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AGU: Geophysical Research Letters

 

Keywords

  • subpolar gyre
  • Atlantic Meridional Overturning Circulation
  • ocean dynamics

Index Terms

  • Oceanography: Physical: General circulation
  • Global Change: Abrupt/rapid climate change
  • Global Change: Oceans
  • Global Change: Climate dynamics
  • Oceanography: Physical: Overflows

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L24605, 6 PP., 2007
doi:10.1029/2007GL031732

Bistability of the Atlantic subpolar gyre in a coarse-resolution climate model

A. Levermann

Earth System Analysis, Potsdam Institute for Climate Impact Research, Potsdam, Germany

Institute of Physics, Potsdam University, Potsdam, Germany

A. Born

Earth System Analysis, Potsdam Institute for Climate Impact Research, Potsdam, Germany

Institute of Physics, Potsdam University, Potsdam, Germany

High resolution models indicate that the dynamics of the Nordic Seas and the subpolar gyre is crucial for deep water formation and overturning circulation in the Atlantic. During the last decades significant changes in ocean properties have been observed in this region. We show that large-scale dynamics, as captured by coarse resolution climate models, allows for a bistability of the Atlantic subpolar gyre. We suggest three positive feedbacks which yield the necessary nonlinearity for this behavior. Transitions between the two states can be triggered by small fluctuations in surface freshwater flux to the Nordic Seas, only slightly larger than natural variability presently observed in the region.

Received 20 August 2007; accepted 19 November 2007; published 22 December 2007.

Citation: Levermann, A., and A. Born (2007), Bistability of the Atlantic subpolar gyre in a coarse-resolution climate model, Geophys. Res. Lett., 34, L24605, doi:10.1029/2007GL031732.

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