CONTROL OF NEAR-SURFACE WINDS OVER AN ANTARCTIC ICE SHELF

Simple models are used to assess the factors controlling near-surface winds over an Antarctic ice shelf. Observations from Halley Station and an automatic weather station situated close to the coastal slopes adjoining the Brunt Ice Shelf are presented. These suggest that katabatic flows originating over the continental slopes adjust more quickly to the regional easterly flow over the ice shelf than is predicted by these simple models. It is suggested that nonlinear mechanisms such as ''hydraulic jumps'' or internal gravity wave radiation could lead to flow adjustment on the short space and time scales observed. In contrast with the present observations, katabatic flows have been observed to propagate across the Ross Ice Shelf for great distances with little modification. However, in this latter region the topography favors the formation of intense, channeled katabatic flow, while the katabatic flow onto the Brunt Ice Shelf is unconfined and consequently much weaker.