The Development of Antarctic Katabatic Winds and Implications for the Coastal Ocean

Abstract

The influence of katabatic winds on the Antarctic coastal waters is examined by using simple models of the ocean and atmosphere. A katabatic flow model incorporating Coriolis dynamics is solved analytically and another with nonlinear friction is solved numerically to provide wind stress to a two-layer coastal ocean model. The resulting solutions are evidently the first to incorporate Coriolis terms with a thermodynamic equation that includes compressional warming effects. The emphasis in this paper is on delineating the parameters that control the relative adjustment of the katabatic wind into alongshore and offshore components. By including nonlinear friction, it is shown that steeper slopes and weaker stratification tend to direct the wind more toward the ocean. It is further demonstrated that the katabatic forcing supports the strong polar easterlies (winds from the east) along the periphery of the continent and that the offshore extent should be dependent on the atmospheric Rossby deformation radius. The ocean model shows that significant downwelling occurs at the coast, while upwelling is predicted at a distance of the order of the ocean Rossby radius. An alongshore coastal jet from the east is found in the model and is evidently the manifestation of the east wind drift. The upwelling offshore may be a significant aspect of polynya formation and maintenance of the Antarctic divergence zone and contribute to the biological productivity of the region.