Oceanographic influences and high productivity recorded in a coastal bay of the Amundsen Sea, West Antarctica, during the Holocene

Reconstructing environmental changes near ice margins that have deglaciated since the Last Glacial Maximum (LGM) is essential for understanding future changes of the Antarctic Ice Sheet. Here, we conducted a multiproxy reconstruction of the Holocene environmental history of Cranton Bay, a small, bathymetrically enclosed, biologically productive embayment north of Pine Island Bay in the Amundsen Sea Embayment (ASE), West Antarctica. We present a detailed analysis of sediment core NBP20-02 KC72, which provides a record of environmental changes in the bay. We analyzed sediment grain size, magnetic susceptibility, computed tomography scans, stable carbon isotopes on bulk sediments, total diatom abundance and assemblages, and radiocarbon-dated calcareous benthic foraminifera. Our findings suggest that an ice canopy covered Cranton Bay early in the Holocene, evidenced by low primary productivity. During the mid-Holocene, the bay was seasonally sea-ice covered, as documented by the increase in total diatom abundance and the presence of diatom taxa with sea-ice affinity. The appearance of the offshore diatom Fragilariopsis kerguelensis during the mid-Holocene may suggest the advection of modified Circumpolar Deep Water (mCDW) into Cranton Bay. This implies that mCDW delivery across the ASE during the Holocene was spatially and/or temporally variable, possibly due to boundary conditions (e.g., bathymetry). Primary productivity increased during the latest Holocene, consistent with longer seasonally open-marine conditions. Absolute diatom abundances in Cranton Bay are among the highest within the ASE. Understanding past environments and drivers of glacial retreat since the LGM will help contextualize recent West Antarctic Ice Sheet changes.