Significant negative trend seen in peripheral seas
By Summit Voice
FRISCO — Arctic sea ice extent stayed well below average during December, especially in the Kara, Barents, and Labrador seas. For the month, the extent was the second-lowest in the satellite record, dating back to 1979.
Sea ice extent is slightly above average on the Pacific side of the Arctic edging farther south into the Bering Sea — the only part of the Arctic that has shown a slightly positive trend in ice extent during the winter months, according to the National Snow and Ice Data Center.
For the month, the average sea ice extent was 4.71 million square miles, almost half-a-million square miles below the 1979 to 2000 average. The Arctic gained 900,000 square miles of ice in December, but ice growth was slow in the Kara and Barents seas where air temperatures were 5 to 9 degrees Fahrenheit higher than normal. Air temperatures over Greenland and the Canadian Archipelago were also slightly above average, while temperatures over Alaska were 4 to 13 degrees Fahrenheit below average.
In its January update, the NSIDC pointed out that successive winters with low sea ice in the North Atlantic have led to higher mortality rates amoing seals in the region. Bearded and ringed seals were recently added to the endangered species list partly because of global warming impacts.
Through 2012, December sea ice extent has been declining 3.5 percent per decade compared to the 1979 to 2000 average. Overall winter sea ice decline has been moderate, but large negative trends are becoming in the peripheral seas, with the exception of the Bering Sea.
Some of the relatively cold conditions seen so far in parts of Asia, northern Europe and most recently in the West are due to a negative phase of the Arctic oscillation, when higher-than-normal pressure persists over the central Arctic. The pattern keeps the high Arctic relatively warm but allows cold air masses to pass in and out of the Arctic more readily.
According to the NSIDC, the pattern tends to favor the retention of thick ice in the Arctic basin by reducing the outflow of ice through the Fram Strait and strengthening the Beaufort Gyre, a clockwise circular pattern of ice drift in the central Arctic. In the past, this pattern has also favored more extensive summer sea ice.