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Science 14 March 2003:
Vol. 299. no. 5613, pp. 1709 - 1713
DOI: 10.1126/science.1081002
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Research Articles

Meltwater Pulse 1A from Antarctica as a Trigger of the Bølling-Allerød Warm Interval

Andrew J. Weaver,1* Oleg A. Saenko,1 Peter U. Clark,2 Jerry X. Mitrovica3

Meltwater pulse 1A (mwp-1A) was a prominent feature of the last deglaciation, which led to a sea-level rise of ~20 meters in less than 500 years. Concurrent with mwp-1A was the onset of the Bølling-Allerød interstadial event (14,600 years before the present), which marked the termination of the last glacial period. Previous studies have been unable to reconcile a warm Northern Hemisphere with mwp-1A originating from the Laurentide or Fennoscandian ice sheets. With the use of a climate model of intermediate complexity, we demonstrate that with mwp-1A originating from the Antarctic Ice Sheet, consistent with recent sea-level fingerprinting inferences, the strength of North Atlantic Deep Water (NADW) formation increases, thereby warming the North Atlantic region and providing an explanation for the onset of the Bølling-Allerød warm interval. The established mode of active NADW formation is then able to respond to subsequent freshwater forcing from the Laurentide and Fennoscandian ice sheets, setting the stage for the Younger Dryas cold period.

1 School of Earth and Ocean Sciences, University of Victoria, Post Office Box 3055, Victoria, British Columbia V8W 3P6, Canada.
2 Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
3 Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada.
*   To whom correspondence should be addressed. E-mail: weaver{at}uvic.ca

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