The 1000-year Duration of the Middle-shelf Grounding Event of West Antarctic Ice Sheet

The WAIS advanced to the outer shelf during the last glacial maximum before beginning a rapid retreat back to the inner shelf. In the Whales Deep paleo-ice-stream trough of the eastern Ross sea, geomorphologic evidence from seismic and multibeam surveys shows that the overall retreat was interrupted by at least four pauses during which a cluster of grounding zone wedges (GZWs) were constructed on the middle shelf. The individual GZWs could not be mapped but seismic correlation and isopach mapping showed that the GZW cluster has a total volume of ~5.34 x 10¹¹ m³. Based on borehole observations at the Bindschadler Ice Stream, we estimate that the total sediment flux during the middle shelf grounding events was ~4.72 x 10⁸ m³/a. On this basis of this sediment flux estimate, we calculate that the four grounding events had an elapsed duration of ~1000 years. Based on our survey of results and previously published data from Ross Sea, we propose that the middle shelf grounding events in the other paleo-ice-stream troughs of Ross Sea had a similar duration.