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Published Online December 6, 2007
Science DOI: 10.1126/science.1148924

Research Articles

Submitted on August 8, 2007
Accepted on November 8, 2007

Reduced North Atlantic Deep Water Coeval with the Glacial Lake Agassiz Fresh Water Outburst

Helga (Kikki) Flesche Kleiven 1*, Catherine Kissel 2, Carlo Laj 2, Ulysses S. Ninnemann 3, Thomas O. Richter 4, Elsa Cortijo 2

1 Bjerknes Centre for Climate Research, University of Bergen, N-5007 Norway.; Department of Earth Science, University of Bergen, N-5007 Norway.
2 Laboratoire des Sciences du Climat et de l’Environnement, 91198 Gif-sur-Yvette, France.
3 Department of Earth Science, University of Bergen, N-5007 Norway.; Bjerknes Centre for Climate Research, University of Bergen, N-5007 Norway.
4 Royal Netherlands Institute for Sea Research, 1790 AB Den Burg, Netherlands.

* To whom correspondence should be addressed.
Helga (Kikki) Flesche Kleiven , E-mail: kikki{at}uib.no

An outstanding climate anomaly 8200 years before the present (B.P.) in the North Atlantic is commonly postulated to be the result of weakened overturning circulation triggered by a freshwater outburst. New stable isotopic and sedimentological records from a northwest Atlantic sediment core reveal that the most prominent Holocene anomaly in bottom water chemistry and flow speed in the deep limb of the Atlantic overturning circulation begins at ~8.38 thousand years (kyr) B.P., coeval with the catastrophic drainage of Lake Agassiz. The influence of Lower North Atlantic Deep Water was strongly reduced at our site for ~100 years after the outburst, confirming the ocean’s sensitivity to freshwater forcing. The similarities between the timing and duration of the pronounced deep circulation changes and regional climate anomalies support a causal link.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)