The study is particularly pertinent because of last year's record melt of Arctic sea ice, when ice cover in the Arctic Sea shrank to 30 percent below average. Another record melt is forecast for this year but it is unknown whether this is the beginning of a trend.

"Our climate model suggests that rapid ice loss is not necessarily a surprise," said David Lawrence of the National Center for Atmospheric Research, an author of the study.

"When you get certain conditions in the Arctic -- thin ice, a lot of first-year ice (as opposed to older, sturdier ice) -- that you can get a situation where ... you get a rapid and steady loss over a period of five to 10 years," Lawrence said by telephone from Colorado.

In such a period of rapid ice loss, autumn temperatures along the Arctic coasts of Russia, Alaska and Canada could rise by as much as 9 degrees F (5 degrees C), the study's climate model found. Autumn is often the warmest season in this area.

INTERCONNECTED ARCTIC

Last year's temperatures from August to October over land in the western Arctic were also unusually warm, more than 4 degrees F (about 2 degrees C) above the average temperatures for 1978-2006, raising questions about the relationship between shrinking sea ice and warmer land temperatures.

The scientists found that when sea ice melts rapidly, Arctic land warms three and a half times faster than the rate predicted in 21st century climate models. The warming is largest over the ocean but simulations indicate that it can extend as far as 900 miles inland.

In places where permafrost is already at risk, such as central Alaska, a quick sea ice melt could lead to a quick permafrost thaw.

The effects of melting are already evident in parts of Alaska, the scientists said: as pockets of soil collapse as the ice it contains melts, highways buckle, houses are destabilized and trees tilt crazily in a phenomenon known as "drunken forests" when the earth beneath them gives way.

"There's an interconnectedness about the Arctic," Lawrence said. "When sea ice retreats and retreats very rapidly it impacts other parts of the system, like warming temperatures over land. And warming temperatures over land can also accelerate the degradation of permafrost, particularly permafrost that's warm right now."

The research will be published on Friday in the journal Geophysical Research Letters. (For more information on the environment, see http://blogs.reuters.com/environment/ )