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An abrupt climate event in a coupled ocean–atmosphere simulation without external forcing

Nature volume 409, pages 171175 (11 January 2001) | Download Citation

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Abstract

Temperature reconstructions from the North Atlantic region indicate frequent abrupt and severe climate fluctuations during the last glacial and Holocene periods1,2,3. The driving forces for these events are unclear and coupled atmosphere–ocean models of global circulation have only simulated such events by inserting large amounts of fresh water into the northern North Atlantic Ocean4,5. Here we report a drastic cooling event in a 15,000-yr simulation of global circulation with present-day climate conditions without the use of such external forcing. In our simulation, the annual average surface temperature near southern Greenland spontaneously fell 6–10 standard deviations below its mean value for a period of 30–40 yr. The event was triggered by a persistent northwesterly wind that transported large amounts of buoyant cold and fresh water into the northern North Atlantic Ocean. Oceanic convection shut down in response to this flow, concentrating the entire cooling of the northern North Atlantic by the colder atmosphere in the uppermost ocean layer. Given the similarity between our simulation and observed records of rapid cooling events, our results indicate that internal atmospheric variability alone could have generated the extreme climate disruptions in this region.

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Acknowledgements

A.H. is supported by a Lamont Postdoctoral Fellowship. We thank G. Bond for useful discussions, and T. Delworth, P. deMenocal, I. Held, M. Elliot, M. Latif, J. Mahlman, S. Manabe and R. Wood for comments on the manuscript.

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Affiliations

  1. *Lamont-Doherty Earth Observatory , Palisades, New York 10964, USA

    • Alex Hall
  2. †Geophysical Fluid Dynamics Laboratory , Princeton, New Jersey 08542, USA

    • Ronald J. Stouffer

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Correspondence to Alex Hall.

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DOI

https://doi.org/10.1038/35051544

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