Depth-Integrated Vorticity Budget of the Southern Ocean from a General Circulation Model

Abstract

An analysis of the depth-integrated vorticity budget of the U.K. Fine Resolution Antarctic Model is used to investigate the mechanisms that maintain and dissipate vorticity in the Antarctic Circumpolar Current (ACC) and adjacent circulations of the Southern Ocean. The individual contributions to the vorticity budget are evaluated over the last six years when the model had reached a quasi-steady state. It is shown that the primary balance in the ACC is between the curl of the wind stress and the bottom pressure torque (BPT). Regional analysis reveals that the predominant contribution to BPT is in the Drake Passage, Scotia Sea, and the Argentine Basin. The region to the south of Tasmania and New Zealand also contributes significantly to BPT in the ACC. In addition it is shown that Drake Passage and the Falkland Current are responsible for the major dissipation of the ACC. Within the ACC between 320° and 290°E, there is good correspondence between the integrated southward flow and the curl of the wind stress.