Sunday, October 24, 2010

Warm Arctic is probably permanent

Warm Arctic is probably permanent

WASHINGTON: The signs of climate change were all over the Arctic this year -- warmer air, less sea ice, melting glaciers -- which probably means this weather-making region will not return to its former, colder state, scientists reported on Thursday.

In an international assessment of the Arctic, scientists from the United States, Canada, Russia, Denmark and other countries said, "Return to previous Arctic conditions is unlikely."

Conditions in the Arctic are important because of their powerful impact on weather in the heavily populated middle latitudes of the Northern Hemisphere.

The heavy snows in the United States, northern Europe and western Asia last winter are linked to higher air temperatures over the Arctic, the scientists found.

"Winter 2009-2010 showed a new connectivity between mid-latitude extreme cold and snowy weather events and changes in the wind patterns of the Arctic, the so-called Warm Arctic-Cold Continents pattern," said the report, issued by the U.S. National Oceanic and Atmospheric Administration (NOAA).

The scientists found evidence of widespread Arctic warming, with surface air temperatures rising above global averages twice as quickly as the rate for lower latitudes, Jackie Richter-Menge of the U.S. Army Cold Regions Research and Engineering Laboratory.

Part of the reason for this is a process called polar amplification. Warming air melts the sun-reflecting white snow and ice of the Arctic, revealing darker, heat-absorbing water or land, spurring the effects of warming. This is further amplified by the action of the round-the-clock sunlight of Arctic summers, Richter-Menge said in a telephone briefing.

Normally cold air is "bottled up" in the Arctic during winter months but in late 2009 and early 2010, powerful winds blew cold air from north to south instead of the more typical west to east pattern, said Jim Overland, an oceanographer at NOAA's Pacific Marine Environmental Laboratory in Seattle.


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