ALBERT

Description: Precise relative sea level (RSL) data are important for inferring regional ice sheet histories, as well as helping to validate numerical models of ice sheet evolution and glacial isostatic adjustment. Here we develop a new RSL curve for Fildes Peninsula, South Shetland Islands (SSIs), a sub-Antarctic archipelago peripheral to the northern Antarctic Peninsula ice sheet, by integrating sedimentary evidence from isolation basins with geomorphological evidence from raised beaches. This combined approach yields not only a Holocene RSL curve, but also the spatial pattern of how RSL change varied across the archipelago. The curve shows a mid-Holocene RSL highstand on Fildes Peninsula at 15.5 m above mean sea level between 8000 and 7000 cal a BP. Subsequently RSL gradually fell as a consequence of isostatic uplift in response to regional deglaciation. We propose that isostatic uplift occurred at a non-steady rate, with a temporary pause in ice retreat ca. 7200 cal a BP, leading to a short-lived RSL rise of ~1 m and forming a second peak to the mid-Holocene highstand. Two independent approaches were taken to constrain the long-term tectonic uplift rate of the SSIs at 0.22-0.48 m/ka, placing the tectonic contribution to the reconstructed RSL highstand between 1.4 and 2.9 m. Finally, we make comparisons to predictions from three global sea level models.

Description: XRF analysis of stomach-oil deposit WMM7.

Description: Total nitrogen %, total organic carbon % and bulk stable isotope ratios of carbon and nitrogen for stomach-oil deposit WMM7. Standard deviations reported for replicate analyses.

Description: Fatty acid and selected pigment distributions from stomach-oil deposit WMM7. Pigments are reported according to the absorbance at 4 key wavelengths (e.g. P410 = absorbance at 410 nm). Absorbances are reported normalised to extracted mass of stomach-oil deposit (abs g-1) and normalised to total organic carbon content (abs gTOC-1).

Description: Fatty acid stable carbon isotope ratios from stomach-oil deposit WMM7. Standard deviations reported for duplicate measurements.

Description: Recent intensification of wind-driven upwelling of warm upper circumpolar deep water (UCDW) has been linked to accelerated melting of West Antarctic ice shelves and glaciers. To better assess the long term relationship between UCDWupwelling and the stability of theWest Antarctic Ice Sheet, we present a multi-proxy reconstruction of surface and bottom water conditions in Marguerite Bay, West Antarctic Peninsula (WAP), through the Holocene. A combination of sedimentological, diatom and foraminiferal records are, for the first time, presented together to infer a decline in UCDW influence within Marguerite Bay through the early to mid Holocene and the dominance of cyclic forcing in the late Holocene. Extensive glacial melt, limited sea ice and enhanced primary productivity between 9.7 and 7.0 ka BP is considered to be most consistent with persistent incursions of UCDW through Marguerite Trough. From 7.0 ka BP sea ice seasons increased and productivity decreased, suggesting that UCDW influence within Marguerite Bay waned, coincident with the equatorward migration of the Southern Hemisphere Westerly Winds (SWW). UCDW influence continued through the mid Holocene, and by 4.2 ka BP lengthy sea ice seasons persisted within Marguerite Bay. Intermittent melting and reforming of this sea ice within the late Holocene may be indicative of episodic incursions of UCDW into Marguerite Bay during this period. The cyclical changes in the oceanography within Marguerite Bay during the late Holocene is consistent with enhanced sensitively to ENSO forcing as opposed to the SWW-forcing that appears to have dominated the early to mid Holocene. Current measurements of the oceanography of the WAP continental shelf suggest that the system has now returned to the early Holocene-like oceanographic configuration reported here, which in both cases has been associated with rapid deglaciation.

Description: Age determination of stomach-oil deposit WMM7. Radiocarbon ages calibrated to calendar ages using MARINE20 (Heaton et al., 2020) using two scenarios: using Holocene deltaR of 670 ± 50 yr (Björck et al. 1991) or using a simulated sea ice deltaR of 2470 ± 50 yr (Heaton et al., 2020). COL3022 was previously published (Berg et al., 2019).

Description: Diatom abundance and assemblage data are presented for JPC43 - a ~12 m marine sediment core recovered from 576 m water depth in Neny Fjord, Marguerite Bay, Antarctic Peninsula (68.2571°S, 66.9617°W). The core was collected aboard the RVIB Nathanial B Palmer in 2002 during the NBP0201 scientific cruise (PI: Prof J B Anderson) to determine the timing of deglaciation in the fjords of the Antarctic Peninsula. The core record spans the Holocene with samples dated using an age model based on 5 reliable radiocarbon dates. Diatom concentrations and the contribution of Chaetoceros resting spores (CRS %) are calculated from counts (mean=474.4 valves) of the whole diatom assemblage - 'total counts' (n=81); relative abundance of all other diatom taxa are based on counts (mean=363.1 valves) excluding CRS - 'CRS-free counts' (n=66). The relevant methods are described and referenced in the associated publication (Allen et al. 2010).

Description: Elemental scans, organic geochemistry and stable isotope analysis is presented here from a stomach-oil deposit collected at Lake Untersee in central Dronning Maud Land (DML). Deposit WMM7 (sometimes called Antarctic mumiyo) was collected at -71.367 degN, 13.317 degE during the GeoMaud expedition (1995/1996), from the Untersee Oasis, Dronning Maud Land. The aim of the analysis is to investigate snow petrel diet during the Last Glacial stage (22-29 ka) and in turn to infer changing sea-ice conditions in the South Atlantic sector of the Southern Ocean (McClymont et al., Climate of the Past Discussions, submitted). The data include results from non-destructive XRF scanning (ITRAX core scanner, National Oceanography Centre, Southampton, U.K.), fatty acid distributions and fatty acid stable isotope ratios (Department of Geography, Durham University, Durham, U.K.) and bulk stable carbon and nitrogen isotope ratios (Department of Earth Sciences, Durham University, Durham, U.K.). The age-depth model is constrained by 6 new bulk radiocarbon measurements (CologneAMS, Cologne, Germany).

Description: Diatom abundance and assemblage data are presented for JPC43 - a ~12 m marine sediment core recovered from 576 m water depth in Neny Fjord, Marguerite Bay, Antarctic Peninsula (68.2571°S, 66.9617°W). The core was collected aboard the RVIB Nathanial B Palmer in 2002 during the NBP0201 scientific cruise (PI: Prof J B Anderson) to determine the timing of deglaciation in the fjords of the Antarctic Peninsula. The core record spans the Holocene with samples dated using an age model based on 5 reliable radiocarbon dates. Diatom concentrations and the contribution of Chaetoceros resting spores (CRS %) are calculated from counts (mean=474.4 valves) of the whole diatom assemblage - 'total counts' (n=81). The relevant methods are described and referenced in the associated publication (Allen et al. 2010).