an amount of liquid water equaling or exceeding that required to fill the voids; soaked snow. Slush avalanches ('slushflows') can be a significant means of downslope transfer of mass, and hence of accelerating ablation by melting because of the increase of temperature with decreasing altitude. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Slush | Snow that is saturated and mixed with water on land or ice surfaces, or as a viscous floating mass in water after a heavy snowfall. | WMO Sea Ice Nomenclature 2017 |
| Slush | Snow which is saturated and mixed with water on land or ice surfaces, or as a viscous floating mass in water after a heavy snowfall. | Bushuyev 2004 |
| Slush | Snow which is saturated and mixed with water, found on land or ice surfaces, or as a viscous floating mass in water after heavy snowfalls. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Slush | 1. Snow or ice on the ground that has been reduced to a soft watery mixture by rain, warm temperature, and/or chemical treatment. 2. Same as sludge. | AMS - glossary of meteorology |
| Slush | Snow which is saturated and mixed with water; found on land or ice surfaces, or as a viscous floating mass in water after heavy snowfall. | Illustrated Glossary of Snow and Ice |
| Slush flow | (Or slush avalanche) A fast-flowing mass of water-saturated snow, most commonly occurring in early summer when melting is at its peak. | Swisseduc - Photo glossary of glaciological terms |
| Slush ice | Ice mass consisting of transformed frazil ice (partly as bunches or lumps of snow slush), anchor ice and shale ice. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Slush icing | The accumulation of ice and water on exposed surfaces of aircraft when the craft is flown through wet snow and liquid drops at temperatures near 0C. | AMS - glossary of meteorology |
| Slush limit | A synonym of runoff limit. See zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Slush zone | Common near the snow line on a relatively flat portion of a glacier where melting snow forms slush. | NSIDC accessed 2016 |
| Slush zone | The part of the glacier between the snowline and the runoff limit, that is, the lowest part of the percolation zone. See zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Slushflow | A mudflow-like outburst of water-saturated, i.e., soaked snow (see slush, mfsl), often along a stream course. Commonly occurring after rainfall and/or intense thawing have produced more water than can drain through the snow. A flowing mixture of snow and water. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Small hail | Technically used to refer to snow pellets or graupel. | NOAA National Weather Service Glossary 2009 |
| Small hail | Precipitation of translucent ice particles, which falls from a cloud. These particles are almost always spherical and sometimes have conical tips. Their diameter may attain or even exceed five millimetres. | WMO METEOTERM accessed 2016 |
| Small hail | Hail with a diameter less than 0.5 cm. | AMS - glossary of meteorology |
| Small ice cake | An ice cake less than 2 m across. | Bushuyev 2004 |
| Small ice cake | An ice cake less than 7 ft (2 m) across. | WMO Sea Ice Nomenclature 2017 |
| Small ice cake | Sea ice terminology that describes an ice cake that is less than 2 meters across. | Environment and Climate Change Canada 2014 |
| Small ice field | An ice field 5 to 10 n mi (10-15 km) across. | WMO Sea Ice Nomenclature 2017 |
| Small ice field | Sea ice terminology that describes an ice field that is 10 km to 15 km across. | Environment and Climate Change Canada 2014 |
| Small Iceberg | Sea ice terminology that describes a piece of glacier ice extending 5 m to 15 m above sea level, and with a length of 15 m to 60 meters. | Environment and Climate Change Canada 2014 |
| Snezhnik (Russian) | A perennial snow patch . | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snotel | Snow telemetry - An automated network of snowpack data collection sites. The Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service (SCS), has operated the Federal-State-Private Cooperative Snow Survey Program in the western United States since 1935. A standard SNOTEL site consists of a snow pillow, a storage type precipitation gage, air temperature sensor and a small shelter for housing electronics. | NOAA National Weather Service Glossary 2009 |
| Snout | The lower part of the ablation area of a valley glacier, commonly shaped like the snout of an animal. In North America, the term toe is more widely used. | Swisseduc - Photo glossary of glaciological terms |
| Snout | Front end of a glacier. Also called the terminus. | PhysicalGeography.net |
| Snow | Frozen precipitation in the form of white or translucent ice crystals in complex branched hexagonal form. It most often falls from stratiform clouds, but can fall as snow showers from cumuliform ones. At temperatures than -5 | Canada National Climate Archive 2015 |
| Snow | (1) an ice particle formed by sublimation of vapor in the atmosphere (2) a collection of loosely bonded ice crystals deposited from the atmosphere; high density snow (greater than 550 kilograms per cubic meter; 34 pounds per cubic foot) is called firn if it is older than one year. | NSIDC accessed 2016 |
| Snow | (1) Solid precipitation in the form of ice crystals, chiefly in complex branched hexagonal form and often agglomerated into snowflakes; or an accumulation of the same on the Earth's surface. (2) Solid precipitation that has accumulated on the summer surface on a glacier and that transforms to firn at the end of the mass-balance year. See zone. In this sense, which prevails almost universally in the study of mass balance, snow may contain ice in the form of lenses or pipes which are the result of refreezing of meltwater. (3) An accumulation of solid precipitation on a glacier that has not yet attained a density through compaction sufficient to restrict the circulation of air and water significantly. In this structural sense, the dividing line between snow and firn is diffuse but is conventionally taken to be near to a density of 400 kg m-3. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snow | Precipitation in the form of ice crystals, mainly of intricately branched, hexagonal form and often agglomerated into snowflakes, formed directly from the freezing [deposition] of the water vapor in the air. | NOAA National Weather Service Glossary 2009 |
| Snow | Precipitation in the form of small ice crystals which may fall singly or in flakes. Deposited snow is a highly porous material that builds up the snow cover on the ground. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow | Precipitation of ice crystals, isolated or as part of a cluster, falling from a cloud. | Environment and Climate Change Canada 2014 |
| Snow | Precipitation of ice crystals, isolated or agglomerated, falling from a cloud. | WMO METEOTERM accessed 2016 |
| Snow | Precipitation of ice crystals, most of which are branched (sometimes star shaped). | Australian Bureau of Meteorology 2016 |
| Snow | (1) Atmospheric precipitation of ice crystals. (2) Loose and porous aggregation of ice crystals or their fragments on any surface. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow | Ice crystals precipitated from the atmosphere, mainly in complex hexagon (plate, column or needle) form, often agglomerated into snowflakes | Van Everdingen International Permafrost Association 2005 |
| Snow | Ice crystals precipitated from the atmosphere, mainly in complex hexagon (plate, column or needle) form, often agglomerated into Snowflakes. | Trombotto et al. 2014 |
| Snow | Precipitation composed of white or translucent ice crystals, chiefly in complex branch hexagonal form and often agglomerated into snowflakes. For weather-observing purposes, the intensity of snow is characterized as 1) light when the visibility is 1 km (5/8 statute mile) or more; 2) moderate when the visibility is less than 1 km (5/8 statute mile) but not more than 1/2 km (5/16 statute mile); and 3) heavy when the visibility is less than 1/2 km (5/16 statute mile). | AMS - glossary of meteorology |
| Snow | A type of solid precipitation that forms in clouds with an air temperature below freezing. Snow forms when water vapor deposits directly as a solid on a deposition nuclei. Snowflakes begin their life as very tiny crystals developing on a six-sided hexagonal deposition nuclei. The developing snowflak, then grows fastest at the six points of the nuclei as these surfaces are more exposed to atmosphere's water vapor. Snowfall is most common with the frontal lifting associated with mid-latitude cyclones during fall, winter, and spring months when air temperatures are below freezing. | PhysicalGeography.net |
| Snow | Precipitation of ice crystals, most of which are branched (sometimes star-shaped). The branched crystals are sometimes mixed with unbranched crystals. At temperatures higher than about -5 C the crystals are generally agglomerated into snowflakes. | Illustrated Glossary of Snow and Ice |
| Snow / drift snow | Snow; Wind transported snow and accumulation in lee sides; Hoar | Illustrated GLIMS Glacier Classification Manual |
| Snow accumulation | A measurement of the depth of snow on the ground made either since the snow began falling or since a previous observation. (also called snow depth.) The total accumulation is equivalent to the total snow depth during a storm, or after any single snowstorm or series of storms. Snow accumulation can vary due to settling and melting and will therefore vary depending on how often it is measured. For example, if new snow is measured every hour during a relatively long duration storm, it is likely that the summed accumulations may exceed a total snow accumulation measured only once at the end of the storm. | AMS - glossary of meteorology |
| Snow accumulation and ablation model | A model which simulates snow pack accumulation, heat exchange at the air-snow interface, areal extent of snow cover, heat storage within the snow pack, liquid water retention, and transmission and heat exchange at the ground-snow interface. | NOAA Glossary of Hydrologic Terms |
| Snow accumulation and ablation model | In hydrologic terms, a model which simulates snow pack accumulation, heat exchange at the air-snow interface, areal extent of snow cover, heat storage within the snow pack, liquid water retention, and transmission and heat exchange at the ground-snow interface. | NOAA National Weather Service Glossary 2009 |
| Snow avalanche | Mass of snow which becomes detached and slides swiftly down a slope. Large snow avalanches may contain rocks, soil, vegetation, or ice. Avalanche formation was comprehensively reviewed by Schweizer et al. (2003). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow banner | Snow being blown from a mountain crest. (Also called snow smoke, snow plume.) It is sometimes mistaken for volcanic smoke or a banner cloud. | AMS - glossary of meteorology |
| Snow banner syn. snow plume, snow smoke | Snow which is being blown from a mountain crest. | WMO METEOTERM accessed 2016 |
| Snow barchan | Horseshoe-shaped snowdrift, with the ends pointing down-wind. | NSIDC accessed 2016 |
| Snow barchan | Horseshoe-shaped snowdrift, with the ends pointing down-wind. | Illustrated Glossary of Snow and Ice |
| Snow blindness | Impaired vision or temporary blindness caused by sunlight reflected from snow surfaces. | WMO METEOTERM accessed 2016 |
| Snow blindness | Impaired vision or temporary blindness caused by sunlight reflected from snow surfaces. The medical name is niphablepsia. "Symptoms of snow blindness are a gritty sensation under the eyelids, excessive watering, double vision. First aid is to place the casualty in the dark or bandage the eyes; application of cool compresses alleviates pain. Most cases will recover in 18 hours without medical treatment"(from Glossary of Arctic and Subarctic Terms 1955). | AMS - glossary of meteorology |
| Snow blink | A relatively bright region on the underside of clouds produced by the reflection of light by snow. (Also called snow sky.) This term is used in polar regions where it contributes to the sky map; snow blink is brighter than ice blink, or reflection of light by land or water. | AMS - glossary of meteorology |
| Snow blink syn. snow sky | A glare on the underside of clouds, produced by the reflection of light from a snow-covered surface. | WMO METEOTERM accessed 2016 |
| Snow board | A specially constructed board used to identify the surface of snow that has been recently covered by snowfall. | NSIDC accessed 2016 |
| Snow board | Marker at least 40 centimetres by 40 centimetres which is laid on a previous accumulation of snow, so that freshly fallen snow can be identified and extracted, and its depth measured. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow board | Specially constructed board used to identify the surface of snow or ice that has been covered by more recent snowfall. Snow boards are used as an aid in obtaining representative samples of solid precipitation at times when the catch in the gauge is considered erroneous, for example, in windy weather and wet snow. They provide the reference level for the measurement of new snowfall and ice. They are constructed of thin metal, wood, or other light material so as to not sink in the snow. They should be at least 40 cm by 40 cm and covered with white cloth or plastic. | AMS - glossary of meteorology |
| Snow bridge | An arch formed by snow which has drifted across a crevasse, forming first a cornice, and ultimately a covering which may completely obscure the opening. | NSIDC accessed 2016 |
| Snow bridge | Snow covering (and often hiding) a crevasse. Snow bridges are a common threat to climbers on a snow-covered part of a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Snow bridge | An arch formed by snow which has drifted across a crevasse, forming first a cornice, and ultimately a covering which may completely obscure the opening. | Illustrated Glossary of Snow and Ice |
| Snow cap | Snow covering the ridges and peaks of mountains when no snow exists at lower elevations. | AMS - glossary of meteorology |
| Snow classification | The systematic description of a snow cover, usually seasonal rather than perennial, recording morphological, process-related and other attributes. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snow cloud | Any cloud from which snow falls; a popular term having no technical connotation. | AMS - glossary of meteorology |
| Snow concrete | Snow that has been compressed at low temperatures and that sets into a tough substance of considerably greater strength than uncompressed snow (from Glossary of Arctic and Subarctic Terms 1955). | AMS - glossary of meteorology |
| Snow core | A sample of either freshly fallen snow, or the combined old and new snow on the ground. This is obtained by pushing a cylinder down through the snow layer and extracting it. | NOAA Glossary of Hydrologic Terms |
| Snow core | A sample of snow, either just the freshly fallen snow or the combined old and new snow on the ground, obtained by pushing a cylinder down through the snow layer and extracting it. | NSIDC accessed 2016 |
| Snow core | A sample of either freshly fallen snow, or the combined old and new snow on the ground. This is obtained by pushing a cylinder down through the snow layer and extracting it. | NOAA National Weather Service Glossary 2009 |
| Snow cornice | A mass of snow or ice projecting over a mountain ridge. | NOAA National Weather Service Glossary 2009 |
| Snow course | Line laid out and permanently marked, along which snow is sampled, or its depth measured, at appropriate times at stations separated by definite distances. (TR) | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow course | An established line or transect of measurements of snow water equivalent across a snow field in representative mountainous terrain, where appreciable snow accumulates, to monitor seasonal snowpack. Although intended to be measured over a distance of several hundred meters, in practice snow courses may consist of four or so individual measurements. The measurements are used for runoff prediction and for assessing the potential for flooding or drought, and they are also used in longer- term climatological studies. Along the snow course, core samples are taken periodically (often monthly) throughout the snow season. Approximately 300 snow courses are operated over the western United States. | AMS - glossary of meteorology |
| Snow cover | (1) in general, the accumulation of snow on the ground surface (2) the areal extent of snow-covered ground, usually expressed as percent of total area in a given region. | NSIDC accessed 2016 |
| Snow cover | In general, the accumulation of snow on the ground surface, and in particular, the areal extent of snow-covered ground (NSIDC, 2008); term to be preferably used in conjunction with the climatologic relevance of snow on the ground. See also snowpack. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow cover | Covering of the ground, either completely or partially, by snow. | WMO METEOTERM accessed 2016 |
| Snow cover | Snow accumulated on the ground. (TR) | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow cover | The Accumulation of fallen Snow covering the ground. | Trombotto et al. 2014 |
| Snow cover | 1. The areal extent of snow-covered ground, usually expressed as percent of total area in a given region. 2. In general, a layer of snow on the ground surface. Compare snowfield, snowpack. 3. The depth of snow on the ground, usually expressed in inches or centimeters. | AMS - glossary of meteorology |
| Snow cover extent | The areal extent of snow covered ground. | IPCC WGI AR5 2013 |
| Snow cover period | Period of consecutive days with snow cover. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow coverage | Ratio of the snow covered area to the total area of a basin. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow covered area | Snow covered area SCA is defined as the areal extent of snow-covered ground, usually expressed as a fraction (%) of the total area investigated. The latter must be defined, e.g., observation site, catchment, district, country, continent. Unless otherwise specified, only seasonal snow cover is considered. Hence, on glaciers and névés, ground refers either to glacier ice or to an old firn surface. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow crust | A crisp, firm, outer surface upon snow. Basically, three types of snow crusts exist, formed by 1) the refreezing of surface snow, after melting and/or wetting, to form a hard layer of snow (sun crust, rain crust, spring crust); 2) the packing of snow into a hard layer by wind action (wind crust, wind slab); and 3) the freezing of surface water, however derived, to form a continuous layer of ice on top of snow (film crust, ice crust). A snow crust is designated as "breakable" or "unbreakable" according to its ability to support a person on skis. | AMS - glossary of meteorology |
| Snow crystal | Any of several types of ice crystal found in snow. A snow crystal is a single crystal, in contrast to a snowflake, which is usually an aggregate of many single snow crystals. | AMS - glossary of meteorology |
| Snow crystals | Ice crystals, mainly branched, sometimes star-shaped, which, isolated or forming agglomerations of flakes, constitute the solid particles of snow. | WMO METEOTERM accessed 2016 |
| Snow day | Day on which a fall of snow is observed. | WMO METEOTERM accessed 2016 |
| Snow day | A day on which a fall of snow is observed. | AMS - glossary of meteorology |
| Snow density | The mass of snow per unit volume which is equal to the water content of the snow divided by its depth. | NOAA Glossary of Hydrologic Terms |
| Snow density | The mass of snow per unit volume which is equal to the water content of snow divided by its depth. | NSIDC accessed 2016 |
| Snow density | See relative density. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow density | The mass of snow per unit volume which is equal to the water content of the snow divided by its depth. | NOAA National Weather Service Glossary 2009 |
| Snow density | Mass of snowpack per unit volume. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow density | The ratio of the volume of meltwater that can be derived from a sample of snow to the original volume of the sample; strictly speaking, this is the specific gravity of the snow sample. Freshly fallen snow usually has a snow density of 0.07 to 0.15; glacial ice formed from compacted snow (or firn) has a maximum density of about 0.91. Values as low as 0.004 have been measured. | AMS - glossary of meteorology |
| Snow density | Snow density ρs is a fundamental parameter of any material. In porous media, density generally refers to the bulk density, which is the total mass per volume (solid material and pore space; kg m–3). Snow exists in nature over a large range of densities. Snow density is normally determined by weighing snow of a known volume. Sometimes total and dry snow densities are measured separately. Total snow density encompasses all constituents of snow (ice, liquid water, and air) while dry snow density refers to the ice matrix and air only. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow depth | Snow depth is the depth of accumulated snow on the ground, measured at several points that appear representative of the immediate area and then averaged. | Canada National Climate Archive 2015 |
| Snow depth | The combined total depth of both the old and new snow on the ground. | NOAA Glossary of Hydrologic Terms |
| Snow depth | The combined total depth of both old and new snow on the ground. | NSIDC accessed 2016 |
| Snow depth | In the firn area, the vertical distance between the glacier surface and the summer surface; outside the firn area, the vertical distance between the glacier surface and the ice surface (which may be superimposed ice or glacier ice) at the time of observation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snow depth | The combined total depth of both the old and new snow on the ground. | NOAA National Weather Service Glossary 2009 |
| Snow depth | Vertical distance between the surface of a snow layer and the ground, assuming the layer is evenly spread over the ground which it covers. (TR) | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow depth | See height of snowpack | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow eater | 1. Any warm wind blowing over a snow surface; usually applied to a foehn wind, that is, schneefresser. See also chinook. 2. A fog over a snow surface; so called because of the frequently observed rapidity with which a snow cover disappears after a fog sets in. As water vapor from the air condenses on the snow, the latent heat of condensation causes the snow to become warmer and melt faster. | AMS - glossary of meteorology |
| Snow extent | The total land area covered by some amount of snow; typically reported in square kilometers. | NSIDC accessed 2016 |
| Snow fence | (1) Form of shelterbelt, generally a fence of open construction erected at some distance from an area which is to be protected from snowdrifts; the action of the fence is to pile up snow on its lee side. (2) Barrier of open construction, generally one to three metres in height, erected at a distance of about 15 m from a railway line or road to protect it from snow. | WMO METEOTERM accessed 2016 |
| Snow fence | 1. An open, slatted board fence usually 1-3 m high, placed upwind of a railroad track or highway. The fence serves to create eddies in the downstream airflow, resulting in a reduced wind speed such that snow is deposited close to the fence on its leeward side. The intent is to provide a comparatively clear zone along the railroad track or highway. A snow fence is also used to accumulate drifting snow in a flat windswept area to reduce the depth of ground frost and increase soil moisture as the snow melts. 2. Same as Wild fence. | AMS - glossary of meteorology |
| Snow flurries | Snow flurries are an intermittent light snowfall of short duration (generally light snow showers) with no measurable accumulation (trace category). | NOAA National Weather Service Glossary 2009 |
| Snow flurry | Snow that falls for short durations and which often changes in intensity; flurries usually produce little accumulation. | NSIDC accessed 2016 |
| Snow flurry | A snow shower, especially if light and brief. | WMO METEOTERM accessed 2016 |
| Snow flurry | Common term for a light snow shower, lasting for only a short period of time. | AMS - glossary of meteorology |
| Snow forest climate | A major category (the D climates) in W. K?ppen's climatic classification, defined by a coldest-month mean temperature of less than -3C (26.6F) and a warmest-month mean temperature of greater than 10C (50F). The first limit separates it from temperate rainy climates, and the second from tundra climates. It is distinguished from the dry climates by a function of annual temperature and precipitation (see formulas under steppe climate). The outstanding feature of these climates is the cold winters with at least a month of snow-covered ground. These are the coldest of the tree climates. In C. W. Thornthwaite's classifications, this general type of climate would be 1) in the 1931 system, humid or subhumid and microthermal climate, or taiga climate; and 2) in the 1948 system, humid or moist subhumid and microthermal climate. | AMS - glossary of meteorology |
| Snow garland | A rare and beautiful phenomenon in which snow is festooned from trees, fences, etc., in the form of a rope of snow, several feet long and several inches in diameter, formed and sustained by surface tension acting in thin films of water bonding individual crystals. Such garlands form only when the surface temperature is close to the melting point, for only then will the requisite films of slightly supercooled water exist. | AMS - glossary of meteorology |
| Snow gauge | (1) Instrument designed to measure the amount of fallen snow. (2) Instrument for measuring the density of snow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow gauge | An instrument for measuring the vertical depth of snow. The eight-inch rain gauge is adapted for snow measurement by removing the funnel and measuring tube so that snow is collected in the overflow can. The weighing rain gauge is also used for measuring snowfall by removing the funnel portion of the collector. Other instruments used for measuring snow depth include the snow sampler and snow stake. | AMS - glossary of meteorology |
| Snow geyser | Fine powdery snow blown upward by a snow tremor. | AMS - glossary of meteorology |
| Snow grains | Frozen precipitation in the form of very small, white opaque grains of ice. The solid equivalent of drizzle. Their diameter is generally 1 mm. When grains hit hard ground, they do not bounce or shatter. They usually fall in very small quantities, mostly from Status clouds or fog and never in the form of a shower. | Canada National Climate Archive 2015 |
| Snow grains | Precipitation in the form of very small, white opaque ice particles; they resemble snow pellets but are more flattened and elongated, with a diameter less than 1 mm; the solid equivalent of drizzle. | NSIDC accessed 2016 |
| Snow grains | Minute, white and opaque grains of ice. When they hit hard ground, they do not bounce or shatter. They usually fall in very small quantities, and never in the form of a shower. | Environment and Climate Change Canada 2014 |
| Snow grains | Precipitation consisting of white, opaque ice particles usually less than 1 mm in diameter. | NOAA National Weather Service Glossary 2009 |
| Snow grains | Precipitation of very small opaque white particles of ice which fall from a cloud and which are fairly flat or elongated with diameters generally less than 1 mm. | WMO METEOTERM accessed 2016 |
| Snow grains | Precipitation in the form of very small, white opaque particles of ice; the solid equivalent of drizzle. (Also called granular snow.) They resemble snow pellets in external appearance, but are more flattened and elongated, and generally have diameters of less than 1 mm; they neither shatter nor bounce when they hit a hard surface. Descriptions of the physical structure of snow grains vary widely and include very fine, simple ice crystals; tiny, complex snow crystals; small, compact bundles of rime; and particles with a rime core and a fine glaze coating. It is agreed that snow grains usually fall in very small quantities, mostly from stratus clouds or from fog, and never in the form of a shower. | AMS - glossary of meteorology |
| Snow hardness | Snow hardness R is the resistance to penetration of an object into snow. Hardness measurements produce a relative index value that depends on both the operator and the instrument; therefore, the device has to be specified. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow ice | Snow ice forms by refreezing flooded snow, creating an ice layer that bonds firmly to the top surface of a floe. Ice formed by this process and makes a significant contribution to the total mass of Antarctic sea ice. The snow cover of sea ice can become flooded by sea water via a number of mechanisms, in particular when the mass of snow becomes great enough to depress the ice/snow interface below sea level. The snow cover is porous and sea water can easily infiltrate from the sides of floes to form a slush layer at the ice/snow boundary. The snow may also become flooded by water rising up brine channels within the sea ice. With sufficiently cold temperatures this slush layer freezes to form snow ice. | ASPECT 2012 |
| Snow ice | Ice formed by the freezing of a mixture of snow and water. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow ice | Ice formed by freezing of a mixture of snow and water. | AMS - glossary of meteorology |
| Snow layer | A layer of ice crystals with similar size and shape. | NSIDC accessed 2016 |
| Snow layer | Due to the intermittent nature of precipitation, the action of wind and the continuously ongoing metamorphism of snow, distinct layers of snow build up the snowpack. Each such stratigraphic layer differs from the adjacent layers above and below by at least one of the following characteristics: microstructure or density, which together define the snow type, additionally snow hardness, liquid water content, snow temperature, or impurities that all describe the state of this type of snow. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow level | The lowest atmospheric level or altitude where hydrometeors remain in the solid (ice) phase. This often occurs within two to three hundred meters below the freezing level (the lowest elevation in the free atmosphere where the air temperature is 0 | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow line | The minimum elevation of snow lying on the ground or glacier surface; the snow line at the end of an ablation season marks a glacier's current equilibrium line. | NSIDC accessed 2016 |
| Snow line | In general, the outer boundary of a snow-covered area. It has at least two specific applications: 1) the actual lower limit of the snow cap on high terrain at any given time; 2) the ever-changing equatorward limit of snow cover, particularly in the Northern Hemisphere winter. | AMS - glossary of meteorology |
| Snow line | Altitudinal or latitudinal limit separating zones where snow does not melt during the summer season from areas in which it does. Similar to the concept of firm limit except that it is not limited to glaciers. | PhysicalGeography.net |
| Snow line | The line or zone on land that separates areas in which fallen snow disappears in summer from areas in which snow remains throughout the year. The altitude of the snow line is controlled by temperature and the amount of snowfall (cf. Equilibrium line and Firn line). | Illustrated Glossary of Snow and Ice |
| Snow load | The downward force on an object or structure caused by the weight of accumulated snow. | NSIDC accessed 2016 |
| Snow lying | The actual depth of snow lying on the ground at a particular instant. | WMO METEOTERM accessed 2016 |
| Snow mat | A special device used to mark the surface between old and new snow. It consists of a piece of white duck 28 inches square, having in each corner triangular pockets in which are inserted slats placed diagonally to keep the mat taut and flat. | AMS - glossary of meteorology |
| Snow melt | (1) Transformation of snow into liquid water. (2) Water from melting snow. | WMO METEOTERM accessed 2016 |
| Snow melt | Conversion of snow into runoff and groundwater flow with the onset of warmer temperatures. | PhysicalGeography.net |
| Snow metamorphism | The transformation that the snow undergoes in the period from deposition to either melting or passage to glacial ice. Meteorological conditions as well as mechanical or gravitational stresses are the primary external factors that affect snow metamorphism. Dry snow metamorphism is governed by both equilibrium and kinetic growth. In presence of liquid water snow transformation is driven by wet snow metamorphism. In English, snow metamorphism is sometimes and incorrectly called snowmetamorphosis. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow on the ground | The depth of snow in centimetres (cm) on the ground. The total depth of snow on the ground at the time of the observation is determined in whole centimetres by making a series of measurements and taking the average. | Canada National Climate Archive 2015 |
| Snow pack | Same as Snowcover; the combined layers of snow and ice on the ground at any one time. | NOAA National Weather Service Glossary 2009 |
| Snow pack | The annual amount of accumulated snow, usually expressed in terms of water equivalent. | WMO METEOTERM accessed 2016 |
| Snow patch | Relatively small area of snow cover remaining after the main snowmelt period. | NSIDC accessed 2016 |
| Snow patch | (1) The snow remaining on the ground close to the end of snowmelt. Such a patchy, discontinuous snow cover is usually the result of slowly melting snow due to shading or areas of high accumulation. (2) An isolated mass of snow, especially one which persists through most or all of the ablation season (see also snezhnik). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow patch | Isolated area covered with snow, lying above or below the regional snowline, which may last throughout the summer. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow patch | An isolated area of snow cover. | AMS - glossary of meteorology |
| Snow patch | An isolated area of snow, lying above or below the regional snow line, which may last throughout the summer and is composed of fern. | Illustrated Glossary of Snow and Ice |
| Snow pellets | Frozen precipitation of particles of either spherical or conical ice; their diameter is about 2 to 5 mm. They are brittle, easily crushed, and unlike hail, when they fall on hard ground, they bounce and often break up. Snow pellets always occur in showers and are often accompanied by snow flacks or raindrops when the surface temperature is around 0 | Canada National Climate Archive 2015 |
| Snow pellets | Precipitation in the form of small, white opaque ice particles; resemble ice grains, but are round (sometimes conical) and about 2-5 mm in diameter. | NSIDC accessed 2016 |
| Snow pellets | Precipitation, usually of brief duration, consisting of crisp, white, opaque ice particles, round or conical in shape and about 2 to 5 mm in diameter. Same as graupel or small hail. | NOAA National Weather Service Glossary 2009 |
| Snow pellets | Snow pellets are brittle and easily crushed; when they fall on hard ground, they bounce and often break up. They always occur in showers. They are often accompanied by snow flakes or rain drops, when the surface temperature is around zero Celsius. | Environment and Climate Change Canada 2014 |
| Snow pellets | Precipitation of white and opaque ice particles, which fall from a cloud and which are generally conical or rounded, with diameters attaining as much as 5 mm. | WMO METEOTERM accessed 2016 |
| Snow pellets | Precipitation consisting of white, opaque, approximately round (sometimes conical) ice particles having a snowlike structure, and from about 2 mm to less than 5 mm in diameter. (Also called soft hail, graupel, tapioca snow.) Snow pellets are crisp and easily crushed, differing in this respect from snow grains. They rebound when they fall on a hard surface and often break up. In most cases, snow pellets fall in shower form, often before or together with snow, and chiefly on occasions when the surface temperature is at or slightly below 0C (32F). It is formed as a result of accretion of supercooled droplets collected on what is initially a falling ice crystal (probably of the spatial aggregate type). | AMS - glossary of meteorology |
| Snow pellets | A form of precipitation also known as graupel. Snow pellets are white, spherical bits of ice with a maximum diameter of 5 millimeters. Snow pellets develop when supercooled droplets freeze on snowflakes. Snow pellets often fall for a brief time period when precipitation transforms from ice pellets to snow. Snow pellets can be easily distinguished from packed snowflakes as they tend to bounce when they strike the ground. Packed snowflakes are not dense enough to cause them to bounce. | PhysicalGeography.net |
| Snow pillow | An instrument used to measure snow water equivalents. Snow pillows typically have flat stainless steel surface areas. The pillow below this flat surface is filled with antifreeze solution and the pressure in the pillow is related to the water-equivalent depth of the snow on the platform. One great advantage of snow pillows over a snow survey is the frequency of observations, which can be as high as twice per day. | NOAA Glossary of Hydrologic Terms |
| Snow pillow | 1) A window of snow deposited in the immediate lee of a snow fence or ridge. or 2) In hydrologic terms, an instrument used to measure snow water equivalents. Snow pillows typically have flat stainless steel surface areas. The pillow below this flat surface is filled with antifreeze solution and the pressure in the pillow is related to the water-equivalent depth of the snow on the platform. One great advantage of snow pillows over a snow survey is the frequency of observations, which can be as high as twice per day. | NOAA National Weather Service Glossary 2009 |
| Snow pillow | Pillow-like device filled with antifreeze solution and fitted with a manometer which indicates the water equivalent of the snow cover which accumulates on it. | WMO METEOTERM accessed 2016 |
| Snow pillow | Device filled with antifreeze solution and fitted with a pressure sensor which indicates the water equivalent of the snow cover. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow pillow | An instrument designed to provide a direct estimate of water equivalence of a snowpack by measuring the pressure due to the mass of overlying snow. | AMS - glossary of meteorology |
| Snow pit | A hole dug into snow or firn to facilitate observation and sampling of density, snow and firn structure and associated grain sizes, layering and other attributes. Snow-pit measurements are part of the basis of the glaciological method (see stake). A snow pit can be excavated by hand using shovels (common on most smaller glaciers) or by trenching using a larger machine such as a tracked vehicle or caterpillar (now common in work on ice sheets). Coring by means of a barrel corer is a much less labour-intensive alternative to, and can to some extent replace, snow pits in determining bulk density of the snow and firn. Cores, however, are not as well suited for detailed observations of stratigraphy because of their small size relative to what can be observed on a snow-pit wall. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snow pit | A pit dug vertically into the snowpack where snowpack stratigraphy and characteristics of the individual layers are observed; see also snow profile. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow profile | A stratigraphic record of the snowpack including characteristics of individual layers. Usually performed in snow pits. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow r gime | The pattern of seasonal and annual (or long-period) variations in snow extent and depth at a particular place or in a particular region. | WMO METEOTERM accessed 2016 |
| Snow roller | Roll-like snow formation, caused by a unique combination of snow, wind, temperature and moisture | NSIDC accessed 2016 |
| Snow roller | A rolled-up, cylindrical mass of snow, rather common in mountainous or hilly regions. It occurs when snow, moist enough to be cohesive, is picked up by wind blowing down a slope and rolled onward and downward until it either becomes too large or the ground levels off too much for the wind to propel it farther. Snow rollers vary in size from very small cylinders to some as large as 1.5 m long and more than 2 m in circumference. | AMS - glossary of meteorology |
| Snow rollers | Cylindrical masses of snow formed, more often in hilly regions, when moist snow is driven by the wind and then rolled onward. | WMO METEOTERM accessed 2016 |
| Snow sampler | Snow gauge composed of a cylinder, closed at one end, that is used to obtain a sample of snow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow sampler | A hollow tube for collecting a sample of snow in situ. (Also called snow tube.) | AMS - glossary of meteorology |
| Snow sampler syn. snow tube | Snow-gauge composed of a metallic cylinder, closed at one end, which is used to collect a sample of snow whose water equivalent is to be measured. | WMO METEOTERM accessed 2016 |
| Snow shed | A protective structure erected over railroad tracks to prevent deep snow from accumulating on the tracks. They are used in deep cuts in mountains where avalanches are common. | AMS - glossary of meteorology |
| Snow shower | A snow shower is a short duration of moderate snowfall. Some accumulation is possible. | NOAA National Weather Service Glossary 2009 |
| Snow shower | A fairly short period of snow precipitation falling from a cumuliform cloud and characterized by its rapid start and finish. | WMO METEOTERM accessed 2016 |
| Snow shower | A brief period of snowfall in which intensity can be variable and may change rapidly. A snow shower in which only light snow falls for a few minutes is typically called a snow flurry. | AMS - glossary of meteorology |
| Snow shower saturation point | Frozen precipitation in the form of snow, characterized by its sudden beginning and ending. | Canada National Climate Archive 2015 |
| Snow squall | A heavy snow shower accompanied by sudden strong winds. | Canada National Climate Archive 2015 |
| Snow squall | A brief, but intense fall of snow that greatly reduces visibility and which is often accompanied by strong winds. | NSIDC accessed 2016 |
| Snow squall | A moderate to heavy snow flurry, which is driven by strong, gusty winds. Visibility during snow squalls is usually poor. | Environment and Climate Change Canada 2014 |
| Snow squall | A snow squall is an intense, but limited duration, period of moderate to heavy snowfall, accompanied by strong, gusty surface winds and possibly lightning (generally moderate to heavy snow showers). Snow accumulation may be significant. | NOAA National Weather Service Glossary 2009 |
| Snow squall warning | A warning issued by Environment Canada's Meteorological Service (MSC) for localized, limited duration, intense snowfall that reduces visibility significantly and may be accompanied by strong, gusty winds and (in some cases) lightning. These weather conditions are produced by the passage of cold air over an open body of water (open water squall) or the passage of a cold front (frontal snow squall). Local snow accumulations may be significant during this type of event. | Environment and Climate Change Canada 2014 |
| Snow stage | Phase of an adiabatic expansion process during which the ascending saturated air condenses some of its water vapour directly into snow. The snow stage begins at the condensation level if it is situated above the freezing level. | WMO METEOTERM accessed 2016 |
| Snow stage | Part of an obsolete conceptual model of air parcel ascent referring to conditions under which the condensation level is at a temperature below freezing and it is assumed that all condensed vapor immediately freezes. Other portions of the ascent were described as the dry stage, the rain stage, and the hail stage. | AMS - glossary of meteorology |
| Snow stake | A 1-3/4 inch square, semi-permanent stake, marked in inch increments to measure snow depth. | NOAA Glossary of Hydrologic Terms |
| Snow stake | A 1-3/4 inch square, semi-permanent stake, marked in inch increments to measure snow depth. | NOAA National Weather Service Glossary 2009 |
| Snow stake | Graduated stake fixed in the ground in regions of abundant snowfall to facilitate the measurement of snow depth. | WMO METEOTERM accessed 2016 |
| Snow stake | Graduated fixed stake to facilitate the measurement of snow depth. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow stake | A wooden scale, calibrated in inches or centimeters, used in regions of deep snow to measure its depth. (Also called snow scale.) The scale is bolted to a wood post or angle iron set in the ground. | AMS - glossary of meteorology |
| Snow stick | A portable rod used to measure snow depth. | NOAA Glossary of Hydrologic Terms |
| Snow stick | A portable rod used to measure snow depth. | NOAA National Weather Service Glossary 2009 |
| Snow strength | Snow strength σ can be regarded as the maximum or failure stress on a stress–strain curve. It is the maximum stress snow can withstand without failing or fracturing. Snow strength depends on the stress state (σ: compressive or tensile; τ: shear) in pascals and the strain, ε, which is dimensionless, as well as on their rates in pascals per second and per second, respectively. Snow strength depends also on microstructure and on the homogeneity of the sample. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow survey | Snow surveys by designated stations are made at regular intervals during the winter months to determine the water equivalent (mm) and depth of the snow pack (cm). 5 points (30 m apart), measurements taken on the 1st, 8th, 15th and 23rd of each month. 10 points (30 m apart), measurements taken on the 1st and 15th days of each month. | Canada National Climate Archive 2015 |
| Snow survey | Determination of the total amount of snow covering a catchment area or a specific region by measurements of snow depth at many sites. | WMO METEOTERM accessed 2016 |
| Snow survey | Determination of the total amount of snow covering a drainage basin or a given region. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snow survey | The process of determining depth and water content of snow at representative points, for example, along a snow course. | AMS - glossary of meteorology |
| Snow swamp | An area of saturated snow lying on glacier ice. | Swisseduc - Photo glossary of glaciological terms |
| Snow telemetry (SNOTEL) | An automated network of snowpack data collection sites. The Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service (SCS), has operated the Federal-State-Private Cooperative Snow Survey Program in the western United States since 1935. A standard SNOTEL site consists of a snow pillow, a storage type precipitation gage, air temperature sensor and a small shelter for housing electronics. | NOAA Glossary of Hydrologic Terms |
| Snow temperature | The temperature of snow Ts(H) at height H should be given in degrees Celsius (°C). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow trails | The trails of precipitation that emerge from the base of generating cells typically observed on time-height displays from vertically pointing radars. (Also called streamers.) Snow trails are also commonly observed on range-height indicator displays. Snow trails emerge from a layer of convective instability that often exists in the middle or upper troposphere in widespread storms. Small convective cells developing within this layer produce the ice crystals that then fall to lower altitudes. The base of the convectively unstable layer is called the snow- generating level. The shape and vertical extent of the streamers depend on the vertical profiles of wind and relative humidity in the layer through which the precipitation falls. | AMS - glossary of meteorology |
| Snow tremor | A disturbance in a snowfield caused by the simultaneous settling of a large area of thick snow crust or surface layer. It occurs when wind action has maintained the top foot or more as closely packed, fine-grained snow rather impervious to air movement. Meanwhile, at lower depths, firnification has caused the larger crystals (depth hoar) to grow at the expense of smaller ones, creating air pockets and a weak structure. The collapse of this structure (a perceptible drop, but rarely as much as 1 in.) may be accompanied by a loud report; over a large, level field, adjacent patches may settle as a series of tremors. Occasionally, a snow geyser may be blown upward through the crack of a settling patch. | AMS - glossary of meteorology |
| Snow type | Snow characterized by its microstructure and density. Note that grain shape and grain size are only an incomplete record of snow microstructure. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow water equivalent | The amount of water, in inches, obtained by melting a snow sample. | NOAA Glossary of Hydrologic Terms |
| Snow water equivalent | The water content obtained from melting accumulated snow. | NOAA Glossary of Hydrologic Terms |
| Snow water equivalent | The water content obtained from melting. | NSIDC accessed 2016 |
| Snow water equivalent | The water content obtained from melting accumulated snow. | NOAA National Weather Service Glossary 2009 |
| Snow water equivalent | Snow water equivalent SWE is the depth of water that would result if the mass of snow melted completely. It can represent the snow cover over a given region or a confined snow sample over the corresponding area. The snow water equivalent is the product of the snow height in metres and the vertically-integrated density in kilograms per cubic metre. It is typically expressed in millimetres of water equivalent, which is equivalent to kilograms per square metre or litres per square metre, thus referring to the unit surface area of the considered snow sample. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snow water equivalent (SWE) | The depth of liquid water that would result if a mass of snow melted completely. | IPCC WGI AR5 2013 |
| Snow worm | An oligochaete worm that lives on temperate glaciers or perennial snow; there are several species that range in color from yellowish-brown to reddish-brown or black; they are usually less than 1 millimeter (0.04 inch) in diameter and average about 3 millimeters (0.1 inch) in length; some feed off red algae. | NSIDC accessed 2016 |
| Snow zone | See recrystallization zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snow-cover chart | A synoptic chart showing areas covered by snow and showing contour lines of snow depth. | AMS - glossary of meteorology |
| Snow-covered ice | Ice covered with snow. | WMO Sea Ice Nomenclature 2017 |
| Snow-covered ice | Ice covered with snow. | Bushuyev 2004 |
| Snow-covered ice | Sea ice terminology meaning ice that is covered with snow. | Environment and Climate Change Canada 2014 |
| Snow-gauge | Instrument to measure the water equivalent of a snowfall, either by weighing the snow or by melting it. | WMO METEOTERM accessed 2016 |
| Snow-generating level | A layer in the middle or upper troposphere in widespread precipitation in which ice crystals form in small convective cells and fall to lower altitudes. Such layers are thought to be characterized by convective instability. Small convective cells called generating cells that develop within the layer may produce ice crystals that then settle into lower altitudes. The base of the convectively unstable layer is called the snow-generating level. On time-height displays from vertically pointing radars, generating cells are typically observed to extend about 1-2 km above the snow-generating level. Snow trails, or streamers, are terms used to describe the trails of precipitation that subsequently emerge from the base of the generating cells. | AMS - glossary of meteorology |
| Snow-line | (1) Climatic snow-line: lowest altitude of continuous snow cover in high mountainous areas in summer. (2) Orographic snow-line: lowest altitude at which isolated patches of snow protected from melting by orographic conditions persist in summer. | WMO METEOTERM accessed 2016 |
| Snowball Earth | The name given to the hypothesis that the Earth was almost completely covered by glacier ice in late Precambrian time (c. 1000 to 542 million years ago). | Swisseduc - Photo glossary of glaciological terms |
| Snowbelt | Areas where prevailing onshore winds are responsible for heavy snowfall is known as a snowbelt, and usually refers to regions southeast of open water. | Environment and Climate Change Canada 2014 |
| Snowblink | A bright white glare on the underside of clouds, produced by the reflection of light from a snow-covered surface; snowblink is lighter than ice blink, and much lighter than land sky or water sky. | NSIDC accessed 2016 |
| Snowboard | A flat, solid, white material, such as painted plywood, approximately two feet square, which is laid on the ground, or snow surface by weather observers to obtain more accurate measurements of snowfall and water content. | NOAA Glossary of Hydrologic Terms |
| Snowboard | A flat, solid, white material, such as painted plywood, approximately two feet square, which is laid on the ground, or snow surface by weather observers to obtain more accurate measurements of snowfall and water content. | NOAA National Weather Service Glossary 2009 |
| Snowbreak | Any barrier designed to shelter an object or area from snow; analogous to windbreak. | AMS - glossary of meteorology |
| Snowbridge | A mass of snow that has accumulated in the top of an open crevasse, masking the existence of the crevasse. Frequently, a large void exists below the snowbridge. | Molnia USGS 2004 |
| Snowbursts | Very intense showers of snow, often of short duration, that greatly restrict visibility and produce periods of rapid snow accumulation. | NSIDC accessed 2016 |
| Snowcover | Also known as Snow Pack; the combined layers of snow and ice on the ground at any one time. | NOAA National Weather Service Glossary 2009 |
| Snowcover | The accumulation of fallen snow covering the ground | Van Everdingen International Permafrost Association 2005 |
| Snowcreep | An extremely slow, continuous, downhill movement of a mass of snow. | AMS - glossary of meteorology |
| Snowdrift | Accumulation of snow heaped together by the wind in the lee of an obstruction due to the local decrease in wind velocity. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snowdrift | An accumulation or bank of snow formed when wind blows snow against an obstruction; often considerably thicker than the surrounding snowcover. | NSIDC accessed 2016 |
| Snowdrift | A mound or bank of snow deposited as sloping surfaces and peaks, often behind obstacles, irregularities, and on lee slopes. Due to eddies in the wind field. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snowdrift | An accumulation of windblown snow deposited in the lee of obstructions or heaped by wind eddies. A crescent-shaped snowdrift, with ends pointing downwind, is known as a snow barchan. | WMO Sea Ice Nomenclature 2017 |
| Snowdrift | Sea ice terminology. Describes an accumulation of wind-blown snow that is deposited in the lee of an obstacle. A crescent-shaped snowdrift, with ends pointing down-wind, is called a snow barchan. | Environment and Climate Change Canada 2014 |
| Snowdrift | Mass of snow heaped up by the wind and deposited along an obstruction or an irregularity of the terrain. | WMO METEOTERM accessed 2016 |
| Snowdrift | An accumulation of wind-blown snow, commonly considerably thicker than the surrounding snowcover | Van Everdingen International Permafrost Association 2005 |
| Snowdrift | A mound or bank of snow deposited as sloping surfaces and peaks, often behind obstacles and irregularities, due to eddies in the wind field. | AMS - glossary of meteorology |
| Snowdrift | An accumulation of wind-blown snow deposited in the lee of obstructions or heaped by wind eddies. | Illustrated Glossary of Snow and Ice |
| Snowdrift glacier | A semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a drift glacier. | NSIDC accessed 2016 |
| Snowdrift glacier | A semipermanent mass of firn formed by drifted snow in depressions in the ground or behind obstructions. | AMS - glossary of meteorology |
| Snowdrift ice | Permanent or semipermanent masses of ice, formed by the accumulation of drifted snow in the lee of projections or in depressions of the ground. | AMS - glossary of meteorology |
| Snowfall | Depth of fresh snow deposited on the ground during a specific period. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snowfall | The depth of new snow that has accumulated since the previous day or since the previous observation. | NSIDC accessed 2016 |
| Snowfall | Pn that does not evaporate or run off must accumulate, contributing to the ice balance I as N. The total runoff is the sum of runoff from snow Qn, runoff from ice and firn Qi and runoff of liquid-water inputs. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snowfall | The depth of snow that falls from the air and accumulates on the surface during a stated period. Snowfall excludes the deposition of windborne snow. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snowfall | The quantity of snow falling within a given area in a given time. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snowfall | (1) Snow falling. (2) Depth of fresh snow deposited on the ground during a specific period. | WMO METEOTERM accessed 2016 |
| Snowfall | 1. In surface weather observations, usually expressed as centimeters or inches of snow depth per six-hourly period. 2. The accumulation of snow during a specified period of time. | AMS - glossary of meteorology |
| Snowfield | A more or less extensive and persistent mass of snow. Snowfields are more extensive than snowpatches, but the distinction is not made precisely in common usage. A snowfield that is perennial may be difficult to distinguish from a glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snowfield | Large expanse of permanent ice and snow which may extend down to sea-level, or may be intermontane, cf. plateau. | UK Antarctic Place-names Committee accessed 2016 |
| Snowfield | 1. Generally, an extensive area of snow-covered ground or ice, relatively smooth and uniform in appearance and composition. This term is often used to describe such an area in otherwise coarse, mountainous, or glacial terrain. 2. In glaciology, a region of permanent snow cover, more specifically applied to the accumulation area of glaciers. | AMS - glossary of meteorology |
| Snowfield | An area of permanent snow accumulation. Usually at high altitudes or latitudes. | PhysicalGeography.net |
| Snowflake | A cluster of ice crystals that falls from a cloud. | NSIDC accessed 2016 |
| Snowflake | An agglomeration of snow crystals falling as a unit. | NOAA National Weather Service Glossary 2009 |
| Snowflake | An interlocked bunch or aggregate of ice crystals that falls from a cloud. Air temperatures near the melting point favour the formation of snowflakes. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snowflake | Agglomeration of snow crystals. | WMO METEOTERM accessed 2016 |
| Snowflake | Colloquially an ice crystal, or more commonly an aggregation of many crystals that falls from a cloud. Simple snowflakes (single crystals) exhibit beautiful variety of form, but the symmetrical shapes reproduced so often in photomicrographs are not found frequently in snowfalls. Broken single crystals, fragments, or clusters of such elements are much more typical of actual snow. Snowflakes made up of clusters of crystals (many thousand or more) or crystal fragments may grow as large as three to four inches in diameter, often building themselves into hollow cones falling point downward. In extremely still air, flakes with diameters as large as 10 inches have been reported. | AMS - glossary of meteorology |
| Snowflakes | Agglomerations of snow crystals. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snowline | (1) Climatic snowline: lowest altitude of a continuous layer of snow on the high mountains in summer. (2) Orographic snowline: lowest altitude at which snow persists on the land surface as isolated coverings on the mountains in summer. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snowline | A set of points forming the lower limit of a snow-covered area; on a glacier, the line separating snow surfaces from ice or firn surfaces, and also separating the percolation zone from either the superimposed ice zone or the ablation zone (see also zone). The set of points need not form a continuous curve. The snow-covered area of the glacier may include outliers (isolated patches of snow surrounded by firn or ice) and may exclude inliers (isolated patches of exposed firn or ice). The snowline is usually easy to see, because the snow above it is brighter than the firn or ice below it. It may therefore be mapped by analysis of suitable imagery. When, and only when, there is no superimposed ice, the snowline coincides with the equilibrium line. Unless qualified by a different adjective, references to the snowline are understood to refer to the Annual snowline. It is common for 'snowline' to be used as an abbreviation of 'average altitude of the snowline'. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snowline | In general the outer boundary of a snow covered area. This may be the ever-changing latitudinal limit of snow cover, particularly in the Northern Hemisphere winter, or the lower limit in altitude of the permanent snow cover in mountainous terrain. The latter strongly depends on the aspect of slope. Snowline should not be confused with snow level. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snowline | The lower boundary of a highland region in which snow never melts | Van Everdingen International Permafrost Association 2005 |
| Snowmelt | (1) Transformation of snow into liquid water. (2) Water from the melting of snow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snowmelt | Melting of the snowcover, and also the period during which melting of the snow cover occurs at the end of the winter. | NSIDC accessed 2016 |
| Snowmelt | Melting of the snowcover, and also the period during which melting of the snowcover occurs at the end of the winter | Van Everdingen International Permafrost Association 2005 |
| Snowmelt | Melting of the Snow Cover, and also the period during which melting of the Snow Cover occurs at the end of the winter. | Trombotto et al. 2014 |
| Snowmelt | The water resulting from the melting of snow. | AMS - glossary of meteorology |
| Snowmelt flood | Significant flood rise in a river caused by the melting of snowpack accumulated during the winter. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snowmelt flood | A substantial rise in stream or river discharge caused by snowmelt runoff. | AMS - glossary of meteorology |
| Snowmelt flooding | Flooding caused primarily by the melting of snow. | NOAA Glossary of Hydrologic Terms |
| Snowmelt flooding | In hydrologic terms, flooding caused primarily by the melting of snow. | NOAA National Weather Service Glossary 2009 |
| Snowpack | Field of naturally packed snow that usually melts slowly and yields water during the early summer months. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snowpack | The total snow and ice on the ground, including the new snow, the previous snow and ice which has not melted. | NOAA Glossary of Hydrologic Terms |
| Snowpack | The total snow and ice on the ground, including both new snow and the previous snow and ice which have not melted. | NSIDC accessed 2016 |
| Snowpack | The accumulation of snow at a given site and time; term to be preferably used in conjunction with the physical and mechanical properties of the snow on the ground. See also snow cover. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Snowpack | The total snow and ice on the ground, including both the new snow and the previous snow and ice which has not melted. | NOAA National Weather Service Glossary 2009 |
| Snowpack | A laterally extensive accumulation of snow on the ground that persists through winter and melts in the spring and summer. | AMS - glossary of meteorology |
| Snowpack yield | Amount of water, from precipitation and/or snowmelt, that is not retained by the snowpack and reaches the soil surface. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Snowpack yield | The amount of water that drains from the snowpack as a result of precipitation and/or snowmelt. | AMS - glossary of meteorology |
| Snowpatch | A mass of snow of restricted extent, especially one that persists through most or all of the ablation season. Snowpatches are less extensive than snowfields, but the distinction is not made precisely in common usage. A snowpatch that is perennial may be difficult to distinguish from a glacieret. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Snowpatch | Relatively small area of snowcover remaining after the main snowmelt period | Van Everdingen International Permafrost Association 2005 |
| Snowstorm | Strong wind with snow. | NSIDC accessed 2016 |
| Snowstorm | Meteorological disturbance giving rise to a heavy fall of snow, often accompanied by strong winds. | WMO METEOTERM accessed 2016 |
| Snowstorm | A storm characterized by a fall of frozen precipitation in the form of snow. | AMS - glossary of meteorology |
| Soft rime | A white, opaque coating of fine rime deposited chiefly on vertical surfaces, especially on points and edges of objects, generally in supercooled fog. On the windward side, soft rime may grow to very thick layers, long feathery cones, or needles pointing into the wind and having a structure similar to that of frost. | AMS - glossary of meteorology |
| Soil moisture | Water contained in the upper part of the soil mantle. This moisture evaporates from the soil and is the used and transpired by vegetation. | NOAA National Weather Service Glossary 2009 |
| Soil temperature | Soil temperature measurements provide a climatology of soil thermal characteristics such as the depth of frost penetration into the soil and the duration that the soil remains frozen. It is of interest to hydrologists because it affects surface runoff, infiltration and snowmelt and to agriculturists because it affects seed germination. Measurements of soil temperature are made in accordance with the World Meteorological Organization (WMO) recommendations at the standard depths of 5, 10, 20, 50, 100, 150 and 300 cm. They are measured daily as close as possible to 08:00 LST and again at the shallowest depth at 16:00 LST. | Canada National Climate Archive 2015 |
| Soil temperature | Temperature observed at different depths in the soil. | WMO METEOTERM accessed 2016 |
| Soil thermometer syn. geothermometer | Thermometer for measuring temperatures in the soil. | WMO METEOTERM accessed 2016 |
| Soil wedge | A wedge-shaped body of soil that is different in structure and texture from the surrounding soil. | NSIDC accessed 2016 |
| Soil wedge | A wedge-shaped body of soil that is different in structure and texture from the surrounding soil | Van Everdingen International Permafrost Association 2005 |
| Solid precipitation | Precipitation that falls in a solid state, such as sleet, snow or hail. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Solidification | The process by which a liquid changes phase into a solid; a synonym of freezing. See latent heat of fusion. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Solifluction | Slow downslope flow of saturated unfrozen earth materials | Van Everdingen International Permafrost Association 2005 |
| Solifluction | Slow downslope flow of saturated unfrozen earth materials. The presence of a frozen substrate, or even freezing and thawing is not implied in the original definition (Andersson, 1906). However, one component of Solifluction can be the Creep of Frozen Ground. Rates of flow vary widely. The term is commonly applied to processes operating in both Seasonal Frost and Permafrost areas. Solifluction in Permafrost is commonly referred to as Gelifluction. | Trombotto et al. 2014 |
| Solifluction | Form of mass movement in environments that experience freeze-thaw action. It is characterized by the slow movement of soil material downslope and the formation of lobe-shaped features. Also see gelifluction. | PhysicalGeography.net |
| Solifluction apron | A fan-like deposit at the base of a slope, produced by solifluction | Van Everdingen International Permafrost Association 2005 |
| Solifluction features | Geomorphological features of varying scale produced by the process of solifluction | Van Everdingen International Permafrost Association 2005 |
| Solifluction lobe | An isolated, tongue-shaped solifluction feature, up to 25 m wide and 150 m or more long, formed by more rapid solifluction on certain sections of a slope showing variations in gradient | Van Everdingen International Permafrost Association 2005 |
| Solifluction sheet | A broad deposit of nonsorted, water-saturated, locally derived materials that is moving or has moved downslope | Van Everdingen International Permafrost Association 2005 |
| Solifluction terrace | A low step, or bench, with a straight or lobate front, the latter reflecting local differences in the rate of solifluction movement | Van Everdingen International Permafrost Association 2005 |
| Sonic ranger | A device that measures the distance to a target, such as the glacier surface, by timing the return of echoes from acoustic (typically ultrasonic) pulses emitted by the device itself. A suitably mounted sonic ranger can yield a continuous record of relative change of surface height and, given information on density changes, can contribute to monitoring of accumulation or ablation. Knowledge is required of the speed of sound in the medium traversed by the pulse and its echo, which may in turn require knowledge of the temperature of the medium. The medium is usually air. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Sorge's law | The proposition that a glacier with a constant accumulation rate and no melting has a constant profile of density as a function of depth beneath the surface; by extension, and more loosely, the proposition that an unchanging density profile is sustained by the climatic mass balance. It follows from Sorge's law that a thickness change can be converted to an equivalent change of mass by multiplying by the density of glacier ice. This approach has been used in most mass-balancecalculations by geodetic methods. Sorge's law was originally introduced to describe densification of high polar snowpacks where melt is negligible. When Sorge's law is invoked in its looser sense, the constancy of the density profile is usually assumed rather than measured. The name, given by Bader (1954) in recognition of Ernst Sorge's observations in Greenland in 19301931, is pronounced as two syllables, the first stressed, with s as English z and with hard g. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Sorted circle | A patterned ground form that is equidimensional in several directions, with a dominantly circular outline, and a sorted appearance commonly due to a border of stones surrounding a central area of finer material. | NSIDC accessed 2016 |
| Sorted circle | A sorted circle is a patterned ground form that is equidimensional in several directions, with a dominantly circular outline, and a sorted appearance commonly due to a border of stones surrounding a central area of finer material | Van Everdingen International Permafrost Association 2005 |
| Sorted net | A type of patterned ground with cells that are equidimensional in several directions, neither dominantly circular nor polygonal, with a sorted appearance commonly due to borders of stones surrounding central areas of finer material. | NSIDC accessed 2016 |
| Sorted net | A sorted net is a type of patterned ground with cells that are equidimensional in several directions, neither dominantly circular nor polygonal, with a sorted appearance commonly due to borders of stones surrounding central areas of finer material | Van Everdingen International Permafrost Association 2005 |
| Sorted polygon | A patterned ground form that is equidimensional in several directions, with a dominantly polygonal outline, and a sorted appearance commonly due to a border of stones surrounding a central area of finer material. | NSIDC accessed 2016 |
| Sorted polygon | A sorted polygon is a patterned ground form that is equidimensional in several directions, with a dominantly polygonal outline, and a sorted appearance commonly due to a border of stones surrounding a central area of finer material | Van Everdingen International Permafrost Association 2005 |
| Sorted step | A patterned ground feature with a step-like form and a downslope border of stones embanking an area of relatively fine-grained bare ground upslope. | NSIDC accessed 2016 |
| Sorted step | A sorted step is a patterned ground feature with a step-like form and a downslope border of stones embanking an area of relatively fine-grained bare ground upslope | Van Everdingen International Permafrost Association 2005 |
| Sorted stripe | Patterned ground with a striped and sorted appearance, due to parallel strips of stones and intervening strips of finer material, oriented down the steepest available slope. | NSIDC accessed 2016 |
| Sorted stripe | Sorted stripes form patterned ground with a striped and sorted appearance, due to parallel strips of stones and intervening strips of finer material, oriented down the steepest available slope | Van Everdingen International Permafrost Association 2005 |
| South magnetic pole | Location in the Southern Hemisphere where the lines of force from Earth's magnetic field are vertical. This point on the Earth gradual changes its position with time. | PhysicalGeography.net |
| South Pole | Surface location defined by the intersection of the polar axis with Earth's surface in the Southern Hemisphere. This location has a latitude of 90 South. | PhysicalGeography.net |
| Spatial dendrite | A complex ice crystal with dendritic arms that extend in many directions (spatially) from a central nucleus, probably a frozen droplet that originally froze as a polycrystal. Its form is roughly spherical. | AMS - glossary of meteorology |
| Specific heat capacity | The amount of heat required to raise the temperature of a unit mass of a substance by one degree. | Van Everdingen International Permafrost Association 2005 |
| Specific mass balance | Mass balance expressed per unit area, that is, with dimension [M L-2] or [M L-2 T-1]; see specific. The prefix 'specific' is not necessary in general. The units in which a quantity is reported make clear whether or not it is specific. Specific mass balance may be reported for a point on the surface, a column of unit cross-section, or a larger volume such as an entire glacier or a collection of glaciers. In the latter two cases the term 'mean specific mass balance' has been used, although the adjective 'mean' is also not necessary. The definition of 'specific' apparently offered by Meier (1962) has led to some confusion. He wrote... Quantities measured at a point will first be discussed. [They] should all be prefaced by the word specific ...Specific budget terms have dimensions of [length] or [length]/[time]. The confusion arises because of the primacy given by Meier to water-equivalent dimensions ('[length]'). The adjective 'specific' indicates that the quantity has dimension [M L-2] or [M L-2 T-1], not that it is being measured at a point. The adjective 'point', as in point mass balance, should be used when clarity is needed. The unit of area lies in the horizontal plane, not a plane parallel to the glacier surface. For mass-balance purposes this rule applies even when the surface is vertical. For example, at a calving front the frontal ablation is equal to the mass of the entire volume lost by calving, melting and sublimation. If quoted as a specific quantity it is divided by the horizontal area over which the balance is to be stated, such as that of the entire glacier for a glacier-wide mass balance. The glaciological usage is not that which prevails in some other sciences, where often a specific quantity is either a dimensionless ratio of the value of a property of a given substance to the value of the same property of some reference substance, or is a quantity expressed per unit mass. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Specific surface area | Specific surface area SSA is an important parameter for characterizing porous materials that is increasingly being used in snow research. Specific surface area is important for applications involving chemical or electromagnetic interactions and is defined as the total surface area of the air/ice interface either per unit mass of a snow sample, SSAm, or per ice volume, SSAV, given in m2 kg–1 or m2 m–3, respectively. The density of ice, ρi, simply relates SSAm to SSAV = ρi SSAm. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Speckle tracking | The measurement of surface velocity as the rate of displacement of correlated patterns of speckle, or noise, in successive radar-interferometric images of the glacier. See insar, radar. The speckle originates from large numbers of statistically independent scatterers in the scene. Small 'chips' or windows from a later image are matched to a similar chip from an earlier image. Measured from the earlier chip, the distance to and bearing of the later chip that exhibits the greatest correlation with the earlier chip is taken to be the vector displacement that has accumulated between the dates of the images. Speckle tracking (e. G. Gray et al. 2001) is less precise than interferometric measurement of velocity but, relying only on image intensity rather than on both the intensity and the phase of the complex radar signal, is more robust. See feature tracking. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Spicule | A spike of ice that has needle-like crystals, which is formed during the freezing of water. | Environment and Climate Change Canada 2014 |
| Spicule | 1. A spike of ice formed during the freezing of a water drop or a contained volume of water (as in a puddle or freezer container); expansion of the inward freezing ice expels any remaining water through a weak point in the shell which then freezes as a spike in the colder environment. 2. Bright spike of luminous gas extending from the chromosphere into the corona of the sun. Spicules are several hundred kilometers in diameter and extend outward 5000-10 000 km. Observed in photographs of the limb, these features have a lifetime of several minutes. | AMS - glossary of meteorology |
| Spire | Spire-like peak | UK Antarctic Place-names Committee accessed 2016 |
| Splay crevasse | A crevasse pattern that forms where ice slowly spreads out sideways; commonly found near a glacier terminus. | NSIDC accessed 2016 |
| Splintering | A process from which ice splinters are produced due to the pressure buildup in the ice shell when a drop is freezing, resulting from the ice-water expansion on phase change. This causes the shell to deform and crack and eject ice splinters. It has been suggested as one of the ice multiplication mechanisms. | AMS - glossary of meteorology |
| Spongy ice | Ice that contains liquid water; a composite of ice and liquid water. Spongy ice is a form of accretion of supercooled drops in which the heat transfer is inadequate to freeze all the water. The excess water is included within the growing ice. Spongy ice may also form during the melting of low-density accretions by the meltwater soaking into the pores. | AMS - glossary of meteorology |
| Sporadic discontinuous permafrost | Permafrost underlying 10 to 35% of the exposed land surface. Individual areas of Permafrost are completely surrounded by Unfrozen Ground. | Trombotto et al. 2014 |
| Sporadic discontinuous permafrost | (1) (North American usage) permafrost underlying 10 - 50% of the exposed land surface (2) (Russian usage) permafrost underlying 5 - 30% of the exposed land surface. | NSIDC accessed 2016 |
| Sporadic discontinuous permafrost | 1. (North-American usage) <B>Permafrost underlying 10 to 35 percent of the exposed land surface; 2.< (Russian usage) Permafrost underlying 5 to 30 percent of the exposed land surface | Van Everdingen International Permafrost Association 2005 |
| Sporadic permafrost | Form of permafrost that exists as small islands of frozen ground in otherwise unfrozen soil and sediments. | PhysicalGeography.net |
| Spring snow | A coarse, granular, wet snow, resembling finely chopped melted ice, generally found in the spring. (Also called corn snow, granular snow.) | AMS - glossary of meteorology |
| Spur | Projection from a mountain or range | UK Antarctic Place-names Committee accessed 2016 |
| Stack | High and precipitous detached rock near shore. | UK Antarctic Place-names Committee accessed 2016 |
| Stadial moraine | See recessional moraine. | PhysicalGeography.net |
| Stagnant ice | Any part of a glacier that does not flow at a detectable rate; a synonym of dead ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Stagnation | The in-situ melting of glacier ice. Many glaciers have stagnant termini, covered by thick sediment debris. Some support vegetation, including mature forests. | Molnia USGS 2004 |
| Stake | A pole or rod that has been emplaced in a vertical hole drilled into the glacier surface; may also be referred to as a mass-balance stake, or as an accumulation stake or ablation stake as appropriate. The change in height of the glacier surface relative to the top of the stake is the basis for a measure of the sum of accumulation and ablation (that is, of surface mass balance). The five quantities measured (Figure 13) over the course of the mass-balance year are at t0, when by definition there is no snow, the distance d0 from the stake top to the summer surface; at tw, the distance dw from the stake top to the surface and (in a nearby snow pit or with a coring device) the mean density w of the snow (if any; the winter balance is not necessarily positive); and at t1, the distance d1 from the stake top to the surface and the mean density 1 of the snow (if any). The layer thicknesses hw and h1are obtained by subtraction, as beneath the figure; note that in the right part of the figure the Annual balance is negative because the thickness h1 is negative. When the balance is positive the stake measurements are often supplemented by digging or probing to sample local variability. It is not possible to measure the density of mass that is lost between any two survey dates. For example the summer balance is commonly evaluated as ba bw; and when h1 is negative an appropriate value (usually, outside the firn area, the density of ice) must be assumed for 1. At the instant following t1, any residual snow is deemed to become firn and the glacier surface, at d1, becomes the summer surface d0 of the next balance year. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Stake farm | A group of stakes placed within a small area on the surface of a glacier, serving to improve estimates of the small-scale variability, and therefore of the sampling uncertainty, of surface mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Stamukha (grounded hummock) | A thick hummocked grounded ice formation. Stamukhas form from floebergs and hummocked grounded ice fragments. They are distinguished by a large height (up to 10 m and more above sea level) and steep slopes. There are single grounded hummocks and lines (or chains) of grounded hummocks. Stamukhas forming at the same place from season to season are termed recurring stamukhas. | Bushuyev 2004 |
| Stamukhi | Thick ridges that become grounded during the winter and become part of the fast ice zone; while the rest of the fast ice melts during the summer, a stamukhi remains throughout the summer attached to the ocean bottom. | NSIDC accessed 2016 |
| Standing cloud | Any stationary cloud maintaining its position with respect to a mountain peak or ridge, such as a banner cloud, cap cloud, crest cloud, or cloud of the species lenticularis. | AMS - glossary of meteorology |
| Standing floe | A separate floe standing vertically or inclined and enclosed by rather smooth ice. | WMO Sea Ice Nomenclature 2017 |
| Standing floe | Sea ice terminology that describes a separate floe standing vertically or inclined, and enclosed by rather smooth ice. | Environment and Climate Change Canada 2014 |
| Standpipe storage precipitation gauge | A precipitation gauge comprising a tall pipe 30.5 cm (12 in.) in diameter designed especially to measure the water content of snow in remote mountainous areas for unattended operation; part of a SNOTEL site. The bottom contains a known amount of an oil-antifreeze mixture. The oil prevents evaporation and the antifreeze melts the snow. A pressure transducer converts the oil-antifreeze-water mixture into a calibrated water depth. Daily changes in depth provide seasonal and annual accumulations. | AMS - glossary of meteorology |
| Stapi | (from the Icelandic; also referred to as Tuya) A subglacially erupted volcano, characteristed by steep flanks and a flat or slightly domed summit. Named after a volcano in Iceland, no longer enveloped in ice. | Swisseduc - Photo glossary of glaciological terms |
| State of snow | Snow characterization by properties such as hardness, liquid water content, temperature, and impurities. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Static cryosol | A mineral soil showing little or no evidence of cryoturbation, with permafrost within 1 meter (3.3 feet) below the surface. | NSIDC accessed 2016 |
| Static cryosol | A mineral soil showing little or no evidence of cryoturbation, with permafrost within 1 m below the surface | Van Everdingen International Permafrost Association 2005 |
| Steady state | A state of the glacier in which over many years the thickness at the end of each mass-balance year remains unchanged, that is, dh/dt = 0 at every point; see equilibrium, Balanced-budget. It follows from the definition that the glacier-wide mass balance, including frontal ablation, is zero, because the glacier must flow at just the rate required to eliminate thickness changes due to the climatic-basal mass balance. Steady state is a valuable idealization, and may be realized roughly when the climate is constant, or changes only slowly, over periods considerably longer than the response time of the glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Steady-state AAR | The AAR of a glacier in steady state. The steady-state AAR is difficult to estimate because glaciers are seldom if ever in steady state. In practice, it must be estimated by modelling. To emphasize that the Balanced-budget AAR and steady-state AAR are distinct concepts, the steady-state AAR should be given a distinctive symbol, perhaps AAR0'. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Steady-state ELA | The ELA of a glacier in steady state. The steady-state ELA is difficult to estimate because glaciers are seldom if ever in steady state. It must usually be estimated by modelling. To emphasize that the Balanced-budget ELA and steady-state ELA are distinct concepts, the steady-state ELA should be given a distinctive symbol, perhaps ELA0. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Steam drilling | A commonly used field technique to drill holes into ice in order to insert stakes for measuring the mass balance (q.v.) of glaciers. | Swisseduc - Photo glossary of glaciological terms |
| Steam fog | A type of fog that forms when an outbreak of cold Arctic air settles over an expanse of open, relatively warmer water (Also called sea smoke, arctic sea smoke and advection fog, or sea fog) | Environment and Climate Change Canada 2014 |
| Stellar crystal | A kind of plane-dendritic crystal, often referring to those with relatively thin branches without elaborate patterns. | AMS - glossary of meteorology |
| Stone garland | A stone garland is the downslope border of stones along a sorted step, embanking an area of relatively fine-grained bare ground upslope | Van Everdingen International Permafrost Association 2005 |
| Stone ring | Structured ground consisting of rings of stones caused by horizontal sorting. These rings are common within permafrost environments. | Trombotto et al. 2014 |
| Stone-banked (solifluction) lobe | A solifluction lobe with a stony front | Van Everdingen International Permafrost Association 2005 |
| Stone-bankeded (solifluction) terrace | A solifluction terrace with a stony front | Van Everdingen International Permafrost Association 2005 |
| Stony earth circle | A type of nonsorted circle developed in gravelly materials. | Van Everdingen International Permafrost Association 2005 |
| Storm | (1) High intensity rain, snow or hail, perhaps accompanied by wind, associated with a separable meteorological event. (2) Wind with a speed between 23 and 26 metres per second. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Stoss | Side of a slope that faces the direction of flow of ice, wind, or water. Opposite of lee. | PhysicalGeography.net |
| Strain | The ratio of change in dimension to the original dimension. A material is said to be strained when a stress acting on it distorts it. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Strain | The amount by which an object becomes deformed as a result of stress, which in glaciers may take place over many years or even millennia. | Swisseduc - Photo glossary of glaciological terms |
| Strand crack | A fissure at the junction between an inland ice sheet, ice piedmont or ice rise and an ice shelf, the latter being subject to the rise and fall of the tide. | NSIDC accessed 2016 |
| Strand crack | Fissure at the junction between an inland ice sheet, ice piedmont or ice rise and an ice shelf, the latter being subject to the rise and fall of the tide, but the term does not arise in place-names. | UK Antarctic Place-names Committee accessed 2016 |
| Strand crack | A fissure at the junction between an inland ice sheet, ice piedmont or ice rise and an ice shelf, the latter being subject to the rise and fall of the tide. | Illustrated Glossary of Snow and Ice |
| Stranded ice | Ice that has been floating and has been deposited on the shore by retreating high water. | WMO Sea Ice Nomenclature 2017 |
| Stranded ice | Sea ice terminology describing ice which had been floating and is then deposited on the shore by retreating high water. | Environment and Climate Change Canada 2014 |
| Stratification | The vertical structure or layering of the snowpack, usually observed in snow pits. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Stratified drift | A type of glacial drift that has been partially sorted by glaciofluvial meltwater. | PhysicalGeography.net |
| Stratified slope waste deposits | A cross-section of periglacial slopes and valleys that shows several alternations of slope stratifications is called stratified slope waste deposits in some literature. These slopes consist of alternating deposited fine and coarse sediments that are oriented downhill. Trombotto (1991) presented different possible genesis for such structures in the periglacial slopes of the Central Andes. | Trombotto et al. 2014 |
| Stratigraphic system | The time system in which the determination of mass balance is based on the identification of successive Annual minima, and for seasonal balances Annual maxima also, in the mass of the glacier or a part of the glacier. In field work, Annual mass balance is determined by the detection of two successive summer surfaces, usually at individual observation sites. In the ablation zone, the earlier summer surface has disappeared by the time the later one is observed, but its vertical position is known from earlier observations. For seasonal balances, it is not possible to determine the Annual maximum of mass with a single field survey that can be scheduled to coincide only roughly with the expected date of the maximum. Thus, in the stratigraphic system, seasonal balances by the glaciological method are actually measured in a combined system. Continuously recording sensors, such as snow pillows and sonic rangers, can yield accurate stratigraphic-system estimates of seasonal balances at single points, but they are not in wide use. The Annual extrema of mass may be reached at different times at different sites on the glacier. Glacier-wide balances in the stratigraphic system can be determined rigorously only by accurate spatially-distributed modeling or by gravimetric methods. Determinations based on field measurements must assume that the diachronous character of the summer surface can be neglected. The duration of the mass-balance year varies in the stratigraphic system. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Stratigraphy | In the context of snow, the definition and description of the stratified, i.e., layered snowpack | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Stratus | Generally grey cloud layer with a fairly uniform base, which may produce drizzle, ice prisms or snow grains. | Environment and Climate Change Canada 2014 |
| Stress | A surface force measured per unit area, for example, the force due to the transport of momentum by turbulent fluid motions. | Environment and Climate Change Canada 2014 |
| Stress | The force per unit area acting on a material and tending to change its dimensions, i.e., to cause a strain. The two main types of stress are direct or normal (i.e., tensile or compressive) stress and shear stress. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Striae or striations | Linear fine scratches formed by the abrasive effect of debris-rich ice sliding over bedrock. Intersecting sets of striae are formed as stones are rotated, or if the direction of flow over bedrock changes. | Swisseduc - Photo glossary of glaciological terms |
| Striation | Easily recognizable convex growth feature across facets or crystal surfaces. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Striations | Striations are the scratches etched into the rock at the bed of a glacier. Their presence indicates grinding of sand and rock particles into the bed under considerable pressure. Glacier ice alone is too soft to be a powerful rock-cutting agent. Many glaciers are armed with rock fragments embedded within the ice that are effective cutting tools. The rock-choked ice grazes over the glacier bed, removign rock obstacles and leaving the bedrock rounded and smoothed. In some places fine-grained debris polishes the bedrock to a lustrous surface finish called glacial polish. Coarser rocks may gouge scratches called striations. | Molnia USGS 2004 |
| Striations | Multiple, generally parallel, linear grooves, carved by rocks frozen in the bed of a glacier into the bedrock over which it flows. | Molnia USGS 2004 |
| Striations | Grooves of scratches found in surface rock that are the result of glacial abrasion. | PhysicalGeography.net |
| String fen | A peatland with roughly parallel narrow ridges of peat dominated by fenland vegetation interspersed with slight depressions, many of which contain shallow pools. | NSIDC accessed 2016 |
| String fen | A peatland with roughly parallel narrow ridges of peat dominated by fenland vegetation interspersed with slight depressions, many of which contain shallow pools | Van Everdingen International Permafrost Association 2005 |
| Strip | A long narrow area of pack ice, about 1 kilometer (0.6 mile) or less in width, usually composed of small fragments detatched from the main mass of ice, and run together under the influence of wind or current. | NSIDC accessed 2016 |
| Strip | A long narrow zone of floating ice, about 1 km or less in width, usually composed of small fragments detached from the main mass of ice, and run together under the influence of wind, swell or current. | Bushuyev 2004 |
| Strip | Long narrow area of pack ice, about 0.5 n mi (1 km) or less in width, usually composed of small fragments detached from the main mass of ice, and run together under the influence of wind, swell, or current. | WMO Sea Ice Nomenclature 2017 |
| Strip | Sea ice terminology. Describes a long narrow area of pack/drift ice, about one (1) km or less in width, usually composed of small fragments detached from the main mass of ice, which run together under the influence of wind, swell or current. | Environment and Climate Change Canada 2014 |
| Strip | A long narrow area of pack ice, about 1 km or less in width, usually composed of small fragments detached from the main mass of ice, and run together under the influence of wind or current. | Illustrated Glossary of Snow and Ice |
| Strip/Patch | The term is applied for characterizing irregularities of the total and partial concentration in a delineated zone when it is impossible to depict the position of strips and patches on the ice chart as separate zones. | Bushuyev 2004 |
| Sub-polar glacier | An obsolete term, due to Ahlmann (1935), describing a glacier with an accumulation zone in which, except for possible seasonal warming and melting near the surface, the temperature is below the freezing point to depths of 100 m or more. The term is sometimes used as if it were a synonym of polythermal glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Subantarctic front | The northern front of the Antarctic Circumpolar Current that separates the polar frontal zone in the south from the subantarctic zone in the north. It is characterized by sea surface temperatures near 7-9C and a salinity minimum of 33.8-34.0 psu produced by high rainfall. | AMS - glossary of meteorology |
| Subantarctic upper water | The water mass of the subantarctic zone. It has a temperature of 4-10C in winter (August) and 4-14C in summer (January) and a salinity of 33.9-34.9 psu in winter, which can decrease to 33.0 in summer from the melting of ice. | AMS - glossary of meteorology |
| Subantarctic zone | The region between the subantarctic front and the subtropical front. | AMS - glossary of meteorology |
| Subarctic intermediate water | A water mass identified by a salinity minimum found at a depth of about 600 m in the North Pacific Ocean. It is formed at various locations along the Arctic Polar Front and spreads toward the equator between the central water and the deep water. The equivalent water mass in the Atlantic Ocean is known as Arctic Intermediate Water. | AMS - glossary of meteorology |
| Subarctic upper water | The water mass found north of the North Pacific subtropical convergence region between 50N and the Alaskan coast. It has a temperature of 2-6C and a salinity below 33 psu. | AMS - glossary of meteorology |
| Subgelisol | Unfrozen ground beneath permafrost. | AMS - glossary of meteorology |
| Subglacial | Pertaining to the glacier bed or to the material below the bed. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Subglacial | Describes features lying under ice cover. The term subglacial precedes the geographical term as in Subglacial Trench, Subglacial Highlands, and Subglacial Lake. | UK Antarctic Place-names Committee accessed 2016 |
| Subglacial debris | Debris which has been released from ice at the base of a glacier. Individual stones usually show signs of rounding as a result of abrasion at the contact between ice and bedrock. | Swisseduc - Photo glossary of glaciological terms |
| Subglacial meltwater channel | A steep, often vertically sided valley cut into bedrock by a subglacial stream under high pressure. It may have a profile with uphill sections, since a sufficient head in the glacier can force water to flow up slope. | Swisseduc - Photo glossary of glaciological terms |
| Subglacial permafrost | Permafrost beneath a glacier. | NSIDC accessed 2016 |
| Subglacial permafrost | Permafrost beneath a glacier | Van Everdingen International Permafrost Association 2005 |
| Subglacial stream | A stream that flows beneath a glacier, and which usually cuts into the ice above to form a tunnel. | Swisseduc - Photo glossary of glaciological terms |
| Subglacial talik | A layer or body of unfrozen ground beneath a glacier in an area with permafrost. | NSIDC accessed 2016 |
| Subglacial talik | A layer or body of unfrozen ground beneath a glacier in an area with permafrost | Van Everdingen International Permafrost Association 2005 |
| Sublimation | The transition of a substance from the solid phase directly to the vapor phase, or vice versa, without passing through an intermediate liquid phase. | NSIDC accessed 2016 |
| Sublimation | The process by which a solid changes phase directly into a vapour without melting. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Sublimation | The process by which solids are transformed directly to the state of vapour or vice versa, without passing through the liquid phase. | Environment and Climate Change Canada 2014 |
| Sublimation | The process in which a solid turns to a gas without first forming a liquid (opposite of deposition). | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Sublimation | The transition of a substance from the solid phase directly to the vapour phase, or vice versa, without passing through the liquid phase. | WMO METEOTERM accessed 2016 |
| Sublimation | Process where ice changes into water vapor without first becoming liquid. This process requires approximately 680 calories of heat energy for each gram of water converted. | PhysicalGeography.net |
| Sublimation ice | Ice formed by reverse sublimation of water vapour on cold surfaces. | NSIDC accessed 2016 |
| Sublimation ice | Ice formed by reverse sublimation of water vapour onto cold surfaces | Van Everdingen International Permafrost Association 2005 |
| Sublimation nucleus | Nucleus on which water vapour is transformed into ice. | WMO METEOTERM accessed 2016 |
| Sublimation of ice | Change in phase from ice directly into water vapour. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Sublimation of ice | The transition of water from solid to gas without passing through the liquid phase. | NOAA National Weather Service Glossary 2009 |
| Sublimation of ice | The change of phase of water from solid to gas without passing through the liquid phase. | AMS - glossary of meteorology |
| Submergence velocity | The vertical component, when it is directed downward, of the glacier-flow velocity vector at the glacier surface, at a point fixed in space. When the component is directed upward, it is called the emergence velocity. The submergence velocity is related through the continuity equation to the climatic-basal mass balance and the rate of thickness change. The component is typically upward in the ablation zone and downward in the accumulation zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Subpermafrost water | Water occurring in the noncryotic ground below the permafrost. | NSIDC accessed 2016 |
| Subpermafrost water | Water occurring in the noncryotic ground below the permafrost | Van Everdingen International Permafrost Association 2005 |
| Subpermafrost water | Water occurring in the non-Cryotic Ground below the Permafrost. | Trombotto et al. 2014 |
| Subpolar glacier | A glacier whose temperature regime is between polar and temperate; usually predominantly below freezing, but could experience extensive summer melt. | NSIDC accessed 2016 |
| Subpolar glacier | In Ahlmann's glacier classification, a polar glacier with 10-20 m of firn in the accumulation area where some melting occurs. | AMS - glossary of meteorology |
| Subpolar glacier | Glacier in which the ice found from the its surface to base has a temperature as cold as -30 Celsius throughout the year. This is well below the pressure melting point. However, melting does occur in the accumulation zone in the summer. One of the three types of glaciers: cold glacier; temperate glacier; and subpolar glacier. | PhysicalGeography.net |
| Subpolar lows | Surface zone of atmospheric low pressure located at about 60 North and South latitude. These low pressure systems are produced by the frontal lifting of subtropical air masses over polar air. | PhysicalGeography.net |
| Subsea permafrost | Permafrost occurring beneath the sea bottom. | NSIDC accessed 2016 |
| Subsea permafrost | Permafrost occurring beneath the sea bottom | Van Everdingen International Permafrost Association 2005 |
| Subsea permafrost | Form of permafrost that exists beneath the sea in ocean sediments. | PhysicalGeography.net |
| Subsea talik | A layer or body of unfrozen ground beneath the seabottom, and forming part of the subsea permafrost. | NSIDC accessed 2016 |
| Subsea talik | A layer or body of unfrozen ground beneath the seabottom, and forming part of the subsea permafrost | Van Everdingen International Permafrost Association 2005 |
| Sugar berg | An iceberg of porous glacier ice. | AMS - glossary of meteorology |
| Sugar snow syn. depth hoar | Ice crystals formed by sublimation within snow, but beneath the snow surface. | WMO METEOTERM accessed 2016 |
| Summer ablation | Ablation integrated over the summer season. Summer ablation is not the same as summer mass balance. It is generally more negative because some of the lost mass may be offset by accumulation. Mass-balance measurements by the glaciological method generally measure summer mass balance and not summer ablation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Summer accumulation | Accumulation integrated over the summer season. Part or all of summer accumulation may be lost by ablation before the end of the summer season. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Summer minimum extent | The permanent ice zone that remains in summer after all melting has occurred. | NSIDC accessed 2016 |
| Summer season | The time span from the end of the winter season to the end of the mass-balance year. The length of the summer season may vary greatly from year to year. The term is best suited to glaciers of winter-accumulation type. In the stratigraphic system the summer season starts when the glacier has attained maximum mass and ends when the glacier has attained minimum mass. In the floating-date system and the fixed-date system, the mass is not necessarily at its Annual maximum or minimum when the summer season starts or ends. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Summer surface | The surface formed at the time of minimum Annual mass at each point on the glacier, marking (in the stratigraphic system) the end of one mass-balance year and the start of the next. In general the summer surface is diachronous. For example, when the higher reaches of a glacier start to gain mass, the lower parts may still be ablating. The summer surface is the surface on which the first snow of the new balance year falls. It is easily detectable when it consists of glacier ice, which now includes superimposed ice added during the previous balance year. In the firn area it is recognizable as a well-marked crust, that is, a thin, relatively strong layer with a density near that of ice, and sometimes also (or instead) as a layer of depth hoar at the base of the current year's accumulation. The crust typically originates by recrystallization of the surface snow in late summer to form glaze. It may also be marked by an accumulation of sediment or wind-blown dust. It can be difficult to detect when melting and snowfall alternate during the transition between the ablation season and the accumulation season. In some mass-balance programmes the summer surface is 'labelled' in the vicinity of stakes with a distinctive material, such as sawdust, during a visit late in the ablation season. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Summer-accumulation type | A type of glacier on which the regional seasonality results in extrema of ablation rate and accumulation rate at roughly the same time. On a glacier of summer-accumulation type, mass balance remains relatively stable throughout the year. This is typical of high-altitude, low-latitude glaciers with a summer precipitation maximum. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Summit | Highest point of a hill or mountain, or the feature itself. | UK Antarctic Place-names Committee accessed 2016 |
| Sun cups | Ablation hollows that develop during intense sunshine. | NSIDC accessed 2016 |
| Sun cups | Ablation hollows that develop during intense sunshine. On low- latitude snow, firn, and ice fields these may grow into spectacular features called snow or ice penitents. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Suncup | A suncup is a small depression on a snow or firn surface formed by melting and evaporation resulting from direct exposure to the sun. | Molnia USGS 2004 |
| Suncups | A series of bowl-like depression melted into a snow or ice surface, separated by a network of connected ridges. Individual suncups may be more than three feet deep and ten feet in diameter. Suncups form during warm, sunny conditions. | Molnia USGS 2004 |
| Sunspot | Dark spot on the sun, with cooler-than-average temperatures and strong magnetic activity | NSIDC accessed 2016 |
| Supercooled water | Water cooled below freezing point without solidification or crystallization. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Supercooling | Cooling of a liquid to a temperature below its freezing point, without causing solidification | Van Everdingen International Permafrost Association 2005 |
| Superimposed ice | Ice accumulated on the current summer surface, during the current mass-balance year, by the refreezing there of rain or meltwater. Superimposed ice is not the same thing as internal accumulation, which represents refreezing below the summer surface. Superimposed ice becomes glacier ice at the end of the mass-balance year. Superimposed ice requires special attention in conventional mass-balance programmes. In a pair of stake measurements, at the start and end of the ablation season, accumulation of superimposed ice causes a decrease of the distance from the top of the stake to the ice surface (regardless of any overlying snow). This decrease is real and not, for example, due to faulty book-keeping. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Superimposed ice | Ice that forms as a result of the freezing of water-saturated snow. It commonly forms at the surface of a glacier between the equilibrium line and the firn line, and gives the glacier additional mass. | Swisseduc - Photo glossary of glaciological terms |
| Superimposed ice | Ice exposed at the surface of a glacier that was formed by the freezing of melted snow after deposition; usually located below the snow line and above the equilibrium line. Although it is ice, it is part of the accumulation area. | AMS - glossary of meteorology |
| Superimposed ice zone | The part of the glacier where superimposed ice is exposed. The superimposed ice zone occupies the range of elevations below the snowline and above the equilibrium line. Superimposed ice may also be found beneath snow of the current year at elevations above the snowline. Whether exposed or beneath the surface, it requires special attention in mass-balance measurements. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Supraglacial | Pertaining to the surface of the glacier or to features on the surface. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Supraglacial debris | Debris that is carried on the surface of a glacier. It is normally derived from rockfalls and tends to be angular in character. More rounded material may also be present, raised from the glacier bed or reworked by surface streams. | Swisseduc - Photo glossary of glaciological terms |
| Supraglacial stream | A stream that flows over the surface of a glacier. Most supraglacial streams descend via moulins (q.v.) into the depths or base of a glacier. | Swisseduc - Photo glossary of glaciological terms |
| Suprapermafrost layer | The layer of ground above permafrost; it includes the active layer and possibly occurrences of talik and pereletok. | AMS - glossary of meteorology |
| Suprapermafrost water | Water occurring in unfrozen ground above perennially frozen ground. | NSIDC accessed 2016 |
| Suprapermafrost water | Water occurring in unfrozen ground above perennially frozen ground | Van Everdingen International Permafrost Association 2005 |
| Suprapermafrost water | Water occurring in Unfrozen Ground above perennially Frozen Ground. It occurs in the Active Layer, between the Active Layer and the Permafrost Table, and in Taliks below don't hyphenate and lakes. It is replenished by infiltration of rain, Snowmelt or surface waters, or from intra- or Subpermafrost Water via open Taliks. Much of the Suprapermafrost Water in the Active Layer may freeze in the winter; the remainder can temporarily become confined and subjected to increasing pressure during progressive freezing of the Active Layer. | Trombotto et al. 2014 |
| Surface ablation | Ablation at the surface of the glacier, generally measured as the lowering of the surface with respect to the summer surface, corrected for the increase in density of any residual snow and firn and multiplied by the density of the lost mass. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Surface accumulation | Accumulation at the surface of the glacier, generally measured as the rise of the surface with respect to the summer surface multiplied by the density of the added mass. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Surface albedo | The ratio, expressed as a percentage, of the amount of electromagnetic radiation reflected by the earth's surface to the amount incident upon it. Value varies with wavelength and with the surface composition. For example, snow and ice vary from 80% to 85% and bare ground from 10% to 20%. | AMS - glossary of meteorology |
| Surface cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles have vertical or near-vertical orientation. | NSIDC accessed 2016 |
| Surface density | The SI name of the derived unit kg m-2, mass per unit area. It can be helpful to regard the product of a thickness and a density as a surface density. For example mass balance, when expressed in specific units, is a surface density. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Surface features | This subsection refers to the general appearance of the snow surface. These surface features SF are due to the following main processes: deposition, redistribution and erosion by wind, melting and refreezing, sublimation and evaporation, and rain. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Surface freezing index | The cumulative number of degree-days below 0 degrees Celsius for the surface temperature (of the ground, pavement, etc.) During a given time period. | NSIDC accessed 2016 |
| Surface freezing index | The cumulative number of degree-days below 0°C for the surface temperature (of the ground, pavement, etc.) during a given time period | Van Everdingen International Permafrost Association 2005 |
| Surface hoar | The deposition (sublimation) of ice crystals on a surface which occurs when the temperature of the surface is colder than the air above and colder than the frost point of that air. | NSIDC accessed 2016 |
| Surface hoar | 1. Fernlike ice crystals formed directly on a snow surface by deposition; a type of hoarfrost. 2. Hoarfrost that has grown primarily in two dimensions, as on a window or other smooth surface. | AMS - glossary of meteorology |
| Surface mass balance | The sum of surface accumulation and surface ablation. This is the sense in which the term is understood in descriptions of measurements by the glaciological method, in which the internal mass balance is treated separately. Recently, in estimates of ice-sheet mass balance by modelling, the term has been extended to include internal accumulation. This extended meaning is discouraged. The unambiguous term climatic mass balance is recommended for the sum of the surface mass balance and the internal mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Surface roughness | Refers to the roughness of a snow surface caused by precipitation or the wind as well as by uneven evaporation, sublimation, or melt. It does not refer to roughness due to snow microstructure. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Surface synoptic station | A surface location from which surface synoptic observations are made. | WMO METEOTERM accessed 2016 |
| Surface thawing index | The cumulative number of degree-days above 0°C for the surface temperature (of the ground, pavement, etc.) during a given period | Van Everdingen International Permafrost Association 2005 |
| Surge | Abnormally fast flow of a glacier over a period of a few months to years, during which the glacier margin may advance substantially. A surge-type glacier exhibits quiescent phases, typically lasting some decades, during which velocities are lower than in a 'normal', non-surge-type glacier. The ice discharge is thus too small to maintain the longitudinal profile of the glacier, which thickens in its upper reaches and thins in its lower reaches. Surges recur at quasi-periodic, glacier-specific intervals, and transfer large quantities of ice from the thickened upper part to the thinned lower part. Velocities during the surge are often greater by an order of magnitude than those during the quiescent phase. A surge-type glacier will almost always be out of balance. That is, a surge-type glacier cannot be in steady state. Surge-type glaciers may end on land or in water, and the proportion of glaciers that are of surge type varies from region to region. The mechanism of surging is poorly understood. Surges seem, however, to be related to changes in the subglacial hydrological regime and not primarily to climatic fluctuations. Although surging is best documented on smaller glaciers, many larger outlet glaciers of ice caps have been observed to surge, and there may be a connection with the unsteady behaviour exhibited by some ice streams. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Surge | A short-lived, frequently large-scale, increase in the rate of movement of the ice within a glacier. Ice velocities may increase 10 to 100 times above normal flow rates. In some surges, the terminus of a glacier rapidly advances. Although not all glaciers surge, those that do often surge with some sort of a periodicity. | Molnia USGS 2004 |
| Surge | A short-lived, frequently large-scale, increase in the rate of movement of the ice within a glacier. Ice velocities may increase 10 to 100 times above normal flow rates. In some surges, the terminus of a glacier rapidly advances. Although not all glaciers surge, those that do often surge with some sort of a periodicity. | Molnia USGS 2004 |
| Surge | (1) Rapid increase or decrease in flow or water level. (2) Abrupt acceleration of glacier flow accompanied by a dramatic forward movement of the glacier terminus. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Surge | A short-lived phase of accelerated flow during which the glacier surface becomes broken up into a maze of crevasses. Surges are often periodic and are separated by longer periods of relative inactivity or even stagnation (cf. quiescence). | Swisseduc - Photo glossary of glaciological terms |
| Surge front | The zone of intense compression between surging ice and non-surging ice. This is commonly marked by a bulge and a transition from heavily crevassed to crevasse-free ice. The surge front rapidly moves through the glacier, and if it reaches the snout, the glacier advances. | Swisseduc - Photo glossary of glaciological terms |
| Surge-type glacier | A glacier that has been observed to surge, or is inferred from evidence such as contorted medial moraines to have surged in the past. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Surging glacier | A glacier that experiences a dramatic increase in flow rate, 10 to 100 times faster than its normal rate; usually surge events last less than one year and occur periodically, between 15 and 100 years. | NSIDC accessed 2016 |
| Suscitic cryogenic fabric | A distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles have vertical or near-vertical orientation | Van Everdingen International Permafrost Association 2005 |
| Syngenetic ice | Ground ice developed during the formation of syngenetic permafrost. | NSIDC accessed 2016 |
| Syngenetic ice | Ground ice developed during the formation of syngenetic permafrost | Van Everdingen International Permafrost Association 2005 |
| Syngenetic ice wedge | An ice wedge developed during the formation of syngenetic permafrost. | NSIDC accessed 2016 |
| Syngenetic ice wedge | An ice wedge developed during the formation of syngenetic permafrost | Van Everdingen International Permafrost Association 2005 |
| Syngenetic permafrost | Permafrost that formed through a rise of the permafrost table during the deposition of additional sediment or other earth material on the ground surface. | NSIDC accessed 2016 |
| Syngenetic permafrost | Permafrost that formed through a rise of the permafrost table during the deposition of additional sediment or other earth material on the ground surface | Van Everdingen International Permafrost Association 2005 |
| Tabular berg | A flat-topped iceberg that shows horizontal banding; typically form by breaking from an ice shelf. | NSIDC accessed 2016 |
| Tabular berg | A flat-topped iceberg. Most tabular bergs form by calving from an ice shelf and show horizontal banding. | WMO Sea Ice Nomenclature 2017 |
| Tabular berg | Most flat-topped icebergs form by calving from an ice shelf and show horizontal banding. | Bushuyev 2004 |
| Tabular berg | A flat-topped iceberg. Most tabular bergs form by breaking from an ice shelf and show horizontal banding. | Illustrated Glossary of Snow and Ice |
| Tabular iceberg | Sea ice terminology describing a flat-topped iceberg; most tabular icebergs show horizontal banding. | Environment and Climate Change Canada 2014 |
| Tabular iceberg | A flat-topped iceberg that has become detached from an iceshelf, ice tongue or floating tidewater glacier; typically several kilometres long. | Swisseduc - Photo glossary of glaciological terms |
| Tabular iceberg | An iceberg that has broken off from an ice shelf. (Also called table iceberg; formerly called barrier iceberg.) Newly formed tabular icebergs have nearly vertical sides and flat tops. In the Antarctic, they may be tens of kilometers wide, up to 160 km (100 miles) long, and as much as 300 m (1000 ft) thick, with about 30 m (100 ft) exposed above the sea surface. In the Arctic, large icebergs of this type are called ice islands, but they are considerably smaller than the largest of the antarctic variety. | AMS - glossary of meteorology |
| Taiga | The open northern part of the boreal forest; consists of open woodland of coniferous trees growing in a rich floor of lichen (mainly reindeer moss or caribou moss), and is generally cold and swampy; lies immediately south of the tundra; in spring, it is often flooded by water from northward flowing rivers, the lower reaches of which are still frozen. | NSIDC accessed 2016 |
| Taiga | The open northern part of the boreal forest. It consists of open woodland of coniferous trees growing in a rich floor of lichen (mainly reindeer moss or caribou moss), and is generally cold and swampy. The taiga lies immediately south of the tundra. In spring, it is often flooded by water from northward flowing rivers, the lower reaches of which are still frozen. | AMS - glossary of meteorology |
| Taiga | See Boreal Forest. | PhysicalGeography.net |
| Taiga climate | In general, a climate that produces taiga vegetation; that is, one that is too cold for prolific tree growth but milder than the tundra climate and moist enough to promote appreciable vegetation. (Also called subarctic climate.) This climate type appears as a subdivision of K?ppen's 1936 snow forest climate and Thornthwaite's 1931 microthermal climate. | AMS - glossary of meteorology |
| Tail cloud | Colloquial expression for a horizontal cloud band, often laminar and tube-shaped, but sometimes ragged and turbulent, that is attached to a wall cloud. | AMS - glossary of meteorology |
| Taku | Name for a katabatic type of cold wind that occurs in Alaska. | PhysicalGeography.net |
| Talik | A layer or body of unfrozen ground occurring in a permafrost area due to a local anomaly in thermal, hydrological, hydrogeological, or hydrochemical conditions. | NSIDC accessed 2016 |
| Talik | A layer of year-round unfrozen ground that lies in permafrost areas. | IPCC WGI AR5 2013 |
| Talik | A layer or body of unfrozen ground occurring in a permafrost area due to a local anomaly in thermal, hydrological, hydrogeological, or hydrochemical conditions | Van Everdingen International Permafrost Association 2005 |
| Talik | A layer or body of Unfrozen Ground occurring in a Permafrost area due to a local anomaly in thermal, hydrological, hydrogeological, or hydrochemical conditions. Taliks may have temperatures above 0C (non-cryotic) or below 0C (cryotic). Some Taliks may be affected by seasonal freezing. Several types of Taliks can be distinguished on the basis of their relationship to the Permafrost (closed, open, lateral, isolated and transient Taliks), and on the basis of the mechanism responsible for their unfrozen condition (hydrochemical, hydrothermal and thermal Taliks): _ Closed Talik - a non-cryotic Talik occupying a depression in the Permafrost Table below a lake or river (also called 'lake Talik' and 'river Talik'); its temperature remains above 0C because of the heat storage effect of the surface water; Hydrochemical Talik - a cryotic Talik in which freezing is prevented by mineralized groundwater flowing through the Talik. _ Hydrothermal Talik - a non-cryotic Talik, the temperature of which is maintained above 0C by the heat supplied by groundwater flowing through the Talik; _ Isolated Talik - a Talik entirely surrounded by perennially Frozen Ground; usually cryotic, but may be non-cryotic; _ Lateral Talik - a Talik overlain and underlain by perennially Frozen Ground; can be noncryotic or cryotic; _ Open Talik - a Talik that penetrates the Permafrost completely, connecting supraPermafrost and Subpermafrost Water. It may be non-cryotic or cryotic. _ Thermal Talik - a non-cryotic Talik, the temperature of which is above 0C due to the local thermal regime of the ground; _ Transient Talik - a Talik that is gradually being eliminated by freezing. | Trombotto et al. 2014 |
| Talik | A Russian term applied to permanently unfrozen ground in regions of permafrost. (Also called tabetisol.) This usually applies to a layer that lies above the permafrost but below the active layer, that is, when the permafrost table is deeper than the depth reached by winter freezing from the surface. Talik is also found within and beneath permafrost; when it occurs beneath the permafrost it is equivalent to subgelisol. | AMS - glossary of meteorology |
| Talik | An unfrozen section of ground found above, below, or within a layer of discontinuous permafrost. These layers can also be found beneath water bodies in a layer of continuous permafrost. A number of different types of talik have been distinguished: closed talik, open talik, and through talik. | PhysicalGeography.net |
| Tarn | A small mountain lake or pool. | NSIDC accessed 2016 |
| Tarn | A lake that develops in the basin of a cirque, generally after the melting of the glacier. | Molnia USGS 2004 |
| Tarn | A lake that develops in the basin of a cirque, generally after the melting of the glacier. | Molnia USGS 2004 |
| Tarn | A small lake occupying a hollow eroded out by ice or dammed by a moraine; especially common in cirques (q.v.). | Swisseduc - Photo glossary of glaciological terms |
| Tarn | A small mountain lake that occurs inside a cirque basin. | PhysicalGeography.net |
| Taryn | Russian term for frozen ground that lasts for more than one season. | AMS - glossary of meteorology |
| Telescoped ice | Deformed sea ice in which one piece has overridden another; also called rafted ice. | NSIDC accessed 2016 |
| Temperate glacier | A glacier consisting of temperate ice over its entire thickness and extent, except for a surface layer of the order of 1015 m thick which may experience seasonal cooling. By definition a temperate glacier is a wet-based glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Temperate glacier | A glacier with a or temperature-regime in which liquid water coexists with frozen water (glacier ice) during part or even all of the year. | Molnia USGS 2004 |
| Temperate glacier | A glacier whose temperature is at the pressure melting point throughout, except for a cold wave of limited penetration that occurs in winter. | Swisseduc - Photo glossary of glaciological terms |
| Temperate glacier | In Ahlmann's glacier classification, a glacier that, at the end of the melting season, is composed of firn, and ice at the melting point. | AMS - glossary of meteorology |
| Temperate glacier | Glacier in which the ice found below 10 to 20 meters from its surface is at the pressure melting point. One of the three types of glaciers: cold glacier; temperate glacier; and subpolar glacier. | PhysicalGeography.net |
| Temperate ice | (1) Ice that contains a liquid phase of no more than moderate salinity with which it is in thermodynamic equilibrium at the solidliquid phase boundaries. (2) Less precisely, ice that is at its pressure-melting point. Other factors, notably the salinity of water inclusions, can be of comparable importance to the hydrostatic pressure for determination of the melting point. Sense 2 is adequate for simple purposes, but the details illuminated by Lliboutry (1971) and Harrison (1972) are likely to be of practical importance in detailed work. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Temperate ice | Ice which is at the pressure melting point, and therefore usually wet. | Swisseduc - Photo glossary of glaciological terms |
| Temperature coefficient of snowmelt | Thickness of the meltwater layer corresponding to an increase in temperature of 1 degree Celsius above freezing point. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Temperature profile | The graphic or analytical expression of the variation in ground temperature with depth | Van Everdingen International Permafrost Association 2005 |
| Temperature-index model | A model of mass balance in which surface ablation is estimated as a function of temperature, usually near-surface air temperature measured either on the glacier or at the nearest weather station; temperatures may also be taken from upper-air soundings, meteorological reanalyses or climate models. A leading form of temperature-index model is the positive degree-day model, in which a degree-day factor represents the dependence of ablation on temperature. Temperature-index models are valuable because they require only simple input variables and perform well when suitably calibrated, for example by allowing for the differences in reflectivity between surfaces of ice and snow by choosing a smaller degree-day factor for snow than for ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Tented ice | Pressure ice in which two floes have been pushed into the air, leaving an air space underneath. | AMS - glossary of meteorology |
| Tephra | Ash and coarse fragments thrown out by a volcano during an eruption. In glacierised areas these layers are preserved in glaciers, deforming slowly during ice flow. | Swisseduc - Photo glossary of glaciological terms |
| Terminal moraine | Terminal moraines are piles of loose unconsolidated rock at the glacier's downvalley end. The rocks may be pushed there by the forward motion of the glacier or dumped from the glacier's rounded surface. As glaciers melt, their remaining load of rocks is distributed in several ways. Rocks may be dropped in place by the melting ice; they may be rolled to the ice margins, or they may be deposited by meltwater streams. Collectively, these deposits are called 'glacial drift'. 'Till' refers to the debris deposited directly by the glacier. Rock debris rolls off the glacier edges and builds piles of loose unconsolidated rocks called 'glacier moraine'. 'Lateral moraines' form along the side of a glacier and curl into a 'terminal moraine' at the glacier's downvalley end. Drift and moraines are valuable to geologists because they outline the boundaries of past glaciations. | Molnia USGS 2004 |
| Terminal moraine | A cross-valley, ridge-like accumulation of glacial sediment that forms at the farthest point reached by the terminus of an advancing glacier. Also called an End Moraine. | Molnia USGS 2004 |
| Terminal moraine | Moraine that marks the maximum advance of a glacier. | PhysicalGeography.net |
| Terminal moraine (or end moraine) | A prominent ridge of glacial debris formed when a glacier reached its maximum limit during a sustained advance. | Swisseduc - Photo glossary of glaciological terms |
| Terminus | The lowest end of a glacier, also called the glacier toe or glacier snout. | NSIDC accessed 2016 |
| Terminus | The lower-most margin, end, or extremity of a glacier. Also called Toe, End or Snout. | Molnia USGS 2004 |
| Terminus | The downvalley end of a glacier. It is sometimes referred to as the glacier snout. The lower-most margin, end, or extremity of a glacier. Also called Toe, End or Snout. | Molnia USGS 2004 |
| Terminus | The lowest end of a glacier, also called glacier snout, glacier front or glacier toe. The term, the plural of which is either 'terminuses' or 'termini', is applicable primarily to glaciers with well-defined tongues, and to ice streams. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Terminus | End or snout of a glacier. | PhysicalGeography.net |
| Terrestrial calving | Dry calving; Ice front breaks off over cliffs or rock steps of different height; This class has been introduced to facilitate a differentiation between calving into water (lakes, sea) and dry calving. | Illustrated GLIMS Glacier Classification Manual |
| Terrestrial glaciers | Glaciers which rest on their entire extent on bedrock and do not have any contact to sea. | Illustrated GLIMS Glacier Classification Manual |
| Thaw | Melting of snow and ice following a temperature rise above 0 degrees Celsius. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Thaw | 1. To melt a substance, ice for example, by warming it to a temperature greater than the melting point of the substance, or to have frozen contents melted. 2. To free something from the binding action of ice by warming it to a temperature above the melting point of ice. 3. A warm spell when ice and snow melt, for example, "January thaw." | AMS - glossary of meteorology |
| Thaw basin | A depression of the permafrost table created by naturally induced thawing | Van Everdingen International Permafrost Association 2005 |
| Thaw bulb | A zone of thawed ground below or surrounding a man-made structure placed on or in permafrost and maintained at temperatures above 0 degrees Celsius. | NSIDC accessed 2016 |
| Thaw bulb | A zone of thawed ground below or surrounding a man-made structure placed on or in permafrost and maintained at temperatures above 0°C | Van Everdingen International Permafrost Association 2005 |
| Thaw consolidation | Time-dependent compression resulting from thawing of frozen ground and subsequent draining of excess water. | NSIDC accessed 2016 |
| Thaw consolidation | Time-dependent compression resulting from thawing of frozen ground and subsequent draining of excess water | Van Everdingen International Permafrost Association 2005 |
| Thaw consolidation | Time-dependent compression resulting from thawing of Frozen Ground and subsequent draining of excess water. If during thaw, the flow of water from the thawed ground is unimpeded, then the variation of thaw settlement with time is controlled solely by the position of the thawing front. If the thawed ground is not sufficiently permeable, and flow is impeded, however, the rate of settlement with time is also controlled by the compressibility and permeability of the thawed ground. In the case of thawing fine-grained soils, if the rate of thaw is sufficiently fast, water is released at a rate exceeding that at which it can flow from the soil, and pore pressures in excess of hydrostatic will be generated. These excess pore pressures may cause severe instability problems in slopes and foundation soils. | Trombotto et al. 2014 |
| Thaw consolidation ratio | A dimensionless ratio describing the relationship between the rate of thaw and the rate of consolidation of a thawing soil, which is considered to be a measure of the relative rates of generation and expulsion of excess water during thaw. | NSIDC accessed 2016 |
| Thaw consolidation ratio | A dimensionless ratio describing the relationship between the rate of thaw and the rate of consolidation of a thawing soil, which is considered to be a measure of the relative rates of generation and expulsion of excess water during thaw | Van Everdingen International Permafrost Association 2005 |
| Thaw consolidation ratio | A dimensionless ratio describing the relationship between the rate of thaw and the rate of consolidation of a thawing soil, which is considered to be a measure of the relative rates of generation and expulsion of excess water during thaw. | Trombotto et al. 2014 |
| Thaw hole | Vertical hole in floating ice formed when a puddle melts through to the underlying water. | NSIDC accessed 2016 |
| Thaw hole | Vertical hole in floating ice formed when a puddle melts through to the underlying water. | Illustrated Glossary of Snow and Ice |
| Thaw holes | Sea ice terminology describing vertical holes in the ice that are formed when surface puddles melt through to the underlying water. | Environment and Climate Change Canada 2014 |
| Thaw holes | Vertical holes in sea ice formed when surface puddles melt through to the underlying water. | WMO Sea Ice Nomenclature 2017 |
| Thaw holes | Vertical holes in sea ice formed when surface puddles melt through to the underlying water. | Bushuyev 2004 |
| Thaw penetration | The downward movement of the thawing front during thawing of frozen ground. | NSIDC accessed 2016 |
| Thaw penetration | The downward movement of the thawing front during thawing of frozen ground | Van Everdingen International Permafrost Association 2005 |
| Thaw settlement | Compression of the ground due to thaw consolidation. | NSIDC accessed 2016 |
| Thaw settlement | Compression of the ground due to thaw consolidation | Van Everdingen International Permafrost Association 2005 |
| Thaw sink | A closed thaw basin with subterranean drainage. | NSIDC accessed 2016 |
| Thaw sink | A closed thaw basin with subterranean drainage | Van Everdingen International Permafrost Association 2005 |
| Thaw slumping | A slope failure mechanism characterized by the melting of ground ice, and downslope sliding and flowing of the resulting debris. | NSIDC accessed 2016 |
| Thaw slumping | A slope failure mechanism characterized by the melting of ground ice, and downslope sliding and flowing of the resulting debris | Van Everdingen International Permafrost Association 2005 |
| Thaw strain | The amount that frozen ground compresses upon thawing. | NSIDC accessed 2016 |
| Thaw strain | The amount that frozen ground compresses upon thawing | Van Everdingen International Permafrost Association 2005 |
| Thaw unconformity | A boundary sometimes identified in perennially frozen ground, representing the base of a relict active layer, as well as the corresponding earlier permafrost table. | NSIDC accessed 2016 |
| Thaw unconformity | A boundary sometimes identified in perennially frozen ground, representing the base of a relict active layer, as well as the corresponding earlier permafrost table | Van Everdingen International Permafrost Association 2005 |
| Thaw unconformity | A boundary sometimes identified in perennially Frozen Ground, representing the base of a Relict Active Layer, as well as the corresponding earlier Permafrost Table. A Thaw Unconformity may be recognized by differences in Ice Contents, stable isotope contents, and heavy mineral and pollen assemblages above and below the unconformity. | Trombotto et al. 2014 |
| Thaw weakening | The reduction in shear strength due to the decrease in effective stresses resulting from the generation and slow dissipation of excess pore pressures when frozen soils containing ice are thawing. | NSIDC accessed 2016 |
| Thaw weakening | The reduction in shear strength due to the decrease in effective stresses resulting from the generation and slow dissipation of excess pore pressures when frozen soils containing ice are thawing | Van Everdingen International Permafrost Association 2005 |
| Thaw weakening | The reduction in shear strength due to the decrease in effective stresses resulting from the generation and slow dissipation of excess pore pressures when frozen soils containing Ice are thawing. The usual effects of Thaw Weakening are a significant decrease in bearing capacity and an increase in instability problems. A soil is called thaw stable if it is not affected by Thaw Weakening. | Trombotto et al. 2014 |
| Thaw-sensitive permafrost | Perennially frozen ground which, upon thawing, will experience significant thaw settlement and suffer loss of strength to a value significantly lower than that for similar material in an unfrozen condition. | NSIDC accessed 2016 |
| Thaw-sensitive permafrost | Perennially frozen ground which, upon thawing, will experience significant thaw settlement and suffer loss of strength to a value significantly lower than that for similar material in an unfrozen condition | Van Everdingen International Permafrost Association 2005 |
| Thaw-stable permafrost | Perennially frozen ground which, upon thawing, will not experience either significant thaw settlement or loss of strength. | NSIDC accessed 2016 |
| Thaw-stable permafrost | Perennially frozen ground which, upon thawing, will not experience either significant thaw settlement or loss of strength | Van Everdingen International Permafrost Association 2005 |
| Thawed ground | Previously frozen ground in which all ice has melted. | NSIDC accessed 2016 |
| Thawed ground | Previously frozen ground in which all ice has melted | Van Everdingen International Permafrost Association 2005 |
| Thawing (of frozen ground) | Melting of the ice in frozen ground, usually as a result of a rise in temperature. | NSIDC accessed 2016 |
| Thawing (of frozen ground) | Melting of the ice in frozen ground, usually as a result of a rise in temperature | Van Everdingen International Permafrost Association 2005 |
| Thawing (of frozen ground) | Melting of the Ice in Frozen Ground, usually as a result of a rise in temperature. | Trombotto et al. 2014 |
| Thawing front | The advancing boundary between thawed ground and frozen ground. | NSIDC accessed 2016 |
| Thawing front | The advancing boundary between thawed ground and frozen ground | Van Everdingen International Permafrost Association 2005 |
| Thawing index | As used by the U.S. Army Corps of Engineers, the number of Fahrenheit degree- days (above and below 32F) between the lowest and highest points on the cumulative degree- days time curve for one thawing season. The thawing index determined from air temperatures at 4.5 ft above the ground is commonly designated the air thawing index, while that determined from temperatures immediately below a surface is called the surface thawing index. | AMS - glossary of meteorology |
| Thawing index | The cumulative number of degree-days above 0 degrees Celsius for a given time period. | NSIDC accessed 2016 |
| Thawing index | The cumulative number of degree-days above 0°C for a given time period | Van Everdingen International Permafrost Association 2005 |
| Thawing index | The cumulative number of degree-days above 0C for a given time period. Four main types of air thawing indices have been used: _ Approximate Thawing Index - calculated from the mean monthly air temperatures for a specific station without making corrections for negative degree-days (T < 0C) in spring and fall (Boyd, 1973, 1979); I_af = SUM (NT) where N = number of days per month for months with a mean monthly temperature above 0C during one complete year. T = mean monthly temperature. _ Total annual Thawing Index - calculated by adding all the positive mean daily temperatures (C) for a specific station during a calendar year (Harris, 1981); I_af = SUM (T) where T = mean daily air temperatures (C) above 0C for one complete calendar year. _ Seasonal Thawing Index - calculated as the arithmetic sum of all the positive and negative mean daily air temperatures (C) for a specific station during the time period between the lowest point in the spring and the highest point the next fall on the cumulative degree-day time curve (Huschke, 1959); I_af = SUM (T) where T = mean daily air temperatures (C) during the time period between the lowest temperature in the Spring and the highest temperature in the Fall. _ Design Thawing Index - calculated by taking the average of the seasonal thawing indices for the three warmest summers in the most recent 30 years of record. If data for 30 years are not available, then the index is based on the warmest summer in the latest 10-year period of record (U.S. Army/Air Force, 1966). | Trombotto et al. 2014 |
| Thawing season | As used by the U.S. Army Corps of Engineers, the period of time between the lowest point and the succeeding highest point on the time curve of cumulative Fahrenheit degree- days above and below 32F; the opposite of freezing season. | AMS - glossary of meteorology |
| Theodolite | An optical instrument used to visually track a radiosonde balloon and determine its bearing and elevation while in flight. | NSIDC accessed 2016 |
| Thermal conductivity | The quantity of heat that will flow through a unit area of a substance in unit time under a unit temperature gradient | Van Everdingen International Permafrost Association 2005 |
| Thermal diffusivity | The ratio of the thermal conductivity to the volumetric heat capacity | Van Everdingen International Permafrost Association 2005 |
| Thermal erosion | The erosion of ice-bearing permafrost by the combined thermal and mechanical action of moving water. | NSIDC accessed 2016 |
| Thermal erosion | The erosion of ice-bearing permafrost by the combined thermal and mechanical action of moving water | Van Everdingen International Permafrost Association 2005 |
| Thermal expansion (or contraction) coefficient | The volume change per unit volume of a substance due to a one degree change in its temperature | Van Everdingen International Permafrost Association 2005 |
| Thermal pile | A foundation pile on which natural convection or forced circulation cooling systems or devices have been installed to remove heat from the ground. | NSIDC accessed 2016 |
| Thermal pile | A foundation pile on which natural convection or forced circulation cooling systems or devices have been installed to remove heat from the ground | Van Everdingen International Permafrost Association 2005 |
| Thermal properties of frozen ground | The properties of the ground governing the flow of heat through it, and its freezing and thawing conditions. | NSIDC accessed 2016 |
| Thermal properties of frozen ground | The properties of the ground governing the flow of heat through it, and its freezing and thawing conditions | Van Everdingen International Permafrost Association 2005 |
| Thermal properties of frozen ground | The properties of the ground governing the flow of heat through it, and its freezing and thawing conditions. The position of the interface between thawed and frozen soil with respect to the ground surface, for a given surface-temperature regime, depends on the thermal properties of the strata located above and immediately below the interface. The basic Thermal Properties of Frozen Ground are Thermal Conductivity, Heat capacity and Latent Heat of Fusion. | Trombotto et al. 2014 |
| Thermal regime of the ground | A general term encompassing the temperature distribution and heat flows in the ground and their time-dependence. | NSIDC accessed 2016 |
| Thermal regime of the ground | A general term encompassing the temperature distribution and heat flows in the ground and their time-dependence | Van Everdingen International Permafrost Association 2005 |
| Thermal talik | A layer or body of unfrozen ground (in a permafrost area) in which the temperature is above 0 degrees Celsius due to the local thermal regime of the ground. | NSIDC accessed 2016 |
| Thermal talik | A layer or body of unfrozen ground (in a permafrost area) in which the temperature is above 0°C due to the local thermal regime of the ground | Van Everdingen International Permafrost Association 2005 |
| Thermal-contraction crack | A tensile fracture resulting from thermal stresses in frozen ground. | NSIDC accessed 2016 |
| Thermal-contraction crack | A tensile fracture resulting from thermal stresses in frozen ground | Van Everdingen International Permafrost Association 2005 |
| Thermal-contraction-crack ice | Ice formed in thermal contraction cracks in the ground. | NSIDC accessed 2016 |
| Thermal-contraction-crack ice | Ice formed in thermal contraction cracks in the ground | Van Everdingen International Permafrost Association 2005 |
| Thermo-erosional cirque | The usually steep, horseshoe-shaped headwall of a retrogressive thaw slump. | NSIDC accessed 2016 |
| Thermo-erosional cirque | The usually steep, horseshoe-shaped headwall of a retrogressive thaw slump | Van Everdingen International Permafrost Association 2005 |
| Thermo-erosional niche | A recess at the base of a river bank or coastal bluff, produced by thermal erosion of ice-bonded permafrost. | NSIDC accessed 2016 |
| Thermo-erosional niche | A recess at the base of a river bank or coastal bluff, produced by thermal erosion of ice-bonded permafrost | Van Everdingen International Permafrost Association 2005 |
| Thermodynamic equilibrium thickness | The thickness at which ice no longer grows because it is so thick that heat from the ocean can no longer be conducted through the ice; it may take several years of growth and melt for ice to reach an equilibrium thickness. | NSIDC accessed 2016 |
| Thermokarst | The process by which characteristic landforms result from the thawing of ice-rich permafrost or the melting of massive ice. | NSIDC accessed 2016 |
| Thermokarst | The process by which characteristic landforms result from the thawing of ice-rich permafrost or the melting of massive ground ice. | IPCC WGI AR5 2013 |
| Thermokarst | The process by which characteristic landforms result from the thawing of ice-rich permafrost or the melting of massive ice | Van Everdingen International Permafrost Association 2005 |
| Thermokarst | The process by which characteristic landforms result from the thawing of Ice-Rich Permafrost or the melting of Massive Ice. Landforms found in Thermokarst terrain include Alases, Thermokarst Lakes, and Thermokarst Mounds. | Trombotto et al. 2014 |
| Thermokarst | Landscape dominated by depressions, pits, and caves that is created by the thawing of ground ice in high latitude locations. Resembles karst landscape but is not created by chemical weathering. | PhysicalGeography.net |
| Thermokarst lake | A lake occupying a closed depression formed by settlement of the ground following thawing of ice-rich permafrost or the melting of massive ice. | NSIDC accessed 2016 |
| Thermokarst lake | A lake occupying a closed depression formed by settlement of the ground following thawing of ice-rich permafrost or the melting of massive ice | Van Everdingen International Permafrost Association 2005 |
| Thermokarst mound | A hummock remaining after melting of the ice wedges surrounding an ice-wedge polygon. | NSIDC accessed 2016 |
| Thermokarst mound | A hummock remaining after melting of the ice wedges surrounding an ice-wedge polygon | Van Everdingen International Permafrost Association 2005 |
| Thermokarst terrain | The often irregular topography resulting from the melting of excess ground ice and subsequent thaw settlement. | NSIDC accessed 2016 |
| Thermokarst terrain | The often irregular topography resulting from the melting of excess ground ice and subsequent thaw settlement | Van Everdingen International Permafrost Association 2005 |
| Thermokarst topography | A pattern of waterfilled sinks, cave-ins, and other small depressions caused by the local melting of permafrost. | AMS - glossary of meteorology |
| Thermometer | Instrument which measures the temperature. | WMO METEOTERM accessed 2016 |
| Thermometer | An instrument for measuring temperature by utilizing the variation of the physical properties of substances according to their thermal states. Thermometers may be classified into six types according to their construction: gas thermometer, liquid-in-glass thermometer, deformation thermometer, electrical thermometer, liquid-in- metal thermometer, and sonic thermometer. | AMS - glossary of meteorology |
| Thermosyphon | A passive heat transfer device installed to remove heat from the ground. | NSIDC accessed 2016 |
| Thermosyphon | A passive heat transfer device installed to remove heat from the ground | Van Everdingen International Permafrost Association 2005 |
| Thick first-year ice | First-year ice over 120 cm thick. | Bushuyev 2004 |
| Thick first-year ice | First-year ice over 4 ft (120 cm) thick. | WMO Sea Ice Nomenclature 2017 |
| Thick first-year ice | Sea ice terminology which describes ice that is between 30 cm to 70 cm thick. | Environment and Climate Change Canada 2014 |
| Thick lake ice | Sea ice terminology which describes ice that is between 30 cm to 70 cm thick. | Environment and Climate Change Canada 2014 |
| Thickness | The vertical distance between any two surfaces, and in particular between the glacier face and the summer surface, or the glacier surface and the bed. Glacier thickness is measured ideally by interpolating from a dense array of point measurements, constructed for example from ground-penetrating radar traverses. However the measurement density is often less than ideal, as when the array consists of a single traverse or even just a small number of boreholes. On most glaciers there are no thickness measurements at all and the thickness must be estimated, for example by volume-area scaling or as a function of surface slope and estimated basal shear stress. The definition of thickness as a vertical distance is adopted almost invariably in studies of mass balance, but not in all branches of cryospheric science. For example Fierz et al. (2009) define thickness as the coordinate normal to the slope, measured from the base of a layer of snow. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Thickness | Thickness D is the slope normal coordinate to be used when measurements are taken perpendicular, i.e., at right angle to the slope on inclined snow covers. It is measured in centimetres from the base and the same comments apply as for height.
When observers use thickness, they should also report the slope angle with respect to either the snow surface or a layer within the snowpack, e.g., the bed surface of an avalanche. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Thickness change | The change in the thickness of the glacier at a defined horizontal location. Thickness can change at a point due to ablation and accumulation at the surface and bottom of the glacier, compaction of snow and firn, or a non-zero emergence velocity or submergence velocity. Thickness change is often used interchangeably with elevation change, but the two are not necessarily the same. For example, elevation can change due to glacial isostatic adjustment or vertical tectonic motions, without a change in glacier thickness. The thickness change at a point is not equivalent to the climatic-basal mass balance at that point because the thickness change may be due in part to emergence or submergence. Thickness change at a point is therefore not a direct indicator of the local climate. The glacier-wide mean thickness change is the volume change of the entire glacier divided by the mean glacier area during the time span of the measurements: 2(h V VS S 21)/(21) , where V is volume, S is area, and subscripts 1 and 2 refer to measurements at an earlier and later time, respectively. The quantity 21( ) V V V is the volume change. Usually the two volumes are not known separately, and: V is obtained from measurements of by geodetic methods. The mean thickness change, if multiplied by the density of the mass gained or lost, is equal to the glacier-wide mass balance over the period of the thickness change. The mean thickness change differs from the change of mean thickness, which is V2/S2 V1/S1. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Thin first year ice/white ice | First-year ice 30-70 cm thick. May be subdivided into thin first-year ice of the first stage 30 to 50 cm thick and thin first-year ice of the second stage 50 to 70 cm. | Bushuyev 2004 |
| Thin first-year ice/white ice | First-year ice 1 to 2 ft (30-70 cm) thick. | WMO Sea Ice Nomenclature 2017 |
| Thin first-year ice/white ice - first stage | Sea ice terminology which describes ice that is 30 cm to 50 cm thick. | Environment and Climate Change Canada 2014 |
| Thin first-year ice/white ice - second stage | Sea ice terminology which describes ice that is 50 cm to 70 cm thick. | Environment and Climate Change Canada 2014 |
| Thin lake ice | Sea ice terminology which describes ice that is 5 cm to 15 cm thick. | Environment and Climate Change Canada 2014 |
| Thinning flux | The mass flux through a vertical cross section corresponding to the decrease of mass upglacier from the section (that is, the integral of density over the thickness of the glacier and the upglacier area). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Thinning velocity | The volumetric thinning flux divided by the area of the vertical cross section through which it passes. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Thomson crystal | A large ice crystal found in deep, stagnant water-filled cavities of a glacier. | NSIDC accessed 2016 |
| Threshold velocity | Velocity required to cause entrainment in the erosional agents of wind, water or ice. Threshold velocity is usually higher than the velocity required for transport because factors like particle cohesion. Also see critical entrainment velocity. | PhysicalGeography.net |
| Through talik | Is a form of localized unfrozen ground (talik) in an area of permafrost. It is open to the ground surface and to an area of unfrozen ground beneath it. Permafrost encases it along the sides. | PhysicalGeography.net |
| Thrust | A low-angle fault, usually formed where the ice is under compression. Thrusts commonly extend from the bed and are associated with debris and overturned folds. | Swisseduc - Photo glossary of glaciological terms |
| Thufur | Perennial hummocks formed in either the active layer in permafrost areas, or in the seasonally frozen ground in non-permafrost areas, during freezing of the ground. | NSIDC accessed 2016 |
| Thufur | Perennial hummocks formed in either the active layer in permafrost areas, or in the seasonally frozen ground in non-permafrost areas, during freezing of the ground | Van Everdingen International Permafrost Association 2005 |
| Thufur | Perennial hummocks formed in either the Active Layer in Permafrost areas, or in the seasonally frozen ground in non-permafrost areas, during freezing of the ground. The hummocks may be as much as 50 cm in height and 160 cm in diameter and can reform within 20 years following destruction. Growth is favoured by silty sediments and reasonably good drainage. | Trombotto et al. 2014 |
| Thundersnow | Thundersnow is a compound of the words 'thunder' and 'snow' used informally to describe an observation of snow at the surface that occurs with lightning and thunder. In the mid-latitudes, thundersnow is prevalent downwind of lakes (e.g., the U.S. Great Lakes) due to sensible and latent heating of the boundary layer, and also in mountainous regions when the environment is sufficiently unstable and/or when significant orographic lifting occurs in preferred areas. Additionally, embedded convective cells producing thundersnow can occur with intensifying extratropical cyclones. Thundersnow can be associated with increased snowfall rates leading to significant visibility reductions and localized areas of higher snow accumulation. | AMS - glossary of meteorology |
| Tidal glacier | A glacier with its terminus in the ocean or sea. | AMS - glossary of meteorology |
| Tide crack | The fissure at the line of junction between an immovable icefoot or ice wall and fast ice, the latter being subject to the rise and fall of the tide. | NSIDC accessed 2016 |
| Tide crack | A crack between fast ice subject to sea level tidal rise and fall and the fast ice foot or ice wall, or shore. | Bushuyev 2004 |
| Tide crack | Crack at the line of junction between an immovable ice foot or ice wall and fast ice, the latter subject to rise and fall of the tide. | WMO Sea Ice Nomenclature 2017 |
| Tide crack | A crack between the moving sea ice and the unmoving ice foot. It may widen to form a shore lead. | AMS - glossary of meteorology |
| Tide crack | The fissure at the line of junction between an immovable icefoot or ice wall and fast ice, the latter being subject to the rise and fall of the tide. | Illustrated Glossary of Snow and Ice |
| Tidewater glacier | Mountain glacier that terminates in the ocean. | NSIDC accessed 2016 |
| Tidewater glacier | A glacier that terminates in the sea, with terminus either floating or grounded below sea level. The adjective indicates geographical setting, and not that tides play a role in the mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Tidewater glacier | A glacier with a terminus that ends in a body of water influenced by tides, such as the ocean or a large lake. Typically, tidewater glaciers calve ice to produce icebergs. | Molnia USGS 2004 |
| Tidewater glacier | A glacier that terminates in the sea. Some writers restrict the term to a glacier with its terminus resting on the sea floor. | Swisseduc - Photo glossary of glaciological terms |
| Tidewater instability | Unsteady, perhaps quasi-periodic, behaviour (Meier and Post 1987) of a tidewater glacier that undergoes alternating episodes of slow advance and rapid retreat. The conditions permitting advance to the advanced position in the first place, and the triggers for subsequent unstable retreat, are both poorly understood, although they may involve variations in basal water pressure and probably involve variations of the climatic mass balance. Once retreat has begun, however, observation and simulation (Schoof 2007) agree that, if the bed is grounded below sea level but has a slope opposed to that of the surface, the retreat will continue until the grounding line reaches a part of the bed that slopes in the same direction as the surface. During this unstable retreat, enhanced calving leads to a positive feedback in which accelerated flow and dynamic thinning extend far upglacier from the part that is grounded below sea level. Mass loss is far greater than, and essentially independent of, the climatic mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Till | Till is the unsorted rock debris deposited directly by the glacier without the extreme reworking by meltwater. As glaciers melt, their remaining load of rocks is distributed in several ways. Rocks may be dropped in place by the melting ice; they may be rolled to the ice margins, or they may be deposited by meltwater streams. Collectively, these deposits are called 'glacial drift'. 'Till' refers to the debris deposited directly by the glacier. Rock debris rolls off the glacier edges and builds piles of loose unconsolidated rocks called 'glacier moraine'. 'Lateral moraines' form along the side of a glacier and curl into a 'terminal moraine' at the glacier's downvalley end. Drift and moraines are valuable to geologists because they outline the boundaries of past glaciations. | Molnia USGS 2004 |
| Till | An unsorted and unstratified accumulation of glacial sediment, deposited directly by glacier ice. Till is a heterogeneous mixture of different sized material deposited by moving ice (lodgement till) or by the melting in-place of stagnant ice (ablation till). After deposition, some tills are reworked by water. | Molnia USGS 2004 |
| Till | A poorly sorted mixture of mud, sand and gravel-sized material deposited directly from glacier ice. The principal types of till are basal, deposited beneath a glacier, and embracing lodgement till (plastered on the bed) and meltout till (released from slow-moving or stagnant ice); and supraglacial meltout till, let down onto the substrate from the glacier surface. | Swisseduc - Photo glossary of glaciological terms |
| Till | Heterogeneous sediment deposited directly by a glacier. The particles within this deposit have not been size sorted by the action of wind or water. | PhysicalGeography.net |
| Till plain | Extensive flat plain of till that forms when a sheet of ice becomes detached from the main body of the glacier and melts in place depositing the sediments it carried. | PhysicalGeography.net |
| Tillite | The hard rock equivalent of till: A mixture of mud, sand and gravel-sized material deposited directly from glacier ice which, later on, solidified. | Swisseduc - Photo glossary of glaciological terms |
| Time system | A protocol for identifying stages in the evolution of the mass balance of the glacier over the mass-balance year, making it possible to quantify the mass change during each stage objectively. Four time systems are recognized. Figure 14 illustrates the differences between the original two. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Tongue | A projection of the ice edge up to several km in length caused by wind and current; usually forms when a valley glacier moves very quickly into a lake or ocean. | NSIDC accessed 2016 |
| Tongue | (1) The lower, elongate part of a valley glacier or outlet glacier. (2) A floating extension of a glacier or ice stream, laterally unconfined but markedly longer than wide. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Tongue | A projection of the ice edge up to several miles (kilometers) in length, caused by wind or current. | WMO Sea Ice Nomenclature 2017 |
| Tongue | Sea ice terminology meaning an extension of the ice edge up to several kilometres in length, caused by wind or current. | Environment and Climate Change Canada 2014 |
| Tongue | A projection of the ice edge up to several km in length caused by wind and current. | Illustrated Glossary of Snow and Ice |
| Tongue activity | Uncertain: unknown or not measured; Marked retreat: more than 20 m per year retreat; Slight retreat: 20m per year retreat; Stationary: Stationary; Slight advance: 20m per year advance; Marked advance: more than 20m per year advancing; Possible surge: possible surge; Known surge: known surge; Oscillating: oscillating; Downwasting: stationary but rapidly losing mass through melting. | Illustrated GLIMS Glacier Classification Manual |
| Tooth | Tooth shaped rock or nunatak | UK Antarctic Place-names Committee accessed 2016 |
| Topographic method | Like cartographic method, a synonym of geodetic method in the context of measurement of mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Tor | Rock outcrop due to incomplete frost weathering. The origin of Tors is strongly related to the rock structure, especially with their degree of fissility. Tors can be classified in slope tors, located along the margins of valleys and surrounded by slopes covered by cryogenic debris with slope angles between 20 and 30, and apical tors, located on mountain summits. The latter are related to cryoplanation terraces and felsenmeer. | Trombotto et al. 2014 |
| Tortuosity | Tortuosity τ is defined as the ratio of two distances: the path between two points through the ice or pore space and the straight line between them. The tortuosity of the ice matrix may be the primary factor determining the thermal conductivity of snow. It also affects the elastic modulus and heat and mass fluxes through the pore space. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Total ablation | A term formerly used in the stratigraphic system (Anonymous 1969; Appendix: A) for Annual ablation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Total accumulation | A term formerly used in the stratigraphic system (Anonymous 1969; Appendix A/1 /2 or Annual accumulation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Total annual freezing index | The cumulative number of degree-days, calculated by adding all the negative mean daily air temperatures (degrees Celsius) for a specific station during a calendar year. | NSIDC accessed 2016 |
| Total annual freezing index | The cumulative number of degree-days, calculated by adding all the negative mean daily air temperatures (°C) for a specific station during a calendar year | Van Everdingen International Permafrost Association 2005 |
| Total annual thawing index | The cumulative number of degree-days, calculated by adding all the positive mean daily air temperatures (degrees Celsius) for a specific station during a calendar year. | NSIDC accessed 2016 |
| Total annual thawing index | The cumulative number of degree-days, calculated by adding all the positive mean daily air temperatures (°C) for a specific station during a calendar year | Van Everdingen International Permafrost Association 2005 |
| Total exchange | A term formerly used (Anonymous1969; Appendix: A) for the difference between Annual accumulation and Annual ablation, ca minus aa, in the stratigraphic system. Note that ablation is defined to be negative. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Total mass balance | The sum of the climatic-basal mass balance and frontal ablation, or equivalently the sum of accumulation and ablation; a synonym of mass balance. The adjective 'total' was formerly a technical term in the stratigraphic system (Anonymous 1969; Appendix: A). It is now needed only when it is important to emphasize that all the components of the mass balance are being studied. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Total water content (of frozen ground) | The total amount of water (unfrozen water plus ice) contained in soil or rock. | NSIDC accessed 2016 |
| Total water content (of frozen ground) | The total amount of water (unfrozen water plus ice) contained in soil or rock | Van Everdingen International Permafrost Association 2005 |
| Tower | Tower-like hill, mountain or nunatak | UK Antarctic Place-names Committee accessed 2016 |
| Traditional knowledge | The knowledge, innovations, and practices of both indigenous and local communities around the world that are deeply grounded in history and experience. Traditional knowledge is dynamic and adapts to cultural and environmental change, and also incorporates other forms of knowledge and viewpoints. Traditional knowledge is generally transmitted orally from generation to generation. It is often used as a synonym for indigenous knowledge, local knowledge, or traditional ecological knowledge. | IPCC WGII AR5 2014 |
| Transient | Of a state or entity, changing with time or persisting for only a short time. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Transient AAR | The AAR at any instant, particularly during the ablation season. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Transient ELA | The ELA at any instant, particularly during the ablation season. The transient ELA is not in general the same as the average altitude of the transient snowline. The superimposed ice zone lies below the transient snowline and above the transient ELA. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Transient equilibrium line | The equilibrium line at any instant, where cumulative ablation balances cumulative accumulation relative to the start of the mass-balance year. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Transient layer | The Transient Layer is the near-surface Ice-Rich layer marking the long term position of the contact between the Active Layer and the upper part of the Permafrost. The Transient Layer is a typically part of the uppermost Permafrost but, under certain conditions, occasionally joins the Active Layer. | Trombotto et al. 2014 |
| Transient snowline | The snowline at any instant, particularly during the ablation season. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Transient talik | A layer or body of unfrozen ground (in a permafrost area) that is gradually being eliminated by freezing. | NSIDC accessed 2016 |
| Transient talik | A layer or body of unfrozen ground (in a permafrost area) that is gradually being eliminated by freezing | Van Everdingen International Permafrost Association 2005 |
| Transverse crevasse | A crevasse oriented more or less perpendicular to the long axis of a glacier. Transverse crevasses typically open on a valley glacier when the terrain becomes steeper, such as above an icefall. | Swisseduc - Photo glossary of glaciological terms |
| Tree line | The upper limit of tree growth in mountains or at high latitudes. It is more elevated or more poleward than the forest line. | IPCC WGII AR5 2014 |
| Tributary glacier | A small glacier that flows into a larger glacier. | NSIDC accessed 2016 |
| Trim-line | A sharp line on a hillside marking the boundary between well-vegetated terrain that has remained ice-free for a considerable time and poorly vegetated terrain that until relatively recently lay under glacier ice. In many areas the most prominent trim-lines date from the Little Ice Age (q.v.). | Swisseduc - Photo glossary of glaciological terms |
| Trimline | A line separating tracts of unglacierized terrain of strikingly different appearance, the appearance of one of the tracts being interpretable as due to recent deglaciation. The trimline usually separates terrain with more mature vegetation, deglaciated in the more distant past or never glaciated at all, from terrain exposed during the retreat of glaciers from their Little Ice Age maximum extents. The separation may also be marked in part by terminal moraines. The trimline can be used to reconstruct former glacier extent and volume. Reliably dated trimlines have been used in this way to estimate long-term average mass balance. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Trimline | A clear boundary line on the wall of a glacier valley that delineates the maximum recent thickness of a glacier. It may be a change in the color of the bedrock, indicating the separation of weathered from unweathered bedrock; the limit of a former lateral moraine or other sediment deposit; or the boundary between vegetated and bare bedrock. | Molnia USGS 2004 |
| Trimlines | Trimlines are the sharp vegetative boundaries delimiting the upper margin of a former glaciation. The age differences of the ground surface are often visible because of different ages of the vegetation. | Molnia USGS 2004 |
| Triple point | The temperature, 273.16 K by definition, and pressure, 611.657 Pa, at which ice, water and water vapour are in thermodynamic equilibrium. The term 'point' derives from the practice in thermodynamics of choosing temperature and pressure as the coordinates of a two- or higher-dimensional phase diagram. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Triple point syn. triple state | (1) The thermodynamic state at which three phases of a substance exist in equilibrium. (2) A junction point of three distinct air masses within the tropics at which cyclogenesis may occur. | WMO METEOTERM accessed 2016 |
| Trough | Depression of sea floor applied in this work to such a feature beneath an ice shelf. | UK Antarctic Place-names Committee accessed 2016 |
| Tundra | Treeless terrain, with a continuous cover of vegetation, found at both high latitudes and high altitudes. | NSIDC accessed 2016 |
| Tundra | A treeless biome characteristic of polar and alpine regions. | IPCC WGII AR5 2014 |
| Tundra | Treeless terrain, with a continuous cover of vegetation, found at both high latitudes and high altitudes | Van Everdingen International Permafrost Association 2005 |
| Tundra | Treeless plains that lie poleward of the tree line. (Also called arctic desert.) The plants thereon are sedges, mosses, lichens, and a few small shrubs. Tundra is mostly underlaid by permafrost, with the result that drainage is bad and the soil may be saturated for long periods. It does not have a permanent snow-ice cover. | AMS - glossary of meteorology |
| Tundra | High latitude biome dominated by a few species of dwarf shrubs, a few grasses, sedges, lichens, and mosses. Productivity is low in this biome because of the extremes of climate. | PhysicalGeography.net |
| Tundra climate | Type of climate which produces tundra vegetation; it is too cold to support the growth of trees but does not have a permanent cover of snow or ice. | WMO METEOTERM accessed 2016 |
| Tundra climate | Generally, the climate that produces tundra vegetation; it is too cold for the growth of trees but does not have a permanent snow-ice cover. In W. K?ppen's 1936 climatic classification it is one of the polar climates, defined as having a mean temperature for the warmest month of less than 10C (50F) (in contrast to snow forest and temperate rainy climates) but higher than 0C (32F) (which is the limit of perpetual frost climate). Tundra is designated ET. Tundra climate appears as a temperature province in C. W. Thornthwaite's 1931 classification. | AMS - glossary of meteorology |
| Turbic cryosol | A mineral soil showing marked evidence of cryoturbation, as indicated by broken horizons and displaced material. | NSIDC accessed 2016 |
| Turbic cryosol | A mineral soil showing marked evidence of cryoturbation, as indicated by broken horizons and displaced material | Van Everdingen International Permafrost Association 2005 |
| Turf hummock | A hummock consisting of vegetation and organic matter with or without a core of mineral soil or stones. | NSIDC accessed 2016 |
| Turf hummock | A hummock consisting of vegetation and organic matter with or without a core of mineral soil or stones | Van Everdingen International Permafrost Association 2005 |
| Turf-banked (solifluction) lobe | A solifluction lobe with its front covered by a vegetation mat. | NSIDC accessed 2016 |
| Turf-banked (solifluction) lobe | A solifluction lobe with its front covered by a vegetation mat | Van Everdingen International Permafrost Association 2005 |
| Turf-banked (solifluction) terrace | A solifluction terrace with its front covered by a vegetation mat. | NSIDC accessed 2016 |
| Turf-banked (solifluction) terrace | A solifluction terrace with its front covered by a vegetation mat | Van Everdingen International Permafrost Association 2005 |
| Tuya | A volcano that erupted under a glacier. Because volcanic activity in western Canada was contemporaneous with the ebb and flow of Cordilleran glaciations, many of the volcanoes display ice contact features. Mount Garibaldi itself is a supraglacial volcano which erupted onto a regional ice sheet. Others, such as Hoodoo Mountain, were contained within basins thawed in the ice and assumed the flat-topped form of tuyas. Still others, such as the subglacial mounds of the Clearwater Field, were erupted under glacial ice to form piles of pillow lava and hyaloclastite. | Molnia USGS 2004 |
| Two-layer permafrost | Ground in which two layers of permafrost are separated by a layer of unfrozen ground. | NSIDC accessed 2016 |
| Two-layer permafrost | Ground in which two layers of permafrost are separated by a layer of unfrozen ground | Van Everdingen International Permafrost Association 2005 |
| Two-phase thermosyphon | A passive heat transfer device, filled with a temperature-dependent liquid/vapour combination, installed to remove heat from the ground. | NSIDC accessed 2016 |
| Two-phase thermosyphon | A passive heat transfer device, filled with a temperature-dependent liquid/vapour combination, installed to remove heat from the ground | Van Everdingen International Permafrost Association 2005 |
| Tyndall flowers | Small water-filled cavities, often of basically hexagonal shape, that appear in the interior of ice masses upon which light is falling. Their formation results from the melting ice by radiative absorption at points of defect in the ice crystal lattice. | AMS - glossary of meteorology |
| U-Shaped valley | A valley with a parabolic or 'U' shaped cross-section, steep walls and generally a broad and flat floor. Formed by glacier erosion, a U-shaped valley results when a glacier widens and over-steepens a V-shaped stream valley. | Molnia USGS 2004 |
| U-Shaped valley | A valley with a parabolic or 'U' shaped cross-section, steep walls and generally a broad and flat floor. Formed by glacier erosion, a U-shaped valley results when a glacier widens and over-steepens a V-shaped stream valley. | Molnia USGS 2004 |
| Ubac | The shady (usually poleward, or north in the Northern Hemisphere) side of a mountain. The term originated and is most often used in reference to mountains in the Alps. It is characterized by a lower timber line and snow line than the sunny side (the adret). | AMS - glossary of meteorology |
| Unbreakable crust | A hard snow surface lying upon a softer layer; may be formed by sun, rain or wind, and is described as breakable crust or unbreakable crust, depending upon weather it will break under the weight of a turning skier. | NSIDC accessed 2016 |
| Unconformity | A discontinuity in the annual layering in firn or ice, resulting from a period when ablation cuts across successive layers. | Swisseduc - Photo glossary of glaciological terms |
| Undermelting | The melting from below of any floating ice. | AMS - glossary of meteorology |
| Unfreezing | The upward movement of stones to the surface as a result of repeated freezing and thawing of the containing soil; a result of congeliturbation. | AMS - glossary of meteorology |
| Unfrozen ground | Soil or rock that does not contain any ice. | NSIDC accessed 2016 |
| Unfrozen ground | Soil or rock that does not contain any ice | Van Everdingen International Permafrost Association 2005 |
| Unfrozen ground | Soil or rock that does not contain any Ice. Unfrozen Ground can be cryotic (T < 0C) if freezing-point depression prevents freezing of the pore water, or if no water is available to freeze (e.g., in Dry Permafrost). It should not be called thawed ground, unless it is known that the ground had previously contained Ice. | Trombotto et al. 2014 |
| Unfrozen water content | The amount of unfrozen (liquid) water contained in frozen soil or rock. | NSIDC accessed 2016 |
| Unfrozen water content | The amount of unfrozen (liquid) water contained in frozen soil or rock | Van Everdingen International Permafrost Association 2005 |
| Upbank thaw | The precedence of a thaw in a valley, sometimes by many hours, by a thaw or marked rise in temperature at mountain level in the same vicinity. The phenomenon is usually caused by the arrival at higher levels of the warm air in advance of a surface warm front. It may also be caused by the subsidence and dynamical heating of air at the higher level. The associated inversion of the normal temperature lapse rate is a contributory cause of glaze. | AMS - glossary of meteorology |
| Upland | High ice covered area with or without nunataks | UK Antarctic Place-names Committee accessed 2016 |
| Upward freezing | The advance of a freezing front upwards from the permafrost table during annual freezing of the active layer. | NSIDC accessed 2016 |
| Upward freezing | The advance of a freezing front upwards from the permafrost table during annual freezing of the active layer | Van Everdingen International Permafrost Association 2005 |
| Valley | Long depression running from a higher level to a lower level (or to the coast), with a glacier completely filling the feature, partly filling it or terminating with it; rarely a valley may be ice-free with a seasonal stream running through it | UK Antarctic Place-names Committee accessed 2016 |
| Valley | A linear depression in the landscape that slopes down to a stream, lake or the ocean. Formed by water and/or ice erosion. | PhysicalGeography.net |
| Valley breeze | Local thermal circulation pattern found in areas of topographic relief. In this circulation system, surface winds blow from the valley bottom to areas of higher elevation during the daytime. | PhysicalGeography.net |
| Valley glacier | A mountain glacier whose flow is confined by valley walls. | NSIDC accessed 2016 |
| Valley glacier | A glacier that flows for all or most of its length within the walls of a mountain valley. Also called an Alpine Glacier or a Mountain Glacier. | Molnia USGS 2004 |
| Valley glacier | A glacier flowing down a valley and in consequence having a distinct tongue. The glacier outline is well-defined. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Valley glacier | Glacier which flows down a valley. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Valley glacier | A glacier bounded by the walls of a valley, and descending from high mountains, from an ice cap on a plateau, or from an ice sheet. | Swisseduc - Photo glossary of glaciological terms |
| Valley glacier | A glacier lying primarily in a mountain valley. | AMS - glossary of meteorology |
| Valley glacier | A glacier which flows down a valley. | Illustrated Glossary of Snow and Ice |
| Valley glacier | Accumulation area is clearly defined and limited by the topography; Ice free slopes normally overlook glacier surface; Follows a preexisting valley; Flows down a valley; the catchment area is well defined | Illustrated GLIMS Glacier Classification Manual |
| Valley train | A linear accumulation of glaciofluvial outwash sediments found in a once glaciated valley. | PhysicalGeography.net |
| Valley wall | The side slope of a stream or glacial valley. | PhysicalGeography.net |
| Valley wind | A wind that ascends a mountain valley (upvalley wind) during the day; the daytime component of a mountain-valley wind system. (Or valley breeze.) | AMS - glossary of meteorology |
| Varve | A varve is a pair of sedimentary layers, a couplet, that form in an annual cycle as the result of seasonal weather changes. Typically formed in glacial lakes a varve couplet consists of a coarser grained summer layer formed during open-water conditions, and a finer grained winter layer formed from deposition from suspension during a period of winter ice cover. Many varve deposits contain hundreds of couplets. | Molnia USGS 2004 |
| Vein ice | A comprehensive term for ice of any origin occupying cracks in permafrost. | NSIDC accessed 2016 |
| Vein ice | A comprehensive term for ice of any origin occupying cracks in permafrost | Van Everdingen International Permafrost Association 2005 |
| Vertical selection | This is a phenomenon of particle sorting caused by multiple freeze-thaw processes. Fine particles move downward whereas larger particles are transported to the surface. The process is correlated to the moisture content of the ground. The particle selection decreases with decreasing moisture content. When the cryogenic process determines a horizontal particle differentiation then this is called a Horizontal Selection. | Trombotto et al. 2014 |
| Very close pack ice | Pack ice in which the floes are tightly packed but not frozen together, with very little, if any, sea water visible; ice cover practically 10/10th. | NSIDC accessed 2016 |
| Very close pack ice | Floating ice in which the concentration is 9/10 and more, but less than 10/10. | Bushuyev 2004 |
| Very close pack ice | Pack ice in which the concentration is nine-tenths to less than ten-tenths. | WMO Sea Ice Nomenclature 2017 |
| Very close pack ice | Pack ice in which the floes are tightly packed but not frozen together, with very little, if any, sea water visible. Ice cover practically 10/10ths. | Illustrated Glossary of Snow and Ice |
| Very close pack/drift | Sea ice terminology that describes floating ice in which the concentration is from 9/10 to less than 10/10. | Environment and Climate Change Canada 2014 |
| Very large iceberg | Sea ice terminology. Describes a piece of glacier ice that extends more than 75 m above sea level, and has a length of more than 200 metres. | Environment and Climate Change Canada 2014 |
| Very open drift | Sea ice terminology describing ice in which the concentration is 1/10 to 3/10 and water dominates over ice. | Environment and Climate Change Canada 2014 |
| Very open pack ice | Pack ice composed of loose, widely spaced floes; ice cover 1/10th to 3/10th. | NSIDC accessed 2016 |
| Very open pack ice | Floating ice in which the concentration is 1/10 to 3/10 and water preponderates over ice. | Bushuyev 2004 |
| Very open pack ice | Pack ice in which the concentration is one-tenth to three-tenths and water preponderates over the ice. | WMO Sea Ice Nomenclature 2017 |
| Very open pack ice | Pack ice composed of loose, widely spaced floes. Ice cover 1/10th to 3/10ths. | Illustrated Glossary of Snow and Ice |
| Very thick lake ice | Sea ice terminology describing lake ice that is greater than 70 cm thick. | Environment and Climate Change Canada 2014 |
| Very weathered ridge | Ridge with tops very rounded, slope of sides usually 20 to 30 degrees. | WMO Sea Ice Nomenclature 2017 |
| Very weathered ridge | Sea ice terminology describing a ridge with tops very rounded. The slope of its sides is usually from 20 to 30 degrees. | Environment and Climate Change Canada 2014 |
| Volume-area scaling | A method of relating glacier volume or volume changes to glacier area or area changes, based on a tendency for glacier thickness to be well correlated (to 'scale') with glacier area. Glacier volume V is the product of area S and mean thickness H. Measured mean thicknesses are well described by a relation of the form H c S1, which is the basis for the volume-area relation V c S . Here c and are parameters estimated from samples of glaciers with measured thicknesses. There is good evidence, as shown by Bahr et al. (1997), that estimates of from observations are nearly consistent with theoretical expectation. Mean thickness is also sometimes estimated as a function of average surface slope and basal shear stress. Volumearea scaling is both a way of estimating regional and global glacier volumes from abundant data on glacier area, and a possible way of estimating (with large random uncertainty) the volume balance of single glaciers from successive measurements of area S1 and S2, for example as2 1 ()2(2V c S S . It can also be used, as a practical alternative to ice-flow modelling, to estimate glacier area changes in attempts to model the response of glaciers to climatic change. Glacier volume is also expected, and found, to scale with glacier length, particularly when the length is that of a flowline. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Volume balance | The change in the volume of a glacier, or part of a glacier, over a stated span of time. A volume balance contains no information about the density of the matter within the volume gained or lost. It is meaningful in itself, but is often an intermediate product in the determination of mass balance by geodetic methods. Balances expressed in ice-equivalent or water-equivalent units, such as m3 w. E. A-1, are not volume balances but mass balances. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Volumetric (total) water content | The ratio of the volume of the water and ice in a sample to the volume of the whole sample, expressed as a fraction (or, less commonly, as a percentage) | Van Everdingen International Permafrost Association 2005 |
| Volumetric balance flux | The balance flux divided by average density (dimension [L3 T-1]). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Volumetric calving flux | The calving flux divided by average glacier density (dimension [L3 T-1]). | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Volumetric heat capacity | The amount of heat required to raise the temperature of a unit volume of a substance by one degree | Van Everdingen International Permafrost Association 2005 |
| Volumetric latent heat of fusion | The amount of heat required to melt all the ice (or freeze all the pore water) in a unit volume of soil or rock | Van Everdingen International Permafrost Association 2005 |
| Volumetric thinning flux | The thinning flux divided by average density. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Warm-based glacier | A glacier whose bed is at its pressure-melting point. Wet-based glacier is a synonym. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Water balance | A relation describing the change in the amount of water stored within a defined volume owing to transfers of water across the boundary of the volume. The general water balance equation is W = P E Q , where P is precipitation, E is evapotranspiration, Q is runoff and W is the change in storage. The water balance is the basis of the hydrological method of determination of glacier mass balance. Typically in glaciological research the defined volume is a drainage basin tributary to a discharge measurement station near to the glacier margin, and not all of the basin is glacierized. Transfers of water by precipitation and evapotranspiration will include transfers not passing through the boundary of the glacier, and stores of water will include lakes, seasonal snowpatches, soil and aquifers as well as the glacier. Changes in each of the non-glacial stores must be accounted for to isolate the glacier mass balance. It can be convenient in glacier hydrology to distinguish between meltwater runoff from glacier iceand firn and runoff from the basin-wide snowpack, the latter including the snow on the glacier. Denoting these stores by I and N respectively, and assuming that changes in other stores are negligible, I = N Ei qin = Pn En Qn. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Water bleeding | Water forced through a crack in an ice cover. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Water equivalent | A unit, in full the 'metre [of] water equivalent', that is an extension of the SI for describing glaciermass in specific units as the thickness of an equal mass having the density of water. 1 kg of liquid water, of density w = 1000 kg m-3, has a vertical extent of exactly 1 mm when distributed uniformly over a horizontal area of 1 m2. More formally, the metre water equivalent (m w. E.) Is obtained by dividing a particular mass per unit area by the density of water:1 m w. E. = 1000 kg m-2 / w . Water equivalents (m w. E.) Can be converted to kg m-2 by multiplying by the density of water, and to ice equivalents (m ice eq.) By multiplying by the density of water and dividing by the density of ice. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Water equivalent | The liquid content of solid precipitation that has accumulated on the ground (snow depth). The accumulation may consist of snow, ice formed by freezing precipitation, freezing liquid precipitation, or ice formed by the refreezing of melted snow. | NOAA National Weather Service Glossary 2009 |
| Water equivalent | The depth of water that would result from the melting of the snowpack or of a snow sample. Thus, the water equivalent of a new snowfall is the same as the amount of precipitation represented by that snowfall. | AMS - glossary of meteorology |
| Water equivalent of snow | Amount of water that would be obtained by completely melting a snow sample. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Water equivalent of snow | The amount of water that would be obtained if the snow sample were completely melted. The snow sample must be obtained from a uniform volume, that is, either by melting snow in a calibrated container (e.g., an 8-in. rain gauge) or determined by weight (e.g., a snow pillow). | AMS - glossary of meteorology |
| Water equivalent of snow cover | Vertical depth of the water layer which would be obtained by melting a snow cover. (TR) | UNESCO-WMO International Glossary of Hydrology 2012 |
| Water equivalent of snow cover | The depth of water that would result from the melting of a snow cover; may be expressed either at a point or as an areal average. | AMS - glossary of meteorology |
| Water equivalent of snowfall | Snow water equivalent of snowfall HNW is typically measured for a standard observing period of 24 hours. Other periods can be specified, e.g., HNW(8h) or HNW(2d) for
periods of 8 hours or 2 days, respectively. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Water sky | Dark streaks on the underside of low clouds, indicating the presence of water features in the vicinity of sea ice. | WMO Sea Ice Nomenclature 2017 |
| Water sky | Sea ice terminology. It describes dark streaks on the underside of low clouds, indicating the presence of water features, in the vicinity of ice. | Environment and Climate Change Canada 2014 |
| Water sky | Dark streaks on the underside of clouds, indicating the presence of open water or broad leads in the floating ice (cf. Ice blink). | Illustrated Glossary of Snow and Ice |
| Water snow | Snow that, when melted, yields a greater-than-average amount of water; thus, any snow with a high water content. (Also called cooking snow.) | AMS - glossary of meteorology |
| Water year | The hydrological year. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Waterbody encircling a palsa | A water-filled depression surrounding a palsa. | Van Everdingen International Permafrost Association 2005 |
| Watermelon snow | Snow with red algae growing on it. | NSIDC accessed 2016 |
| Wave ogives | Ogives that show some vertical relief on a glacier; usually the dark bands are in the hollows and the light bands are in the ridges; form at the base of steep, narrow ice falls. | NSIDC accessed 2016 |
| Weather window | An interlude in a period of predominantly inclement weather during which a weather-sensitive operation may be carried out successfully. | AMS - glossary of meteorology |
| Weathered ice | Glacier ice that has been exposed to sun or warm wind so that the boundaries between ice crystals are partly disintegrated. | NSIDC accessed 2016 |
| Weathered ice | Ice modified by exposure to weather; usually applied to polar ice where melting does not occur, such as blue ice areas of Antarctica. | AMS - glossary of meteorology |
| Weathered ridge | Ridge with peaks slightly rounded and slope of sides usually 30 to 40 degrees. Individual fragments are not discernible. | WMO Sea Ice Nomenclature 2017 |
| Weathered ridge | Sea ice terminology describing a ridge with peaks slightly rounded, and slope of its sides that is usually 30 to 40 degrees. Individual fragments of ice are not visible. | Environment and Climate Change Canada 2014 |
| Weathering | Processes of ablation and accumulation that gradually eliminate irregularities in an ice surface. | WMO Sea Ice Nomenclature 2017 |
| Weathering | Sea ice terminology. Describes the processes of ablation and accumulation, which gradually eliminate irregularities in an ice surface. | Environment and Climate Change Canada 2014 |
| Weathering | The mechanical, chemical, or biological action of the atmosphere, hydrometeors, and suspended impurities on the form, color, or constitution of exposed material; to be distinguished from erosion. Mechanical weathering results from the disintegrating action of high or low temperature, large changes of temperature, frost, or the impact of wind-borne sand or water (e.g., frost action, scouring, etc.). Chemical weathering is due to the chemical action of atmospheric constituents, especially acid impurities, in a moist atmosphere or in rainwater (e.g. corrosion, oxidation, etc.). Biological agents are mainly fungi that attack organic material (e.g., rotting, mildew, etc.). | AMS - glossary of meteorology |
| Weathering | The processes of ablation and accumulation which gradually eliminate irregularities in an ice surface. | Illustrated Glossary of Snow and Ice |
| Weathering crust | A friable surface layer, of reduced density, that develops due to small-scale variations of the melting rate of ice in the presence of cryoconite. Short-term measurements of surface lowering are unreliable as estimates of surface ablation when there is a weathering crust. The crust may reach a thickness of the order of 100200 mm over several days, only to be removed abruptly by rain or strong winds. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Weddell deep water | The water mass in the center of the cyclonic Weddell Sea gyre. It is formed by local cooling, has a temperature of 0.4-0.7C, and contributes to Antarctic Bottom Water formation. | AMS - glossary of meteorology |
| Wedge ice | Ice occurring in an ice wedge. | NSIDC accessed 2016 |
| Wedge ice | Ice occurring in an ice wedge | Van Everdingen International Permafrost Association 2005 |
| Wedged iceberg | Sea ice terminology. Describes an iceberg which is rather flat on top, with steep vertical sides on one end, sloping to less steep sides on the other end. | Environment and Climate Change Canada 2014 |
| Weighing rain gauge | A recording rain gauge in which the weight of water collected is measured as a function of time and converted to rainfall depth. The weight-sensing mechanism is typically mechanical (springs). The output can be a pen trace on a strip chart, voltage from a potentiometer, punched paper tape, or other electronic means. Weighing gauges with continuous output can be used for determining rainfall rate and depth. | AMS - glossary of meteorology |
| Well-bonded permafrost | Ice-bearing permafrost in which all the soil particles are held together by ice. | NSIDC accessed 2016 |
| Well-bonded permafrost | Ice-bearing permafrost in which all the soil particles are held together by ice | Van Everdingen International Permafrost Association 2005 |
| West Antarctic Ice Sheet | That portion of the Antarctic Ice Sheet lying predominantly in the Western Hemisphere. A line following the Transantarctic Mountains to the Antarctic Peninsula serves as the boundary between the East and West Antarctic Ice Sheets. | AMS - glossary of meteorology |
| West Greenland current | A current of the North Atlantic subpolar gyre flowing northward along the west coast of Greenland. It is fed from the East Greenland Current and from the cyclonic circulation of the Labrador Sea and achieves a transport of over 30 Sv (30 x 10^6 m^3/s). Some of its water turns westward at 64N to join the Labrador Current; the remainder continues northward as a relatively warm current through Davis Strait and into Baffin Bay, where it can be seen as a temperature maximum of greater than 1C at a depth of 500 m. This water eventually turns westward as well to feed the Baffin Current and through it the Labrador Current. | AMS - glossary of meteorology |
| West Spitzbergen current | The continuation of the Norwegian Current. It carries 3-5 Sv (3-5 x 10^6 m^3/s) of water from the Atlantic into the Arctic Ocean. Another 1 Sv enters the Arctic Ocean through the Barents Sea. | AMS - glossary of meteorology |
| Wet snow | Snow which contains a great deal of liquid water. If the water entirely fills the air spaces which originally existed in the snow, it is classified as very wet snow. | WMO METEOTERM accessed 2016 |
| Wet snow | Snow which contains a large amount of liquid water. If the water completely fills the air spaces which originally existed in the snow, it is classified as very wet snow. | UNESCO-WMO International Glossary of Hydrology 2012 |
| Wet snow | Deposited snow that contains a great deal of liquid water. If free water entirely fills the air space in the snow it is classified as "very wet" snow. | AMS - glossary of meteorology |
| Wet-based glacier | A glacier the bed of which is at its pressure-melting point. Warm-based glacier is a synonym. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Wet-snow line | The set of points on a glacier separating the upper percolation zone, at higher elevation, from the lower percolation zone or wet-snow zone. The wet-snow line has no surface expression, but is significant as the upper limit of the region where internal accumulation may happen. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Wet-snow zone | The part of the accumulation zone of a cold glacier or polythermal glacier where all of the snow reaches the melting point during the ablation season. The wet-snow zone is sometimes referred to as the lower percolation zone. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Wetness | Synonymous with liquid water content. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Whaleback | A smooth, scratched, glacially eroded bedrock knoll several metres to a few hundred metres high, and resembling a whale in profile. | Swisseduc - Photo glossary of glaciological terms |
| Whirlies | A name given by Sir Douglas Mawson (1915) to violent, snow-carrying whirlwinds, from a few to over one hundred meters in diameter, that occur in otherwise calm air on the slopes of Ad lie Land, Antarctica, at about the time of the equinoxes. Over the sea, reportedly, they may lift brash 70-140 m into the air and form columns of water drops 1250 m high. | AMS - glossary of meteorology |
| White band | Ice band composed of bubbly ice. | AMS - glossary of meteorology |
| White dew | Dew that has frozen as the result of a fall in temperature to below freezing after the original formation of the dew. | AMS - glossary of meteorology |
| White frost | 1. A relatively heavy coating of hoarfrost. With respect to vegetation, a white frost is less damaging than a black frost for at least two reasons: 1) it tends to insulate the plant from further cold; and 2) it releases latent heat of fusion (albeit slight) to the environment. 2. Colloquial term for a deposit of fine rime. | AMS - glossary of meteorology |
| White ice | Same as thin first-year ice. | WMO Sea Ice Nomenclature 2017 |
| White ice | Ice with a white appearance caused by the occurrence of bubbles within the ice. The bubbles increase the scattering of all wavelengths of light in contrast to the appearance of bubble-free blue ice. | AMS - glossary of meteorology |
| Whiteout | A condition in which daylight is diffused by multiple reflections between a snow surface and an overcast sky; contrasts vanish, and the observer is unable to distinguish the horizon or any snow surface feature. | NSIDC accessed 2016 |
| Whiteout | An atmospheric optical phenomenon in which the observer appears to be engulfed in a uniformly white glow. (Also called milky weather.) Neither shadows, horizon, nor clouds are discernible; sense of depth and orientation is lost; only very dark, nearby objects can be seen. Whiteout occurs over an unbroken snow cover and beneath a uniformly overcast sky, when, with the aid of the snow blink effect, the light from the sky is about equal to that from the snow surface. Blowing snow may be an additional cause. This phenomenon is experienced in the air as well as on the ground. | AMS - glossary of meteorology |
| Whiteout | A condition in which daylight is diffused by multiple reflection between a snow surface and an overcast sky. Contrasts vanish and the observer is unable to distinguish the horizon or any snow surface feature. | Illustrated Glossary of Snow and Ice |
| Wild snow | (Rare.) Newly deposited snow that is very fluffy and unstable. In general, it falls only during a dead calm at very low air temperatures and will usually have a low liquid to snow depth ratio. | AMS - glossary of meteorology |
| Wind ablation mass loss by wind scour | Snow lost to wind ablation on one part of the glacier surface is often re-deposited in more sheltered parts of the glacier surface, making no contribution to glacier-wide ablation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Wind chill | The portion of the cooling of a human body caused by air motion. Air motion accelerates the rate of heat transfer from a human body to the surrounding atmosphere, especially when temperatures are below about 7C (45F). | AMS - glossary of meteorology |
| Wind crust | A type of snow crust formed by the packing action of wind on previously deposited snow. Wind crust may break locally, but, unlike wind slab, does not constitute an avalanche hazard. | AMS - glossary of meteorology |
| Wind ridge | A feature of hard snow formed by wind. | AMS - glossary of meteorology |
| Wind ripple | One of a series of wavelike formations on a snow surface, an inch or so in height, at right angles to the direction of wind. | AMS - glossary of meteorology |
| Wind scoop | Hollow around rock outcrop caused by wind erosion or enhanced ablation. | Swisseduc - Photo glossary of glaciological terms |
| Wind scoop | A saucerlike depression in the snow near obstructions such as trees, houses, and rocks, caused by the eddying action of the deflected wind. | AMS - glossary of meteorology |
| Wind scour | The entrainment and removal of surface snow by the wind. The resulting windborne snow may be re-deposited elsewhere in more sheltered parts of the glacier surface, or may be transported off the glacier. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Wind slab | A type of snow crust; a patch of hard-packed snow that is packed as it is deposited in favored spots by the wind (in contrast to wind crust, which is packed after deposition). Wind slabs can be quite rigid, but they adhere poorly to the underlying snow and hence may be readily dislodged, causing an avalanche. | AMS - glossary of meteorology |
| Wind-chill index | A means of quantifying the threat of rapid cooling during breezy or windy conditions that may result in hypothermia in cold conditions. The index is used to remind the public to minimize exposure when outdoors and to take precautionary actions. In the late 1940s, Antarctic explorers Siple and Passel experimented with measuring the time it took to freeze 250 grams of water in different temperature and wind conditions. They developed empirical formulas relating these data to the rate of heat loss from exposed human skin. They developed the following formula which was used to determine the wind-chill index. At wind speeds of 4 mph or less, the wind chill temperature is the same as the actual air temperature: T_WC = 0.0817(3.71V^0.5 + 5.81 - 0.25V)(T-91.4)+91.4 where V is wind speed in mph and T is temperature in F. | AMS - glossary of meteorology |
| Windborne snow | Blowing snow or drifting snow. Windborne snow may be redistributed from one part of the glacier to another. It contributes to the glacier-wide mass balance only when it is carried across a lateral boundary of the glacier, either inward or outward, or when it suffers sublimation instead of being redeposited. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Windbreak | Any device designed to obstruct wind flow and intended for protection against any ill effects of wind. Installations of this type include agricultural shelterbelts, snow fences, and rain-gauge wind shields. | AMS - glossary of meteorology |
| Windrow | A compact layer of ice cake and small ice cake formed as a result of repeated hummocking and rafting. In the coastal zone and near the fast ice boundary, the windrow thickness can achieve 10-20 m. In some cases it extends down to the bottom. Windrow presents a serious obstacle for shipping. | Bushuyev 2004 |
| Winter | 1. Astronomically, between the winter solstice and vernal equinox in the Northern Hemisphere, and the summer solstice and autumnal equinox in the Southern Hemisphere; the coldest season of the year; the "low sun" season during which the sun is over the opposite hemisphere; the "hibernal" season. Popularly and for most meteorological purposes, winter is taken to include December, January, and February in the Northern Hemisphere, and in the Southern Hemisphere, June, July, and August; the opposite of summer. 2. See Blackthorn winter. | AMS - glossary of meteorology |
| Winter ablation | Ablation integrated over the winter season. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Winter accumulation | Accumulation integrated over the winter season. Winter accumulation is not the same as winter mass balance. It is generally larger because some of the accumulated mass may be lost by ablation. Mass-balance measurements by the glaciological method generally measure winter mass balance and not winter accumulation. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Winter ice | Level sea ice more than eight inches thick and less than one year old; the stage that follows young ice. | AMS - glossary of meteorology |
| Winter mass balance | The sum of accumulation and ablation over the winter season. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Winter season | The time span from the start of the mass-balance year to the time of maximum glacier mass. The term is best suited to glaciers of winter-accumulation type. In the stratigraphic system the winter season ends when the glacier has attained maximum mass. In the floating-date system and the fixed-date system, the mass is not necessarily at its Annual minimum or maximum when the winter season starts or ends. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Winter-accumulation type | A type of glacier, typically at mid-latitudes or high latitudes, on which the regional seasonality leads to accumulation predominating in the winter season and ablation predominating in the summer season. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Winterization | The preparation of equipment for operation in conditions of winter weather. This applies to preparation not only for cold temperatures, but also for snow, ice, and strong winds. | AMS - glossary of meteorology |
| Yalca | A local name for a severe snowstorm with a strong squally wind that occurs in the Andes Mountain passes of northern Peru. | AMS - glossary of meteorology |
| Year | The duration of the Earth's revolution round the Sun, forming a natural but slightly variable unit of time. In glaciology, as in other disciplines concerned with the natural progression of the seasons, the year may vary in length for reasons of necessity or convenience, and depending on whether the particular investigation requires precise treatment of calendar time. In mass-balance practice the year is always either exactly or approximately 365 calendar days long (the duration of a calendar year which is not a leap year. However the sidereal year is very nearly equal to 365.2564 mean solar days. In turn, the mean solar day is very nearly equal to 86 400 seconds, and 1 day is defined in the Syst | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Year-round ablation type | A type of glacier on which ablation by melting or sublimation occurs throughout the year. Year-round ablation is typical of glaciers in the inner tropics, where there are two seasonal temperature maxima each year, and seasonal temperature variations are smaller than diurnal temperature variations. The seasonal variation of mass balance is affected more by variation of accumulation rates between wet and dry seasons than by variation of ablation rates between winter and summer. Year-round ablation is also observed at low altitude on glaciers in some warm maritime climates, as in Norway, and on high-latitude glaciers where ablation is predominantly by sublimation, as in the Dry Valleys of Antarctica. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Yedoma | A type of Pleistocene-age (formed 1.8 million to 10,000 years before present) permafrost that contains a significant amount of organic material with ice content of 50 | NSIDC accessed 2016 |
| Yellow snow | Snow given a golden or yellow appearance by the presence in it of pine, cypress pollen, or anthropogenic material or animal-produced material. | NOAA National Weather Service Glossary 2009 |
| Yellow snow | Snow given a golden or yellow appearance by the presence of pine or cypress pollen. | AMS - glossary of meteorology |
| Young coastal ice | Sea ice terminology. Describes the initial stage of fast ice formation consisting of nilas or young ice; its width varying from a few metres up to 200 metres from the shoreline. | Environment and Climate Change Canada 2014 |
| Young costal ice | The initial stage of fast ice formation consisting of nilas or young ice, its width varying from a few yards (meters) up to 110 to 220 yd (100-200 m) from the shoreline. | WMO Sea Ice Nomenclature 2017 |
| Young ice | A general category of ice that represents the transition between nilas and first-year ice; usually 10 to 30 centimeters (4 to 12 inches) thick. | NSIDC accessed 2016 |
| Young ice | Ice in the transition stage between nilas and first-year ice, 10-30cm in thickness. May be subdivided into grey ice and grey-white ice. | ASPECT 2012 |
| Young ice | Ice in the transitioning stage between nilas and first year ice, 4 to 12 inches (10-30 cm) in thickness. May be subdivided into gray ice and gray-white ice. | WMO Sea Ice Nomenclature 2017 |
| Young ice | Ice in the transition stage between nilas and first-year ice, 10-30 cm in thickness. May be subdivided into grey ice and grey-white ice. | Bushuyev 2004 |
| Young ice | Sea ice terminology which describes ice in the transition stage between nilas and first-year ice. It is of between 10 cm and 30 cm in thickness, and may be subdivided into grey ice and grey-white ice. | Environment and Climate Change Canada 2014 |
| Young ice | Newly formed, flat sea or lake ice, usually between 2 and 8 in. thick. Further growth renders it winter ice. | AMS - glossary of meteorology |
| Young ice | Floating ice in the transition stage between new ice and first-year ice, about 10-30 cm in thickness. Snow cover is normally moist and slushy. | Illustrated Glossary of Snow and Ice |
| Young's modulus | The ratio of increase in stress acting on a test specimen, to the resulting increase in strain, under constant transverse stress. | NSIDC accessed 2016 |
| Young's modulus | The ratio of increase in stress acting on a test specimen, to the resulting increase in strain, under constant transverse stress | Van Everdingen International Permafrost Association 2005 |
| Younger Dryas | A period 12.85 to 11.65 ka (thousand years before 1950), during the deglaciation, characterized by a temporary return to colder conditions in many locations, especially around the North Atlantic. | IPCC WGI AR5 2013 |
| Younger Dryas | The period from approximately 10 800 to 9600 BC when climate in the region around Greenland cooled by 5-7C within a few decades and recovered with similar rapidity at the end of the period; named for the expansion of the geographic range of the arctic herb Dryas octopetala. Evidence is accumulating for a wider, perhaps global, extent, but the Younger Dryas was most strongly felt around the North Atlantic Ocean. Changes in the thermohaline circulation of the oceans are widely believed to be implicated in the onset and ending of the Younger Dryas cooling. These were in turn associated with a switch to the St. Lawrence River as the major route for meltwater reaching the North Atlantic from the retreating continental ice cap. Other similarly rapid oscillations in climate are recorded through much of the last glacial in ice cores from Greenland and in marine sediment cores from the North Atlantic (Dansgaard-Oeschger events). The period since the Younger Dryas (the Holocene) lacks such extreme excursions. | AMS - glossary of meteorology |
| Zastrugi | (from Russian, plural form of 'zastruga'; variant spelling sastrugi) Ridges of hard snow alternating with wind-blown furrows running parallel with the direction of the wind. This surface formation results from the erosion of transverse waves previously formed. Zastrugi may be up to several meters long and up to several tens of centimetres high. | Fierz et al. IACS-UNESCO Seasonal Snow on the Ground 2009 |
| Zastrugi | Ridges of hard snow alternating with wind-eroded furrows parallel to the wind direction, with typical lengths of metres and heights less than a metre. The word is the plural of Russian 'zastruga', and alludes to the result of planing a wooden surface with a jackplane. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Zastrugi | Variant spelling of sastrugi. | AMS - glossary of meteorology |
| Zero curtain | The persistence of a nearly constant temperature, very close to the freezing point, during annual freezing (and occasionally during thawing) of the active layer. | NSIDC accessed 2016 |
| Zero curtain | The persistence of a nearly constant temperature, very close to the freezing point, during annual freezing (and occasionally during thawing) of the active layer | Van Everdingen International Permafrost Association 2005 |
| Zero curtain | The persistence of a nearly constant temperature, very close to the Freezing Point, during annual freezing (and occasionally during thawing) of the Active Layer. The Zero Curtain results from the dissipation of the Latent Heat of fusion of water during freezing or thawing of the ground. It can persist for several hours or several weeks depending largely on the total water content of the ground, Snow Cover and air temperatures. | Trombotto et al. 2014 |
| Zone | A part of the glacier, and especially of the glacier surface, distinguished from other parts by the prominence or predominance of a particular mass-balance process. The temperate glacier of Figure 15 and the cold glacier of Figure 16 are end members of a continuum. Many glaciers have attributes, including patterns of zonation, that are intermediate between these end members. The conventional system of zones in the English-language literature diverges in part from that in Russian-language work (Shumskiy 1955). For the latter, which is based on the relative magnitudes of accumulation, melting and cold content. | Cogley et al. IACS-UNESCO Glacier Mass Balance 2011 |
| Zone | Part of the water area contoured on an ice chart in the form of a closed polygon within which the ice cover characteristics given for this zone are considered similar. A zone can be sub-divided into a basic zone and additional zones. | Bushuyev 2004 |
| Zone of ablation | Area of a glacier where losses of ice from melting, evaporation, and sublimation exceed additions of snow annually. | PhysicalGeography.net |
| Zone of accumulation | Area of a glacier where additions of snow exceed losses of ice from melting, evaporation, and sublimation. | PhysicalGeography.net |
