Highlights
Arctic sea ice grew more slowly than average in November, leading to the second-lowest ice extent for the month. At the end of November, Hudson Bay was still nearly ice-free.
Arctic sea ice extent averaged over November 2010 was 9.89 million square kilometers (3.82 million square miles). This is the second-lowest November ice extent recorded over the period of satellite observations from 1979 to 2010, 50,000 square kilometers (19,300 square miles) above the previous record low of 9.84 million square kilometers (3.80 million square miles) set in 2006.
Ice extent was unusually low in both the Atlantic and Pacific sectors of the Arctic and in Hudson Bay. Typically by the end of November, nearly half of Hudson Bay has iced over. But on November 30, only 17% of the bay was covered by sea ice. Compared to the 1979 to 2000 average, the ice extent was 12.4% below average for the Arctic as a whole.
Conditions in context
As temperatures drop in autumn, open water areas on the Arctic coastal seas quickly refreeze. After this rapid increase in ice extent during October, ice growth slows in November. This November, ice extent over the entire Arctic grew at an average rate of 74,000 square kilometers per day (28,600 miles per day), which is slower than average. However, local weather conditions kept ice extent very low in some locations, contributing to the low extent for the month.
Near-surface air temperatures over the Siberian and Alaskan side of the Arctic were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) warmer than normal in November. Air temperatures over Baffin Bay were also unusually warm (8 degrees Celsius, or 14 degrees Fahrenheit above average). The warm air came from two sources: unfrozen areas of the ocean continued to release heat to the atmosphere; and a circulation pattern brought warm air into the Arctic from the south.
November 2010 had the second-lowest ice extent for the month since the beginning of satellite records. The linear rate of decline for the month is –4.7 % per decade.
The loss of multiyear ice has contributed to low summer ice extents in recent years, because thinner first-year ice melts out more easily than older, thicker ice. Last summer, multiyear ice that had moved into the Beaufort and Chukchi seas during the previous winter largely melted out (see our October post).
Recent research from scientists at the NASA Jet Propulsion Laboratory shows that summer melt of old, thick ice in the Beaufort Sea has contributed substantially to the overall loss of thick multiyear ice in the Arctic. Using data from the QuikSCAT satellite, researchers Ron Kwok and Glenn Cunningham found that the Beaufort Sea lost 947,000 square kilometers (366,000 square miles) of multiyear ice during the summers of 1993 to 2009.
The study also showed that multiyear ice loss increased in the last few years. From 2005 to 2008, the Beaufort Sea lost 490,000 square kilometers (189,000 square miles) of multiyear ice, 32% of the total loss of multiyear ice in the Arctic Ocean during that time period.
