Glaciological studies on Rutford Ice Stream, Antarctica

Rutford Ice Stream drains part of the West Antarctic ice sheet into Ronne Ice Shelf. Much of the drainage basin has a bed well below sea level and is therefore an area which could undergo substantial change if a climatic warming were to cause sustained thinning of Ronne Ice Shelf. Snow accumulation data suggest that an accumulation rate of 0.51 ± 0.12 Mg m−2 yr−1 is required for balance. An extensive ice movement survey network was established across the grounding line in 1978–1980 and was extended for more than 100 km upstream in 1984–1986. Velocities at five sites have been calculated using doppler satellite position measurements. When the velocities are combined with cross‐sectional areas of the ice stream measured by radio echo sounding, mass flux figures show that drag at the sidewalls and on the base must decrease downstream toward the grounding line. The increasing influence of buoyancy forces on ice stream motion is also shown by the steady rise in the ratio of bedrock depth to ice thickness going downstream along the network. Below the grounding line that was found to cross the middle part of the earlier network is a zone stretching for a further 100 km where it can now be shown that the ice stream is intermittently grounded. In these grounded areas the glacier bed is raised with respect to the surrounding seabed and forms eskerlike features. Surface elevations over the grounded areas are less than 30 m above those needed for hydrostatic equilibrium.

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