The area of West Antarctica which drains into the Ross Ice Shelf is examined for the purpose of understanding its dynamics and developing a numerical model to study its reaction to environmental changes. A high resolution ZO km grid is used to compile a database for surface and bedrock elevation, accumulation, and surface temperatures . Balance velocities Vb are computed and found to approximate observed velocities. These balance velocities are used with basal shear stress Tb and ice thickness above buoyancy z* to derive parameters kZ, p and q for a slidding relation of the form Vb = k2Tb/Z~· Reasonable matching is obtained for p = 1, q = 2 and k2 = 5 x 10 6 m 3 bar-1 a-t. This sliding relation is then used in a first complete dynamic and thermodynamic velocity calculation for West Antarctica and for an improved simulation of the whole Antarctic ice sheet.

The area of West Antarctica which drains into the Ross Ice Shelf is examined for the purpose of understanding its dynamics and developing a numerical model to study its reaction to environmental changes. A high resolution 20 km grid is used to compile a database for surface and bedrock elevation, accumulation, and surface temperatures. Balance velocities Vbare computed and found to approximate observed velocities. These balance velocities are used with basal shear stress and ice thickness above buoyancy Z*to derive parameters k2, p and q for a sliddinq relation of the formReasonable matching is obtained for p = 1, q = 2 and k2= 5 × 106m3bar−1a−1. This sliding relation is then used in a first complete dynamic and thermodynamic velocity calculation for West Antarctica and for an improved simulation of the whole Antarctic ice sheet.

A three-dimensional model of the temperature and velocity distribution within any arbitrary-shaped ice mass is described. There is a mutual interaction in the model between the flow of the ice and its thermodynamics, since the flow law used in the model is temperature-dependent. Ice growth in three dimensions is governed by mass accumulation through precipitation, by mass depletion through loss of ice over the ocean, and by continuity requirements. Phase changes at the base of the ice are accounted for. The model has been applied in art exploratory manner to the Greenland ice sheet. Changes in the ice shape and temperature are presented and discussed. The basic shortcoming of the model as here presented appears primarily due to the coarse finite-difference mesh used, and to an unsophisticated approach to modelling the boundary ice.

The three-dimensional ice-sheet model of the West Antacrtic Ross Ice Shelf Basin, developed by Budd et ale (1984), has been used to compute basal temperatures and melt rates for a wide range of values of the geothermal flux. Steady state is assumed and ice "balance velocities" are computed from continuity and used in the heat-conduction equation. As the geothermal flux increases, the melt area increases and becomes connected to the water under the Ross Ice Shelf via the major ice streams.The large-scale average surface and bed slopes are used to determine the broadscale pattern of flow of the basal meltwater on the assumption that it flows as a film at the ice-bedrock interface. The total water volume flux for steady state is determined from the basal melt rates and continuity, and the film assumption then allows the mean water film thickness and velocities to be computed. The resulting pattern of steady-state mean water-film thickness is then interpreted in terms of its possible relationships to the basal sliding rates and the basal shear stress particularly under the major ice streams.C. J. van der Veen andJ. Oerlemans (eds.), Dynamics of the West Antarctic Ice Sheet, 293-320.

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