The marine-based sectors of the East Antarctic Ice Sheet (EAIS) are increasingly recognised as sensitive to ocean-driven change, yet its response to past warm periods remains poorly constrained. The Middle-to-Late Miocene (~16-5 Ma) – encompassing the Miocene Climatic Optimum, Middle Miocene Climate Transition, and Late Miocene Cooling – provides a valuable natural analogue for future climates. During this period, interactions between EAIS extent, Southern Ocean (SO) circulation, and marine productivity likely modulated ice-ocean feedbacks through changes in carbon and nutrient cycling, heat transport, and ice sheet stability. However, few palaeo-records close to the Antarctic margin exist, limiting our ability to assess these feedback mechanisms.
This project investigates environmental changes along the understudied Knox Coast margin during the Middle-to-Late Miocene using the Deep Sea Drilling Project (DSDP) Leg 28 Site 268 sediment core (drilled in 1973). The multi-proxy analysis includes elemental proxies (e.g., X-ray fluorescence scanning, total organic carbon, inorganic carbon, bulk sediment digestion) and isotopic proxies (e.g., Neodymium isotopes), and will constrain changes in environmental conditions, such as biological productivity, bottom water oxygenation, and sediment provenance.
Together, they will allow us to identify key Miocene stratigraphic intervals and evaluate the EAIS and SO feedback mechanisms. This project will generate the first multi-proxy-based reconstruction of the Knox Coast margin and DSDP Site 268, providing new insights into EAIS and SO sensitivity to Miocene climate variability.

Lake sediments provide continuous, datable archives of environmental change and atmospheric deposition. This study investigates anthropogenic radionuclides, including plutonium isotopes (²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu) and uranium-236 (²³⁶U), preserved in surface sediments from twenty lakes in the Windmill Islands, East Antarctica. Radionuclide activities and concentrations derived from legacy nuclear weapons testing were measured using accelerator mass spectrometry (AMS) and integrated with sediment geochemical datasets, including ion beam analysis (PIXA/PIGE), high-resolution μ-XRF scanning (ITRAX), Fourier-transform infrared spectroscopy (FTIR), and lake-water hydrogeochemistry, including δ¹⁸O, specific conductance, ORP, total alkalinity and pH.
Anthropogenic radionuclides were detected in all lakes. Combined ²³⁹+²⁴⁰Pu activity concentrations varied by more than two orders of magnitude, from 0.092 ± 0.002 to 9.88 ± 0.23 mBq g⁻¹, indicating pronounced spatial variability across the lakes. Results indicate that higher radionuclide concentrations were associated with transition metals, redox-sensitive elements and organic functional groups, particularly Amide II, suggesting that these specific conditions can influence radionuclide retention within these environments.
The results demonstrate that Antarctic lakes can act as effective sinks for anthropogenic radionuclides. These findings have broader implications for contaminant cycling under a warming climate, where increased meltwater flux and changing hydrological connectivity may influence the redistribution and remobilisation of legacy radionuclides stored in Antarctic landscapes.

Keywords: Antarctica; anthropogenic radionuclides; geochemistry; isotopes.

PENDING APPROVAL FROM SWAIS2C PROGRAM

Antarctica’s paleoecosystem can reveal insights into historical impacts of a changing climate. Here we evaluated two surface sediment cores collected from 600 m below the West Antarctic Ice Sheet, near the Kamb Ice Stream (KIS-3) as part of the Sensitivity of the West Antarctic Ice Sheet to 2°C of Warming (SWAIS2C) project in 2023/2024 and 2024/2025. We compared two sedaDNA extraction protocols, Armbrecht et al. (2020) and Rohland et al. (2018), for their ability to extract high-quality sedaDNA as a proxy for paleoecosystems. We investigated the eukaryote paleocommunity composition with increasing sediment depth. Our study identified the Rohland et al. (2018) protocol generated higher quality sedaDNA extracts than the Armbrecht et al. (2020) protocol. Our sedaDNA extracts indicated diatom species are more likely to co-occur across multiple depths than for individual species to dominate, with Chaetoceros gelidus and Pahetodactylum triconutum in higher relative abundance. We investigated correlations between diatom distribution and the barium/aluminium ratio, finding little or no relationship at this location. Our findings indicate weak correlations between sedaDNA damage and sediment deposition depth, suggesting this subglacial zone may not be conducive to preserving genetic signals over geological timescales. This study demonstrates that peoleocological investigations utilising subglacial sedaDNA are possible and justifies multi-disciplinary investigations into Antarctica’s paleobiodiversity.

Obtaining near-field histories of former Antarctic ice sheet retreat inland of the modern margin is challenging. However, inner moraines at terrestrial ice sheet margins present an opportunity to sample subglacial material with limited logistical effort. Here, we apply a new proxy (Beryllium isotopes) from inner moraine sediments to identify subglacial basins that have experienced past collapse.

Preliminary investigations from cores extracted from the Loken Moraine at Windmill Islands indicated that the upper few metres of ice laden sediment preserve a ‘pristine’ signal of Be-isotopes present in the inland subglacial environment. Further, the spatial pattern of Be-10 concentrations and Be isotope ratios correlates with other evidence of Holocene collapse and re-advance of Law Dome, indicating that this proxy can detect past retreat.

Here, we discuss recently completed AMS and ICP-MS measurements of beryllium isotopes from four cores recovered from the Denman Glacier region. Be-10 concentrations and Be isotope ratios from the eastern Bunger Hills were low, consistent with sediments eroded from the crystalline bedrock inland of this ice margin. However, at Cape Jones, just upstream from the modern grounding line of Denman Glacier, subglacial sediments returned Be-isotope concentrations that match sediments deposited in modern open marine environments. This evidence, combined with the surface weathering and structural characteristics of the inner moraine, demonstrate the Denman Glacier retreated and re-advanced in response to late Holocene climate fluctuations.

Interglacial shifts in radiogenic isotope provenance records from offshore the Wilkes Subglacial Basin (WSB) have previously been interpreted as evidence for large-scale retreat of the East Antarctic Ice Sheet (EAIS) into regions underlain by Ferrar Large Igneous Province (FLIP) rocks. These interpretations have influenced ice-sheet reconstructions and numerical modelling of WSB stability. However, the assumption that local subglacial erosion is the primary driver of observed geochemical variability remains poorly constrained.
Here we present new detrital Nd and Sr isotope records from Late Pleistocene gravity cores collected offshore George V Land, integrated with clast petrography and heavy mineral analyses. Our results show that interglacial intervals are characterised by an increase in volcanic sediment input consistent with Ross Sea and West Antarctic sources, rather than enhanced erosion of local FLIP units within the WSB.
These findings suggest that previously identified interglacial volcanic isotope excursions are best explained by enhanced distal sediment delivery via iceberg rafting and the Antarctic Slope Current, rather than localised ice-sheet retreat. This challenges a widely used interpretation for the region and highlights the need for multiproxy approaches when disentangling Antarctic sediment provenance. More broadly, our results suggest that one of the strongest geochemical arguments for large-scale EAIS retreat may instead reflect enhanced sediment supply from the Ross Sea and West Antarctica.

Dust-derived iron has been thought to fertilize the high-nutrient, low-chlorophyll Southern Ocean and boost the local producitivity, while iron inputs from other processes and its cycling remain less constrained. Dissolved ²³²Thorium (Th) and ²³⁰Th have been used as geochemical proxies for estimating dust deposition fluxes and constraining other source and sink processes.
Here, I present full depth dissolved ²³²Th and ²³⁰Th profiles from six stations along 115°E between Australia and Antarctica. Thorium isotope distributions show contrasting patterns across the Subantarctic Front (SAF). North of the SAF, high but decreasing surface ²³²Th suggests declining dust influence away from Australia, while near-linear ²³⁰Th increases with depth indicate dominant reversible scavenging. South of the SAF, elevated surface ²³²Th in the middle of the transect suggests upstream lithogenic inputs rather than local dust input. Increasing Th isotope concentrations with depth further indicate the influence of Th-rich deep waters supplied by upwelling. At the southernmost station on the Antarctic continental slope, high dissolved ²³²Th indicates Antarctic margin sediments as a potential lithogenic source extending northward.
Together with published Southern Ocean Th datasets and the newest Th biogeochemical modelling, these observations help constrain the processes controlling Th isotope distributions across the Southern Ocean and Antarctic margin.