Residual Circulation

Residual circulation is the net transport that remains after the Eulerian-mean flow and the eddy-driven (bolus) transport are combined, the quantity that actually advects tracers in an averaged ocean. In the Southern Ocean it is the small difference between the large wind-driven Eulerian overturning and the opposing eddy transport along sloping isopycnals, which is why the apparent Deacon Cell nearly cancels. The transformed Eulerian-mean framework formalizes this by working in density coordinates. The residual circulation, not the Eulerian mean, sets the rate of Southern Ocean upwelling and overturning.