Despite above-average growth, the ice sheet did not catch up to average
By Summit Voice
SUMMIT COUNTY — Even though Arctic sea ice grew at an above-average pace during November, the overall extent still remained one of the lowest on record during the satellite era, reaching 9.9 million square kilometers. Only a couple of other years have seen a lower sea ice extent at the end of November, according to the National Snow and Ice Data Center.
During November, the ice sheet grew at an average rate of 98,600 square kilometers per day. The ice extent remained below the all-time record low for most of November before just matching those record low levels at the end of the month.
Specifically, 2012 is only the third time that sea ice extent was below 10 million square kilometers at the end of November. Sea ice extent has been declining at a linear rate of 4.8 percent per decade compared to the 1979 to 2000 average.
Arctic sea ice extent generally grows fast during November because there is hardly any incoming solar energy and the ocean is quickly losing heat gained during the previous summer.
November air temperatures remained above average over most of the Arctic Ocean, with particularly warm temps over the Barents and Kara seas. In those regions, air temperatures up to 6 degrees Celsius above average in part were due to the remaining areas of open water, which enables strong upward transfers of heat from the ocean to the atmosphere. Unusually strong winds from the south contributed to the warmth and also helped keep the region ice free.
According to the NSIDC, unusually warm conditions also prevailed over the ice-covered East Siberian Sea, where temperatures were also 6 degrees Celsius (11 degrees Fahrenheit) above average. According to the ice researchers, the warmth was probably due to persistent high pressure over the Bering Strait. Southerly winds on the west side of the high-pressure zone brought warm air into the East Siberian region.
Colder, northerly winds on the east side of the high-pressure zone help explain the higher-than-average extent in the Bering Sea, where sea ice has was at record high extent last winter.