Northern hemisphere snow cover well above average
By Summit Voice
SUMMIT COUNTY — Arctic sea ice extent in February tied with 2005 for lowest on record since 1979, when satellite measurements began. Ice covered about 5.54 million square miles of the Arctic area, about half a million square miles below the average.
The sea ice extent was below average in both the Atlantic and Pacific sectors, especially in the Labrador Sea and the Gulf of St. Lawrence, according to the monthly update from the National Snow and Ice Data Center. Here’s an excerpt:
“While ice extent has declined less in winter months than in summer, the downward winter trend is clear. The 1979 to 2000 average is 15.64 million square kilometers (6.04 million square miles). From 1979 through 2003, the February extent averaged 15.60 million square kilometers (6.02 million square miles). Every year since 2004 has had a mean February extent below 15 million square kilometers (5.79 million square miles).”
The lack of sea ice in the Gulf of St. Lawrence poses a challenge for Harp Seal populations, which generally breed in the ice in February and March.
Sea ice grew at an average rate for the month, but the overall extent remained low as warm air dominated over much of the Arctic Ocean, with temperatures between 4 and 7 degrees above average, and even warmer (9 to 13 degrees) over the East Greenland Sea and toward the North Pole.
Temperatures 4 to 11 degrees below average prevailed over western and east-central Eurasia and parts of the Canadian Arctic in a pattern linked with the Arctic Oscillation, when the distribution of high and low pressure systems shift dramatically over the Arctic and sub-Arctic region. Last winter’s negative phase of the Arctic Oscillation was the most pronounced since 1951, bringing harsh winter weather to the northeastern U.S. and parts of Europe, but shifting ice patterns to deplete some of thickest and oldest ice in the region.
The NSIDC, together with the Rutgers University Global Snow Lab also tracks winter snow cover, using records going back 45 years in an effort to track climate change. During that span, snow cover in February averages about 17.8 million square miles.
February 2011 had the sixth-largest snow cover extent on record, at 18.3 million square miles, with more snow than usual in the western and central U.S., eastern Europe, Tibet and northeastern China.
Below-average sea ice extent and extensive snow cover are not contradictory:
“Both (are) linked to a strong negative phase of the Arctic Oscillation (see our January 5, 2011 post). A strongly negative AO favors outbreaks of cold Arctic air over northern Europe and the U.S., as many people experienced first-hand these last two winters. Whether this is a trend, or in any way linked to ongoing climate warming in the Arctic, remains to be seen.”