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Sub-Glacial Deformation |
Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol BS8 1SS, UK m.j.siegert{at}bristol.ac.uk
Ice-penetrating airborne radar data from East Antarctica were examined in order to identify regions of the ice-sheet base where water-saturated sediments are thought to occur. Distinctive radar returns are identified from three subglacial environments as follows. (1) A frozen ice-bedrock interface, which shows scattering of a weak radar signal. (2) An ice-water contact above a subglacial lake where the radar reflections are bright, and horizontally flat. (3) The surfaces of two regions of water-saturated basal sediment, one at the centre of the ice sheet and one near the ice margin, where the radar returns are almost as bright as those from the subglacial lake, but not as flat. Characterization of radar signals from these regions is valuable since the results can be compared with data from other areas of the ice-sheet base to establish the nature of the sub-ice contact at a continental scale. The subglacial geomorphology of sediments near the ice margin displays large-scale (c. 10 km long, c. 200 m high) features with slopes that are relatively steep up-glacier, and shallow down-glacier, plus small-scale (<1 km long, <50 m high) regularly spaced undulations. Such sub-ice physiography indicates that the radar data may display in-situ sedimentary structures.
