ANCHORAGE (AP) -- Scientists presenting research findings on arctic environmental changes reported Wednesday that the polar ice cap has thinned by 40 percent in just three decades.
The findings, though tentative, could mean that the polar ice cap is retreating and that the Arctic Ocean could become ice-free during summer months. That would open the way to further warming and the mixing of waters and sea life between the Pacific and Atlantic oceans.
''This has implications for the long term,'' said James Morison of the University of Washington's Polar Science Center. ''We'd like to make predictions, but we can't. That's why we are so concerned.''
One theory is that the fast-changing arctic environment could cause a new ice age by warming waters in the North Atlantic that serve as the ''engine'' for recharging the world's oceans.
Ocean circulation is stimulated through convection when relatively warmer Atlantic currents collide with frigid arctic saltwater. If enough warmer fresh water from the arctic reaches the North Atlantic, it could upset this process.
''There is evidence in the past that when convection shuts down, there is increased glaciation,'' said Alison York, project manager for the Arctic Research Consortium of the United States.
The new findings were delivered at the first day of a two-day conference the consortium is holding in Washington D.C. The consortium, based at the University of Alaska Fairbanks, was formed in 1988 to serve as a forum gathering and synthesizing arctic research.
Morison said in an interview that some of the changes are well known to Alaska and Canada Natives who are having to travel further to find traditional game because of the thinning ice fields.
''I think you can see connections between what the Natives find and what we are seeing,'' Morison said.
It appears that there may be an escalating tempo to the changes, he said. As the ice retreats on land and sea, there is less reflection of the sun's heat and the land and water grow even warmer. Morison said that in some areas of the Russian Arctic, the ambient air temperature has risen by four degrees in the past 20 to 30 years.
What's behind the changes is still a mystery. But scientists at the conference said they believe it had its beginnings in the 1980s during a phenomenon called ''Arctic oscillation,'' a sort of northern equivalent to the El Nino phenomenon that periodically warms the equatorial Pacific and triggers major weather changes.
Satellite imagery over the past couple of decades has shown the ice cap shrinking. But what wasn't known until recently was that what remains has thinned dramatically.
Drew Rothrock of the University of Washington's polar science center reported that his analysis of data gathered as far back as 1957 by submarines confirmed that the ice has thinned by an average of about one meter -- 39.37 inches -- since then, a decline of as much as 40 percent.
''If the ice cover were to disappear, the Arctic Ocean would be dark and absorb a lot more heat,'' he said in an interview. ''The thought is that this would enhance the whole process of global (climate) change. When you see sea ice diminish, people get interested.''
Much more research will be needed to determine whether these patterns are continuing, the scientists said.
Eddy Carmack with Canada's Department of Fisheries and Oceans said the environmental consequences of the arctic climate changes are showing up, with ring seals disappearing and salmon moving into river systems where they've not been before, including the Mackenzie River in the Yukon Territory east of the Alaska border.
''The arctic is not only going to see the most changes, it is probably the most sensitive to the changes,'' he said.
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