Fast advective recovery of the Atlantic meridional overturning circulation after a Heinrich event

Ice core reconstructions and ocean sediment analysis have revealed that the climate of the last glacial period was highly variable with rapid stadial-interstadial transitions and glacial meltwater pulses (Heinrich events) modulating the climate evolution in the Northern and Southern hemispheres. Heinrich events had the potential to weaken the Atlantic meridional overturning circulation (AMOC) substantially. Mechanisms that led to the resumption of the AMOC after such events have not been fully disentangled yet. Here a coupled atmosphere-ocean–sea ice model of intermediate complexity is employed to identify important negative climate feedbacks that contribute to a fast recovery of the glacial AMOC. Shortly after the AMOC collapse, thermal processes weaken the stratification in the northern North Atlantic making it more vulnerable to perturbations. Eventually, 300–400 years after the main collapse of the AMOC the mean advection of salinity anomalies within the horizontal gyres generates an unstable stratification that will be homogenized through the resumption of convective activity. Eventually, isopycnal slopes in the North Atlantic are readjusted, thereby reinitiating the large-scale meridional overturning flow