Summary
Oversnow traverses have collected a variety of glaciological measurements around the interior drainage basin of the Lambert Glacier, East Antarctica (longitudes 54°-78°E, latitudes 67°-76°S), between 1989-90 and 1994-95. The main traverse route covers approximately 2000 km with surface elevations in the range 1000-3000 m. An offset route, running parallel some 50 km west and south of the main line, has been completed for the western half of the basin. This report details ice sheet thicknesses, derived from digital radio echo sounding records augmented by gravity measurements, together with surface and bedrock elevations measured along the various traverse routes established within the basin. Major sub-glacial topographic features identified include: the western margin of the Lambert Graben upstream of the Mellor Glacier in the southern Prince Charles Mountains on both the main traverse route and parallel offset line; a deep 20 km wide trench with a maximum ice thickness in excess of 3500 m along the upstream extension of the main body of the Lambert Glacier on the eastern edge of the graben; and upland areas apparently linking the northern Prince Charles Mountains with the Hansen Mountains to the northwest, plus an extension of the Grove Mountains on the eastern side of the basin. Average ice thickness along the main traverse route is 2030 m with an average bedrock elevation of 410 m, asl, whilst within the 350 km wide Lambert Graben ice thickness averages 2630 m, with an average bedrock elevation of 300 m below sea level. Zones of near-specular reflections in localised bedrock depressions are evidence for pressure melting at these sites though the great majority of the bed is at a lower temperature. Relative reflection coefficients have been calculated for the bed and one internal reflecting horizon and show spatial variability due to small-scale heterogeneities at the interface or thermal characteristics within the ice sheet not accounted for in the estimated