Late Quaternary climate variability as recorded by micropalaeontological diatom data and geochemical data in the western Ross Sea, Antarctica

AbstractCores acquired from the Ross Sea continental shelf and continental slope during the XXX Italian Programma Nazionale di Ricerche in Antartide (PNRA) were analysed and yielded interesting micropalaeontological, biostratigraphic diatom results and palaeoceanographic implications. These multi-proxy analyses enabled us to reconstruct the glacial/deglacial history of this sector of the Ross embayment over the last 40 000 years, advancing our understanding of the Last Glacial Maximum (LGM) environmental and sedimentological processes linked to the Ross Sea ice sheet/ice shelf fluctuations in a basin and continental-slope environment, and allowed us to measure some of the palaeoceanographic dynamics. The central sector of the Ross Sea and part of its coast (south of the Drygalski Ice Tongue) enjoyed open marine conditions in the pre-LGM era (27 500–24 000 years bp). The retreat of the ice sheet could have been influenced by a southward shift of a branch of the Ross gyre, which triggered early deglaciation at c. 18 600 cal bp with a significant Modified Circumpolar Deep Water inflow over the continental slope at c. 14 380 cal BP. We assume that a lack of depositional material in each core, although at different times, represents a hiatus. Other than problems in core collection, this could be due to the onset of modern oceanographic conditions, with strong gravity currents and strong High Salinity Shelf Water exportation. Moreover, we presume that improvements in biostratigraphy, study of reworked diatom taxa, and lithological and geochemical analyses will provide important constraints for the reconstruction of the LGM grounding line, ice-flow lines and ice-flow paths and an interesting tool for reconstructing palaeo-sub-bottom currents in this sector of the Ross embayment.