Numerical Simulation of Winter Katabatic Winds from West Antarctica Crossing Siple Coast and the Ross Ice Shelf

David H. Bromwich Byrd Polar Research Center and Atmospheric Sciences Program, The Ohio State University, Columbus, Ohio

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Yang Du Byrd Polar Research Center and Atmospheric Sciences Program, The Ohio State University, Columbus, Ohio

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Thomas R. Parish Department of Atmospheric Science, University of Wyoming, Laramie, Wyoming

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Abstract

Twenty-four-hour numerical simulations of wintertime surface winds under clear sky conditions over the West Antarctic ice sheet and its vicinity are performed using a hydrostatic, three-dimensional primitive equation model. Two initial states are examined: a state of rest, and a prescribed pressure field associated with katabatic winds from West Antarctica propagating across the Ross Ice Shelf. The Antarctic katabatic winds are mainly due to the strong radiative cooling of the ice slopes. The West Antarctic terrain is different from that of East Antarctica in two respects: its mean elevation is much lower, and the slope in the interior is steeper than near the margin at Siple Coast.

The simulated surface wind regime reveals confluence zones just inland from the coast and diffluence zones around the crest of the terrain. The model results suggest that the continuation of katabatic winds beyond coastal confluence zones, which are sustained by cold-air drainage in the interior, has an important impact on airflow over the flat Ross Ice Shelf adjacent to the Transantarctic Mountains. The prescribed pressure disturbance has little impact on the surface winds in the interior but markedly impacts those over and beyond the gently sloping coastal areas. Discussion of the impact of the surface wind on the polynya northwest of the Ross Ice Shelf is also provided. It is shown that the simulated surface-wind regime is consistent with the available, mostly surface observational data.

Abstract

Twenty-four-hour numerical simulations of wintertime surface winds under clear sky conditions over the West Antarctic ice sheet and its vicinity are performed using a hydrostatic, three-dimensional primitive equation model. Two initial states are examined: a state of rest, and a prescribed pressure field associated with katabatic winds from West Antarctica propagating across the Ross Ice Shelf. The Antarctic katabatic winds are mainly due to the strong radiative cooling of the ice slopes. The West Antarctic terrain is different from that of East Antarctica in two respects: its mean elevation is much lower, and the slope in the interior is steeper than near the margin at Siple Coast.

The simulated surface wind regime reveals confluence zones just inland from the coast and diffluence zones around the crest of the terrain. The model results suggest that the continuation of katabatic winds beyond coastal confluence zones, which are sustained by cold-air drainage in the interior, has an important impact on airflow over the flat Ross Ice Shelf adjacent to the Transantarctic Mountains. The prescribed pressure disturbance has little impact on the surface winds in the interior but markedly impacts those over and beyond the gently sloping coastal areas. Discussion of the impact of the surface wind on the polynya northwest of the Ross Ice Shelf is also provided. It is shown that the simulated surface-wind regime is consistent with the available, mostly surface observational data.

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