Changes in iceberg discharge and bottom current activity during the last Glacial to Holocene along the Ross Sea continental margin, Antarctica

Glaciomarine sediments along the continental margins record dynamic depositional processes modulated by ice-ocean interactions. To better understand the changes in iceberg discharge and bottom current activity since the late Last Glacial (Marine Isotope Stage 2 - MIS 2), we investigated glaciomarine sediment cores from the Ross Sea continental margin. Three sediment cores (IT17RS-BC008, IT17RS-BC010, and IT17RS-BC006) were analyzed using multiple proxies, including iceberg-rafted debris (IBRD), sortable silt (SS), grain-size end-member analysis (EMA), total organic carbon (TOC), δ13Corg, and biogenic opal. Notably, this study is the first application of SS and EMA techniques to sediment cores from the Ross Sea, and provides new insights into bottom current variability. We identify four phases in the MIS 2 to Holocene depositional evolution: (1) the early MIS 2 (> 21.5 ka) characterized by strong bottom currents and reworked sediments transported by buoyant meltwater plumes, with minimal iceberg input; (2) the final late glacial (21.5 to about 19 ka), marked by a weakening of bottom currents; (3) the deglacial to mid-Holocene period (19 to 7.5 ka), showing increased iceberg calving and strengthened bottom currents; and (4) the mid-to-late Holocene (7.5 to 2 ka), featuring persistently high iceberg and bottom current activity, probably related to a re-advance of the West Antarctic Ice Sheet. A pronounced tipping point around 19 ka suggests that enhanced basal melting may have triggered the destabilization of the ice sheet and a reorganization of abyssal circulation. This study presents new sedimentological evidence and methodological approaches for reconstructing the coupled dynamics of iceberg-ocean circulation along the Antarctic continental margin.