Results from the I.A.G.P. Flow-Line Study Inland of Casey, Wilkes Land, Antarctica

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Abstract
In order to determine accurate velocities of the ice sheet in the interior of Antarctica, approximately along a flow line, a detailed trilateration net was established in 1973 from the summit of Law Dome (100 km inland) to about 250 km south near the 2000 m contour. The net consisted of a double line of markers approximately 10 km apart with all sides and diagonals of the quadrilaterals measured with telluro-meters. In addition, satellite doppler survey positions and astronomical azimuths were determined at about 50 km intervals to control the net on the large scale. Other measurements carried outen routeincluded: continuous barometric levelling, radio echo-sounding, gravimetry, accumulation, and surface sampling. The route was close to an earlier traverse route which reached Vostok in 1962 and along which other data, including snow-surface temperatures and temperature–depth gradients, were determined.The trilateration net was re-surveyed in 1975 allowing velocities and strain-rates to be determined. The results indicate that the ice sheet is close to balance in this region.Therefore, the measured velocities were used together with “balance velocities”, further inland, to carry out a modelling study of a flow line, to derive particle trajectories, ages, temperature profiles, and “dynamics velocities”, from a flow law. The results provide further insight into the dynamics and flow properties of the ice sheet.