AFI 02/48_01 - Ice-rafted debris on the Antarctic continental margin and dynamics of the Antarctic Ice Sheet - Swath Bathymetry, EM120 and TOPAS data collected from the Weddell Sea and Marguerite Bay, Feb - March 2002

Ice-rafted (Heinrich) layers in the North Atlantic provide clear evidence that basins of large Quaternary ice sheets have, in the past, exhibited major dynamic instabilities. The presence of large ice sheets on the modern Antarctic continent provides an important opportunity to investigate the deposition of ice-rafted debris in a region where the dynamics of the parent drainage basins are known. The aim of the project was to reconstruct the Late Quaternary dynamics of the Antarctic Peninsula Ice Sheet in Marguerite Bay and to compare sedimentation and IRD records with the Larsen Ice Shelf area, on the other side of the Antarctic Peninsula. Two cruises were undertaken to collect the data. The JR71 (2002) cruise builds on the swath bathymetry and TOPAS survey undertaken on the JR59 (2001) cruise. The mapping of streamlined sedimentary bedforms on the outer shelf has allowed the dimensions of a former fast-flowing ice stream present at the Last Glacial Maximum to be defin
ed. This, in turn, enabled estimates of the past magnitude of ice flow through this glacial system to be calculated. Data was collected using Kongsberg-Simrad EM120 multibeam swath bathymetry and a TOPAS sub-bottom profiler. EM120 data was processed using the Kongsberg-Simrad bathymetric processing package &NEPTUNE&. These ice flux estimates were compared with computer-model reconstructions of former ice-sheet dynamics as a robust test of model performance.