December ice declining at a rate of 3.5 percent per decade
By Summit Voice
SUMMIT COUNTY — Arctic sea ice extent remained unusually low in December, despite a positive phase in the Arctic Oscillation. At the end of the month, the extent was the third-lowest in the satellite record. Five of the lowest December readings have been in the past six years, reflecting the steady shrinkage of Arctic, now declining at a linear rate of 3.5 percent per decade.
The lowest sea ice was on the Atlantic side of the Arctic in the Barents and Kara seas, according to the Jan. 5 update from the National Snow & Ice Data Center.
According to the monthly report, the eastern coast of Hudson Bay this year did not freeze over until late in December; in most years, it’s frozen over by the beginning of the month. On the other side of North America, ice extent in the Bering Sea was slightly above average.
Arctic sea ice extent grew at a faster-than-average rate during December but still didn’t catch up from the below-average levels at the beginning of the month.
The positive phase of the Arctic Oscillation resulted in below-average temperatures over much of the Arctic Ocean, but warmer than average temps in the Kara and Barents sea regions, where open water helped warm air temperatures.
The switch to the positive phase of the Arctic Oscillation was also reflected by conditions in Europe and North America, which both have experienced mild early winter conditions.
Some studies suggest that, during the positive phase of the Arctic Oscillation, thick ice tends to move out of the Arctic through Fram Strait, leaving the Arctic with thinner ice that melts out more easily in summer. That means Arctic sea ice could shrink to near record low levels next summer.
In Antarctica, sea ice extent remained unusually high in December, especially in the northern Ross Sea and the eastern Weddell Sea. But overall, Antarctic sea ice extent remained below or near normal for most of 2011. Antarctic sea ice data are available on the Sea Ice Index Web site.