Orals: Wed, 30 Apr | Room 1.61/62
While most of West Antarctic ice shelves are thinning due to ongoing oceanic warming, East Antarctic ice shelves, except a few ones, are apparently more stable. East Antarctica represents most of the ice volume stored on the Antarctic continent. Understanding its potential response to climate warming through its history can inform the implementation of adaptation plans and associated costs. Combining geological observations and knowledge with the glaciological and climatic observations of the past decades can help understand how East Antarctica responds to climate warming in general. Paleoclimate have now the potential to provide insights on processes and interactions, where present-day glaciological and oceanic observations networks fail, for example, within cavities. With the technological progresses and the advances in understanding of ice-ocean or ice-atmosphere interactions, our understanding of the role of Antarctica in the climate system has made some progresses. But numerous knowledge gaps remain and rely on our capacity to set-up successful expeditions to explore the mostly unknow East Antarctic margins.
How to cite: Colleoni, F. and the Members of the SCAR INSTANT Scientific Programme: Exploring East Antarctica from past to future, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3689, https://doi.org/10.5194/egusphere-egu25-3689, 2025.
Along with glaciers, polar ice sheets are a major contributor to sea level rise and their losses are accelerating. Since 2012, intercomparison exercises have combined estimates of ice sheet mass change from various methods (gravimetry, altimetry and input/output method). However, the consensus displayed in these intercomparisons hides sometimes strong divergences between these different methods because each one presents drawbacks. In particular, the altimetry method, whether based on radar or laser measurements, has a resolution of generally one kilometer. This resolution, although perfectly suited in the central and flat areas of the polar ice sheets, does not allow to solve the complexity of the elevation changes of the coastal glaciers, especially along the sloping coasts of the Antarctic Peninsula and Greenland. Yet, it is at their margins that ice sheets respond dynamically to rising atmospheric and oceanic temperatures.
The objective of the study is to build high resolution estimates of ice sheet elevation changes. It exploits an archive of stereo pairs acquired by the SPOT5-HRS sensor mostly during the International Polar Year (IPY, 2007-2009) to build a topography of the polar ice sheet periphery. A vertical correction of each digital terrain model (DEMs) is performed using the elevation measurements, partly simultaneous, of the ICESat laser altimeter (2003-2008). This IPY topography is then used as a reference to estimate more than 15 years of volume changes of the ice sheet periphery by comparison with measurements from recent missions, in particular ICESat-2 and REMA (Reference Elevation Model of Antarctica) /ArcticDEM.
The Antarctic Peninsula was selected to develop the methodology and to estimate 15 years of evolution. This is one of the regions where recent estimates of mass loss diverge the most and where glacier dynamics are complex. The elevation change maps reveal, at a high resolution, the spatial pattern of changes over the past 15 years.
How to cite: Bernat, M., Berthier, E., Dehecq, A., MC Belart, J., and Youssefi, D.: Mass losses of the Antarctic Peninsula. New constraints from stereoscopic imagery and laser altimetry., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1428, https://doi.org/10.5194/egusphere-egu25-1428, 2025.
The near-surface stratigraphy of ice sheets provides a unique archive of past specific surface mass balance (SMB), usually on the order of years to millennia. In the context of ongoing climate change, a warming atmosphere is expected to increase SMB over the East Antarctic plateau due to enhanced snowfall. However, the scarcity of observational data across this vast region complicates the quantification of recent SMB changes, contributing to uncertainties in future sea level projections.
In this study, we reconstruct SMB over the last millennium along 3,000 km of airborne radar profiles on the plateau in Dronning Maud Land, East Antarctica. Multiple internal reflection horizons in the firn column are traced in the ultra-wideband radar data. The flight lines overlap with firn core positions, which allow dating of the horizons and thus an interpretation of the data as a proxy for time-averaged SMB. More specifically, we cover decadal to centennial time intervals going back to the 12th century. The spatial variability (coefficient of variation) reaches more than 120% of the mean value inferred at the firn cores.
For time periods prior to 1975, we find temporally and spatially stable SMB patterns that do not change significantly within our error estimates. After 1975, the data suggest an increase of specific SMB up to 30%. We use environmental information such as wind direction and surface slope to generate spatial SMB fields that highlight spatio-temporal SMB changes. We also present robust uncertainty estimates that will help refine sea level projections and improve our understanding of East Antarctica’s role in the global climate system.
How to cite: Zuhr, A. M., Franke, S., Eisen, O., Muhle, L. S., Schlegel, R., Steinhage, D., Hörhold, M., and Drews, R.: Exploring spatiotemporal patterns of surface mass balance in East Antarctica: Insights from Dronning Maud Land using airborne radar observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5596, https://doi.org/10.5194/egusphere-egu25-5596, 2025.
The intrusion of relatively warm Circumpolar Deep Water (CDW) onto the Antarctic continental shelf is widely recognized as a threat to ice shelves and glaciers grounded below sea level, as enhanced ocean heat increases their basal melt. CDW incursion onto the continental shelf is currently causing ice mass loss, thinning and extensive grounding line retreat of the Totten Glacier (Sabrina Coast), which drains one of the vastest East Antarctic subglacial basin complexes, the Aurora-Sabrina subglacial basin, and holds more than 3.5 m of Sea Level Equivalent (SLE). Another ice stream, the Ninnis Glacier, buttressing a large sector of the East Antarctic Ice Sheet (EAIS), is currently losing mass, although its melting from CDW incursion near the grounding zone is prevented by the formation of Antarctic Bottom Water that currently maintains a cold subglacial cavity. However the geological record indicates that the Ninnis glacier retreated inland during past warmer and prolonged interglacials, e.g., the Marine Isotope Stage 11 about 425 Ky ago. While the intrusion of warm water has been documented on the East Antarctic continental shelf, the locations where such warm water transport is sustained through time are still uncertain. The recognition of preferential conduits for enhanced CDW incursions toward the ice grounding zone is key to predict rates and modes of future responses of major Antarctic marine-based ice streams, such as the Totten and the Ninnis glaciers. We provide new evidence of the role of East Antarctic submarine canyons in conveying southward flowing currents that transport CDW toward the shelf break, thus facilitating relatively warm water intrusion on the continental shelf. The discovery of dozen-meter-thick sediment drifts on the eastern flank of the canyons testifies to the occurrence of sustained southward-directed bottom flows potentially prone to enhanced ocean heat transport toward the continental shelf. The investigated canyons and sediment drifts indicate that long-lasting flow of CDW onto the continental slope and rise have occurred offshore of both the Aurora and Wilkes sub-glacial basins, thus likely helping trigger and/or accelerate the destabilization of these key marine based sectors of the EAIS, with implications to global sea level both in the past and future. New, deep sediment archives from the sediment drifts flanking these canyons are, however, required to document the response and sensitivity of the EAIS, particularly the marine-based Aurora Basin system, to climate changes throughout the Neogene especially during warmer than pre-industrial climate states. To partially fill this knowledge gap, the new, multidisciplinary DIONE project, funded by the Italian Antarctic Research Program (PNRA), will collect geological, geophysical and oceanographic data, which will provide a comprehensive reconstruction of the climatic and environmental evolution of the Sabrina Coast since the Pliocene. However, a complete history of the ice sheet-climate interactions will only be achieved with a new deep sea drilling campaign.
Donda F., et al 2024. Footprint of sustained poleward warm water flow within East Antarctic submarine canyons. Nature Communications, 15, 6028 (2024) https://doi.org/10.1038/s41467-024-50160-z
How to cite: Donda, F., Rebesco, M., Kovacevic, V., Silvano, A., Bensi, M., De Santis, L., Rosenthal, Y., Torricella, F., Baradello, L., Gei, D., Leventer, A., Post, A., Leitchenkov, G., Noble, T., Zgur, F., Cova, A., O'Brien, P., and Romeo, R.: Footprint of sustained poleward warm water flow within East Antarctic submarine canyons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7999, https://doi.org/10.5194/egusphere-egu25-7999, 2025.
Changes in flow speed of large Antarctic outlet glaciers are a key indicator of the stability of the ice sheet. West Antarctica, primarily along the Amundsen Sea facing coast, is known to be in dynamic imbalance and losing significant mass, but a less clear picture exists in East Antarctica. Observing ice dynamic change in East Antarctica, and identifying its drivers, will allow us to better constrain estimates of future ice mass loss.
The Cook Glacier system in George V Land drains a large volume of ice from the Wilkes Subglacial Basin. This is one of the largest regions in East Antarctica susceptible to the marine ice sheet instability and contains 3-4m of sea level rise equivalent. Cook Glacier has two distinct flow units: Cook West Glacier (CWG), which has a readily calving ice front near the grounding line; and the slower but larger Cook East Glacier (CEG), which flows into an extensive ice shelf.
By offset tracking of high-resolution imagery from the Sentinel-1 synthetic aperture radar satellites, we generate a dense data cube of ice velocity observations in this region from 2015-2024. In this period, ice speeds on CWG have followed a sinusoidal pattern (with an approximately 2-year period), superimposed on a positive linear trend. Meanwhile, neither this variability nor trend have been observed on CEG, where the speed of grounded ice has been stable through the study period.
To investigate drivers of this speed variability on CWG we compare our dense time series of ice speed observations with climate reanalysis data. We present the propagation and timings of speed change along CWG and using the Copernicus Marine Service Global Ocean Physics reanalysis and ECMWF ERA5 atmospheric reanalysis, investigate correlation of this variability with environmental variables including wind speed, air temperature, ocean temperature, sea surface height, and surface pressure.
How to cite: Slater, R. A. W., Hogg, A. E., Dutrieux, P., and Wallis, B. J.: Drivers of recent ice speed variability on Cook West Glacier, East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12810, https://doi.org/10.5194/egusphere-egu25-12810, 2025.
Adjacent to Thwaites Ice Shelf in the Amundsen Sea, Antarctica, Dotson Ice Shelf is experiencing rapid grounding line retreat and high melt rates. Here we present oceanographic observations from a propeller-driven autonomous underwater vehicle sent into the Dotson Ice Shelf cavity, to study the inflow of relatively warm water into the cavity.
In February 2022, during the TARSAN research voyage on RV Nathaniel B Palmer, an Autosub Long Range (ALR) completed four missions under Dotson Ice Shelf. The mission tracks ventured ~20km into the eastern cavity (inflow region) and ~40km into the central cavity (central trough), with one mission travelling along the ice-shelf front. During its missions, the ALR recorded seawater temperature and salinity, chlorophyll concentration and turbidity, current velocity, and turbulent microstructure approximately 80 m above the seabed.
We present an analysis of this unique dataset. Turbulent energy dissipation rate (ε) in the cavity is on the order of 10-10 to 10-8 W/kg. Outside of the cavity ε is higher, with values ranging from 10-9 to 10-8 W/kg. These values are similar to ε values measured under Pine Island Ice Shelf. We are able to show that turbulent mixing is higher in the inflow and bottom intensified, it is influenced by interactions with bathymetry and current speed. Our measurements are able to resolve the warm, dense inflow of water in the eastern cavity with average southward velocities of -7 cm/s at the ice shelf front and variable flow patterns deep into the central cavity. We show the near-bed currents in context with water-mass properties, turbulence, and conditions in the embayment immediately in front of Dotson. This dataset opens up exiting opportunities for collaboration, including with other datasets collected in the Dotson Ice Shelf cavity during the TARSAN campaign and with modelling efforts.
How to cite: Richter, M. E., Heywood, K., Hall, R., and Wåhlin, A.: Observations of turbulent mixing and ocean currents in Dotson Ice Shelf cavity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-951, https://doi.org/10.5194/egusphere-egu25-951, 2025.
East Antarctic Ice Sheet (EAIS) dynamics are source of uncertainty in past and future sea level variations. The assessment of the EAIS stability lies on a lack of data, especially since the Last Glacial Maximum (LGM). Although previous works focused on the LGM ice sheet front at the shelf break or its modern position reached ~8 ka ago, these offshore marine records did not document the post-LGM to Holocene ice sheet fluctuations driven by climatic or oceanic circulation variations. In Adélie Land (136°E-142°E), glacial landforms (i.e., morainic ridges, erratics and glacially polished bedrocks) as well as sedimentary deposits (i.e., along the Adélie bank) suggest multiple post-LGM oscillations of the EAIS front position which have not yet been fully assessed so far. With a new set of cosmogenic nuclides data on well preserved terrestrial and marine archives, we aim to shed new light on the EAIS response to both climatic and oceanic changes with improved spatial and temporal resolution.
We propose new data using terrestrial cosmogenic nuclides - 10Be and 26Al - from morainic ridges (Lacroix moraine) and glacially-polished bedrocks scattered on the Pointe Géologie archipelago (Dumont d’Urville basecamp). We combine these results with more distal marine data proxies through meteoric 10Be/9Be ratios measured on the authigenic phase of the sediment core MD03-2601 (66°03.07’S; 138°33.43’E, 746m water depth), collected on the continental shelf of Adélie Land and already investigated with environmental proxies over the Holocene.
10Be/26Al exposure dating of glacially polished bedrocks displays complex exposure histories and diachronous timing for ice sheet retreat along the coastline and within Pointe Géologie archipelago. Here, the onset of ice sheet retreat appears to range from > 60 ka to the LGM period, linked to the Astrolabe ice-stream dynamics. In contrast, the inland Lacroix moraine documents a more recent deglaciation period around 2.5 ka. These terrestrial deposits thus record non-synchronous late-Pleistocene ice sheet dynamics and final withdraw along the Terre Adélie.
Comparatively, in the marine sediment core, we evidence a major meteoric 10Be input around 6 ka associated to changes in sedimentation rates. Based on the distal core location, we propose this event to be linked with either a modified Circumpolar Deep-Water or easterly currents incursions. 9Be data are in agreement with other environmental proxies and record ice-sheet oscillations: (1) a major ice-sheet re-advance and detrital input at 4.2ka; and (2) ice-sheet retreat since around 2.5 ka, synchronous to deglaciation ages on the coast. Our results record at least three main oscillations of the EAIS at different space and time during the late Pleistocene to Holocene period, illustrating its sensitivity to short-term climate forcing.
How to cite: Péan, M., Rolland, Y., Valla, P., Braucher, R., Schimmelpfenning, I., Crosta, X., Étourneau, J., Jomelli, V., Favier, V., and Louis, M.: Late Pleistocene to Holocene fluctuations of the East Antarctic Ice Sheet in Adélie Land using cosmogenic nuclides: combining in situ 10Be/26Al on glacial landforms with meteoric 10Be in marine sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1662, https://doi.org/10.5194/egusphere-egu25-1662, 2025.
The East Antarctic Ice Sheet (EAIS) has long been assumed to remain relatively stable under current climatic forcing. Recently, however, this assumption has been challenged by the observation of increased ice mass loss, improved subglacial topography data, and extensive geological and geophysical data of past glacial change from the Sabrina Coast. Glacial-marine sediments deposited on the continental shelf, slope, and rise record past ice sheet expansion and retreat periods that have occurred since the onset of Southern Hemisphere glaciations. The Vanderford Glacier is the main glacial outlet in Vincennes Bay (eastern Mawson Sea shelf), which together with the Totten Glacier drains the large Aurora Subglacial Basin.
We use deep-penetrating seismic reflection data collected during the RV Polarstern Expedition PS141 (EASI-3) in early 2024 combined with existing data to construct a seismic stratigraphic model of the continental shelf, slope, and rise in Vincennes Bay. The newly acquired seismic data reveal pre-glacial sedimentary strata and glacially-transported sequences on the continental shelf and slope in a previously unmapped area near the Vanderford Glacier. We analyze pre-glacial and glacial sedimentation processes on the East Antarctic continental shelf in this region, which so far remained poorly constrained. This allows us to decipher dominant phases of early Oligocene to Pleistocene EAIS development in this sector.
Long-distance seismic horizon correlation with deep-sea scientific drill records from DSDP, ODP, and IODP sites in the northern Mawson Sea, Prydz Bay, and offshore Wilkes Land provides age estimates for the seismostratigraphic sequences on the continental shelf. The earliest clear indications of grounded ice advancing onto the middle continental shelf are inferred in the Early Miocene (~24-14 Ma) from buried subglacial channel systems. The middle shelf consists of older preglacial sequences of Late Cretaceous to Late Miocene age and is overlain by a much younger (Quaternary?) gigantic grounding zone wedge. The outer continental shelf is dominated by prograding glacially-transported sequences of inferred Late Miocene to Pliocene age (14-5 Ma), indicating repeated advances of grounded ice with a high sediment influx from the hinterland. In contrast to the neighbouring Totten Glacier of the Sabrina Coast, the distribution of glacial sedimentary features across sequences suggests that the EAIS was more stable in the Vincennes Bay region, highlighting how differently these two systems might have reacted to changing conditions.
How to cite: Mühlberger-Krause, T., Gohl, K., Hochmuth, K., Barrett, R., Leitchenkov, G., Tobisch, C., Klages, J. P., and Krastel, S.: Past ice sheet dynamics from seismic reflection data of Vincennes Bay, East Antarctica – was the Vanderford Glacier more stable than presumed?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4396, https://doi.org/10.5194/egusphere-egu25-4396, 2025.
The Thwaites Interdisciplinary Margin Evolution (TIME) project, part of the International Thwaites Glacier Collaboration (ITGC), examines the physical processes and properties at the Eastern Shear Margin of Thwaites Glacier in West Antarctica using geophysical imaging and monitoring. During 2023-24, the TIME field team collected controlled-source seismic reflection and refraction data across the Thwaites’ Eastern Shear Margin, with 1000 3-component seismic nodes deployed in a 27-km line and a 3-km by 5.5-km seismic grid. We detonated 671 seismic sources, mostly “Poulter” sources with 4-kg explosive boosters suspended on a 6-foot bamboo pole. We use these controlled-source seismic data to image the shear margin in two and three dimensions, including englacial, bed, and sub-ice geologic imaging and interpretation. Seismic sources were recorded with high signal to noise ratios across the full extent of the seismic line and grid and penetrated into the bed beneath the ice (~2000-km-thick). We present two- and three-dimensional seismic reflection images of the shear margin environment as well as seismic refraction velocity models. We compare the seismic images and seismic refraction velocity models to co-located airborne radar data. The seismic images, seismic velocity models, and radar data shed new light on physical properties of the ice and bed across the shear margin.
How to cite: Karplus, M., May, D., Zhang, Z., Nakata, N., Kaip, G., Ayala Cortez, S., Gonzalez, L., Seldon, Y., Pretorius, A., Walter, J., Booth, A., Young, T. J., and Tulaczyk, S.: Controlled-source seismic imaging of the Eastern Shear Margin of Thwaites Glacier , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14849, https://doi.org/10.5194/egusphere-egu25-14849, 2025.
There is little known about dynamics of mélange inside large rifts in Antarctic ice shelves and its role in rift propagation and the weakening of shelf stability. This lack of knowledge hinders our capability for long-term forecasting of the Antarctic ice sheet contribution to global sea level rise. We propose an innovative multi-temporal DEM adjustment model (MDAM) that builds a multi-satellite DEM time series from meter-level resolution small DEMs across large Antarctic ice shelves by removing biases, as large as ~6 m in elevation, caused by tides, ice flow dynamics, and observation errors. Using 30 REMA and ZY-3 sub-DEMs, we establish a cross-shelf DEM time series from 2014 to 2021 for the Filchner-Ronne Ice Shelf, the second largest in Antarctica. This unified and integrated DEM series, with an unprecedented submeter elevation accuracy, reveals quantitative 3D structural and mélange features of a ~50 km long rift, including rift lips, flank surface, pre-mélange cavities, and mélange elevations. We report that while the mélange elevation decreased by 2.1 m from 2014 to 2021, the mélange within the rift experienced a rapid expansion of (7.93±0.03) × 109 km3, or 130%. This expansion is attributed to newly calved shelf ice from rift walls, associated rift widening, and other factors related to rift-mélange interactions. The developed MDAM system and the 3D mélange dynamics analysis methods can be applied for research on ice shelf instability and the future contribution of the Antarctic Ice Sheet to global sea level rise.
How to cite: Li, R., Xia, M., Scaioni, M., An, L., Li, Z., and Qiao, G.: 3D characterization of mélange dynamics inside large rifts in Filchner ice shelf in east Antarctica , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15117, https://doi.org/10.5194/egusphere-egu25-15117, 2025.
Recent intercomparisons of ice sheet mass balance estimates derived from altimetry and from the input output method (IOM) have revealed significant discrepancies for the East Antarctic Ice Sheet. Modelled SMB, as a main input to the IOM, differs considerably between different models.
We explore comparisons between the altimetric mass balance method and the IOM for selected subregions of the Antarctic Ice Sheet. Rather than evaluating entire drainage basins, we aim at regions for which uncertainties in the horizontal mass flux through the region boundaries as well as in the altimetric mass balance are small. For this purpose, we choose subregions of the East Antarctic Plateau. We explore the hypothesis that this allows us to benchmark SMB modeling results in these regions, assuming that SMB is the most uncertain part in a comparison of net mass flux and altimetric mass change.
We apply the IOM using outputs from different SMB models (such as RACMO and MAR). We apply the altimetric method using different altimetric surface elevation change products (such as CryoSat2-AWI, and Multi-mission-JPL, ICESat-2-ATL-15) as well as firn air content changes from firn densification models (such as IMAU-FDM). We perform the evaluation for different regions with sizes ranging from about 6x104 to 1.5x102 km2 and for different time intervals, such as 1992-2019, or 2010-2019, or 2019-2024.
Discrepancies between the mass-flux-based IOM mass balance and the volume-based altimetric mass balance are significant for a number of regions, time intervals, and choices of input data product. The discrepancies are up to the order of some 10 percent of the SMB of the region. In particular, discrepancies (or their absence) are sensitive to input SMB modeling results. In the light of uncertainties assessed for all inputs, we discuss conclusions regarding the evaluation of SMB modeling results.
How to cite: Langen, T., Horwath, M., Helm, V., van den Broeke, M. R., Kappelsberger, M., and Willen, M. O.: Assessing the consistency of modelled surface mass balance and observed ice flux and surface elevation change on the East Antarctic Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18616, https://doi.org/10.5194/egusphere-egu25-18616, 2025.
Ice rises and rumples are common features of the Antarctica ice sheet margin that appear where thick ice shelves are grounded to an underlying shallow submarine bank. The ice rises buttress ice flow, partly controlling the extent of both grounded and floating ice. Here we reconstruct the unpinning of the Ross Ice Shelf (RIS) from Ross Bank, a broad, shallow submarine bank located approximately 100 km north of the current RIS calving front in the central Ross Sea. The Ross Bank Ice Rise formed after the retreat of grounded ice from the adjacent deep-water Glomar Challenger and Pennell troughs following the Last Glacial Maximum. High resolution seafloor bathymetry reveals small-scale, concentric backstepping moraines marking the progressive contraction of the edges of the ice rise toward the shallow bank crest. Kasten and piston cores from the crest recovered clay-poor, winnowed glacimarine sediment rich in carbonate macrofossils, with radiocarbon ages indicating that the unpinning proceeded over several thousand years. The long-lived pinning point eventually failed, with the RIS fully unpinning from the shallowest crest by 4160 ± 20 14C year BP (uncorrected). This ultimately led to the shift of the RIS calving front to its current location. Our reconstructions validate concerns that destabilizing ice rises could lead to significant reorganization of grounded and floating ice.
How to cite: Bart, P., Prothro, L., Leventer, A., Venturelli, R., Majewski, W., Danielson, M., Lindsey, B., Szemak, M., Meyne, R., Tenti, M., Ruggiero, J., and He, S.: A Holocene Collapse of a Ross Ice Shelf Ice Rise, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20649, https://doi.org/10.5194/egusphere-egu25-20649, 2025.
The evolution of Thwaites Glacier represents the largest uncertainty in sea level rise forecasts over the next few centuries. To address this concern, the International Thwaites Glacier Collaboration (ITGC) was co-sponsored by the US and UK polar research agencies with contributions from Sweden, Germany, and South Korea. The program investigated all aspects of the climate-ice-ocean-earth system in the Thwaites-Amundsen region, in eight coordinated projects. Several of the scenarios of highest concern for rapid increase in ice flux from the system are found to be less likely than initially thought. However, newly discovered processes that could accelerate ice loss, and additional considerations of the processes investigated, mandate that the region receive continued focus. Modelling and observational data show that the impending loss of the remaining ice shelf will result in only a small (order 10%) increase in grounded glacier flow speed, at least initially. Runaway ice cliff failure, while a valid process with several forms, is difficult to sustain in model scenarios so far; however, concerns remain about the effects of damaged ice on the ice-cliff calving thresholds and rates. Studies of the Holocene and recent pre-satellite evolution of the system show that the region has experienced very rapid retreat in the recent past, and that ice elevation near the Holocene Optimum was around 35 m lower than the present day, but then recovered as climate slowly cooled and bed elevation increased due to glacial isostatic adjustment to ice loss following the Last Glacial Maximum. Modern retreat at the Thwaites and Pine Island glaciers appears to have been initiated in the 1940s after a series of very strong El Niño–Southern Oscillation (ENSO) effects. In considering the future retreat and ice loss from the Thwaites catchment, studies of the shear margins and bed imply that further ice loss will likely widen the glacier, and that the pattern of mixed resistant and slick bed conditions will actually lead to slightly faster retreat of the Thwaites Glacier basin in the coming centuries. Lastly, significant concerns remain about a tidal pumping process, inferred from satellite and field observations as part of the project, that may be driving warm near-bottom seawater several kilometers upstream of the nominal grounding line. This process, and in general the oceanography near the ice front and basal geology of the glacier bed, remain areas in need of continuing study by the community.
How to cite: Scambos, T., Larter, R., Davis, P., Karplus, M., Dinar, A., and Turrin, M. and the The International Thwaites Glacier Collaboration: Research results and new frontiers for the International Thwaites Glacier Collaboration, 2018-2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2904, https://doi.org/10.5194/egusphere-egu25-2904, 2025.
The thick and cold East Antarctic Ice Sheet (EAIS) is apparently stable and melts only slightly due to atmospheric warming. However, it is predicted that the EAIS sectors, whose base is below sea level, will partially shrink or retreat over the next three centuries, mainly due to ocean warming. One of these sectors is located in George V Land (GVL), where ice flow and ice mass loss have increased in recent decades. The intrusion of warm Circumantarctic Deep Water (CDW) was observed between 1996 and 2019 in the mid-continental shelf of GVL off the Ninnis Glacier, but did not reach the subglacial sea cave. Whether and when this phenomenon will progress and lead to ice melt and dynamic changes in the GVL sector remains to be proven.
We present a new geomorphologic map and sedimentary paleoceanographic archives obtained from the GVL continental margin in front of the Cook and Ninnis glaciers by the Cook glacier-Ocean Antarctic Past Stability (COLLAPSE) project funded by the Italian Antarctic Research Program (PNRA), providing evidence for their fluctuations and instability during the Pleistocene. Our results show that the Cook and Ninnis glaciers responded to increased continental shelf warming with partial melting and calving.
Our analysis reconstructs the erosion and deposition processes on the continental slope and sheds light on the dynamics of the EAIS and its interaction with the bottom current during warmer periods with increased CDW rise on the slope. The Pleistocene was the coldest period of the last 100 million years on Earth, during which the Antarctic ice sheet remained roughly stable even during the interglacials. The global sea level change was mainly caused by the volume fluctuations of the Northern Hemisphere ice sheet. Our results show that the marine EAIS sector of the GVL responded to ocean warming and thus contributed to global sea level changes, although major ice mass loss occurred before MIS 9, possibly as a consequence of prolonged warm climate periods such as MIS11.
How to cite: De Santis, L. and the Cook glacier-Ocean Antarctic Past Stability (COLLAPS) project scientific team: Were the Cook and Ninnis glaciers stable in the Pleistocene?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4186, https://doi.org/10.5194/egusphere-egu25-4186, 2025.
Reconstructions of the East Antarctic Ice Sheet based on geological records commonly assume that the relationship between a given proxy and changes in ice mass remains constant in time, and that this relationship is independent of climate state. This assumption, however, has yet to be comprehensively tested. To address this shortcoming, we use a coupled ice sheet--ice shelf model representing an East Antarctic-type ice sheet to determine how ice sheets respond to ocean--atmosphere states ranging from warm and wet with weak ocean forcing, to cold and arid with strong ocean forcing.
We find that where warm climates are accompanied by a weak sensitivity to ocean forcing, net ice volume oscillates in phase with oceanic and atmospheric forcing, whereas under cold climates with strong ocean forcing the behaviour is anti-phased. Transitions between these two regimes are characterised by ice volume fluctuations that resonate at half the frequency of the forcing. Calving, reflecting ice discharge, exhibits a highly complex relationship to imposed forcings, transitioning from smooth oscillations to abrupt pulses as the dominance of ocean forcing increases.
Focusing on the evolving balance between surface melt, basal melt, and calving, we are also able to demonstrate that the local Shannon entropy signature of our simulations maps out specific ice sheet regime types. Under both warm and cold extremes the ice sheet exists in a low entropy state of high predictability. Between these end-members, however, the ice sheet exhibits less predictable and more variable behaviour, characterised by overall higher entropy but also abrupt flickering between states. The transition from the cold to intermediate regime can occur under an atmospheric temperature change of as little as 0.5 - 1 K, whereas the transition to the warmest regime occurs over a 1 - 2 K range.
Our findings are based on an ensemble of coupled ice sheet--ice shelf model simulations totalling 100 million model years, spanning climates from five degrees colder than present to fifteen degrees warmer than present. As such they provide a comprehensive framework for interpreting future East Antarctic Ice Sheet changes over multi-centennial to multi-millennial timescales. Most importantly, our results suggest that ice sheet reconstructions based on geological proxy records must take into account the background climate state and behavioural regime of the ice sheet in order to be most accurate.
How to cite: Golledge, N., Levy, R., Meyers, S., Weber, M., Clark, P., Burns, J., Ishii, H., Knahl, H., Lowry, D., McKay, R., Naish, T., Grant, G., and Sullivan, N.: East Antarctic Ice Sheet regime shifts during climate transitions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1272, https://doi.org/10.5194/egusphere-egu25-1272, 2025.
Thomas Island (Bunger Hills, East Antarctica) is a 34 square kilometre, deglaciated area potentially impacted by the East Antarctic ice sheet and Remenchus Glacier from the east, Shackleton Ice Shelf from the north and Edisto Glacier from the west. Its glacial geology reveals a complex interplay between these ice masses, which operate with different spatial and temporal dynamics. This poster maps glacial erosional and depositional features and allows inference of the history of ice advance and retreat, and sets a framework for quantitative dating of its deglaciation history. Overriding by the ice sheet created flutes and striations, showing regional iceflow to the northwest. Retreat of ice from this advance was succeeded by a shelf glacier impinging from Edisto Channel to the north and Cacapon Inlet to the south, creating moraine ridges along the northern and southern shores. The final stage of glaciation occurred via the tongue of Edisto Glacier impacting the island from the southwest, creating prominent moraine ridges along the island’s western edge. This is a more complex history than hitherto appreciated for the main oasis forming southern Bunger Hills.
How to cite: Gore, D., Berg, S., Whitmore, R., Weber, M., Wagner, B., Scheidt, S., Lange, T., Howard, A., Dägele, D., and White, D.: Glacial geology of Thomas Island, Bunger Hills, East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15311, https://doi.org/10.5194/egusphere-egu25-15311, 2025.
Recent observations and model simulations show that the inflow of warm Circumpolar Deep Water (CDW) causes rapid and significant melting and thinning of the ice shelves of the West Antarctic Ice Sheet, contributing to the ongoing increase in the discharge of grounded ice. This process is also thought to contribute to the deglaciation of the West Antarctic Ice Sheet after the Last Glacial Maximum (LGM). However, the role of the CDW in a potential large-scale ice-mass loss in East Antarctica is largely unknown. In this study, we present new, well-dated sedimentary core records of the ice sheet and ice shelf retreat since the LGM, including a signature of the ice shelf collapse in Lützow-Holm Bay (LHB), eastern Dronning Maud Land, East Antarctica. Foraminiferal C-14 ages indicate the ice shelf collapses occurred at ca. 9 ka, which is consistent with the initiation of the thinning of the East Antarctic Ice Sheet revealed by Be-10 surface exposure dating along the southern coast of the bay. In addition, foraminiferal carbon isotope data from the cores suggest that the CDW inflow had intensified and reached the southern coast during this period. Using a hierarchical modelling approach that combines climate and high-resolution ocean simulations, we find that freshwater discharge from adjacent sectors of the AIS into the Southern Ocean likely enhanced regional CDW inflow into submarine troughs in the LHB between 10 and 9 ka. Our results suggest that a series of cascading tipping points propagated around the Antarctic margin during the last glacial termination, highlighting the importance of feedbacks between meltwater input, CDW intrusion onto the continental shelf, ice shelf stability and ice sheet dynamics, and relative sea level rise for both historical and future changes in the AIS.
How to cite: Suganuma, Y., Itaki, T., Haneda, Y., Kusahara, K., Obase, T., Ishiwa, T., Omori, T., Ikehara, M., McKay, R., Seki, O., Hirano, D., and Fujii, M.: Holocene Ice Shelf Collapse and Subsequent Antarctic Ice Sheet Retreat in Lützow-Holm Bay, East Antarctica, Driven by Warm Deep Water Inflow and Sea Level Rise, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5515, https://doi.org/10.5194/egusphere-egu25-5515, 2025.
The future behaviour of the Antarctic Ice Sheet is considered as one of the largest unknowns in global climate predictions and dramatically accelerated ice loss has been observed over the past few decades for numerous of its drainage basins. However, those records only reflect a short moment of limited informative value when considering the length of a full cycle of ice sheet build-up and retreat. The deglaciation history of the East Antarctic sector is largely understudied compared to the West Antarctic margin. This emphasizes the urgent need for reliable long-term spatiotemporal data of mass balance change, particularly for sectors along the East Antarctic margin that play key roles in supplying the world’s oceans with dense bottom water. Marine ice sheet dynamics are strongly influenced by interactions between ocean, ice, and bedrock, which so far remain poorly understood along the East Antarctic margin. Here, we performed a multi-proxy analysis on numerous sediment cores recovered from two prominent glacial cross-shelf throughs on the Mac. Robertson Shelf. Combined sedimentological, sediment-physical, and geochemical analysis as well as radiocarbon dating of calcareous foraminifers reveal the onset of deglaciation on the Mac. Robertson Shelf and the subsequent retreat of the grounding line (GL). Additionally, we analyzed submarine glacial landforms on the shelf along both troughs from combined multibeam swath bathymetry and sub-bottom profiler data, providing new evidence on initial GL retreat and the pattern of its subsequent retreat. Our study reveals a retreat at or shortly after the Antarctic Cold Reversal ~12,5 cal. kiloyears before the present (cal. ka BP), it did not contribute to meltwater pulse (MWP) 1A but may have contributed to MWP-1B. Glacial bedforms indicate an episodic retreat of the ice sheet’s GL starting with a slow retreat on the outer shelf, accelerating towards the retrograde mid shelf part. At the mid shelf, the retreat underwent a further stagnation leading to the formation of two small grounding zone wedges. A mid-shelf bedrock sill likely acted as a pinning point representing an additional ice sheet stabilization event. We conclude GL advance to the continental shelf break until ~12.5 cal. ka BP. This maximum position implies the prevention of dense shelf water formation on the Mac. Robertson shelf in its current form, and therefore suggests either an absent or a different formation mechanism of Antarctic Bottom Water under full glacial conditions.
How to cite: Güntzel, J., Müller, J., Lembke-Jene, L., Tiedemann, R., Mollenhauer, G., Weigelt, E., Schopen, L., Wesch, N., Mackintosh, A., and Klages, J. P.: Maximum extent and subsequent retreat of the grounding line from the Mac. Robertson Shelf (East Antarctica) during and since the Last Glacial Maximum and its implications for Antarctic Bottom Water formation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10979, https://doi.org/10.5194/egusphere-egu25-10979, 2025.
The West Antarctic Ice Sheet (WAIS) presumably collapsed multiple times during past warm periods, significantly influencing past sea levels. Recent studies have shown that different parts of the WAIS advanced and retreated asynchronously during the Mid-Pliocene Warm Period, posing a key uncertainty in ice sheet reconstruction. Along the West Antarctic continental margin, deep-sea contourite drifts receive fine-grained sediments from mixed down-slope (turbidite) and along-slope (contourite) deposition, alongside ice-rafted debris (IRD) of various densities. These sediments reflect interactions between ice sheet dynamics and ocean circulation and are therefore important indicators of the glaciation history.
This study focuses on the Bellingshausen Sea sector of WAIS, a region with high sensitivity to climate changes and a well-preserved sedimentary record. Using seismic stratigraphy and deep-sea proxies, we constrain the timing of major changes in ice volume and ocean conditions. Analysis of seismic data collected in the area of Drift 7 off the western Antarctic Peninsula identified six seismic subunits within Pliocene–Pleistocene sequences. Drill-core evidence from ODP Leg 178 suggests a warm Mid-Pliocene (4.2–3.4 Ma) with at least five ice sheet retreats, consistent with the so-called Pliocene Amundsen Sea Warm Period (4.2–3.2 Ma), but preceding the global Mid-Piacenzian Warm Period (3.3–3.0 Ma). A cooling trend began in the Late Pliocene (3.4–2.6 Ma), evidenced by reduced bio-productivity and low IRD content. Glacial conditions persisted in the Pleistocene with widespread ice rafting. Multiple intervals with abundant calcareous microfossils suggest intermittent warm periods with probably open ocean conditions.
The seismic profiles also reveal sediment transport patterns and unconformities across contourite drifts. Correlations between Drift 7 and Drift 6 reveal disparities in sedimentation rates since the late Miocene, along with the abandonment of a Miocene-Pliocene channel on Drift 6’s northeast flank. During the late Pliocene, a more erosive and far-reaching deep-sea channel formed between Drifts 6 and 7, possibly due to large amounts of downslope sediments from massive ice advance and reorganization of drainage pathways.
This work is the first step towards quantifying any asynchronicity in ice-sheet dynamics along the broader West Antarctic margin, aiding future refinements in ice-sheet modeling and climate reconstructions.
How to cite: Luo, L., Uenzelmann-Neben, G., and Gohl, K.: Sedimentary evidence of asynchronous glacial evolution along the Bellingshausen Sea sector of the West Antarctic Ice sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11220, https://doi.org/10.5194/egusphere-egu25-11220, 2025.
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.
The East Antarctic Ice Sheet (EAIS) is the largest reservoir of frozen freshwater on Earth, with the potential to raise global sea levels by approximately 52.2 meters if fully melted. Despite its critical role in the global climate system, significant uncertainties remain regarding its sensitivity to past and future warming scenarios. Marine-based sectors of the EAIS, such as the Wilkes Subglacial Basin (WSB) and Aurora Subglacial Basin (ASB), are particularly vulnerable to climate-induced instability due to their grounding below sea level. Recent studies have documented mass loss from these sectors during past warm periods (Blackburn et al., 2020), and numerical models predict their substantial contributions to future sea-level rise under warming scenarios (DeConto and Pollard, 2016).
This study aims to reconstruct the behavior of the WSB and ASB during past climatic warm periods using glaciomarine sediments deposited along the continental margins of the Sabrina Coast (draining ASB via Totten Glacier) and the George V Coast (draining WSB via the Mertz, Cook, and Ninnis glaciers). Recovered during IODP Leg 318 and DSDP Leg 28 expeditions, these sediments archive multiple glacial cycles and capture evidence of ice sheet advances and retreats.
Preliminary results focus on characterizing iceberg-rafted debris (IRD) and integrating Nd-Sr isotopic data to infer sediment provenance and ice sheet dynamics. Data reveals that during the Pliocene, shifts in sediment origins were highlighted by significant increases in the accumulation rates of ice-rafted debris. These findings suggest that deglacial warming led to accelerated iceberg calving, followed by the retreat of the ice margin further inland (Bertram et al, 2018).
These findings, combined with available ice core records and numerical ice sheet models, aim to provide a multi-dimensional understanding of EAIS stability under projected warming scenarios. The results will refine predictions of sea-level rise, enhance understanding of glacial-climate interactions, and inform evidence-based strategies for mitigating climate change impacts.
How to cite: Gupta, R. and Kiro, Y.: Reconstructing the Dynamics of Marine-Based East Antarctic Ice Sheet Sectors During Past Warm Periods: Insights from Glaciomarine Sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6269, https://doi.org/10.5194/egusphere-egu25-6269, 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.
Abstract: The deepest area of the continental shelf is located at the Drygalski Trough, western Ross Sea, with a water depth over 1,100 m. Sedimentation in Drygalski Trough is mainly controlled by the past East Antarctic Ice Sheet (EAIS). Previous studies discussed the sediment facies and sedimentary environments, but the analysis of sediment source provenance is poor, transport dynamics and post-transport processes are not clearly, the correspondence between sedimentary events and paleoclimate changes still needs to be explored. We analyzed the grain size, XRF, biogenic silica, and isotope dating to obtain the information of the composition and access the sedimentation mechanism from the two new gravity cores collected in the Drygalski Trough by Chinese Antarctic Expedition. The preliminary results indicate that the sediments are characterised by coarse diamictons with low biological productivity and stronger hydrodynamics during the glacial, and by clay and silt deposits with increased biological productivity and lower hydrodynamics during the interglacial, and what appears to be a renewed trend toward stronger hydrodynamics in the present. Several thin interbedded deposits on the gravity core contain high amounts of ice rafted debris (IRD), presumably controlled by formation of the polynya and density shelf water discharge. The adjacent cores support that Drygalski trough had received subglacial sediments since 20 ka. The aim of this study is to reveal the sediment events under the complicated palaeoceanographic conditions and ice sheet-ocean interaction based on the changes in biological productivity and the formation of polynya since the ending of Last Glacial Maximum. The reconstruction of the evolution of the depositional environment in the Drygalski trough, western Ross Sea, analyzing the past glacial activities and history of Paleocean ventilation provides key information for predicting the impacts of future glacier changes and improving the accuracy of glacier-ocean models.
Key Words: Drygalski Trough; Ross Sea; marine sedimentology; ice sheet dynamics; sediment cores; palaeoceanographic evolution; Antarctica.
How to cite: Xiao, Z., Huang, X., and Yang, X.: Tracing palaeoceanographic archives of ice sheet-ocean interaction of the western Ross Sea since Last Glacial Maximum, Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9982, https://doi.org/10.5194/egusphere-egu25-9982, 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 eNd (< –5 eNd) 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.
