Summary
Between 1989/90 and 1994/95, geodetic GPS surveying techniques were used to measure ice sheet surface velocities at approximately 30 km intervals around an oversnow traverse route in the interior drainage basin of the Lambert Glacier, East Antarctica (longitude 54°-78°E, latitude 67°-76°S). The main traverse route extends over 2000 km approximately along the 2500-m surface elevation contour. This report details the methodology, processing and results of the GPS measurements taken over the entire route. After a least squares adjustment of the entire network, all but one of 73 ice velocity determinations had an estimated accuracy of better than 1 m a-1, and about 60% had an estimated accuracy better than 0.3 m a-1. For most of the route ice sheet surface velocities are less than 20 m a-1, peaking at 62 m a-1 for station LGB71 on the steep coastal slopes of the eastern side of the basin. Velocities around 50 m a-1 occur along the south-eastern corner of the route where the upstream extensions of the Lambert and Mellor glaciers, flowing along a graben some 350 km wide, intersect the track. From these velocity measurements, plus ice thickness data from radio-echo sounding, it is estimated that an ice flux of 47.5 Gt a-1 crosses the entire traverse line, and 44 Gt a-1 flows through that section of the line that eventually discharges via the Amery Ice Shelf.