The Southern Ocean Momentum Balance: Evidence for Topographic Effects from Numerical Model Output and Altimeter Data

Abstract

Abstract The momentum balance of the Antarctic Circumpolar Current is investigated using both output from a high-resolution primitive equation model and sea surface height measurements from the Geosat altimeter. In the Semtner–Chervin general circulation model, run with approximately one-quarter degree resolution and time-varying ECMWF winds, topographic form stress is the dominant process balancing the surface wind forcing. Detailed examination of form stress in the model indicates that it is due to three large topographic obstructions located at Kerguelen Island, Campbell Plateau, and Drake Passage. The difference between wind stress and form stress represents the lateral transfer of momentum into and out of the ACC. It is examined both in zonal coordinates to conform to the model architecture and along mean streamlines in order to reduce the effects of standing eddies. In this particular model, in stream coordinates, biharmonic friction dominates the lateral transfer of momentum. Since biharmonic frict...