Two-layer model of wind-driven circulation in the Antarctic Ocean

In this study, we investigate the wind-driven circulation in the Antarctic Ocean using a primitive two-layer model with realistic topography. A prominent feature of steady circulation driven by the annual mean wind stress is a clockwise(cyclonic) circulation in the lower layer at the Weddell Basin and the Australia Antarctic Basin. In particular, the circulation pattern in the Australia Antarctic Basin agrees with the observations. In these basins, negative vorticity input from the wind stress is transmitted to the lower layer through the diffusion term(Gent and McWilliams term) and causes prominent cyclonic gyres within closed geostrophic contours of f/H(f: Coriolis parameter, H: water depth). The model result forced by the seasonal wind stress shows that variations of the Antarctic Coastal Current are explained by wind stress variations along the coast. The transport of this current is determined by the integration of onshore Ekman transport along the coast. It is also shown that this Antarctic Coastal Current can be a part of the western boundary current in the Weddell Sea. On a time scale of 10 to 100 days, the variation of the upper layer thickness coincides with the sea level variation at Syowa Station. This variation might be attributed to coastal trapped waves driven by the alongshore wind stress.