Based on coupled model simulations (ECBilt-Clio), we investigate the atmospheric and oceanic response to sustained freshwater input into the North Atlantic under the glacial maximum background state. The results demonstrate that a weakening of the thermohaline circulation triggered by weaker density flux leads to rapid changes in global sea-ice volume and reduced poleward heat transport in the Northern Hemisphere (NH). In the Southern Hemisphere (SH), however, the oceanic heat transport increases substantially. This in turn leads to strong cooling over the North Atlantic whereas the SH extratropical region warms up. The suppression of the NADW also drastically changes the atmospheric circulation. The associated northward wind anomalies over the North Atlantic increase the warm air advection from the tropics and induce the transport of tropical saltier water to mid-latitudes. This negative atmospheric-oceanic feedback should play an important role to resume the NADW, after the freshwater forcing ends up.
Thermohaline circulation; climate changes; baroclinic activity
