for National Geographic News
The Arctic Ocean's sea ice has shrunk to its second smallest area on record, close to 2007's record-shattering low, scientists report.
The ice is in a "death spiral" and may disappear in the summers within a couple of decades, according to Mark Serreze, an Arctic climate expert at the National Snow and Ice Data Center in Boulder, Colorado.
Each winter, sea ice fills most of the Arctic Ocean. The ice pack then melts and shrinks in the summer heat.
With additional heating due to global warming, the extent of sea ice cover has gotten smaller and smaller over the summers since the 1980s.
This has scientists concerned—and not just because the ice melt is a symptom of global warming. Sea ice has a cooling effect by reflecting sunlight back into space. So when the ice shrinks and opens up more ocean, more of the sun's heat is soaked up by the dark sea.
This heats up the Arctic—and the planet—more than the greenhouse effect on its own, in turn melting even more ice.
"With the climate feedbacks kicking in," Serreze said by email, "we'll lose the summer ice cover probably by the year 2030."
The 2007 melt last year smashed a previous record set in 2005.
But 2007 saw special conditions that favored melting, researchers say. "The most important factor in 2007," Serreze said, "was an unusual pattern of atmospheric circulation in summer that brought warm, southerly winds north of eastern Siberia, promoting strong melt."
(Related: "Warming Oceans Contributed to Record Arctic Melt" [December 14, 2007].)
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