Paleocirculation of the North Atlantic Ocean at the last glacial maximum (LGM) is simulated using a large-scale ocean general circulation model (OGCM). The model is driven by glacial sea surface thermohaline conditions and wind stress. For comparison of past and present circulation patterns, a separate run provides the Holocene/modern circulation patterns based on the present day sea surface climatology. The output of the OGCM is then used in a sedimentation model and in a model to trace water parcel trajectories. The sedimentation model reveals the differences in sediment deposition in the North Atlantic linked to past and present circulation regimes. The trajectory-tracing model facilitates a better understanding of the thermocline and deep ocean ventilation, the actual three-dimensional conveying of water, and the role of convection in maintaining the meridional thermohaline overturning. The results of the trajectory-tracing technique indicate stronger subtropical thermocline ventilation during the LGM. For the deep ocean currents, we find severe alteration of three-dimensional water motion in response to weakening of the LGM convection and its retreat to the southwest from its present locations. Ocean circulation models can provide sedimentation studies with information on the circulation regime that proxy data used alone cannot. These is because such models furnish both circulation patterns and the ventilating convection depths.
All Science Journal Classification (ASJC) codes