EFFECT OF DRAKE PASSAGE ON THE GLOBAL THERMOHALINE CIRCULATION

The Ekman divergence around Antarctica raises a large amount of deep water to the ocean's Surface. The regional Ekman transport moves the upwelled deep water northward out of the circumpolar zone. The divergence and northward surface drift combine, in effect, to remove deep water from the interior of the ocean. This wind-driven removal process is facilitated by a unique dynamic constraint operating in the latitude band containing Drake Passage. Through a simple model sensitivity experiment we show that the upwelling and removal of deep water in the circumpolar belt may be quantitatively related to the formation of new deep water in the northern North Atlantic. These results show that stronger winds in the south can induce more deep water formation in the north and more deep outflow through the South Atlantic. The fact that winds in the southern hemisphere might influence the formation of deep water in the North Atlantic brings into question long-standing notions about the forces that drive the ocean's thermohaline circulation.