Fragilariopsis kerguelensis is the most abundant diatom in the Southern Ocean, and a promising morphometric proxy for paleo-environmental sea surface reconstruction due to its excellent preservation potential in Southern Ocean and Antarctic sediments. However much remains unknown regarding its application, especially in the Indian Sector of the Southern Ocean and East Antarctica.

Here we examine latitudinal patterns in F. kerguelensis valve “rectangularity” (the ratio of valve area to its enclosing rectangle) across the Indian sector of the Southern Ocean, including the Denman region in East Antarctica. Rectangularity increased from northern, warmer waters to southern, polar regions, with peaks near the Subantarctic Front (~53°S) and the Southern Boundary of the Antarctic Circumpolar Current (>60°S), reflecting hydrographic and ecological gradients. Statistical modelling demonstrated that sea surface temperature (SST), salinity, and macronutrient availability interactively shaped valve morphology, highlighting the importance of environmental context in interpreting rectangularity. Comparisons between water column and surface sediments revealed some depositional filtering but confirmed rectangularity preserved large-scale SST and ecological signals. These findings reinforce the potential of F. kerguelensis valve rectangularity as a quantitative SST proxy in the Southern Ocean, and demonstrate that morphometric responses are influenced by multiple, interacting factors.

The Denman region has gained increasing scientific focus due to its vulnerability to warm deep-water incursions, and the Denman Glacier’s capacity to contribute 1.5 metres of sea-level rise if completely melted. With modern observations only recording the past five decades of change in this region, there is a need to examine the region on a broader timescale, particularly through high amplitude climate variability in the middle to late Pleistocene (0-350 kyrs).
To investigate how the Denman region responded to these past warm periods, we used quantitative diatom counts from three slope cores collected during the RSV Nuyina 2025 Denman Marine Voyage. The low absolute abundance of diatoms and high relative abundances of ancient (Miocene-aged) species during cold glacial periods suggests a northward expansion of the grounding line and permanent sea ice edge. During these periods, primary productivity was limited and sedimentation was heavily influenced by reworked material from the shelf to the slope and rise. Termination events marking the end of the glaciations and initiation of climate warming were revealed by an increase in both absolute diatom abundances and the contribution of sea ice associated taxa, indicative of sea ice and grounding line retreat. Preliminary interpretations of the interglacial diatom assemblages indicate sea surface variability between different interglacial intervals.

A dual capillary ion chromatography-mass spectrometry (Cap-IC-MS) method was developed for the simultaneous determination of 26 inorganic and organic ions in Antarctic ice cores using only 190 µL per analysis. Importantly, the low sample volume requirement makes the method compatible with high-resolution ice cores, enabling sub-monthly resolved records. By combining capillary IC with suppressed conductivity and MS detection, this integrated approach enables direct measurement of different chemicals within the same sample, rather than across multiple analyses.

Application to 259 samples from Dome Summit South (Law Dome, East Antarctica) spanning 2011-2021 reveals clear seasonal trends and chemical associations. Marine-derived species show strong coupling, with methanesulfonic acid, non-sea-salt sulfate, and bromine enrichment exhibiting pronounced summer maxima, consistent with marine biogenic activity. Sea-salt ions display enhanced winter concentrations, reflecting seasonal variability in marine influence.

Episodic increases in biomass-burning tracers, including vanillic acid and p-hydroxybenzoic acid, are consistent with long-range transport from major fire events such as the 2019-2020 Australian 'Black Summer'. This study provides the first seasonal-resolution record of these aromatic acids in Antarctic ice cores. These results demonstrate how comprehensive, single-run measurement of multiple chemical species within the same sample enables direct assessment of co-variation and chemical linkages, providing new insights into atmospheric processes and their representation in ice core records.

Long term climate variability in East Antarctica is difficult to study due to short and sparse instrumental records, which are mostly limited to the satellite era. Paleoclimate data, such as those derived from ice cores, can be used to extend the climate record and contextualise recent trends and extremes in precipitation variability on annual to multi-centennial time scales. Here we present the new millennial-scale annual snow accumulation history from the Mount Brown South (MBS) ice core. The record spans 873-2015 CE, and displays a high degree of annual, decadal and centennial variability in show accumulation. The long-term mean snow accumulation rate at MBS is 0.276 ± 0.08 m yr-1 ice equivalent, while the mean accumulation rate in the satellite era (1979-2017) is 0.302 ± 0.08 m yr-1 ice equivalent. Snow accumulation at MBS during the satellite era is not representative of the past millennium, and highlights the need for more climate records with greater spatial and temporal coverage.

This study reports the first seasonal record of trifluoroacetic acid (TFA) in an Antarctic ice core, providing new insight into the long-range transport of persistent anthropogenic chemicals to remote polar regions. TFA is an ultra-short chain perfluoroalkyl acid (PFAA) known for its high environmental stability, mobility, and resistance to degradation. It is primarily formed in the atmosphere from the breakdown of halogenated refrigerants and blowing agents, particularly hydrofluorocarbons (HFCs) and unsaturated HFCs (u-HFCs).
TFA was quantified in a 12.9 m Antarctic ice core from East Antarctica, covering the period 2011 to 2021 using a high-sensitivity non-suppressed ion chromatography–tandem mass spectrometry method. Based on direct injection of only 20 μL of sample, without any additional sample preparation, the method achieved a limit of detection of 0.3 ng L⁻¹ and repeatability better than 7% for both intra-day and inter-day measurements. Ice core sample results show a consistent increase in TFA concentrations over time, with an average annual rise of 5.8% over the studied decade. Seasonal trends, supported by comparison with methanesulfonic acid, indicate enhanced deposition during September–November, suggesting that polar vortex weakening releases both pre-formed TFA and additional TFA from the breakdown of more stable precursors.
Taken together, these findings provide chemical evidence of an anthropogenic footprint in Antarctica, reflected in increasing TFA deposition driven by sustained emissions of volatile precursors, their degradation, and long-range transport.

The Southern Hemisphere Westerly Winds (SHW) are a major driver of climate and ecosystem dynamics across the Southern Hemisphere mid- to high latitudes, with broader implications for global climate. Instrumental records show SHW intensification and poleward migration in response to warming, yet little is known about how the SHW respond to temperature change on longer timescales. Understanding long-term SHW and temperature variability is essential for assessing how large-scale climate processes, particularly the Southern Ocean carbon sink, may respond to future warming. We present multi-proxy reconstructions of SHW and temperature variability from lake sediment records on Macquarie Island, spanning the last c. 12,000 years. Results indicate a dynamic relationship between SHW variability and temperature throughout the Holocene. The early Holocene was characterised by reduced mid-latitude westerly airflow despite relatively warm conditions, likely reflecting a poleward displacement of the westerly belt during the Early Holocene Thermal Maximum. The mid-Holocene (c. 8.3–4 ka) was characterised by variable SHW and temperature conditions, while the late Holocene shows a strong positive relationship between SHW strength and temperature, with sustained mid-latitude westerly influence. Intensification of the SHW during warmer Holocene intervals provides an important analogue for future warming, suggesting enhanced impacts on Southern Hemisphere mid- to high-latitude climate and oceanographic processes, particularly Southern Ocean CO₂ exchange and carbon storage dynamics.