Response of the Denmark Strait overflow to Nordic Seas heat loss

The impact of extreme Nordic Seas heat loss on Denmark Strait (DS) dense water transport is examined in (1) control runs of the Hadley Centre HadCM3 and HadGEM1 coupled climate models and (2) perturbation experiments with the fast coupled model FORTE that allow heat flux effects to be isolated from wind stress. All three models show an approximately linear increase in southward DS transport of cold dense water with increasing Nordic Seas winter heat loss in the range -80 to -250 Wm(-2). The propagation of the cold anomaly from the Nordic Seas source along a trajectory through the DS and into the Irminger Basin is also examined. A common response time is found with the strongest decrease in DS temperature occurring within 8-12 months of the heat loss signal. Our results show that Nordic Seas heat loss must be considered in addition to other processes in understanding DS variability.