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Science 15 August 2003:
Vol. 301. no. 5635, pp. 922 - 923
DOI: 10.1126/science.1085921
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Perspectives

Also see the archival list of Science's Compass: Enhanced Perspectives

PALEOCLIMATE:
Enhanced: Superlakes, Megafloods, and Abrupt Climate Change

Garry Clarke, David Leverington, James Teller, Arthur Dyke

About 8200 years ago, the climate of much of the Northern Hemisphere cooled abruptly for a period of about 200 years. In their Perspective, Clarke et al. examine the most likely culprit for this cooling: an outburst of fresh water from a vast, ice-dammed glacial lake in North America. The superlake had formed when the kilometers-thick ice sheet covering much of North America disintegrated. When the ice dam became unstable, fresh water flooded from the lake into the North Atlantic. It remains unclear how this fresh water affected ocean circulation or whether the outburst occurred in more than one stage, but the timing points strongly to the outburst flood as the trigger of the 8200-year climate event.

G. Clarke is in the Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada. E-mail: clarke{at}eos.ubc.ca D. Leverington is at the Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC 20560, USA. J. Teller is in the Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada. A. Dyke is in the Terrain Sciences Division, Geological Survey of Canada, Ottawa, Ontario K1A 0E8, Canada.

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