The stability of ice sheets and their contributions to sea level are modulated by high-pressure water that lubricates the base of the ice, facilitating rapid flow into the ocean. In Antarctica, subglacial processes are poorly characterized, limiting understanding of ice-sheet flow and its sensitivity to climate forcing. Here, using numerical modelling and geophysical data, we provide evidence of extensive, up to 460 km long, dendritically organized subglacial hydrological systems that stretch from the ice-sheet interior to the grounded margin. We show that these channels transport large fluxes (~24 m3 s−1) of freshwater at high pressure, potentially facilitating enhanced ice flow above. The water exits the ice sheet at specific locations, appearing to drive ice-shelf melting in these areas critical for ice-sheet stability. Changes in subglacial channel size can affect the water depth and pressure of the surrounding drainage system up to 100 km either side of the primary channel. Our results demonstrate the importance of incorporating catchment-scale basal hydrology in calculations of ice-sheet flow and in assessments of ice-shelf melt at grounding zones. Thus, understanding how marginal regions of Antarctica operate, and may change in the future, requires knowledge of processes acting within, and initiating from, the ice-sheet interior.
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The Glacier Drainage System (GlaDS) model code is available by contacting Mauro Werder (firstname.lastname@example.org) and is also now included in the Ice-Sheet and Sea-Level System Model (ISSM), which is freely available.
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We thank M. Werder for use of the Glacier Drainage System (GlaDS) model and M. Morlighem for provision of ISSM basal ice velocity and melt rates. C.F.D. was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC; RGPIN-03761-2017) and the Canada Research Chairs Program (950-231237). M.J.S. and N.R. acknowledge support by the UK Natural Environment Research Council AFI grant NE/G013071/1. N.R. acknowledges funding from the Newcastle University Humanities and Social Science (HASS) bid preparation fund. K.S. was supported by NSERC and the University of Waterloo. We thank Compute Canada for provision of supercomputer resources. We acknowledge the use of data and/or data products from CReSIS generated with support from the University of Kansas, NSF grant ANT-0424589 and NASA Operation IceBridge grant NNX16AH54G.
The authors declare no competing interests.
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Channel discharge for the FIS-AG catchment for the standard (base) model run. The dots show regions of positive radar reflectivity (calculated as relative values with a zero mean22) at the ice-bed interface assumed to indicate the presence of water50; negative relative reflectivity values are not plotted. Background image is the ice surface MODIS mosaic43. The extent of this region is shown by the grey box in Fig. 2c.
Basal melt rate from ISSM15 with basal drainage catchments outlined for IIS (red), MIS (yellow), FIS-AG (green) and SFG (blue).
MODIS ice-surface imagery of the Weddell Sea (WS) sector of West Antarctica43. The location of radar transects for IIS (A-A’), MIS (B-B’), and FIS-AG (C-C’) are plotted with white dashed lines. These radar transects are shown in Extended Data Fig. 4. The red dots are the location of modelled channel outlets over the grounding line (Fig. 2c, d) and the yellow squares, the location of sub ice-shelf channels (shown as yellow bars in Extended Data Fig. 4).
Channels are incised upwards beneath floating ice for the following ice streams: (a,b) IIS (A–A’), (c,d) MIS (B–B’), and (e,f) FIS-AG (C–C’), with transects shown in Extended Data Fig. 3. Surface elevation profiles from an aircraft altimeter are plotted above each radargram (a,c,e) with depressions as a result of hydrostatic adjustment from the incised basal channels. Yellow bars show the location of the ice shelf channel as indicated by the yellow boxes in Extended Data Fig. 3.
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Dow, C.F., Ross, N., Jeofry, H. et al. Antarctic basal environment shaped by high-pressure flow through a subglacial river system. Nat. Geosci. 15, 892–898 (2022). https://doi.org/10.1038/s41561-022-01059-1