The Topography and Flow of the Antarctic Ice Sheet
been used to investigate the form and topography of the Antarctic ice sheet and to relate these to the physical processes of ice flow and basal conditions. Topographic roughness typically increases towards the thin ice of coastal reg ions as surface undulation wav el eng ths decrease and amplitudes increase. Temperature and velocity variations also have significant effects. The coastal zone is punctuated by embayments of severe topography immediately inland of outlet glaciers. This topographic variability has been summarized in a statistical model for the purposes of simulating satellite radar altimeter waveforms. Consideration of the relationship between bedrock and surface profiles has shown that ice temperature is a major influence on the response of the surface to bedrock irregularities. Regional subglacial water layers may al so have an important effect on surface topography. A re-analysis of models of longitudinal stress grad i ents suggests that er ystal fabrics favouring faster flow develop with distance from ice divides and that the relative depth of the zone of maximum shear fluctuates in response to topographic and glaciological constraints. Driving stress patterns have been associated with characteristic glaciological regimes and have suggested a qualitative difference between outlet glaciers and ice streams. The transition to high velocity flow in outlet glaciers has been shown to be triggered ab ruptly in response to subglac ial fjord heads. The dependence of fast flow on subglacial topography indicates a significant stabilizing effect on discharge from ice sheets and suggests that surge behaviour is unlikely within existing ice sheet outlets. The onset of basal sliding at the head of subglac ial fjords suggests a mechanism for the production of overdeepened fjords and steep headwalls through concentrated erosion. This may help in the reconstruction of the dynamics of former ice sheets. Some West Antarctic ice streams do not exhibit this rapid transition in behaviour.