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Over the past decade, satellite observations of ice surface height haverevealed that active subglacial lake systems are widespread under theAntarctic Ice Sheet, including the ice streams. For some of these systems,additional observations of ice-stream motion have shown that lake activitycan affect ice-stream dynamics. Despite all this new information, we stillhave insufficient understanding of the lake-drainage process to incorporateit into ice-sheet models. Process models for drainage of ice-dammed lakesbased on conventional <q>R-channels</q> incised into the base of the ice throughmelting are unable to reproduce the timing and magnitude of drainage fromAntarctic subglacial lakes estimated from satellite altimetry given the lowhydraulic gradients along which such lakes drain. We have developed analternative process model, in which channels are mechanically eroded into theunderlying deformable subglacial sediment. When applied to the known activelakes of the Whillans–Mercer ice-stream system, the model successfullyreproduced both the inferred magnitudes and recurrence intervals of lake-volume changes, derived from Ice, Cloud and land Elevation Satellite (ICESat)laser altimeter data for the period 2003–2009. Water pressures in our modelchanged as the flood evolved: during drainage, water pressures initiallyincreased as water flowed out of the lake primarily via a distributed system,then decreased as the channelized system grew, establishing a pressuregradient that drew water away from the distributed system. This evolution ofthe drainage system can result in the observed internal variability of iceflow over time. If we are correct that active subglacial lakes drain throughcanals in the sediment, this mechanism also implies that active lakes aretypically located in regions underlain by thick subglacial sediment, whichmay explain why they are not readily observed using radio-echo-soundingtechniques

Antarctic subglacial lakes drain through sediment-floored canals: theory and model testing on real and idealized domains