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Since the beginning of the 1980s, deep convection has ceased in the Greenland Sea. The effects of this halt on the intense warming and salinification of Greenland Sea deep waters and on the dome collapse (sinking of the dome) have been intensively studied. However, their causes and the potential outflow of Greenland Sea deep and bottom waters toward southern adjacent basins have remained less investigated and are the focus of this work. Combining oceanic and atmospheric in situ data, together with satellite and reanalysis data, it is found that there is not a unique factor responsible for the halt of deep convection in the Greenland Sea. Changes in the Ekman pumping seem to only explain one tenth of the observed deepening of isopycnals of 1,300m in the central Greenland Sea (dome collapse). Since the early 1980s, in addition, a decrease in the mean net heat loss from the ocean to the atmosphere and in the intensity and number of intense heat loss events would have contributed to the decrease in both the intensity of convective mixing and the generation of dense deep waters. The generation of waters not sufficiently dense to contribute to the reservoir of water below the Greenland Sea dome would have led to its emptying and sinking. More importantly, it is found that in situ evidence of a sustained bottom-water upwelling driven by a secondary circulation cell whose major role in ventilating and draining the Greenland Sea deep and bottom waters has been largely underestimated.

Plain Language Summary The Arctic Mediterranean shows one of the highest sensitivities to recent climate change, as the sea ice retreat or surface temperature increase reflects. However, although less known, these changes extend to the deep waters of the Arctic that are warming in the Greenland Sea at a rate 10 times higher than the temperature increase in the global ocean on average. These changes are the result of halt of deep convection in the Greenland Sea since the early 1980s. Based primarily on observations, the present manuscript investigates the causes for the halt of deep convection in the Greenland Sea. Its is found that changes in air-sea exchanges and preconditioning have been mostly responsible for the halt of deep convection. More importantly, it is also noticed that the halt of deep convection may be nondetermining in the ventilation of Greenland Sea deep waters since a sustained bottom-water upwelling seems to occur. These results are not only of crucial importance for the Greenland Sea. They are another indication that the mechanism that drives deep water ventilation may be not related to the push of dense waters to great depths but with the pull of mixing those waters upward and into the surrounding boundary currents.