Antarctic subglacial lakes

Abstract

Antarctic subglacial lakes were first identified by Robin et al. (1970) after airborne radio-echo sounding (RES) investigations of the ice-sheet interior. Recently, satellite altimetry was used to measure anomalous near-flat regions on the ice-sheet surface that represent a manifestation of the subglacial lake beneath. Using RES and satellite altimetry, the location and extent of Antarctic subglacial lakes can be identified. The largest subglacial lake exists beneath Vostok Station, and is 14,000 km 2 in area. The combined area of additional subglacial lakes beneath Dome C is 15,000 km 2 and at least 15,000 km 2 of lake surface lies beneath the remainder of the ice sheet. The water depth of subglacial lakes can be estimated through seismic investigations (although data exist only for Lake Vostok) and consideration of the bedrock slopes that border subglacial lakes. The depths of many subglacial lakes are of the order of 10's–100's of metres. The total volume of water held beneath the ice sheet is estimated between 4000 and 12,000 km 3. To date, there are six known examples of radio-echo reflections from the lake floors (at a depth of no more than 20 m). Since e/m attenuation through water is related to the salinity, these data indicate that subglacial water is very pure and fresh. Some near-flat surface regions that usually occur over lakes have been observed where no lakes exist. Such features are may be caused by water-saturated basal sediments rather than subglacial lakes. Finally, the spatial variation in geothermal heat flux around the central regions of Antarctica can be established estimated by employing a simple thermal model of the ice sheet under an assumption that the basal ice temperature above subglacial lakes is equal to the pressure melting value. Calculations indicate that the geothermal heat flux varies spatially over the Antarctic Plate between 37 and 65 mW m −2.