West Antarctic Ice Sheet grounding events on the Ross Sea outer continental shelf during the middle Miocene

New seismic–stratigraphic analysis of the Ross Sea continental shelf suggests that there were a at least five shelf-wide grounding events of the West Antarctic Ice Sheet (WAIS) during the middle Miocene. Although the number of WAIS grounding events generally matches the number of extreme δ18O enrichments and eustatic lowstands, these results do not support the long-standing assumption that West Antarctica was substantially ice-free. Instead, seismic–stratigraphic evidence from the Ross Sea shelf documents waxing and waning of a well-developed WAIS in the marine environment at least on the Pacific sector of the West Antarctic continental shelf.