The East Antarctic Ice Sheet (EAIS) is losing mass from its marine-based portions in response to a warming climate. This warming causes the west wind drift to migrate southwards leading to upwelling of relatively warm deep waters. The assumed future behaviour of the EAIS mainly relies on numerical models, which, however, are rarely validated against precise past ice sheet constraints. This significantly affects their ability to reliably simulate potential future change. In particular, there is a dearth of data for the sectors of the East Antarctic continental shelf situated offshore major subglacial basins, such as Vincennes Bay on the Mawson Sea shelf offshore the Aurora Subglacial Basin. Past dynamic grounding zone changes are recorded here by glacial morphological structures. Those structures, including glacial troughs, glacial lineations, and grounding zone wedges (GZW), can be systematically mapped to provide important information about regional fast and slow flowing ice sheet portions, meltwater pathways, ice sheet extent, and grounding zone stabilisation processes. Here we particularly focus on GZWs, which record grounding zone stabilisation periods in a particular location during overall post-Last Glacial Maximum retreat.

We collected 230 km of high-resolution 2D multi-channel seismic reflection as well as deep-penetrating seismic profiles, multibeam and sediment echo-sounding data, during RV Polarstern Expedition PS141 (EASI 3) in early 2024 to study the morphology and architecture of glacial structures seaward of the Vanderford glacier front in Vincennes Bay. These data reveal a giant GZW that is up to 260 m high and extends 60 km along the previous ice stream bed. To our knowledge, this is the largest GZW discovered on the Antarctic continental shelf to date. The GZW consists of prograding sequences of different inclinations, suggesting multi-phase development of the GZW and a stabilisation process that led the grounding zone to grow and re-advance by several kilometres. Our findings present a significant step forward in understanding past ice sheet behaviour in Vincennes Bay, and thus provide important constraints for the evolution of the EAIS. Our new data therefore provide an important benchmark for testing and improving numerical ice sheet simulations.

How to cite: Tobisch, C. A., Barrett, R., Klages, J. P., Hochmuth, K., Mühlberger-Krause, T., Gohl, K., Baumann, L. M., and Krastel, S.: A Giant Grounding Zone Wedge in Vincennes Bay, East Antarctica: Geomorphological Characteristics and Internal Structure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-813, https://doi.org/10.5194/egusphere-egu25-813, 2025.

One of the biggest uncertainties in future global sea level rise is the stability of the East Antarctic Ice Sheet and its response to anthropogenic climate change. However, to understand future glacial retreat, we must consider paleoclimate proxies to inform our models.

In a recent study, Jamieson et al. [2023, Nature Communications] discovered a relic landscape formed by rivers millions of years ago and preserved beneath the East Antarctic Ice Sheet. The existence of this landscape beneath the modern ice sheet in the Aurora Subglacial Basin region can help us constrain past glacial collapse in this region. In this investigation, we use high-resolution model simulations to better understand if the preservation of this landscape precludes significant glacial retreat into the basin in past warm periods, with a focus on the mid-Pliocene. We apply new subglacial topography maps to resolve mesoscale features within the model, and a range of geothermal heat flux maps. We use simulations with different parameterisations of glacial processes such as ocean temperature sensitivity and hydrofracture (driving marine ice cliff instabilities) to assess which processes might have influenced glacial retreat while allowing for the preservation of the relic landscape.

How to cite: Knight, R., Gasson, E., Littler, K., and Noble, T.: Did past warm periods see glacial collapse into the East Antarctic Aurora Subglacial Basin? An experiment of geologically constrained modelling., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3557, https://doi.org/10.5194/egusphere-egu25-3557, 2025.

From instrumental observations, we know that the East Antarctic Ice Sheet (EAIS) has experienced mass loss over recent decades, with a higher potential for climate change-induced ice loss than previously assumed. While instrumental data only allow for reconstructing high-latitude ice-sheet dynamics over some decades, little is known about the long-term EAIS development over geological timescales. One possibility to overcome this lack of data is to study the geomorphological record imprinted on the Antarctic continental shelf. Here, we visualize the paleo-ice sheet bed on the Mawson Sea shelf with a focus on the shelf offshore Vanderford Glacier – EAIS’s fastest-retreating glacier forced by increasing intrusions of modified Circumpolar Deep Water. The study uses multibeam bathymetry and sediment echosounder data collected on the continental shelf in front of the Vanderford Glacier terminus during RV Polarstern and RSV Nuyina expeditions in 2024 and 2022 respectively.  A large assemblage of subglacial bedforms was imaged revealing past hydrological and glacial conditions at the former ice sheet bed. An over-deepened glacial trough system right in front of the modern glacier terminus suggests intense past meltwater discharge beneath the Vanderford glacier, possibly reactivated during several glacial cycles. Further seawards, a giant grounding-zone wedge records past subglacial sediment accumulation at the convergence zone of fast-flowing ice streams from various glaciers. The presented glacial landform assemblage reveals a major paleo-ice stream system including corridors of fast-flowing ice, distinct regions of ice flow acceleration, and inter-ice stream regions characterized by slowly moving or even stagnant ice masses. Our new geomorphological data from Vincennes Bay provides crucial information on the EAIS’s past behaviour in a region that currently changes rapidly. As it is directly situated seawards of the vast Aurora Subglacial Basin, it will allow for constraining regional ice sheet and oceanographic models more reliably.

How to cite: Baumann, L. M., Geersen, J., Klages, J. P., Tobisch, C. A., McNeil, M., Weigelt, E., and Krastel, S.: Geomorphological record of East Antarctic Ice Sheet dynamics in front of Vanderford Glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4166, https://doi.org/10.5194/egusphere-egu25-4166, 2025.

The attention on the current enormous ice mass loss of the West Antarctic Ice Sheet (WAIS) leads to questions about its behavior in the geological past, in particular during past extended warm periods such as those in the Miocene and Pliocene. The compilation of the network of seismic lines linked to relevant ocean drilling sites of ODP Leg 178 at the western Antarctic Peninsula and IODP Expedition 379 on the Amundsen Sea continental rise enables analyses of the temporal and spatial evolution of the WAIS in the southeastern Pacific sector from early expansions to the continental shelves in the Oligocene-Miocene to variations in its dynamic behavior up to the Pliocene/Pleistocene. This includes significant warm periods with major grounded ice retreat events in the middle to late Pliocene. Our analyses indicate that long-period expansion and retreat phases of the main ice-stream outflow systems in the Bellingshausen Sea sector and the Amundsen Sea sector occurred less synchronously than previously assumed. In the Bellingshausen Sea sector, the earliest high-intensity advances of grounded ice occurred in the Miocene with mid- to low-intensity advances in the Pliocene. Extended ice sheet retreat periods during the Pliocene warm times are not as clearly observed as in the Amundsen Sea sector. On the other hand, the Amundsen Sea sector experienced its earliest low-intensity ice advances in the Miocene and high-intensity advances in the Pliocene with extended ice-sheet retreat periods embedded during the so-called Pliocene Amundsen Sea Warm Period from 4.2 to 3.2 Ma. Different paleotopographic conditions of the respective hinterlands likely caused different ice-stream/ice-sheet dynamics. In addition, regional ocean circulation patterns, that were prevalent at particular times, seem to have had a major control on expansion and retreat phases. We show newest seismic data analyses and try to synthesize our observations into a consistent model for past WAIS dynamics from the Miocene to the Pleistocene.

How to cite: Gohl, K., Uenzelmann-Neben, G., Klages, J., Luo, L., Larter, R., Hillenbrand, C.-D., and Salzmann, U.: Miocene to Pliocene/Pleistocene shift in West Antarctic Ice Sheet dynamics in the Bellingshausen Sea and Amundsen Sea sectors, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5704, https://doi.org/10.5194/egusphere-egu25-5704, 2025.

Geological fieldwork in the Vestfold Hills, a 413 km² ice-free area on the eastern margin of Prydz Bay, Antarctica, was carried out during the R/V Polarstern cruise PS140 to support the research objectives of the Eastern Antarctic Ice Sheet Instabilities (EASI) initiative. A 12 m sediment core composite obtained from Watts Lake provides a high-resolution record of the climatic, glacial, and relative sea-level history of the region, as well as the first evidence of ice-free conditions in the Vestfold Hills prior to the Last Glacial Maximum (LGM). A series of 24 radiocarbon ages from bulk organic carbon, mollusk shells, and lacustrine moss remains collected throughout the core will provide the basis for a detailed age-depth model going back over 50 ka, and provide insight into the rate and timing of deglaciation ~10 ka. Ongoing biogeochemical analyses, including XRF, biomarker, TOC and CNS profiling, will provide proxies for biological productivity and changes in meltwater supply, allowing us to reconstruct Holocene climate trends. A combination of radiocarbon ages from surrounding marine terraces, field geodetic data, and lacustrine-marine transitions identified and dated in the core will allow us to develop updated relative sea level curves that are prerequisites to track isostatic uplift during deglaciation and model past ice thickness. These data will be integrated with other sediment records from the same field campaign, collected along a 10 km E-W transect of the adjacent Ellis Fjord, which will provide further spatial and temporal detail on deglaciation processes and evaluate possible ice readvances in the Vestfold Hills. Overall, the results will improve our understanding of the dynamics of the East Antarctic Ice Sheet and its role in a warming world.

How to cite: Feller, J., Melles, M., Berg, S., and Wagner, B.: East Antarctic Ice Sheet instability: insights from a > 50 ka sediment record from the Vestfold Hills, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5738, https://doi.org/10.5194/egusphere-egu25-5738, 2025.

Circumpolar Deep Water (CDW) poses a major threat for the future stability of the Antarctic Ice Sheet. In the Southern Ocean, CDW encroaches onto the Antarctic continental shelf in East Antarctica. CDW is the warmest deep-water mass within the Southern Ocean, and thus, harbours large amounts of heat with the potential to drive large basal melting under the ice shelf cavities it reaches. The PS141 expedition focused on the Denman Glacier, one of the fastest retreating glaciers in the East Antarctic Aurora subglacial basin. It holds a sea level rise equivalent of up to 1.6 m. However, the processes behind the Denman retreat remain undocumented. During PS141, found warm modified CDW intrusions in the immediate vicinity of the Denman ice shelf. mCDW temperature reached up to -0.1 °C, more than 1.5 °C higher than ambient water masses. It was present as the deepest water mass below 330 m on the continental shelf along a cross-shelf-transect at 100° E. Its minimum thickness was 50 m at the ice shelf and reached up to 100 m thickness mid shelf, where the warmest temperatures were measured. Predictions into how future climate scenarios may affect how CDW interacts with the Antarctic Ice Sheet suggest an increasing presence of mCDW within the Antarctic continental shelf. This could be a major threat to the stability of the East Antarctic Ice Sheet, especially if it reaches vulnerable regions such as the Aurora subglacial basin and Denman glacier. By documenting the ocean state near this critical region, we can deliver better climate-related advice to policy makers working on mitigating and adapting to future sea level rise.

How to cite: Ferber, J., Kreps, G., Lembke-Jene, L., Herraiz Borreguero, L., Rieke, O., and Keul, N.: Warm water intrusion onto the East Antarctic Shelf, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6827, https://doi.org/10.5194/egusphere-egu25-6827, 2025.

Along the Sabrina Coast, extensive canyon systems, mapped in high resolution during the RV Investigator voyage IN2017_V01, cut through the continental slope and rise. These essential conduits for transporting water masses to and from the continental shelf provide a pathway for upwelling warm deep water (e.g., Donda et al., 2024). Beryllium isotope ratios (¹⁰Be/⁹Be) can be used as an indicator of upwelling deep water due to differing beryllium concentrations in surface water, deep water (von Blanckenburg et al., 1996; Jeromson et al., 2024), and meltwater from continental ice shelves (Yokoyama et al., 2016, Valletta et al., 2018) in that deep ocean water beryllium isotope ratios are higher than that sourced from continents (Wittmann et al., 2017, Jeromson et al., 2024). Records of beryllium isotope variability from the Southern Ocean are scarce, and primarily encompass the Last Glacial Period through the Holocene (Sjunneskog et al., 2007, Yokoyama et al., 2016, Behrens et al., 2022, Sproson et al., 2022) or focus on spatial variability (White et al., 2019, Jeromson et al., 2024). 

Here, we present the longest known beryllium isotope record from the continental rise, extracted from between two canyons off the Sabrina Coast. The site is adjacent to the Sabrina Subglacial Basin, the Totten Glacier, and Moscow University Ice Shelf. This 16 m-long beryllium isotope record elucidates the relationship between the Antarctic Ice Sheet and upwelling Circumpolar Deep Water from 350,000 years ago to the present. Glacial periods exhibit low beryllium ratios, indicating a greater contribution of beryllium from the continent due to the more proximal location of the Antarctic Ice Sheet to the study site and absence of upwelling deep water. The balance shifts during interglacial periods, and higher beryllium ratios indicate a greater presence of upwelling deep water through canyons along the continental slope and rise. The data presented here demonstrates the usefulness of beryllium isotopes in determining periods with higher ‘continental’ or ‘oceanic’ beryllium contribution along the Antarctic continental rise, which may be used as a proxy for ice sheet advance or retreat as it relates to upwelling Circumpolar Deep Water.

How to cite: Behrens, B., Yokoyama, Y., Miyairi, Y., Huang, Z., Suga, H., Ohkouchi, N., Obrochta, S., Post, A., O'Brien, P., and Armand, L.: Beryllium isotope record from the Sabrina Coast details ice sheet dynamics related to upwelling deep water from 350,000 years ago to the present, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7698, https://doi.org/10.5194/egusphere-egu25-7698, 2025.

Over the last decades, climate change led to only moderate changes of the East Antarctic Ice Sheet (EAIS). In recent years, however, modelling approaches and field experiments have shown that also the EAIS is increasingly affected by ice mass losses. In order to obtain information on temporal/spatial ice sheet changes at the margins of the major glaciers in East Antarctica, northern Bunger Hills were visited within the frame of the EASI3 "RV Polarstern" expedition in the period between 19. and 29. February 2024. From a ca 1-km-long lake, here informally named Western Ear Lake (S 66.10621°, E 100.95924°), on Thomas Island, several gravity cores and hammering cores of up to 112-cm-length were recovered in the central part of the ice-covered lake at 14.4 m water depth. Very stiff, greyish to olive sediments sticking to the outer core barrel at sediment depths >110 cm imply that the recovered sediment successions contain the entire environmental history of the lake since the deglaciation of the basin. Greyish and clastic, coarse to fine grained sediments at the base of the sediment succession represent the retreat of the ice sheet after deglaciation of the lake basin. Sediments with fine lamination ranging from submillimeter to centimeter scale characterize the uppermost ~80 cm of the recovered sediment succession. Individual layers show distinct changes in granulometric and geochemical characteristics, particularly with respect to organic matter and calcite contents. The detailed study of these layers will allow a better understanding of lake internal sedimentation processes and related environmental changes. Bulk organic matter from nine horizons throughout the core is used for radiocarbon dating and will set the chronological framework for the reconstructed environmental changes. The radiocarbon ages may support an ice retreat during the early Holocene, as it is reported from geomorphological evidence and glacial deposits from the closer surrounding of the lake. Despite distinct changes in lamination with respect to lamination thickness or internal structures and geochemical composition in the uppermost ~80 cm of the sediment succession, large scale environmental changes that might be related to a marine transgression after ice retreat cannot be observed. The lack of evidence for marine conditions in the basin supports a marine limit several meters below the lake level of 14.8 m asl during the time of visit and/or the sill height of the outflow of the outflow at 16.3 m asl. Moreover, despite a long-term trend of sediments more enriched in organic matter towards the sediment surface, there is no indication for distinct long-term changes in environmental conditions. This may indicate that sedimentation conditions in the lake remained relatively constant after the ice retreat until today and were mainly controlled by small scale changes, such as lake ice coverage, meltwater supply, light and/or nutrient conditions. It also indicates that a major glacial advance of the ice sheet or of outlet glaciers into the lake catchment after the presumed early Holocene ice retreat can be discarded.

How to cite: Wagner, B., Gore, D. B., Dägele, D., Howard, A., Lange, T., Scheidt, S., Weber, M., White, D., and Berg, S.: Holocene environmental history of Thomas Island, Bunger Oasis, East Antarctica, inferred from a lake sediment record, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8151, https://doi.org/10.5194/egusphere-egu25-8151, 2025.

The Antarctic Ice Sheet (AIS) holds the largest potential for global sea-level rise (SLR), yet it remains the greatest source of uncertainty in future SLR projections. While the physical processes driving AIS mass loss are qualitatively well understood, significant uncertainties persist due to the challenging representation in models of these processes such as ice-ocean interactions and basal friction at the ice-bed interface. Satellite observations from the last decade reveal accelerated AIS mass loss in regions experiencing enhanced oceanic warming. Such warming thins ice shelves, reducing their buttressing effect and accelerating the flow of grounded ice. This can trigger a retreat of the grounding line into deeper bedrock, activating the Marine Ice Sheet Instability (MISI) feedback mechanism. Understanding the proximity to this tipping point is crucial for accurate sea-level rise projections and for developing effective adaptation strategies. From modeling and paleo-climatic studies it is well established that oceanic warming of 1–3°C in the Amundsen Sea Embayment could instigate MISI in West Antarctica. In addition, the spread and reliability of climate projections in future warming scenarios derived from Earth System Models (ESMs) remains a large source of uncertainty. However, a systematic study of this possible threshold with multiple models is needed. To address this, we conducted simulations of the AIS forced by CMIP6 ESMs under a scenario of 1% annual CO₂ increase until 2300, including simulations that branch off with a constant imposed forcing at different global warming levels. The simulations are run until year 3000 with a constant climate to study committed impacts to ice loss. For this, we use an ensemble produced with the ice-sheet-shelf model Yelmo, initialized with varying configurations to account for key uncertainties, including ice-ocean interactions and basal friction, as well as climatic forcing obtained from various CMIP6 ESMs that were assessed for their performance in Antarctica. This approach provides insights into the differential warming of the Southern Ocean relative to global temperatures, the AIS’s committed response, and its proximity to triggering the MISI.

How to cite: Blasco, J., Grusdt, B., Montoya, M., Alvarez-Solas, J., and Robinson, A.: The Antarctic response to 1% annual atmospheric CO2 concentration increase, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8552, https://doi.org/10.5194/egusphere-egu25-8552, 2025.

Changes in snow accumulation on the Antarctic Ice Sheet are of significant relevance
to global mean sea level. Measurements taken over a 33-year period near the Neumayer
Stations, Dronning Maud Land (DML), Antarctica, were used to statistically
analyse both interannual and intraannual trends and variability of snow accumulation.
While a significant increases in snow accumulation have been observed at
Kohnen Station on the DML plateau in the interior of the continent, the question
arises as to whether the coastal measurements near Neumayer show similar trends.
This study reveals that two unprecedented accumulation years, 2021 and 2023, were
recorded near Neumayer; however, no statistically significant long-term trend could
be identified in the time series, which shows several periods of increasing and decreasing
mulit-annual means in snow accumulation. Despite this, shifts in certain
accumulation characteristics during the study period suggest the possible onset of
a positive trend. Specifically, positive annual accumulation anomalies have become
more frequent and more intense, the rate of interannual accumulation increase has
accelerated, and the current period reflects a prolonged state of above-average accumulation.
High interannual variability, however, prevents the identification of a
significant trend within the available data period.
Periodicities observed in the time series suggest possible links to larger atmospheric
patterns, such as the Antarctic Circumpolar Wave. Further research is required to
also investigate the role of the major climate modes such as the Southern Annular
Mode (SAM) and El Nino-Southern Oscillation (ENSO) and how these might influence
local accumulation trends. This climatological analysis offers valuable data
that could be used for future ground-truthing of satellite observations and benchmarking
of climate models, especially given the higher temporal resolution of these
measurements compared to firn and ice core records.

How to cite: Reppert, V., Eisen, O., and Prinz, R.: Climate Signals from Neumayer, Coastal Dronning Maud Land, Antarctica: A 33 Year Statistical Analysis of Snow Accumulation in a Stake Farm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10222, https://doi.org/10.5194/egusphere-egu25-10222, 2025.

As meso-order predators, snow petrels (Pagodroma nivea) play a significant role in the Antarctic food web. Changes in their abundance can be related to the availability of prey and thus provide an indication of ecosystem health. The foraging grounds of snow petrels lie within the pack ice and open waters of the Southern Ocean, while their nesting sites are restricted to ice-free areas on the Antarctic mainland and surrounding islands. Modern observations of the birds allow conclusions to be drawn about their breeding performance and foraging ecology in relation to environmental parameters, such as sea-ice extent. Biological studies on the distribution of nesting sites and the response of the birds to changing environmental conditions can be complemented by the analysis of fossil stomach oil deposits produced by snow petrels, the so-called 'Antarctic mumiyo'. Stomach oil is composed of lipid-rich dietary components and can therefore provide information on the composition of the diet, which consists mainly of different fish and krill species.

Fossil stomach oil deposits provide information on the timing of snow petrel occupation of a particular nesting site and can be used as an indicator of ice sheet retreat. However, 'Antarctic mumiyo' also serves as a novel terrestrial archive for paleoenvironmental reconstructions in the Southern Ocean. Analyses of the organic and inorganic composition of the stomach oil deposits allow assumptions to be made about the paleodiet of the snow petrels, which in turn depends on the oceanic environmental conditions prevailing at the time of deposition. We investigate stomach oil deposits from several coastal sites in East Antarctica (including the Vestfjella, Framnes Mountains, Bunger Hills, and Windmill Islands) to develop new proxies for the composition of the paleodiet and to link these to marine environmental conditions (e.g., sea-ice variability and polynya occurrence) during the Holocene.

The fossil stomach oil deposits are examined using inorganic, lipid, and isotopic geochemical methods, as well as radiocarbon dating for temporal constraints. Evidence for regional differences in the paleodiet comes from lipid data, such as n-C14 to n-C24 alcohol and fatty acid distributions, reflecting either a more fish or krill dominated paleodiet. We will present initial regional reconstructions based on ¹⁴C-dated stomach oil deposits from Bunger Hills and Framnes Mountains and discuss potential links between paleoenvironmental conditions and paleodiet.

How to cite: Raffelsiefen, L., Dägele, D., Gore, D., Heim, C., Melles, M., and Berg, S.: Paleoenvironmental insights into ice-ocean interactions in East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10652, https://doi.org/10.5194/egusphere-egu25-10652, 2025.

Wilkes Subglacial Basin covers an area of 400,000 km², and stores a volume of ice equivalent to approximately 3 to 4 metres of sea-level rise. Both model simulations and observational evidence from offshore sediment cores indicate that the ice within the basin is susceptible to significant instability, and has seen extensive deglaciation and retreat in periods during the Pleistocene and Pliocene. Two ice cores are located proximal to the Wilkes Subglacial Basin: (i) EPICA Dome C ice core, situated at the ice divide in the upstream section of the catchment, with a record dating back to approximately 800 ka; and (ii) Talos Dome ice core, situated closer to the coast, and extending back to approximately 350 ka. Englacial stratigraphy imaged by radio-echo sounding can be dated at intersections with the ice cores, therefore extending the observational evidence of palaeo-behaviour of ice sheets beyond these isolated point-based measurements. To date, the englacial stratigraphy between these two ice cores has not been comprehensively investigated.

Here, we analyse the englacial stratigraphy using an airborne radio-echo sounding dataset comprising 61,000 km of along-track data, jointly acquired in 2005-2006 by the British Antarctic Survey (BAS) and the Italian Programma Nazionale di Ricerche in Antartide (the WISE-ISODYN survey). Data were acquired with the 150 MHz BAS Polarimetric Survey Instrument (PASIN). We have traced multiple englacial layers between Dome C and Talos Dome ice cores, with at least one layer of age 38 ka directly connecting the 1,100 km distance between the two ice cores. Our findings here provide robust geophysical confirmation that englacial layers across Antarctica correspond to chemically dated layers measured in deep ice cores more than 1,000 km apart. Overall, the architecture of englacial layers spanning between the two ice cores indicates a pervasive and stable ice geometry in the upper Wilkes Subglacial Basin during the last 60 ka. Future work will be directed towards extending the tracing of englacial stratigraphy towards the grounding line of Wilkes Subglacial Basin as calibration for ice-dynamic modelling to investigate the stability of the entire basin.

How to cite: Nyqvist, C., Bingham, R. G., Hein, A. S., Ross, N., Sutter, J. C. R., Bodart, J. A., Ferraccioli, F., and Armadillo, E.: Stability of Wilkes Subglacial Basin since before the Last Glacial Maximum signalled by englacial stratigraphy connecting Dome C and Talos Dome Ice Cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11233, https://doi.org/10.5194/egusphere-egu25-11233, 2025.

The sensitivity of the East Antarctic Ice Sheet (EAIS) to the advection of relatively warm circumpolar deep water and changes in sea-ice cover, both affecting the stability of ice-shelf fronts, remains poorly constrained for the past deglacial period. Accordingly, projections of how (rapidly) the EAIS will respond to ongoing climate warming lack solid information to quantitatively evaluate the ice-ocean feedback mechanisms that drive ice-sheet disintegration. Here, we investigate the biomarker inventory (highly branched isoprenoids, phytosterols, GDGTs) of two sediment cores recently collected from the Nielsen Basin on the Mac. Robertson Shelf, East Antarctica, to evaluate if and how sea-ice variability was related to local ice-sheet dynamics and the occurrence of polynyas. Sediment core PS128_39-1, retrieved from a sedimentary basin on the mid shelf, reveals a reduced sea ice cover permitting higher phytoplankton productivity during the deglacial and an expanded sea-ice cover limiting the marine productivity during the Holocene. Sediment core PS128_41-1, obtained from a grounding zone wedge from the outer basin, also records a higher deglacial phytoplankton productivity, but a less expanded sea-ice cover and rather polynya-like conditions throughout the Holocene. Further analyses are pending and, together with refined age models and sedimentological analyses, will allow to robustly track the retreat behavior of the EAIS on the Mac. Robertson Shelf and associated oceanic drivers.

How to cite: Cardinahl, L., Sonnemann, P., Güntzel, J., Klages, J., and Müller, J.: Deglacial and Holocene sea ice variability along the East Antarctic continental margin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11290, https://doi.org/10.5194/egusphere-egu25-11290, 2025.

The East Antarctic Ice Sheet (EAIS) formed circa 34 million years ago and is now the largest reservoir of freshwater on Earth, containing an ice volume equivalent to ~52 metres of global sea-level rise. Although the EAIS is approximately in balance today, there is substantial uncertainty as to the sensitivity of certain sectors, particularly those underlain by widespread low-lying bed topography. The Wilkes and Aurora Subglacial Basin catchments have notably been the focus of recent observation- and modelling-based work, but comparatively little is known about the long-term history of Coats Land and the eastern margin of the Weddell Sea, which is the third major marine-based catchment of the EAIS. In total, the eastern Weddell Sea catchments contain ~9 metres of sea-level equivalent, which is more than the entire West Antarctic Ice Sheet.

However, offshore and onshore geological records of past ice-sheet change are particularly sparse in this region, and the subglacial landscape has been little studied. Here, we describe the use of radio-echo sounding and ice-surface morphology data to characterise distinct physiographic regions of the ice-sheet bed in Coats Land. Our mapping reveals a widespread low-relief, seaward-dipping topographic surface immediately inland of the grounding line, which resembles similar features documented around the East Antarctic margin that are inferred to be remnants of once-contiguous coastal plains formed by fluvial erosion after the separation of East Antarctica from Gondwana (ca. 180 Ma) and prior to glaciation. The preservation of these landforms indicates a lack of intense, selective erosion of the surfaces throughout Antarctica’s glacial history.

We also identify deep subglacial troughs that crosscut (i.e., post-date) these pre-glacial erosion surfaces. The morphology of these troughs resembles that of typical half-graben basins associated with continental rifting; the overlying ice is largely stagnant, indicating that these features did not form beneath the modern EAIS. Based on these observations, geophysical measurements, and geomorphological and geochronological constraints from local nunataks, we infer that these troughs originally formed as ‘failed rift branches’ during Gondwana breakup and were subsequently overdeepened by ice in the Oligocene–Miocene (ca. 34–14 Ma), when ice first expanded to continental-scale but in a different configuration to the modern EAIS. Together, our observations provide new insights into the Mesozoic–Cenozoic tectonic and geological evolution of this sector of East Antarctica, as well as the long-term behaviour of the ice sheet that initially modified this landscape but now acts to preserve signatures of pre- and early-glacial processes.

How to cite: Paxman, G., Jordan, T., Bentley, M., and Small, D.: Subglacial topography of Coats Land records the geological evolution and past ice behaviour of the eastern Weddell Sea, East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11885, https://doi.org/10.5194/egusphere-egu25-11885, 2025.

Previous studies showed that during the Last Glacial Maximum one of the largest palaeo-ice streams around West Antarctica flowed along Belgica Trough in the Bellingshausen Sea. Based on radiocarbon dates on acid insoluble organic matter in shelf sediment core samples, grounding zone retreat has been interpreted as having started before the global glacial maximum and as having reached Eltanin Bay on the inner shelf before the start of the Holocene. A contributing factor to an early start to retreat could have been the fact that the continental shelf break in the trough is unusually deep (>650 m). Previous sparse bathymetry data showed that, unusually among palaeo-ice stream troughs on the continental shelves around West Antarctica, the shallowest part of the trough is on the middle shelf. The outer shelf part of the trough slopes down at a very gentle gradient towards the shelf edge, whereas inshore from the middle shelf “saddle” the trough is inclined more steeply towards a >1000 m deep basin in Eltanin Bay 

New multibeam bathymetry, acoustic sub-bottom profiler and multichannel seismic data were collected along the axis of Belgica Trough during RV Polarstern expedition PS134 in January and February 2023. These new data reveal a set of six grounding zone wedges (GZWs) on the gentle seaward-inclined slope from the middle to the outer shelf, with along-trough extents between 15 and 45 km and frontal heights between 20 and 40 m. A multichannel seismic profile shows the thickness of GZW deposits is mostly between 20 and 60 ms two-way time (~15–55 m) above angularly truncated older strata. The maximum thickness observed is 90 ms two-way time (70–80 m), at a location where deposits of one GZW extend over the backslope of an earlier one.  In contrast to the slope seaward of the mid-shelf saddle, we identify only three possible GZWs on the retrograde slope inshore from it, which are thinner and more widely spaced. The contrasting geomorphological character and GZW sediment volume either side of the mid-shelf saddle are consistent with what would be expected to result from a faster retreat with fewer pauses once the grounding zone moved onto the retrograde slope. The regularity of GZW formation on the seaward-inclined slope outboard of the mid-shelf saddle suggests the possibility of autocyclic ice stream behaviour during this phase of grounding zone retreat.

How to cite: Larter, R., Klages, J., Hillenbrand, C.-D., Dreutter, S., Weigelt, E., Uenzelmann-Neben, G., and Gohl, K. and the CoReBell Team: Change in geomorphological expression of palaeo-ice stream grounding zone retreat associated with change in bed slope along Belgica Trough, Bellingshausen Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13677, https://doi.org/10.5194/egusphere-egu25-13677, 2025.

The timing and nature of changes to the East Antarctic Ice Sheet (EAIS) and adjacent ocean since the Last Glacial Maximum (LGM) is still considered somewhat uncertain in the Weddell Sea region and at the Ronne-Filchner Ice Shelf. This is on account of high regional variability in ice-ocean dynamics, paired with a relative lack of sedimentary data from the Weddell Sea Embayment.  Here, we present a multi-proxy analysis of marine gravity core GC569 (77°15’.80S, 33°27’.93W), recovered from the Albert Trough offshore of Coats Land, East Antarctica.  GC569 is located close to several moraines and a post-glacial sediment drape. The sediments include both biogenic and terrigenous material and have been analysed using diatom assemblages, biomarker analysis, and XRF scanning. Here, we identify intervals of ice sheet retreat, changes to sea ice, and ocean-ice sheet interactions. We also assess the response of the marine biosphere to these Holocene environmental changes. This study will help to refine existing records and generate new data in an area of great uncertainty, enhancing the understanding of ice-ocean interactions in the South-East Weddell Sea and the East Antarctic Ice Sheet.

How to cite: Meddins, K., McClymont, E., Small, D., and Allen, C.: A Multi-Proxy Analysis of Holocene Ice-Ocean Interactions in the South-East Weddell Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13894, https://doi.org/10.5194/egusphere-egu25-13894, 2025.

The stability of the West Antarctic Ice Sheet (WAIS), crucial for preventing major future sea-level rise, is threatened by ocean-forced melting in the Pacific sector, especially in the Amundsen Sea. So far, direct evidence of the extent and rate of WAIS retreat during past warm periods has been lacking. Here, we analyzed detrital Nd, Sr, and Pb isotope data of sediments (<63 µm) recently drilled at International Ocean Discovery Program (IODP) Site U1532 on the Amundsen Sea continental rise to assess WAIS behavior, particularly the extent of its retreats, during glacial–interglacial cycles of the Pliocene (5.33–2.58 million years ago, Ma), a time warmer than present.

The Pliocene sediments of Site U1532 are marked by alternations of thick, gray, predominantly terrigenous laminated silty clays with relatively thin, greenish, biosilica-bearing/rich, bioturbated muds containing dispersed ice rafted debris (IRD), whose abundance usually increases towards the top of the muds. The IRD-bearing greenish mud intervals are typically less than 1.7 m thick and are characterized by a lower natural gamma ray (NGR) signal and negative a*-values. Fourteen prominent greenish mud intervals are identified between 4.65 Ma and 3.33 Ma. The diatom assemblages in the IRD-bearing muds are dominated by open water taxa, heavily silicified Fragilariopsis (F. barronii, F. interfrigidariata, and F. praeinterfrigidariata) and Dactyliozolen antarcticus, and significant biological productivity is indicated by relatively high diatom concentrations and elevated Ba/Ti ratios, which are a proxy for biogenic barium. The abundance of IRD and the presence of diatom taxa suggest that the IRD-bearing muds formed during interglacial periods, potentially reflecting past retreat events of the WAIS.

At Site U1532, we observe significant variations in Nd, Sr, and Pb isotopes of detrital sediments throughout glacial–interglacial cycles, indicating substantial changes in WAIS extent. A notable provenance signal emerges at the onset of some glacial intervals (3.88 Ma 3.6 Ma, and 3.33 Ma), characterized by high Pb (> 18.93 for ²⁰⁶Pb/²⁰⁴Pb) and low e_Nd (< –5 e_Nd) values. This distinct isotopic signature suggests long-distance supply of detritus sourced from plutonic rocks located in the continental interior. The presence of this material at Site U1532 indicates major inland retreat of the WAIS during the immediately preceding interglacials, which allowed icebergs to transport and deposit the detritus on the Amundsen Sea shelf. Our Pliocene records reveal multiple major inland retreats of the WAIS, highlighting the extent of possible WAIS response to ongoing global warming.

How to cite: Horikawa, K., Iwai, M., Hillenbrand, C.-D., Siddoway, C. S., Halberstadt, A. R., Cowan, E. A., Penkrot, M. L., Gohl, K., Wellner, J. S., Asahara, Y., and Shin, K.-C.:  Major West Antarctic Ice Sheet retreat events during the Pliocene: Evidence from the sediment provenance analyses of Amundsen Sea IODP U1532 records, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14512, https://doi.org/10.5194/egusphere-egu25-14512, 2025.

Deploying long-term, passive acoustic sensors in the polar ocean allows us to record a wide variety of sounds related to air-sea interactions, including icequakes from sea-ice, icebergs, and ice shelves, as well as vocalizations of marine mammals and ocean noise from human activities. The combination of these sounds in a specific location and time period is often referred to as the “soundscape,” and the characteristics of these sounds serve as a tool to monitor changes in the local ocean environment.

The Korea Polar Research Institute and NOAA/Pacific Marine Environmental Laboratory have jointly operated two Autonomous Underwater Hydrophones in Pine Island Bay and the Dotson Ice Shelf region in the Amundsen Sea during the periods of February 2020 to August 2022 and February 2022 to January 2024, respectively. The broadband cryogenic signals recorded at these sites exhibit correlations with local wind speeds and tidal forces. In the Pine Island Bay data, we detected signals from a large iceberg (B-49) that calved from the Pine Island Glacier ice shelf in February 2020, and noise levels steadily declined after 2020, coinciding with changes in sea ice concentration and the movement of icebergs and the ice shelf.

Seasonal variations in icequake activity were particularly prominent in the Dotson Ice Shelf region, with the highest noise levels occurring during the austral summer when nearby sea ice concentration approached zero. These signals were likely caused by iceberg movements in the nearby Bear Ridge region. Leopard seal vocalizations were successfully detected exclusively in the Dotson Ice Shelf region, whereas whale calls, commonly recorded in other Antarctic regions, were absent in both regions. Despite the logistical challenges and harsh environmental conditions associated with long-term hydroacoustic monitoring in polar regions, the data can help us understand environmental changes in the Southern Ocean and provide information about the status and trends of biodiversity.

How to cite: Yun, S., Lee, W. S., Dziak, R. P., Roche, L., Lee, C.-K., and Kim, B.-H.: Ocean Soundscapes in Antarctica's Amundsen Sea: Insights from Long-Term Hydroacoustic Monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14733, https://doi.org/10.5194/egusphere-egu25-14733, 2025.

In the recent past, the Antarctic ice sheet has experienced significant ice mass loss, which is suggested to be driven primarily by the intrusion of relatively warm deep waters on continental shelves. Given its vast ice shelves and bedrock below sea level, the West Antarctic Ice Sheet has been considered to be strongly sensitive to oceanic forcing and associated heat supply to its margins. Recently, however, also marine-based portions of the East Antarctic Ice Sheet (EAIS) were identified of reacting sensitively to oceanic changes with a direct consequence for rising sea levels as large subglacial areas such as the Aurora or Wilkes Basin hold a sea level equivalent of around 20 meters. So far, past EAIS dynamics and their interaction with ocean dynamics remain poorly understood. Here, we reconstruct past EAIS dynamics from ice-rafted detritus (IRD) counts and estimates of marine productivity in the Indian Southern Ocean. Our opal and carbonate percentages derive from sediment core PS141_49-3 (64° 55.795' S, 106° 51.606' E, 2454 m) retrieved during RV Polarstern Expedition PS141 on the upper East Antarctic continental slope offshore Vanderford Glacier, reaching back to marine isotope stage (MIS) 8, i.e., ~300 ka before present. During glacials, the dominant input of terrigenous sediments suggests a decrease of marine productivity, possibly due to enhanced sea-ice cover extending over the continental slope region. Deglacial phases coincide with high IRD input indicating enhanced iceberg discharge during periods of increased ice mass loss. In contrast, high interglacial opal contents suggest enhanced surface ocean productivity likely associated with a reduced seasonal sea-ice cover. Comparison of our findings with other marine records from offshore Sabrina Coast, Prydz Bay and Wilkes Land reveals consistency of this glacial-interglacial pattern to slope and abyssal sediments around the East Antarctic margin. Our data therefore contributes to an Indian Southern Ocean-wide perspective on terrigenous sediment mobilisation on the slope and EAIS-proximal marine productivity, likely controlled by the grounding line migration across the shelf, sea-ice extent, and oceanic heat supply towards the EAIS margin.

How to cite: Matzerath, P., Gottschalk, J., Müller, J., Lembke-Jene, L., Klages, J. P., and Krastel, S.: Glacial-interglacial variations in marine productivity and ice-rafted debris supply in the Indian Southern Ocean: Implications for East Antarctic ice sheet variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15496, https://doi.org/10.5194/egusphere-egu25-15496, 2025.

The East Antarctic Ice Sheet (EAIS) is often seen as less vulnerable to climate change than the West Antarctic or Greenland Ice Sheets, but studies show that some regions of the EAIS have been losing mass over recent decades. In particular, Wilkes Land, which overlies the Aurora Subglacial Basin, is thought to have been losing mass at accelerating rates over the past two decades. Several large outlet glaciers drain this region, but very few have been studied in detail. This paper presents new data on the recent ice dynamics of three outlet glaciers in Porpoise Bay, Wilkes Land. This includes Frost and Holmes glaciers, which may have generated almost a quarter of the EAIS’s sea-level contribution over the past four decades. We use optical satellite imagery and a range of previously published datasets to measure changes in the glacier terminus, grounding line position, ice surface velocity and ice surface elevation over the last three decades. These data are used to assess the likelihood of any dynamic imbalance and explore the potential drivers of change to help inform future projections of this critically important region.

How to cite: Weatherley, M., Stokes, C., and Jamieson, S.: Recent Changes in Ice Dynamics of Frost and Holmes Glaciers, Porpoise Bay, Wilkes Land, East Antarctica , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17788, https://doi.org/10.5194/egusphere-egu25-17788, 2025.

The Denman–Scott Glacier system in East Antarctica holds an ice-volume equivalent to 1.5 m of sea-level rise. Warm ocean waters under its ice shelf have the potential to drive ice mass loss, and the bedrock topography underlying the glacier makes it vulnerable to irreversible retreat. Worryingly, extensive grounding-line retreat and dynamic thinning have been observed over the last few decades. However, these observations are not long enough to determine whether this mass loss is unprecedented or reflects natural variability in the system.

We aim to extend the period of observations for the Denman-Scott glacier system from decades to millennia. As part of the Denman Terrestrial Campaign 2023-24 field season, we collected a series of geological records based on three main approaches: (1) ¹⁰Be and ¹⁴C dating of glacial erratics and bedrock on elevation transects adjacent to the glacier to directly constrain past ice-thickness change; (2) radiocarbon dating of isolation basin sediment cores and OSL dating of raised beach deposits in Bunger Hills to determine past sea-level and corresponding regional ice-mass change; and (3) cosmogenic nuclide analysis of shallow bedrock cores to test if the ice margin has been stable or fluctuating over recent millennia.

We present preliminary results that help reconstruct the magnitude and rate of past changes. This includes evidence of glacier thinning during the Holocene and relative sea-level fall of ~4 m over the last millennium. Further analysis will allow us to establish whether currently observed ice loss is unprecedented, and also determine the mechanisms that drove changes in the past, ultimately helping us to reduce uncertainty in future sea-level projections.

How to cite: Jones, R., O'Connor, J., Port, C., Tielidze, L., Mackintosh, A., May, J.-H., Fulop, R., Wilcken, K., Sefton, J., Saunders, K., and White, D.: Are Denman Glacier mass losses unprecedented in recent millennia?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17970, https://doi.org/10.5194/egusphere-egu25-17970, 2025.

The West Antarctic Ice Sheet (WAIS) is thought to be highly vulnerable to global warming. With this in mind, we analyzed sediments from the Ross Sea during the mid-Pliocene warm period (mPWP), the last period when atmospheric CO₂ levels were comparable to those of today. Using IODP site 1524 cores, we analyzed the organic carbon (OC) and total nitrogen contents and δ¹³C-OC values. The ~ 300,000-year interval between the Kaena top magnetic reversal (3.032 Ma) and the Mammoth bottom reversal (3.330 Ma) reveals 21 glacial beds characterized by strongly negative δ¹³Corg values (~ -28‰) and low OC-contents (<0.3 dw-dry weight-%). In contrast, interglacial layers exhibit δ¹³C values around ~ -25‰ and a consistent OC-content of ~0.6 dw% .We propose   the organic carbon deposited during glacial intervals was predominantly refractory carbon, eroded from continental rocks, whereas the interglacial intervals displayed a stronger contribution from marine primary productivity and/or terrestrial fluxes. Assuming the robustness of the paleomagnetic stratigraphy, the number of glacial beds within the mPWP interval indicates a frequency of approximately 14,000 years per glacial pulses, which is notably more dynamic than the obliquity-paced oscillations reported in previous studies.

How to cite: Sousa, I., Hillaire-Marcel, C., and de Vernal, A.:  High-frequency Antarctica climate oscillations during the mid-Pliocene Warm Period, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20491, https://doi.org/10.5194/egusphere-egu25-20491, 2025.

The middle Miocene climate optimum (c. 14.2 to 13.8 Ma), a significant warm period, was followed by a series of step-wise global cooling and Antarctic ice-sheet expansion events visible in marine isotope records (e.g., Holbourn et al., 2013), the oldest of which is termed the mid-Miocene climate transition. Associated episodes of ice-sheet instability and iceberg calving are recorded by ice-rafted debris in mid- to high-latitude marine sediment, accessible via deep-sea sediment cores around the Antarctic margin. Paleo-ice sheet models indicate that step-wise ice-sheet growth in part reflects ice expansion across previously ice-free low-elevation regions (Gasson et al., 2016; Halberstadt et al., 2021). Such predictions are amenable to testing by detrital provenance analysis of ice-rafted debris. However, the small-volume and mineralogically impoverished samples which are typically recovered from distal marine sediment preclude use of conventional accessory heavy-mineral proxies: instead, use of a rock-forming mineral is necessitated. 

Here, we present in-situ Rb-Sr, Ar-Ar, and Pb-isotope data from ice-rafted K-feldspar collected from mid-Miocene marine sediment in the Weddell Sea (Neofitu et al., 2024) and offshore Prydz Bay. Source regions for these depocenters respectively include the Recovery and Aurora sub-glacial basins, where ice-sheet embayment formation during warm periods is predicted. Our data suggest that the Wilkes and Aurora subglacial basins were free of marine-terminating ice during the middle Miocene climate optimum. During the transition, ice advanced to the coast across the Aurora sub-glacial basin, and both the Recovery and Aurora basins at least intermittently hosted marine-terminating ice during the subsequent cooling step.

Halberstadt et al., 2021, EPSL, 564, 116908, 10.1016/j.epsl.2021.116908;

Holbourn et al., 2013, Paleoceanography 28, 688–699, 10.1002/2013PA002538;

Gasson et al., 2016, PNAS 113, 3459–3464, 10.1073/pnas.1516130113;

Neofitu et al., 2024, EPSL, 641, 118824, 10.1016/j.epsl.2024.118824.

How to cite: Mark, C., Neofitu, R., Rösel, D., Zack, T., Barfod, D., Mark, D., Flowerdew, M., O'Connell, S., Kelley, S., Halpin, J., and Daly, J. S.: Where did the ice reach the sea? The utility of coupled K-feldspar Rb-Sr, Ar-Ar, and Pb-isotope analysis applied to mid-Miocene ice-rafted debris in Antarctic marine sediment , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12219, https://doi.org/10.5194/egusphere-egu25-12219, 2025.