22A.5 Low-Level Sublimation of Snowfall on the Antarctic Margins Due to Katabatic Winds

Thursday, 31 August 2017: 2:30 PM
Vevey (Swissotel Chicago)
Jacopo Grazioli, MeteoSwiss, Locarno, Switzerland; and J. B. Madeleine, H. Gallée, R. Forbes, C. Genthon, G. Krinner, and A. Berne

Over the Antarctic continent precipitation (snowfall) is the most important input of the ice sheet mass budget. Changes in snowfall may eventually result into changes of sea level at global scale. The margins of Antarctica are characterized by persistent katabatic winds, making the continent the windiest place (on average) on Earth. Katabatic winds supply the low level of the atmosphere with air masses of low relative humidity, originating from the elevated Antarctic plateau. Despite the importance of these winds for the climate of coastal regions, their interaction with snowfall has not been quantified nor described before. This is due to the lack of spatial measurements of precipitation, that only recently have been conducted by means of weather radars and in-situ instruments, in some locations of Antarctica. In this contribution, we show, using unprecedented remotely-sensed data (X-band and long series of K-band radar data) collected in Dumont d’Urville on the coast of Adélie Land, that katabatic winds lead to a significant low-level sublimation of snowfall. At the scale of individual precipitation events, sublimation is inversely proportional to the intensity of precipitation, because more developed systems can extend further into the continent and eventually saturate the low levels of the atmosphere. This phenomenon is reproduced as well with the simulations of three different atmospheric models, that are used to extend our findings to the entire continent. In quantitative terms, sublimation in the lowest kilometer of the atmosphere, before deposition, accounts for about a 17% reduction of total snowfall over the entire continent and up to 35% on the margins of East Antarctica.

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