Warm Arctic, lowest sea ice extent

NSIDC Arctic News and Analysis, January 5, 2011

http://nsidc.org/arcticseaicenews/2011/010511.html

Repeat of a negative Arctic Oscillation leads to warm Arctic, low sea ice extent

Arctic sea ice extent for December 2010 was the lowest in the satellite record for that month. These low ice conditions are linked to a strong negative phase of the Arctic Oscillation, similar to the situation that dominated the winter of 2009-2010.

Overview of conditions

Arctic sea ice extent averaged over December 2010 was 12.00 million square kilometers (4.63 million square miles). This is the lowest December ice extent recorded in satellite observations from 1979 to 2010, 270,000 square kilometers (104,000 square miles) below the previous record low of 12.27 million square kilometers (4.74 million square miles) set in 2006 and 1.35 million square kilometers (521,000 square miles) below the 1979 to 2000 average.

As in November, ice extent in December 2010 was unusually low in both the Atlantic and Pacific sides of the Arctic, but particularly in Hudson Bay, Hudson Strait (between southern Baffin Island and Labrador), and in Davis Strait (between Baffin Island and Greenland). Normally, these areas are completely frozen over by late November. In the middle of December, ice extent stopped increasing for about a week, an unusual but not unique event.

Conditions in context

The low ice conditions in December occurred in conjunction with above-average air temperatures in regions where ice would normally expand at this time of year. Air temperatures over eastern Siberia were 6 to 10 degrees Celsius (11 to 18 degrees Fahrenheit) above normal in December. Over the eastern Canadian Arctic Archipelago, Baffin Bay/Davis Strait and Hudson Bay, temperatures were at least 6 degrees Celsius (11 degrees Fahrenheit) higher than average. Southern Baffin Island had the largest anomalies, with temperatures over 10 degrees Celsius (18 degrees Fahrenheit) higher than normal. By sharp contrast, temperatures were lower than average (4 to 7 degrees Celsius, 7 to 13 degrees Fahrenheit) over the Alaska-Yukon border, north-central Eurasia, and Scandinavia.

The warm temperatures in December came from two sources: unfrozen areas of the ocean continued to release heat to the atmosphere, and an unusual circulation pattern brought warm air into the Arctic from the south. Although the air temperatures were still below freezing on average, the additional ocean and atmospheric heat slowed ice growth.