The Thermally Driven Ocean Circulation with Realistic Bathymetry

AbstractThe global circulation driven solely by relaxation to an idealized surface temperature profile and to interior mixing is examined. Forcing by winds and evaporation/precipitation is excluded. The resulting circulation resembles the observed in many ways, and the overturning is of similar magnitude. The overturning is driven by large-scale upwelling in the interior (which is relatively large, because of the use of a constant mixing coefficient). The compensating downwelling occurs in the northern North Atlantic and in the Ross and Weddell Seas, with an additional, smaller contribution from the northern North Pacific. The latter is weaker because the Bering Strait limits the northward extent of the flow. The downwelling occurs in frictional layers near the boundaries and depends on the lateral shear in the horizontal flow. The shear, in turn, is linked to the imposed surface temperature gradient via thermal wind, and as such, the downwelling can be reduced or eliminated in selected regions by removin...