Atmosphere Assessments


2016 Arctic Atmosphere Temperature


Aaron Letterly
28 July 2017

Arctic Oscillation Leads to High Temperatures in January - March


Uncharacteristically high temperatures in the early winter of 2016 contributed toward the record low sea ice extents in January and February 2016. A negative phase of the Arctic Oscillation (AO) beginning in early January allowed the jet stream to move very far northward over Siberia, which brought warm air into the Kara Sea and the central Arctic. Air temperature anomalies in these regions were as high as 8°C. Figure 1 not only shows the extreme temperature anomalies over Svalbard and the surrounding Barents Sea, but also the geopotential height anomalies resulting from the northward position of the jet stream over Siberia.

Figure 1
Figure 1: Januarly 2016 geopotential height anomalies at the 850mb pressure level (left) show positive anomalies due to warm surface air over Siberia and the Barents Sea. Warm southern air brought into this region caused startling temperature anomalies east of Svalbard and in the Central Arctic (right). Anomalies are for January 2016 relative to the 1980-2010 mean. Data are from NOAA/ESRL, Boulder, CO.

Above-average temperatures persisted into February and led to a record low ice extent for the second month in a row. Continued warm surface air temperatures throughout the Arctic stifled ice growth into March, when ice extent tied for the lowest on record. The warm air brought northward from Siberia due to the general circulation pattern over the Arctic was one of the leading factors in record low sea ice extents that went on to occur in April, May, and June. Throughout most of July and August, surface air temperatures moved back towards normal. In late August, however, two cyclones approximately one week apart entered into the Siberian region of the Central Arctic. Figure 2 shows these low pressure systems tracking along very similar paths. When these storms collided with multi-year ice at 75-80° N, strong winds and increased wave action may have fractured the thicker ice and spread the ice into a larger area, increasing sea ice extent. These storms also brought more clouds to the region. Even with back-to-back cyclones inhibiting ice loss, the 2016 sea ice minimum extent was tied with 2007, the second-lowest in the satellite record.

Figure 2
Figure 2: Sea level pressure on August 15 (left) and August 23 (right) showing intense low pressure systems tracking similar paths off of Siberia into the thicker ice of the Central Arctic. These storms may have brought enhanced cloud cover as well as wind patterns that spread ice into a larger area. Data are from NOAA/ESRL, Boulder, CO.

October air temperatures remained above average as the negative AO continued to pull in warm air from the Barents and Kara seas. By the end of October, the Bering Strait and Chukchi Seas experienced surface air temperature anomalies of 8-10°C. Figure 3 shows the October 27 temperature anomalies in these regions, with lesser (but still positive) anomalies throughout much of the Arctic Ocean. The uncharacteristically high temperatures resulted in record low in sea ice extent in both October and November.

Figure 3
Figure 3: Surface air temperatures in late October show unseasonably warm air entering the Arctic from both the Atlantic and the Pacific. Consistently above-average temperatures increased the sea-surface temperature in these areas, slowing and even halting ice growth in late 2016. (From Climate Change Institute/ University of Maine.)

Antarctic Sea Ice Departs “Near-Average” Conditions for Record Lows


From mid-2015 through May 2016, Antarctic monthly sea ice did not fall far below the 1981-2010 average. Slow ice growth in May 2016 coupled with warmer-than-average temperatures over the Antarctic Peninsula, Weddell Sea, and Bellingshausen Sea resulted in a very low (and early) sea ice maximum on August 31. By the middle of September, sea ice extent had already decreased to levels typically seen two months later. And throughout November, ice extent anomaly was more than two times below the previous November record, set in 1986.

Air and sea surface temperature anomalies may have influenced the record lows in ice extent from October through December, but wind shifts around the Antarctic continent also contributed. Periods of northerly winds around the Antarctic ice edge corresponded to the rapid ice retreat during November 2016, when this anomalous flow may have compressed the newly-formed ice around the continent (Turner et al. 2017). Typical wind patterns in this region disperse the thin ice.


Hemispheric Temperature Anomalies


According to NOAA’s 2016 State of the Climate, 2016 was the hottest year on record for land and sea surface average temperatures in both hemispheres. This is the 40th consecutive year that average annual temperatures have been above the 20th century average, and, furthermore, the fifth record-setting year to occur since 2010. Figure 4 shows yearly temperature anomalies in the left column, for the Northern and Southern Hemisphere, and month-by-month temperature anomalies in the right column. Every month, in both hemispheres, has had an anomaly of +0.5°C from January 2016 to May 2017.

Figure 4
Figure 4: Annual temperature anomaly for the Northern Hemisphere (top left) and Southern Hemisphere (bottom left), and monthly temperature anomaly for the Northern Hemisphere (top right) and Southern Hemisphere (bottom right) over all land and sea pixels.

References


NOAA National Centers for Environmental Information, State of the Climate: Global Climate Report for Annual 2016, published online January 2017, retrieved on July 27, 2017 from https://www.ncdc.noaa.gov/sotc/global/201613.

NSIDC, 2016: 2016 melt season in review, National Snow and Ice Data Center, http://nsidc.org/greenland-today/category/analysis/, October 26, 2016.

Turner, J., T. Philips, G.J. Marshall, J.S. Hosking, J.O. Pope, T.J. Bracegirdle, and P. Deb. Unprecedented springtime retreat of Antarctic sea ice in 2016, Geophys. Res. Lett., 44, 6868-6875, doi:10.1002/2017GL073656.

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