A Subglacial Lake Flood Model For Antarctic Lakes Based On High Resolution Radar Sounding And Validated With Satellite Altimetry And GPS

Since 2007, ICESat data have revealed at least 124 active subglacial lakes under the Antarctic ice sheet. In locations where subglacial lakes are present, the volume change they undergo appears to account for the entire regional water budget. Consequently a full understanding of the interactions between the subglacial water system and the flow of the overlying ice sheet requires an understanding of lake drainage events. Here we make modify the Kingslake and Ng (2013) model for a subglacial conduit eroding into the overlying ice (also known as an R-channel), and apply it to several observed lake drainage events in Siple Coast of West Antarctica. To reproduce many of the essential qualities of these events, we find it necessary to increase rates for channel enlargement and ice deformation by two and three orders of magnitude respectively. With these parameter values, our model can predict the following: i) onset elevation of flood at a height a few meters below the floatation level of the downstream lake seal; ii) ongoing drainage of the lake through lowering of water pressure at the seal site; iii) filling and drainage rates to within a factor of 2; iv) of a conduit system somewhere downstream of the lake; and v) the timing of the drainage - refilling cycle. The necessity of such large modifications of model parameters appears to indicate a system that mechanically erodes the soft subglacial sediment, as opposed to thermally eroding the ice, making it more akin to canals predicted by Walder and Fowler (1994), than to the classic R-channel invoked for lake drainage events in temperate ice. Through further modeling we explore the role of such a system in transport of sediments, and how this may affect the flux of materials both into subglacial lakes and ultimately across the grounding line.