Paleo-ice sheet dynamics and climate history: West Antarctic Ice Sheet

Seismic stratigraphic model of the Amundsen Sea Embayment shelf showing thick glacial-marine deposits and glacial unconformities (modified from Gohl et al., Marine Geology, 2013).

The reconstruction of the dynamic history of Antarctic Ice Sheet expansion and retreat since the onset of Southern Hemisphere glaciation improves our understanding of ice sheet growth and melting processes and thus predictions of future ice-sheet behavior. Because the West Antarctic Ice Sheet (WAIS) has a lower elevation than the East Antarctic Ice Sheet and most of its base is grounded below sea level, the WAIS is likely to have been more sensitive to changes in atmospheric and oceanographic conditions. The WAIS volume corresponds to an equivalent of 3-5 m eustatic sea level change, and about one third of it is stored in drainage basins that discharge through outlet glaciers onto the Amundsen Sea Embayment. The largest drainage systems are those of the Pine Island and Thwaites glaciers, which are known for their current flow acceleration, fast retreat, rapid thinning and high basal melt rates of floating ice at their termini that exceed those of any other Antarctic outlet glacier outside the Antarctic Peninsula. The incursion of warm Circum-Polar Deep-Water into the deeply incised glacial troughs of the shelves has been recognized as the major mechanism for subglacial melt. The important question is how the WAIS has behaved in times when the climatic conditions were close or similar as observed today or in the near future.

Past expansion and retreat of grounded and floating ice across the continental shelf of the Amundsen Sea Embayment must have left signals and traces of glacial sediment accumulation, transport and erosion. Thus, our studies of the sedimentary architecture and characteristics of the Amundsen Sea Embayment margin provides clues of past ice sheet advance-retreat cycles and help improve constraints for paleo-ice dynamic models of the WAIS since early glacial periods. The Amundsen Sea Embayment is our preferred study area for understanding the past West Antarctic Ice Sheet dynamics, because ice sheet discharge into this embayment is entirely sourced from the WAIS and unaffected from the dynamics of other ice sheets.

Numerous seismic profiles and other geophysical data (magnetics and gravity) have been collected by the Geophysics Section of AWI to build seismostratigraphic, glacial-marine sedimentation and paleo-current models of the continental rise and shelf of the Pacific margin of West Antarctica The results call for an urgent case of scientific drilling, in particular in the Amundsen Sea Embayment.

 

 

 

 

 

Contacts:

Dr. Karsten Gohl

Dr. Gabriele Uenzelmann-Neben