1. Centre for Polar Observation and Modelling, Department of Space and Climate Physics, Pearson Building, University College London, Gower Street, London WC1E 6BT, UK
2. Centre for Polar Observation and Modelling, Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK
3. Centre for Polar Observation and Modelling, Scott Polar Research Institute, University of Cambridge, Lensfield Road, Cambridge CB2 1ER, UK
4. †Present address: School of Geosciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK

Correspondence to: Duncan J. Wingham¹Martin J. Siegert² Correspondence and requests for materials should be addressed to D.J.W. (Email: djw@cpom.ucl.ac.uk) or M.J.S. (Email: m.j.siegert@bristol.ac.uk).

The existence of many subglacial lakes¹ provides clear evidence for the widespread presence of water beneath the East Antarctic ice sheet, but the hydrology beneath this ice mass is poorly understood². Such knowledge is critical to understanding ice flow, basal water transfer to the ice margin, glacial landform development and subglacial lake habitats. Here we present ice-sheet surface elevation changes in central East Antarctica that we interpret to represent rapid discharge from a subglacial lake. Our observations indicate that during a period of 16 months, 1.8 km³ of water was transferred over 290 km to at least two other subglacial lakes. While viscous deformation of the ice roof above may moderate discharge, the intrinsic instability of such a system³ suggests that discharge events are a common mode of basal drainage⁴. If large lakes, such as Lake Vostok or Lake Concordia¹, are pressurizing, it is possible that substantial discharges could reach the coast^{5, 6}. Our observations conflict with expectations that subglacial lakes have long residence times and slow circulations^{2, 7, 8}, and we suggest that entire subglacial drainage basins may be flushed periodically. The rapid transfer of water between lakes would result in large-scale solute and microbe relocation, and drainage system contamination from in situ exploration is, therefore, a distinct risk.

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