DETERMINING BASAL ICE-SHEET CONDITIONS IN THE DOME C-REGION OF EAST ANTARCTICA USING SATELLITE RADAR ALTIMETRY AND AIRBORNE RADIO-ECHO SOUNDING

Large subglacial lakes manifest themselves as flat regions on the ice surface. ERS-1 satellite radar altimetry of the Dome C region of East Antarctica was analyzed to correlate unusually flat areas on the ice s urface with known locations of subglacial lakes identified from airbor ne radio-echo sounding (RES) data. The mean length of subglacial lakes which have an expression in the ice-sheet surface was similar to 8.3 km, whilst those that did not exhibit a surface morphological manifest ation had a mean length of similar to 3.3 km. Thus, lakes up to about 4 km in length are unlikely to be detected from satellite radar altime try of the ice surface. Given that the spacing of radio-echo flight tr acks within the SPRI-NSF-TUD Antarctic database is 50-100 km in many a reas, a number of subglacial lakes probably lie undetected beneath the ice sheet. RES information from two large, flat surface regions withi n Dome C, and a further flat area located at 80 degrees S, 127 degrees E, indicates the absence of subglacial lakes beneath the ice-surface features. However, these areas are characterised by relatively strong radio-echo returns which may indicate the presence of water-saturated basal sediments. We suggest that (1) blankets of water-saturated basal sediments may cause similar surface morphological features to those p roduced by subglacial lakes; and (2) misidentification of subglacial l akes from satellite altimeter observations of the ice-sheet surface is possible without the support of RES information relating to the ice-s heet base. Furthermore, our study indicates a lack of subglacial lake signals from RES data over relatively thick regions of East Antarctica such as the Adventure Subglacial Trough. We conclude that subglacial water produced in such regions may be transported by a basal hydrologi cal system, driven by overburden pressure, to less thick regions of th e ice sheet where subglacial lakes have been identified.