Graeme Eagles

Improved satellite‐derived gravity data support updated interpretations and models of ancient plate boundaries and plate motions affecting Zealandia and West Antarctica. The models combine to confidently resolve hundreds of kilometres of Late Cretaceous–Eocene motion between the Pacific and Lord Howe plates, confirming that plate circuit constructions via the Southeast Indian Ridge and Tasman Sea cannot resolve absolute Pacific plate motion. Calculated motion instead contextualises evidence for oblique collision and subduction east of Lord Howe Rise and, less confidently, transtension followed by transpression at a proto‐Alpine Fault plate boundary in Aotearoa New Zealand. Southwards, a diffuse or unstable Palaeogene plate boundary produced scattered faults and narrow basins in the outer Ross Sea before Australian–Antarctic plate motion focussed on a mid‐ocean ridge segment east of the Balleny Fracture Zone by 54 Ma. Trends of fracture zones in the Amundsen and Bellingshausen seas and off Chatham Rise infer the Bellingshausen plate is a product of ~87 Ma fragmentation of the Phoenix plate by pivoting subduction. New calculations of Bellingshausen–Antarctic displacements permit interpretation of the Antarctic margin in the Amundsen Sea as a site of collision and subduction that transitioned around 71 Ma to a wide continental rift zone in the east and, further west, a more focussed rift that evolved to a mid‐ocean ridge.

The Aurora hydrothermal vent field (AVF) is the first confirmed active vent system on the Arctic Ocean seafloor, located at the western end of the ultraslow spreading Gakkel Ridge. It marks a distinctive endmember among ridge‐axis hydrothermal systems, where volcanic construction and ultramafic influence co‐exist. The region's perennial ice cover and remoteness have left the crustal and lithospheric structure, including the underlying subseafloor processes, largely unconstrained. In 2023, the RV Polarstern PS137 expedition investigated how lithosphere forms in this region and how it interacts with the AVF's hydrothermal system. Here, we present results from a ∼11‐month passive seismic data set, recorded by a network of eight ice‐going ocean bottom seismometers and complemented by a coincident aeromagnetic survey. Together, these data reveal a transition from magmatic to non‐volcanic spreading between the Western Volcanic Zone and the Lena Trough. With the AVF located at its onset, seismicity and magnetic anomaly patterns are consistent with progressively thicker and colder lithosphere and reduced melt supply toward the Lena Trough. A localized and likely thermally controlled gap in seismicity may indicate a small gabbroic intrusion northeast of the AVF that could provide a heat source for the hydrothermal system. Abundant seismicity surrounding the AVF indicates that tectonic processes continuously influence the lithosphere, whereas evidence for transient magmatic activity near the vent field is limited. These findings suggest that the AVF represents a long‐lived hydrothermal system and provide new insights into the geological controls on hydrothermal systems at ultraslow spreading ridges.

Understanding the coastal zone of the Antarctic Ice Sheet (AIS), where it interacts with the Southern Ocean and warmer air masses, is crucial for predicting Antarctica's influence on the global climate and sea level. This region has multiple tipping mechanisms that could trigger large, rapid, and potentially irreversible changes in the AIS, the Southern Ocean and their global connections in the coming centuries. The AIS remains the largest source of uncertainty in future sea‐level projections. Bed topography beneath the ice shelves and the coastal ice sheet is not yet well documented, and is a major source of this uncertainty. This review assesses current knowledge of the coastal zone and highlights methods to investigate it, including aerogeophysical surveys, ground‐ and ship‐based measurements, satellite observations, and computer modeling. An ensemble analysis of published bed topography data sets identifies significant data gaps and their regional distribution, framed in the context of current ice‐sheet behavior and potential instability. We propose scientific priorities and guidelines for future aerogeophysical surveys, advocating for a comprehensive, coordinated international effort to build a next‐generation data set of Antarctic bed properties. Such an initiative would significantly advance understanding of the role of coastal processes in ice‐sheet dynamics, reducing uncertainties in sea‐level rise projections and improving predictions of future ocean and climate changes.

Ice shelves exert a buttressing effect on the Antarctic ice sheets that can reduce as basal melting drives their thinning and destabilization. This process is strongly affected by the depths and morphologies of the underlying cavity floors, which regulate ice-ocean interactions, but remain poorly constrained. We created a new model of the bathymetry beneath a section of the Ronne Ice Shelf downstream of the Evans Ice Stream by inversion of carefully selected airborne gravity data constrained by seismic and ice-penetrating radar depth references. The model reveals a deep, asymmetric and U-shaped trough aligned with the ice flow direction, reflecting glacial erosion and tectonic inheritance. The persistent retrograde slope of the seafloor potentially allows warm water intrusion from the open ocean up to the grounding line. Our model thus provides critical constraints for estimating basal melt rates and assessing ice shelf and ice sheet stability with regard to large-scale climate changes.

The Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), has conducted airborne radar campaigns since 1994 across Antarctica and Greenland, utilizing six different radar systems to study ice sheets and their interactions with climate, ocean and the solid Earth. Over the past three decades, AWI has collected more than one million profile-kilometres of radar data, covering approximately one quarter of the Antarctic and the Greenland Ice Sheet, respectively. In this review article, we describe AWI's airborne radar systems and their deployments over the Greenland and Antarctic Ice Sheet. Moreover, we summarize application and usage of AWI's radar systems, which provided crucial insights into e.g., ice dynamics, mass balance, and ancient landscapes buried beneath the ice. The integration of radar data with other geophysical methods has enhanced bathymetric models, improving predictions of ice–ocean interactions and ice-shelf stability and contributed to a better understanding of crustal and geological evolution of the Antarctic continent. As part of this paper, and to support scientific progress, AWI made its airborne radar data publicly accessible through the Radar Data over Polar Ice Sheets viewer hosted by the Marine Data Portal (https://marine-data.de/viewers/, last access: 19 April 2026) and PANGAEA (https://doi.org/10.1594/PANGAEA.972094; Eisen et al., 2024), ensuring compliance with FAIR (Findable, Accessible, Interoperable, Reusable) data principles. Future research will expand on these contributions, focusing on refining ice-sheet models and exploring new areas of glaciological and geological interest.

Antarctic geothermal heat flow (GHF) is one of the least constrained basal boundary conditions affecting subglacial hydrology and ice sheet dynamics. Furthermore, the paucity of knowledge about GHF hampers our understanding of the linkages between geodynamic evolution and tectono-thermal conditions in Antarctica.Here we present the results of enhanced spectral analysis of a new Antarctic aeromagnetic anomaly compilation, conformed at long wavelengths with SWARM satellite magnetic data. We apply manual picking of defractal magnetic power spectra on several different major subglacial lake districts in both West and East Antarctica and compare our results with those obtained using automated workflows implemented in PyCurious. Furthermore, we compare our results with independent GHF estimates from seismology, multivariate-similarity approaches and previous magnetic studies.We show that in the Amundsen Sea Embayment in West Antarctica manual spectral picking resolves the spatial heterogeneity in GHF anomalies better than automated approaches. We newly define a wide coastal region of relatively lower values corresponding to recently inferred mafic intrusions within this sector of the West Antarctic Rift System and higher GHF in the Byrd Subglacial Basin. This is highly significant as it suggests that elevated GHF may contribute to the onset of enhanced ice flow in the interior of the Thwaites Glacier catchment. Additionally, we find localised GHF anomalies in the area of the Thwaites active lakes that may affect subglacial water availability and promote reduced basal shear stress despite the widespread hard bed conditions related to the occurrence of predominantly crystalline rocks.In East Antarctica, the manual approach confirms the existence of elevated GHF beneath the Dome C subglacial lake district. However, the anomaly is more linear than previously recognised and better aligned with the trend of major aeromagnetic anomalies interpreted as reflecting extensive Paleo to Mesoproterozoic basement in the sector of East Antarctica. Notably, remarkably similar magnetic anomalies are imaged in formerly contiguous Australia where highly radiogenic igneous provinces significantly enhance GHF.Overall, we find that the choice of appropriate window sizes and spectral ranges coupled with careful inspection of individual power spectra (including the recognition of outliers) and the choice of defractal parameters is important to better define regional scale heterogeneity in Curie Depth estimates. We also find that incorporating the results of independent seismic, multivariate approaches, and expert knowledge in the geological settings of the different study regions is beneficial to better define the realistic ranges of average Curie Depth and for the conversion from Curie Depth to GHF.The results of our magnetic studies need to be integrated into thermal modelling frameworks together with the evolving knowledge of crustal and lithospheric properties in Antarctica, including intracrustal heat production and sedimentary basin distribution. This approach will yield improved spatial resolution and accuracy of Antarctic GHF and better understanding of the geological origin and significance of major GHF anomalies.

The ice sheets of the Antarctic continent are supported and stabilised by floating ice shelves. Any future decrease in ice shelf mass and stability is expected to increase ice sheet drainage thus potentially contributing to a rise in the global sea level. Basal melting is a critical factor concerning ice shelf stability. Its rates are strongly dependent on the bathymetry underneath the ice shelves, as this directly influences sub-ice water circulation and its interactions with the open ocean. Therefore, accurate knowledge of sub-ice bathymetry is crucial to estimate the exchange of water masses and heat with the open ocean. We have created a model of the seafloor topography beneath the Evans Ice Stream - draining into the Ronne Ice Shelf, one of the world’s largest ice shelves - by the inversion of legacy airborne gravity data constrained by seismic and ice-penetrating radar depth references. The new bathymetric model is a distinct improvement over existing topographic compilations based on interpolated depths, providing a range of new information on topographic characteristics beneath the ice shelf with increased resolution and detail. The model shows a deep, asymmetric and U-shaped trough beneath the Evans Ice Stream that follows the ice stream’s flow direction. The bathymetry shows that the retrograde slope of the seafloor on the continental shelf and beneath the outer Ronne Ice Shelf continues as far as the ice stream’s grounding line. Should warm water masses from the open ocean cross the continental shelf edge, this slope would permit intrusion of these water masses all the way up to the grounding line. The new bathymetric model thus enables a step towards being able to more confidentially estimate basal melt rates beneath the Evans Ice Stream and their effect on ice shelf and ice sheet stability. The depth and shape of the seabed beneath numerous other ice shelves and areas of permanent sea ice coverage around the Antarctic margins remains poorly constrained or completely unknown. As well as the Evans cavity model, new data and plans for upcoming bathymetric modelling of some of these other areas are highlighted.

The Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), has conducted airborne radar campaigns since 1994 across Antarctica and Greenland, utilizing six different radar systems to study ice sheets and their interactions with climate, ocean and the solid Earth. In this review article, we describe AWI's airborne radar systems and their deployments over the Greenland and Antarctic Ice Sheet. Moreover, we summarize application and usage of AWI radar systems, which provided crucial insights into e.g., ice dynamics, mass balance, and ancient landscapes buried beneath the ice. The integration of radar data with other geophysical methods has enhanced bathymetric models, improving predictions of ice–ocean interactions and ice-shelf stability and contributed to a better understanding of crustal and geological evolution of the Antarctic continent. To support scientific progress, AWI made its airborne radar data publicly accessible through the Radar Data over Polar Ice Sheets viewer hosted by the Marine Data Portal (https://marine-data.de/viewers/) and PANGAEA (https://doi.org/10.1594/PANGAEA.972094), ensuring compliance with FAIR principles. Future research will expand on these contributions, focusing on refining ice-sheet models and exploring new areas of glaciological and geological interest.