Expanding surface sediment proxy calibration to improve reconstructions of ocean-ice interactions in West Antarctica

Biomarkers and dinoflagellate cyst assemblages are valuable proxies for reconstructing palaeoceanographic conditions and past ocean-ice interactions in polar regions. However, in the modern Southern Ocean, the sparse and uneven distribution of  surface sediment samples of these proxies limits our ability to fully evaluate their oceanic and environmental affinities. This is particularly problematic in the West Antarctic region, where upwelling of Circumpolar Deep Water (CDW) onto the continental shelf influences the dynamics and stability of the West Antarctic and Antarctic Peninsula ice sheets. Because these ice sheets could together, if destabilised, contribute an equivalent of 4.5 m to global sea-level rise, better tools for reconstructing CDW and its interactions with the ice sheets are needed. Here we expand the surface sediment database for this region by analysing dinoflagellate cyst assemblages and organic geochemical biomarkers (isoGDGTs, OH-GDGTs, di-unsaturated highly branched isoprenoids) in a new set of 80+ surface sediment samples. We constrain the relationships between dinoflagellate cyst assemblages and surface oceanographic conditions, IPSO₂₅ and sea ice occurrence, and assess TEX₈₆ and TEX₈₆^OH as potential proxies for CDW-influenced (sub)surface ocean temperatures. Our refined transfer functions are then used to generate a new GDGT-based temperature record covering 2.5–0.6 million years from IODP Site U1537 in the Scotia Sea’s “Iceberg Alley”. Together, these expanded proxy calibration datasets and their down-core application contribute new insights into past ocean-ice interactions, knowledge vital for understanding future cryosphere and sea level changes.