2015 saw a continuation of the worldwide long-term trend of negative glacial mass balance (Figure 1). Over 140 glaciers were studied in 2014/2015, 27 of which were WGMS reference glaciers that have been undergoing continuous observation since 1980. A preliminary estimate from WGMS shows that mass balances of a large majority of the reporting reference glaciers were negative (not yet finalized). Of note, early measurements of the reference glacier Sarennes in the French Alps showed a dramatic loss of 3.4 meters of water equivalent (m w.e.) and the Alaskan Gulkana glacier lost a startling 1.5 m w.e. compared to last year’s loss of 0.3 m w.e. Initial measurements show 2015 to be the fourth-largest year of glacial mass loss, and the 32nd consecutive year of negative glacial mass balance. The extreme amount of glacial mass loss in 2015 corresponds to highest temperatures for any 12-month period on record, globally (NOAA, 2016).
The 37 reference glaciers span five continents (Australia and Africa are excluded), where each individual glacier has its yearly mass reported to WGMS by a team of independent researchers. Though Figure 1 shows minor year-to-year variation, the trends of mean specific mass balance of the reference glaciers and all reported glaciers over the last 30+ years are very similar.
Glaciers across North America experienced a dramatic level of melt in 2015. Glaciers surveyed within the Gulf of Alaska retained almost no snow cover by mid-August, which not only increased surface melting but also has consequences for glacial accumulation the following years (Pelto, 2015).
Surface melting is an important mechanism for glacial loss in both alpine (mountainous) and tidewater (coastal) glaciers, and has contributed to a loss in mass across the heavily-glaciated Alaskan and Canadian Pacific Coast Ranges (Larsen et al., 2015). Besides a few isolated areas in the interior, glaciers in this region have experienced an average yearly decrease in mass balance near 0.5 m w.e. every year since 1994 (Figure 2).
NOAA, 2016: National Centers for Environmental Information, State of the Climate: Global Analysis for Annual 2015, published online January 2016, retrieved on November 21, 2016 from http://www.ncdc.noaa.gov/sotc/global/201513.
Larsen, C.F., E. Burgess, A. A. Arentdt, S. O’Neel, A.J. Johnson, and C. Kienholz (2015): Suface melt dominates Alaska glacier mass balance, Geophysical Research Letters, 42, p. 5902-5908, doi: 10.1002/2015GL064349.
Pelto, M., 2015: “From a Glacier’s Perspective”, http://blogs.agu.org/fromaglaciersperspective/2015/08/20/disastrous-year-for-north-cascade-glacier-mass-balance-snowice-economy.
WGMS (2008): Global Glacier Changes: facts and figures. UNEP/UNESCO/WMO, World Glacier Monitoring Service, Zurich: 88 pp.
