Glacial-interglacial variations in marine productivity and ice-rafted debris supply in the Indian Southern Ocean: Implications for East Antarctic ice sheet variability

In the recent past, the Antarctic ice sheet has experienced significant ice mass loss, which is suggested to be driven primarily by the intrusion of relatively warm deep waters on continental shelves. Given its vast ice shelves and bedrock below sea level, the West Antarctic Ice Sheet has been considered to be strongly sensitive to oceanic forcing and associated heat supply to its margins. Recently, however, also marine-based portions of the East Antarctic Ice Sheet (EAIS) were identified of reacting sensitively to oceanic changes with a direct consequence for rising sea levels as large subglacial areas such as the Aurora or Wilkes Basin hold a sea level equivalent of around 20 meters. So far, past EAIS dynamics and their interaction with ocean dynamics remain poorly understood. Here, we reconstruct past EAIS dynamics from ice-rafted detritus (IRD) counts and estimates of marine productivity in the Indian Southern Ocean. Our opal and carbonate percentages derive from sediment core PS141_49-3 (64° 55.795' S, 106° 51.606' E, 2454 m) retrieved during RV Polarstern Expedition PS141 on the upper East Antarctic continental slope offshore Vanderford Glacier, reaching back to marine isotope stage (MIS) 8, i.e., ~300 ka before present. During glacials, the dominant input of terrigenous sediments suggests a decrease of marine productivity, possibly due to enhanced sea-ice cover extending over the continental slope region. Deglacial phases coincide with high IRD input indicating enhanced iceberg discharge during periods of increased ice mass loss. In contrast, high interglacial opal contents suggest enhanced surface ocean productivity likely associated with a reduced seasonal sea-ice cover. Comparison of our findings with other marine records from offshore Sabrina Coast, Prydz Bay and Wilkes Land reveals consistency of this glacial-interglacial pattern to slope and abyssal sediments around the East Antarctic margin. Our data therefore contributes to an Indian Southern Ocean-wide perspective on terrigenous sediment mobilisation on the slope and EAIS-proximal marine productivity, likely controlled by the grounding line migration across the shelf, sea-ice extent, and oceanic heat supply towards the EAIS margin.