On the Role of Topography and Wind Stress on the Stability of the Thermohaline Circulation

Abstract

A frictional geostrophic model is used to examine how the stability of the thermohaline circulation is affected by idealized topographic variations and the presence or absence of wind stress. If the flow exhibits collapses, the authors consider how topography and wind stress affect the ensuing oscillations. Large-scale slope up toward the north or the west can significantly destabilize the circulation by modifying the barotropic flow and reducing the depth of convection. Wind stress stabilizes the circulation by deepening the thermocline in the subtropical gyre. Wind driving can also radically reduce the period of oscillations by destabilizing the northern halocline in the collapsed phase. The overall period of the oscillation is usually governed by the time taken for diffusive warming to destabilize the deep ocean.