Subglacial bedforms reveal complex basal regime in a zone of paleo–ice stream convergence, Amundsen Sea embayment, West Antarctica

The fl ow of ice streams, which account for most discharge from large ice sheets, is controlled
by processes operating at the ice stream bed. Data from modern ice stream beds are
diffi cult to obtain, but where ice advanced onto continental shelves during glacial periods,
extensive areas of the former bed can be imaged using modern swath sonar tools. We present
new multibeam swath bathymetry data analyzed alongside sparse preexisting data from the
Amundsen Sea embayment. The compilation is the most extensive, continuous area of multibeam
data coverage yet obtained on the inner continental shelf of Antarctica. The data reveal
streamlined subglacial bedforms that defi ne a zone of paleo–ice stream convergence, but, in
contrast to previous models, do not show a simple downfl ow progression of bedform types
along paleo–ice stream troughs. We interpret high spatial variability of bedforms as indicating
a complex mechanical and hydrodynamic regime at the former ice stream beds, consistent
with observations from some modern ice streams. We conclude that care must be taken when
using bedforms to infer paleo–ice stream velocities.