Surface melt and subsequent firn air depletion can ultimately lead to disintegration of Antarctic ice shelves1,2 causing grounded glaciers to accelerate3 and sea level to rise. In the Antarctic Peninsula, foehn winds enhance melting near the grounding line4, which in the recent past has led to the disintegration of the most northerly ice shelves5,6. 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 hydrofracturing7.
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Field data were collected in the framework of the BENEMELT project, in collaboration with the BELSPO project ICECON. BENEMELT benefits from the InBev-Baillet Latour Antarctica Fellowship, a joint initiative of the InBev-Baillet Latour Fund and the International Polar Foundation (IPF) that aims to promote scientific excellence. We gratefully acknowledge field support from IPF, BELSPO, AntarctiQ, the Belgian Polar Secretariat and the Belgian military. We thank G. Eagles, T. Binder and C. Müller from the Alfred Wegener Institute, who first discovered the circular melt feature in 2015. This study is partly funded by Utrecht University through its strategic theme Sustainability, sub-theme Water, Climate & Ecosystems. This work was carried out under the programme of the Netherlands Earth System Science Centre (NESSC), financially supported by the Ministry of Education, Culture and Science (OCW). J.T.M.L. is supported by NWO ALW through a Veni postdoctoral grant. S.L. was supported as a post-doc by FWO. R.D. was funded by the FNRS Project MEDRISSM and partial support by the Deutsche Forschungsgmeinschaft with a grant SPP ‘Antarctic Research’ MA 3347/10-1. Analysis and graphics are made using QGIS package Quantarctica, and the NCAR Command Language (http://dx.doi.org/10.5065/D6WD3XH5). TanDEM-X SLC data were provided by the German Space Agency (DLR) within the proposal ATI_GLAC0267.