Past ice sheet dynamics from seismic reflection data of Vincennes Bay, East Antarctica – was the Vanderford Glacier more stable than presumed?

The East Antarctic Ice Sheet (EAIS) has long been assumed to remain relatively stable under current climatic forcing. Recently, however, this assumption has been challenged by the observation of increased ice mass loss, improved subglacial topography data, and extensive geological and geophysical data of past glacial change from the Sabrina Coast. Glacial-marine sediments deposited on the continental shelf, slope, and rise record past ice sheet expansion and retreat periods that have occurred since the onset of Southern Hemisphere glaciations. The Vanderford Glacier is the main glacial outlet in Vincennes Bay (eastern Mawson Sea shelf), which together with the Totten Glacier drains the large Aurora Subglacial Basin.

We use deep-penetrating seismic reflection data collected during the RV Polarstern Expedition PS141 (EASI-3) in early 2024 combined with existing data to construct a seismic stratigraphic model of the continental shelf, slope, and rise in Vincennes Bay. The newly acquired seismic data reveal pre-glacial sedimentary strata and glacially-transported sequences on the continental shelf and slope in a previously unmapped area near the Vanderford Glacier. We analyze pre-glacial and glacial sedimentation processes on the East Antarctic continental shelf in this region, which so far remained poorly constrained. This allows us to decipher dominant phases of early Oligocene to Pleistocene EAIS development in this sector.

Long-distance seismic horizon correlation with deep-sea scientific drill records from DSDP, ODP, and IODP sites in the northern Mawson Sea, Prydz Bay, and offshore Wilkes Land provides age estimates for the seismostratigraphic sequences on the continental shelf. The earliest clear indications of grounded ice advancing onto the middle continental shelf are inferred in the Early Miocene (~24-14 Ma) from buried subglacial channel systems. The middle shelf consists of older preglacial sequences of Late Cretaceous to Late Miocene age and is overlain by a much younger (Quaternary?) gigantic grounding zone wedge. The outer continental shelf is dominated by prograding glacially-transported sequences of inferred Late Miocene to Pliocene age (14-5 Ma), indicating repeated advances of grounded ice with a high sediment influx from the hinterland. In contrast to the neighbouring Totten Glacier of the Sabrina Coast, the distribution of glacial sedimentary features across sequences suggests that the EAIS was more stable in the Vincennes Bay region, highlighting how differently these two systems might have reacted to changing conditions.