Drilling in the Amundsen Sea Embayment: Reconstructing West Antarctic Ice Sheet dynamics (IODP 784-Full proposal)

The West Antarctic Ice Sheet (WAIS), which is grounded below present sea level and, thus, is highly sensitive to climatic changes, is likely to have had a very dynamic history over the last several million years. Its collapse would result in a global sea-level rise of 3-5 m over present levels yet the world’s scientific community is not able to predict how it might behave in the future, nor is much known of how it has behaved in the past. The reconstruction and quantification of partial or complete WAIS collapses in the geological past are needed in order to provide necessary constraints for ice sheet models predicting future WAIS behaviour and its potential contributions to global sea-level rise. Large uncertainties exist regarding the chronology, extent, rates, and spatial and temporal variability of past advances and retreats of the WAIS across the continental shelves. These uncertainties are mainly due to the fundamental lack of data from drill core. A series of drill sites are proposed for the Amundsen Sea Embayment shelf where seismic data reveal oceanward dipping sedimentary sequences that span the time from the pre-glacial depositional phase to the youngest glacial periods. Our drilling strategy is to target a transect from the oldest sequences close to the bedrock-basin boundary in the south to the youngest sequences in the north of the western and eastern Amundsen Sea Embayment continental shelf. This transect will yield a detailed history of the glacial cycles in the Pine Island-Amundsen Sea region and allow correlations to the WAIS history known from the Ross Sea. In addition, deep-water sites on the continental rise of the embayment are selected for recovering continuous records of glacially transported sediments and the details of climatic and oceanographic changes throughout glacial-interglacial cycles