Arctic Ice in "Death Spiral," Is Near Record Low
for National Geographic News
|September 17, 2008|
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].)
This makes 2008's near record all the more striking, researchers say.
"The remarkable thing about this summer is that we got all the way down to second lowest without especially favorable atmospheric patterns that would hasten melt," Serreze said.
This near record low in 2008 was expected because warming has melted much of the older ice pack, resulting in thinner sea ice, which melts rapidly.
Last winter, some parts of the Arctic were colder than normal. Overall its sea ice grew to a larger area than the ice had in the past few years. Some observers hailed this as a slight recovery.
But then the ice melted rapidly through the summer, with the ice cover shrinking faster this August than in any other August on record. "Not much of a 'recovery'," Serreze said.
"The most interesting aspect [of this year's melt] was the rapid loss of ice in August," said Sheldon Drobot, a climate scientist at the University of Colorado, Boulder.
"The ice always melts during August, but typically the rate of melt begins to decline as fall begins to set in. However, the rate of decline remained high this year."
The remaining ice pack is younger and thinner than ever, "which is something we'll see next year too," Drobot said.
So even without special conditions like those seen in 2007, next summer could set a new record low, he added.
|© 1996-2008 National Geographic Society. All rights reserved.|