November Arctic Sea Ice Extent Third Lowest On Record

December 14, 2009

Reductions in arctic sea ice during the past decade have elevated scientific and societal questions about the likelihoods of future scenarios. Photo courtesy USGS

Arctic sea ice levels over the Barents Sea and Hudson Bay were the third lowest on record since officials began monitoring the area by satellite in 1979, according to the National Snow and Ice Data Center (NSIDC). Last month the sea ice extent averaged 3.96 million square miles, 405,000 square miles less than the average from the period between 1979 and 2000.

Monthly November ice extent for 1979 to 2009 shows a decline of 4.5% per decade. Source: NSIDC

Arctic sea ice experiences significant melting during the summer months. By November, darkness sweeps the Arctic, air temperatures plummet, and sea ice grows rapidly. However, both the Barents Sea and Hudson Bay experienced a slow freeze-up this fall.

In the Barents Sea, ice growth was slowed by winds that pushed the ice northwards into the central Arctic. The deepest of the Arctic’s coastal seas, the Barents Sea is open on its southern and northern boundaries, which creates a significant wind corridor. Southerly winds created a high-pressure area over Siberia and low pressure in the northern Atlantic Ocean in November. Those winds transported warm air and water from the south, and pushed the ice edge northwards out of the Barents Sea.

The map of sea level pressure (in millibars) for November 2009, shows low pressure in the North Atlantic and high pressure over Russia, which led to winds that brought warmth to the Barents Sea and pushed the ice northward. Source: NSIDC

By contrast, the Hudson Bay is a nearly enclosed, relatively shallow body of water that tends to capture ice. The lack of ice is likely related to warmer-than-normal air temperatures in the region.

The map of air temperature anomalies for November 2009. Source: NSIDC

Sea ice in the Arctic is now declining at a rate of about 4.5 percent per decade, according to researchers.