The Gulf Stream's extension toward the Arctic is an important contributor to the temperate climate of Northwestern Europe. As it approaches the Arctic proper, the surface current has been cooled to the extent that it sinks and thus becomes part of the Atlantic Ocean's deep return current that balance the northward surface flow. The Greenland Sea is the location of the "deepest" deep water formation, and the region has therefore been a focus of climate research.
The new paper by Oliver et al. explains the present operation of deep water formation in the Greenland Sea, including the subsequent export of deep water from the region of formation. The researchers find that newly generated deep water is organized in large, subsurface vortices (similar to Tropical storms of the atmosphere). The finding is supported by observations and model studies. The vortices composition is such that 1) they self-propagate toward the lighter waters neighboring the Greenland Sea, and 2) their propagation is arrested by the interaction with sea mounts. This explains, respectively, how newly formed deep water is exported from the generation region, and why the vortices actually observed have appeared rather locked to the observed position.
One would expect that the mechanisms described are of general relevance for other sites of deep water formation in the world oceans.
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