Role of localized mixing around the Kuril Straits in the Pacific thermohaline circulation

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Abstract

[1] We investigate the Pacific thermohaline circulation induced by the locally enhanced vertical mixing around the Kuril Straits by using a general circulation model. When the strong vertical mixing reaches the sea surface, localized upwelling is induced from the depth to the surface. On the contrary, in the cases where the strong vertical mixing does not reach the sea surface, downwelling of surface water is induced in the shallow layer while upwelling of deep water is induced below. The structure of the meridional overturning circulation in the Pacific Ocean significantly differs depending on whether the surface buoyancy flux is large enough to sustain upwelling of deep water or not. The mixing-induced downwelling of shallow water is not associated with the sea surface cooling, and the source of dense water is in the deep ocean. Among the non-surface-reaching mixing cases, the depth that separates the downwelling and upwelling is found to be relatively insensitive to the depth where the vertical diffusivity sharply changes.

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