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 δ 18O 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.