Subglacial Lake Whillans - Ice-penetrating radar and GPS observations of a shallow active reservoir beneath a West Antarctic ice stream

Ice-penetrating radar and kinematic GPS observations from Subglacial Lake Whillans (SLW), West Antarctica, reveal a shallow lake that is confined by steep basal topographic features. Radar imaging of SLW, although indicating wet basal conditions, is consistent with a water column depth of only similar to 6 m or less during the near low-stand state at the time of the survey. Kinematic GPS profiles reveal that SLW is generally defined by a similar to 15 m surface depression centered at S 84.237 degrees W 153.614 degrees. This point coincides with the area of lowest hydropotential in the lake basin and also the largest surface elevation range in ICESat data. Therefore this location appears to be an opportune site for subglacial access drilling of this active subglacial lake. A distinct basal topographic ridge on the grid south side of the basin is coincident with a strong contrast in relative basal reflectivity (similar to 6 dB), which we interpret as the lake boundary. Mapped hydropotential (calculated assuming hydrostatic equilibrium) shows that water enters the lake from the upstream direction and drains downstream. We hypothesize that a lake-level rise of similar to 5 m plus flexural effects is sufficient to overtop a drainage divide. Thus SLW acts as a temporary storage basin for water beneath Whillans Ice Stream. (C) 2012 Elsevier B.V. All rights reserved.