Within a century the melting could lead to summertime ice-free ocean conditions not seen in the area in a million years, the group said Tuesday.

Melting of land-based glaciers could take much longer but could raise the sea levels, potentially affecting coastal regions worldwide.

And changes to the permafrost could undermine buildings, drain water into bogs and release additional carbon into the atmosphere.

"What really makes the Arctic different from the rest of the non-polar world is the permanent ice in the ground, in the ocean, and on land," said Jonathan T. Overpeck of the University of Arizona and chairman of the National Science Foundation's Arctic System Science Committee that issued the report.

"We see all of that ice melting already, and we envision that it will melt back much more dramatically in the future, as we move towards this more permanent ice-free state," Overpeck said in a statement.

The panel's findings were published in Tuesday's issue of Eos, the weekly newspaper of the American Geophysical Union.

The report comes just days after environmental ministers and officials from 23 countries met in Greenland to call on governments to stop arguing over global warming and start acting.

That session was held in the town of Ilulissat, near the edge of the Sermeq Kujalleq glacier that has retreated nearly seven miles since 1960 and has become a symbol of fears that the planet is approaching a dangerous warming.

The report was issued following a weeklong meeting of scientists that examined how the Arctic environment and climate interact and how that system would respond as global temperatures rise.

In the past, Arctic climate has included glacial periods with ice sheets extending into North America and Europe, and other times of relative warming.

After studying how various parts of the climate system interact, the researchers said there are two major feedback systems influencing the region — ocean circulation in the North Atlantic and the amount of precipitation and evaporation that takes place.

Feedback can accelerate changes in the system, they said. For example, the white sea ice reflects solar radiation back into space, but as the ice melts the dark water will absorb some of the light, warming and melting more ice.

The scientists said they did not see any natural mechanism that could stop the loss of ice.

"I think probably the biggest surprise of the meeting was that no one could envision any interaction between the components that would act naturally to stop the trajectory to the new system," Overpeck said.

In addition to sea and land ice melting, Overpeck said that the frozen soil layer called permafrost will melt and eventually disappear in some areas. That could release additional greenhouse gases stored in the permafrost for thousands of years, he said.

© 2005 Associated Press

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