The catastrophic draining of two gigantic glacial lakes in Canada's Hudson Bay region some 8,200 years ago appears to have caused the most abrupt, widespread cold spell on Earth during the last 10,000 years, according to a group of scientists.

Don Barber, a geological sciences doctoral student at the University of Colorado at Boulder, said the lakes, Agassiz and Ojibway, contained more water than all of the Great Lakes combined. Barber and his colleagues estimated that when an ice dam from a remnant of the Laurentide Ice Sheet collapsed, the flow of lake water rushing through the Hudson Strait and into the Labrador Sea was about 15 times greater than the present discharge of the Amazon River.

The fresh water probably gushed into the Labrador Sea in the North Atlantic for about a year, reducing sea-surface salinity and altering ocean circulation patterns at the time, said Barber, also a researcher at CU-Boulder's Institute of Arctic and Alpine Research. Ocean circulation models suggest massive influxes of freshwater can disrupt heat transport in currents flowing from the tropics to temperate regions.

Ice core data taken by scientists in Greenland show temperatures dropped by as much as 15 degrees Fahrenheit in central Greenland and by nearly 6 degrees F in Western Europe following the catastrophic lake drainage. "This was the coldest climate event in the last 10,000 years," Barber said.

A paper on the subject by Barber, published in the July 22 issue of Nature, was co-authored by INSTAAR's John Andrews, Anne Jennings, Mike Kerwin and Mark Morehead. Other co-authors include John Southon of the Lawrence Livermore National Lab in Livermore, Calif., Art Dyke and Roger McNeely of the Geological Survey of Canada, Claude Hillaire-Marcel and Guy Bilodeau of the University of Quebec and Jean-Marc Gagnon of the Canadian Museum of Nature.

The surface currents of the Atlantic act much like conveyor b
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Contact: Don Barber
barberdc@ucsub.colorado.edu
303-492-7641
University of Colorado at Boulder
21-Jul-1999