Subantarctic Indian Ocean export production and frontal dynamics over the last glacial-interglacial cycle

The Southern Ocean’s frontal system controls nutrient availability and sea-ice extent in the region, thus participating in the regulation of biological productivity and the export of carbon to the deep ocean. Sedimentary evidence indicates that latitudinal migrations of frontal boundaries accompanied glacial-interglacial transitions, with implications for spatial patterns of export production. Here, we present new biostratigraphic, geochemical, and sedimentological results of a sediment core transect along 100°E from the Antarctic coast to the Southeast Indian Ridge from the expedition PS140 of R/V Polarstern to address Pleistocene dynamics of oceanic fronts within the Antarctic Circumpolar Current, changes in sea surface water temperatures, sea-ice extent, and surface water productivity. A profile of eight piston cores was retrieved, comprising three sediment cores from the Seasonal Ice Zone (SIZ) and Permanent Open Ocean Zone (POOZ) south of the Antarctic Polar Front, and five sediment cores from the Polar Frontal Zone (PFZ) to the Subantarctic Zone (SAZ). Our stratigraphic framework is based on a combination of lithostratigraphic correlations, benthic foraminiferal oxygen-isotope data, and the tuning of dust records from our cores to Antarctic reference records. We also obtained planktic radiocarbon dates for younger sections. We use XRF-scanning-based element ratios, magnetic susceptibility, GRAPE densities, and bulk inorganic geochemistry data to reconstruct changes in export production and terrigenous sediment delivery via dust and ice transport. Major lithologies in the SIZ and POOZ are mainly diatom oozes with minor terrigenous components. The multiproxy data from the PFZ to the SAZ indicate a transition from biosiliceous to calcareous sediments. The northernmost cores of the transect are characterized by alternating sequences of foraminifera-bearing nannofossil ooze and diatom ooze. These alterations are likely derived from lateral migrations of the subantarctic frontal system and may reflect the frontal movement during glacial-interglacial changes. Our findings serve as the basis for ongoing and upcoming studies that will generate complementary paleoceanographic and paleoclimatic information in this to date poorly studied region of the Southern Ocean.