On the response of Southern Ocean water‐masses to atmospheric meridional moisture advection

Abstract

We investigate the role of atmospheric moisture advection in determining Southern Ocean water‐mass properties in a coupled climate model. Two sensitivity experiments are presented in which the winds advecting moisture are either reduced or enhanced south of 45°S. It is shown that a variation in meridional winds in the Southern Ocean can generate large anomalies of subsurface potential temperature (T) and salinity (S). A reduction (increase) in southward atmospheric moisture advection tends to be balanced by a corresponding reduction (increase) in northward freshwater transport in Antarctic Intermediate Water. The response of both T and S is larger in the case of reduced southward moisture advection, as this corresponds to an overall reduction of Southern Ocean stratification. The interior ocean T–S response is not always density‐compensating, particularly in the Indian and Pacific Oceans. This is unlike zonal wind variations which have a tendency to change T–S in a density‐conserving manner. Our study suggests that variability in meridional winds over the Southern Ocean can alter local water‐mass formation rates significantly.