SJ MERCURY NEWS:Freshwater flood cooled the atmosphere

[Betty Cunningham <bettyc@flyinggoat.com>]

http://www.sjmercury.com/breaking/docs/001801.htm

Freshwater flood cooled the atmosphere at the end of the Ice Age

Global warming sometimes can lead to cold weather, researchers said 
today in a report that outlines how a giant flood can trigger a 
worldwide freeze in a matter of decades.

Scientists say that as the glaciers melted at the end of the Ice Age, 
so much cold fresh water gushed into the North Atlantic 8,200 years 
ago that it cooled the atmosphere for hundreds of years.

The cold spell has been well known to researchers, but its cause was a 
mystery.

 The flood scenario, described in today's issue of the journal Nature, 
demonstrates how global warming can, paradoxically, provoke a global 
freeze.

 If a modern glacier such as the Greenland Ice Sheet melts as a result 
of rising temperatures in the next century, it could trigger a similar 
flood and climate fluctuation, researchers said.

``Ultimately, that's the interest here,'' said Richard Alley, a climate 
expert at Penn State University. ``We've been pretty lucky, the climate 
hasn't varied much in 8,000 years. But could the big changes come
back?''

 The study by University of Colorado and Canadian researchers examines 
evidence of a huge flood in the Hudson Bay region of Quebec and Ontario.

The Laurentide Ice Sheet covered parts of North America with ice up to 
2 miles thick for more than a million years. As it retreated toward the 
poles, the ice sheet left in its wake at least two lakes containing 
more water than the Great Lakes combined.

In the Hudson Bay, ice held the water in place like a plug in a bathtub. 
But when the plug finally melted, trillions of gallons gushed into the 
Labrador Sea, shooting out at 100 times the rate water leaves the 
Mississippi.

Independent research showed the temperature dropped significantly within 
several hundred years of the flood. But nobody could pinpoint if these 
two events were connected, said the study's lead author, University of 
Colorado geologist Don Barber.

The evidence linking the temperature drop to the flood includes 
radiocarbon dating of clams in the flood sediment.

The Atlantic Gulf Stream normally acts like a conveyor belt to deliver 
warm tropical water to temperate regions. By adding so much fresh water 
in such a short time, the flood shut down the Gulf Stream, Alley said.

Temperatures in Greenland and Europe dropped by 6 to 15 degrees for at 
least 200 years, according to ice core data.
-- 
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