Air-sea interactions during glacial Heinrich events

Krebs, Uta

'Heinrich events' - massive iceberg discharges from Northern Hemisphere ice sheets during the last ice age - coincided with cold periods and subsequent abrupt warmings on the Northern Hemisphere. Climate reconstructions suggest that the associated freshwater pulses caused a temporary collapse of the Atlantic Meridional Overturning Circulation (AMOC) by stabilizing stratification in the regions of deep water formation. In the present work a coupled atmosphere-ocean-sea ice model is employed under glacial boundary conditions to assess climate feedbacks during a freshwater induced collapse of the AMOC. Emphasis is placed on mechanisms which facilitate a fast recovery of the AMOC. It is found that air-sea coupling in the tropical Atlantic strongly influences the recovery time scale. Reduced poleward heat transport in the North Atlantic leads to a cooling north of the equator and reduced north equatorial precipitation. When transported northward by the wind driven circulation the arising salinity anomaly stabilises the stratification in the deep water formation regions and large-scale meridional overturning is re-initiated.



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Krebs, Uta: Air-sea interactions during glacial Heinrich events. 2006.


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