IMAGE: ILLUSTRATION OF WARMING SCENARIOS
Steve Deyo  /  UCAR
The image at left shows simulated autumn temperature trends during rapid sea-ice loss. The accelerated warming signal (red to dark red) reaches 900 miles inland. The image at right shows milder but still substantial warming rates.
msnbc.com
updated 6/12/2008 3:05:25 PM ET 2008-06-12T19:05:25

Rapid Arctic sea ice loss could triple the rate of warming over northern Alaska, Canada and Russia and trigger permafrost thawing that unleashes extremely potent greenhouse gases, according to a new study.

"Our study suggests that, if sea ice continues to contract rapidly over the next several years, Arctic land warming and permafrost thaw are likely to accelerate," lead author David Lawrence of the National Center for Atmospheric Research said in a statement.

"The loss of sea ice can trigger widespread changes that would be felt across the region," added co-author Andrew Slater, a scientist at the National Snow and Ice Data Center.

Arctic sea ice extent shrank to a record low last summer, more than 30 percent below average, while air temperatures over land in the western Arctic were unusually warm from August to October — reaching more than 4 degrees F above average.

Researchers used a climate model to study whether the two events were related, and found that when sea ice melts quickly, the rate of Arctic land warming is 3.5 times greater than the average 21st century warming rates predicted in climate models.

"While this warming is largest over the ocean, the simulations suggest that it can penetrate as far as 900 miles inland," NCAR said in the statement. "The simulations also indicate that the warming acceleration during such events is especially pronounced in autumn. The decade during which a rapid sea-ice loss event occurs could see autumn temperatures warm by as much as 9 degrees F along the Arctic coasts of Russia, Alaska, and Canada."

The experts then used the model to determine that in areas where permafrost is already at risk, such as central Alaska, a period of abrupt sea-ice loss could lead to rapid and long-term soil thaw.

A worst-case scenario would be thawing that unleashes vast amounts of carbon dioxide and methane, an even more potent greenhouse gas.

Thawing could also destabilize oil installations and other infrastructure. Parts of Alaska, Canada and Russia have already seen buckled roads, sunken homes and "drunken forests" of trees leaning at wild angles.

"An important unresolved question is how the delicate balance of life in the Arctic will respond to such a rapid warming," Lawrence said. "Will we see, for example, accelerated coastal erosion, or increased methane emissions, or faster shrub encroachment into tundra regions if sea ice continues to retreat rapidly?"

The study, which will be published Friday in Geophysical Research Letters, was funded by the U.S. Department of Energy and the National Science Foundation.

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