Geophysical exploration of a West Antarctic subglacial lake

Abstract

NERC GPS units were deployed above Subglacial Lake Ellsworth during two austral summer field campaigns (2007/8 and 2008/9). During the first season four base stations were deployed. Two base station sites were reoccupied in the second field season. Base stations were used to monitor ice flow over SLE and to correct: i) stop-and-collect GPS data from a stake network positioned over and around SLE, ii) kinematic GPS data collected during radio-echo sounding profiles, and iii) stop-and-collect short occupancy records used to locate seismic shot hole positions. All activities requiring GPS positioning were successfully completed. Results from base stations and the stake survey show convergent ice flow over SLE, increasing ice flow along the lake length and greatest ice flow over the middle of the lake, decreasing towards the lateral margins. The GPS records were unable to detect a tidal cycle from the lake though may indicate gradual filling of the lake relative to the off-lake base station, though this could be an artefact of differential snow densification beneath the GPS units.