IDENTIFICATION OF SUBGLACIAL LAKES USING ERS-1 RADAR ALTIMETER

Radar-altimeter data from ERS-1 allow detailed topographic mapping of Antarctica to 82-degrees-S to be carried out, revealing several notabl e surface features. Among these is the large subglacial lake near Vost ok which is mapped here in detail. The central part of the lake is fou nd to have an exceptionally smooth surface with r.m.s. elevation varia tions of less than 0.2 m. A search for other large Antarctic lakes in the data is made based on the smoothness and low gradient of the surfa ce. A number of other flat areas are identified with lake locations pr eviously determined from radio-echo sounding observations. However, ra dar-altimeter observations show that a minimum lake size of 20 km is r equired for a surface above a lake to become flat. Numerous bowl-like features can be seen in the surface topography, and these may be assoc iated with intermediate-sized subglacial lakes. It is determined that high spatial-resolution radar altimetery could be used to identify sub glacial lakes greater than 10 km in lateral extent. Flat regions of th e ice sheet are particularly useful as they may be used as height-refe rence surfaces to help fix the orbits of radar-altimeter satellites.