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Meltwater produced by wind-albedo interaction stored in an East Antarctic ice shelf

par Lenaerts, Jan T M;Lhermitte, Stef;Drews, Reinhard ;Ligtenberg, S.R.M.;Berger, Sophie ;Helm, Veit;Smeets, C.J.P.P.;Van den Broeke, Michiel;Van De Berg, Willem Jan;Van Meijgaard, Erik;Eijkelboom, M.;Eisen, Olaf;Pattyn, Frank
Référence Nature climate change, doi:10.1038/nclimate3180
Publication Publié, 2016-12

Article révisé par les pairs

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Résumé :

Surface melt and subsequent firn air depletion can ultimately lead to disintegration of Antarctic ice shelves causing grounded glaciers to accelerate and sea level to rise. In the Antarctic Peninsula, foehn winds enhance melting near the grounding line, which in the recent past has led to the disintegration of the most northerly ice shelves. Here, we provide observational and model evidence that this process also occurs over an East Antarctic ice shelf, where meltwater-induced firn air depletion is found in the grounding zone. Unlike the Antarctic Peninsula, where foehn events originate from episodic interaction of the circumpolar westerlies with the topography, in coastal East Antarctica high temperatures are caused by persistent katabatic winds originating from the ice sheet's interior. Katabatic winds warm and mix the air as it flows downward and cause widespread snow erosion, explaining >3 K higher near-surface temperatures in summer and surface melt doubling in the grounding zone compared with its surroundings. Additionally, these winds expose blue ice and firn with lower surface albedo, further enhancing melt. The in situ observation of supraglacial flow and englacial storage of meltwater suggests that ice-shelf grounding zones in East Antarctica, like their Antarctic Peninsula counterparts, are vulnerable to hydrofracturing.