Arctic sea ice rebounds, but don't jump to 'global cooling' conclusions
Parts of the Arctic Ocean containing at least 15 percent sea ice have increased by 78 percent when compared with the extent last year at this time, according to data compiled by the National Snow and Ice Data Center.
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Despite some media reports of ice stretching in an unbroken expanse from Canada to Russia, the current ice extent appears to be anything but chockablock. Around the perimeter of the Arctic basin, from Canada's western Arctic coast west to northern Scandinavia, large regions of open water remain, particularly along Russia's Arctic coast, according to the latest data from the National Snow and Ice Data Center.Skip to next paragraph
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Indeed, through August, Russia reportedly issued permits to more than 400 ships seeking to ply its Northeast Passage, which has been open since July. Chinese cargo ships reportedly have been among the vessels taking advantage of the shortcut from Asia to Europe this year.
Last year's record decline, Arctic specialists have noted, was driven largely by a vast storm in early August that lingered over the central Arctic Ocean. High winds, along with rough seas around the periphery of the ice, sped up the disintegration of large expanses of single-year ice, while rain accelerated surface melting. Single-year ice is thinner and more vulnerable than multi-year ice, whose contribution to Arctic sea ice also has been declining – by at least 15 percent per year by some estimates.
This year, the summer has been 1 to 5 degrees F. cooler from northern Greenland through the North Pole, compared with the 1981-2010 average. Off western Canada's and Alaska's Arctic coasts, temperatures have run about 4 degrees above that average. Perhaps as important, the basin hasn't seen storms anywhere near the strength of last year's August monster.
At the same time, ice volume – combining thickness as well as area – continues to decline, a trend that has been under way since at least 1979. Volume is thought to be a better indicator of climate change than ice extent because it also takes into account the impact of warming ocean waters, which melt the ice from underneath.
Researchers at the University of Washington's Polar Science Center in Seattle who are keeping track of volume are puzzling over an unusually deep dip in estimated sea-ice volume over the past three years.
That dip also appears to be recovering slightly compared with 2012. But the August 2013 estimate remains 66 percent lower than the 1979-2013 average for the month. And it's 76 percent lower than the maximum volume estimated for 1979.
With its sometimes-dramatic yearly ups and downs, the long-term decline in summer sea ice extent and volume continues to raise questions about when the world might expect to see a largely ice-free Arctic each summer.
If wording in the final-draft summary of the next Intergovernmental Panel on Climate Change report on global climate science holds up, it offers that a nearly ice-free Arctic Ocean in September is likely before midcentury.
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