Abstract
This study uses a three-dimensional thermo-mechanical model to investigate the internal flow dynamics of the West Antarctic Ice Sheet (WAIS). The model allows ice thickness, flow and temperature to interact freely. Its domain is prescribed as that of the present-day grounded WAIS. Realistic present-day climatic and topographical boundary conditions are employed. The analysis of a series of experiments pays particular attention to the location and dynamics of concentrations of ice flow (ice streams). Underlying topographic troughs are crucial in determining the strength and location of these concentrations of flow. The flow pattern generated by subglacial troughs is made more distinct by the inclusion of ice flow/temperature coupling. The inclusion of sliding leads to the generation of limit cycles in the ice flow. They are concentrated around the present-day ice streams B and C of the Siple Coast and have a period of 5 to 10 ky. There appears to be competition between several preferred ice flow pathways in this area. The two end members of the flow regime are a strong ice stream C with a weakened ice stream A/B complex, and strong ice streams A and B with a dormant ice stream C. Ice streams appear to require ice discharges above a certain threshold in order to maintain frictional heat generation and fast flow. Individual ice streams can therefore interact through changes in catchment-area size: a reduction in catchment area reduces the volume of ice entering a stream and can cause stagnation as the amount of frictional heating falls.
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