Sea ice induced changes in ocean circulation during the Eemian
We argue that Arctic sea ice played an important role during early stages of the last glacial inception. Two simulations of the Institut Pierre Simon Laplace coupled model 4 are analyzed, one for the time of maximum high latitude summer insolation during the last interglacial, the Eemian, and a second one for the subsequent summer insolation minimum, at the last glacial inception. During the inception, increased Arctic freshwater export by sea ice shuts down Labrador Sea convection and weakens overturning circulation and oceanic heat transport by 27 and 15%, respectively. A positive feedback of the Atlantic subpolar gyre enhances the initial freshening by sea ice. The reorganization of the subpolar surface circulation, however, makes the Atlantic inflow more saline and thereby maintains deep convection in the Nordic Seas. These results highlight the importance of an accurate representation of dynamic sea ice for the study of past and future climate changes.
KeywordsSea ice Ocean circulation Eemian Glacial inception Subpolar gyre North Atlantic
We gratefully acknowledge Oliver Marti for technical assistance as well as discussions with Tor Eldevik, Bjørg Risebrobakken, Tore Furevik and Uwe Mikolajewicz. We further thank two anonymous referees whose reviews improved our earlier manuscript. A. Born was funded by the Marie Curie Actions project NICE (MRTN-CT-2006-036127). Computer time was provided by the Centre National de la Recherche Scientifique (IDRIS computing center) and the Commissariat à l’Energie Atomique (CCRT computing center). This work is a contribution to the French ANR blanc “PICC”. This is publication number A260 from the Bjerknes Centre for Climate Research.
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