Variability of the deep water formation in the North Atlantic

M. Rhein, G. Lohmann, P. Scholz, A. Stroeh

Climate model experiments suggested that deep-water formation in the North Atlantic may drop in the 21st century. Evidence from geological records suggests that the ocean circulation had almost ceased at various times in the geological past, and these shut-downs were linked to abrupt climate changes. Using an integrated approach of data and model simulations, we will examine the processes in the atmosphere-ocean–sea ice system responsible for the fluctuations in deep water formation rates on interannual to longer time scales. We identify sensitive sites for the ocean circulation changes. The formation of deep water masses north of Iceland and in the Labrador Sea may have different effects for the strength of the large-scale ocean circulation: the dense water formed north of Iceland results in the overflow water, whereas open ocean convection dominates in the Labrador Sea. Finally, these changes are compared to recent salinity anomaly events as well as the 8.2 kyr event which is a distinct example of rapid climate change that occurred in the relatively stable Holocene period.

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