Abstract 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.

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.

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.

In dynamic gravimetry, i.e. airborne and shipborne gravimetry, levelling methods are used to refine gravity disturbance results based on neighbouring trajectories. In the traditional crossover adjustment, line biases are estimated using gravity disturbance residuals at trajectory line crossings as input to a least-squares adjustment. In an alternative method, the results along the complete trajectory are used to estimate the gravity disturbance field in the survey area and line biases in a one-step least-squares adjustment applying spherical radial basis functions. This makes the bias estimation more robust since the observations are not restricted to a small number of residuals at crossings strongly affected by random errors. Adjustment becomes applicable to a wider range of campaigns including irregular trajectories without many crossings. Within the scope of this work, existing methods that estimate line biases are extended to bias estimation based on trajectory segments with inter-bias interpolation. The extended method can be particularly useful for irregular trajectories without a sufficient number of line crossings. The introduced levelling methods are evaluated at the example of three airborne campaigns: a fixed wing survey at Germany with a very dense grid, a fixed wing survey in East Antarctica with varying line separation, and a helicopter survey on Svalbard with highly irregular trajectories. It is shown that the levelling method based on spherical radial basis functions improves the precision in all evaluated campaigns, even when a traditional crossover levelling is not possible.

Airborne gravimetry is an important technique for gravity field determination and sub-surface interpretations in geophysics and exploration. Traditionally, stable platform gravimeters were used, which maintained the gravity sensor's alignment with the local vertical. Recent advancements resulted in an increased utilisation of strapdown gravimeters. This study compares the performance of a GT-2A stable platform gravimeter and an iMAR iNAVRQH-1003 strapdown gravimeter, which were operated simultaneously in an airborne campaign at East Antarctica. Furthermore, novel combination approaches for the individual gravimeter solutions are presented and assessed. The strapdown gravimeter demonstrated superior overall precision (1.71 mGal without crossover adjustment, 1 mGal = 10-5 m/s2), lower high-frequency noise and lower line-to-line biases compared to the GT2A (2.40 mGal) but was susceptible to significant flight-to-flight biases. However, the elimination of these flight biases is possible through the estimation of a single bias per flight via crossover adjustment. Moreover, the benefits of strapdown technology, including reduced space, weight, and operational requirements, contribute to the growing preference for strapdown over stable platform gravimeters. All combination approaches yielded improved solutions compared to the single gravimeter results, despite the different noise levels of the single gravimeter results. After crossover adjustment, a precision of 1.0 mGal was obtained. This highlights the potential for enhanced gravity field determination when using two or more high-precision gravimeters, provided that their frequency-dependent noise characteristics are considered appropriately.

Most models on the early continental drift of the Indian continent from Antarctica are guided by the existence of microcontinents that are supposed to be located beneath Elan Bank and the Southern Kerguelen Plateau in the Enderby Basin off East Antarctica. Two deep seismic lines were acquired to test these ideas by investigating the distribution of oceanic and continental crust in the Enderby Basin. In this contribution, we discuss the results of the eastern profile which images the crustal structure of the southernmost Kerguelen Plateau. The new deep seismic data show that the seismic velocity structure of the southernmost Kerguelen Plateau is different to that of extended continental crust but similar to other igneous oceanic plateaus worldwide. At the northern end of the profile, the Moho discontinuity lies at a depth below sea level of approximately 25 km. The position of the East Antarctic continent-ocean boundary is located close to its continental shelf edge. The maximum thickness of the East Antarctic transitional crust, at the southern termination of our line, is 22 km. Extrapolating our seismic reflection and refraction results show that the oceanic crust at 50 degrees- 90 degrees E in the Enderby Basin and Princess Elizabeth Trough formed whilst in receipt of excess melt from the Kerguelen plume around magnetic chron M4n causing a northward thickening of the oceanic crust since 130 Ma. These results strongly support a one-phase model for the drift of the Indian plate.

We present Bedmap3, the latest suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 °S. Bedmap3 incorporates and adds to all post-1950s datasets previously used for Bedmap2, including 84 new aero-geophysical surveys by 15 data providers, an additional 52 million data points and 1.9 million line-kilometres of measurement. These efforts have filled notable gaps including in major mountain ranges and the deep interior of East Antarctica, along West Antarctic coastlines and on the Antarctic Peninsula. Our new Bedmap3/RINGS grounding line similarly consolidates multiple recent mappings into a single, spatially coherent feature. Combined with updated maps of surface topography, ice shelf thickness, rock outcrops and bathymetry, Bedmap3 reveals in much greater detail the subglacial landscape and distribution of Antarctica’s ice, providing new opportunities to interpret continental-scale landscape evolution and to model the past and future evolution of the Antarctic ice sheets.

Knowledge of the bathymetry of Antarctica’s margins is crucial for models and interpretations of ice-ocean interactions and their influence on ongoing and future sea level change, but remains patchy where ice shelves and multi-year sea ice block measurements. Here, we present a bathymetric model for the central Dronning Maud Land margin, based on a constrained inversion of airborne gravity data. It shows the cavities beneath the region’s two ice shelves to be much deeper than in existing bathymetric compilations, but to be shielded from Warm Deep Water ingress and basal melting by the presence of shallow bathymetric sills along the continental shelf. Over areas of multi-year sea ice, the model returns bathymetric estimates of similar accuracy to gravity interpolation-based methods over open water. Airborne gravity thus presents an opportunity to bathymetrically map hundreds of thousands of square kilometres of the most inaccessible margins of Antarctica at resolutions adequate for regional and global oceanographic and glaciological modelling and interpretation.

One of the key components of this research has been the mapping of Antarctic bed topography and ice thickness parameters that are crucial for modelling ice flow and hence for predicting future ice loss and the ensuing sea level rise. Supported by the Scientific Committee on Antarctic Research (SCAR), the Bedmap3 Action Group aims not only to produce new gridded maps of ice thickness and bed topography for the international scientific community, but also to standardize and make available all the geophysical survey data points used in producing the Bedmap gridded products. Here, we document the survey data used in the latest iteration, Bedmap3, incorporating and adding to all of the datasets previously used for Bedmap1 and Bedmap2, including ice bed, surface and thickness point data from all Antarctic geophysical campaigns since the 1950s. More specifically, we describe the processes used to standardize and make these and future surveys and gridded datasets accessible under the Findable, Accessible, Interoperable, and Reusable (FAIR) data principles. With the goals of making the gridding process reproducible and allowing scientists to re-use the data freely for their own analysis, we introduce the new SCAR Bedmap Data Portal (https://bedmap.scar.org, last access: 1 March 2023) created to provide unprecedented open access to these important datasets through a web-map interface. We believe that this data release will be a valuable asset to Antarctic research and will greatly extend the life cycle of the data held within it. Data are available from the UK Polar Data Centre: https://data.bas.ac.uk (last access: 5 May 2023​​​​​​​). See the Data availability section for the complete list of datasets.

Over the past 60 years, scientists have strived to understand the past, present and future of the Antarctic Ice Sheet. One of the key components of this research has been the mapping of Antarctic bed topography and ice thickness parameters that are crucial for modelling ice flow and hence for predicting future ice loss and ensuing sea level rise. Supported by the Scientific Committee on Antarctic Research (SCAR), the Bedmap3 Action Group aims not only to produce new gridded maps of ice thickness and bed topography for the international scientific community, but also to standardize and make available all the geophysical survey data points used in producing the Bedmap gridded products. Here, we document the survey data used in the latest iteration, Bedmap3, incorporating and adding to all of the datasets previously used for Bedmap1 and Bedmap2, including ice-bed, surface and thickness point data from all Antarctic geophysical campaigns since the 1950s. More specifically, we describe the processes used to standardize and make these and future survey and gridded datasets accessible under the ‘Findable, Accessible, Interoperable and Reusable’ (FAIR) data principles. With the goals to make the gridding process reproducible and to allow scientists to re-use the data freely for their own analysis, we introduce the new SCAR Bedmap Data Portal (bedmap.scar.org, last access: 18 October 2022) created to provide unprecedented open access to these important datasets, through a user-friendly webmap interface. We believe that this data release will be a valuable asset to Antarctic research and will greatly extend the life cycle of the data held within it. Data are available from the UK Polar Data Centre: https://data.bas.ac.uk.

Abstract. Over the past 60 years, scientists have strived to understand the past, present and future of the Antarctic Ice Sheet. One of the key components of this research has been the mapping of Antarctic bed topography and ice thickness parameters that are crucial for modelling ice flow and hence for predicting future ice loss and ensuing sea level rise. Supported by the Scientific Committee on Antarctic Research (SCAR), the Bedmap3 Action Group aims not only to produce new gridded maps of ice thickness and bed topography for the international scientific community, but also to standardize and make available all the geophysical survey data points used in producing the Bedmap gridded products. Here, we document the survey data used in the latest iteration, Bedmap3, incorporating and adding to all of the datasets previously used for Bedmap1 and Bedmap2, including ice-bed, surface and thickness point data from all Antarctic geophysical campaigns since the 1950s. More specifically, we describe the processes used to standardize and make these and future survey and gridded datasets accessible under the ‘Findable, Accessible, Interoperable and Reusable’ (FAIR) data principles. With the goals to make the gridding process reproducible and to allow scientists to re-use the data freely for their own analysis, we introduce the new SCAR Bedmap Data Portal (bedmap.scar.org, last access: 18 October 2022) created to provide unprecedented open access to these important datasets, through a user-friendly webmap interface. We believe that this data release will be a valuable asset to Antarctic research and will greatly extend the life cycle of the data held within it. Data are available from the UK Polar Data Centre: https://data.bas.ac.uk.

Future sea-level predictions require that the history of the Antarctic Ice Sheet is well understood and constrained by observations. Much of the ice sheets’ ice-dynamic properties are governed by processes at the ice-bed interface which can be imaged with radar sounding surveys. Here we use a combination of ultra-wideband radio-echo sounding data, satellite radar and laser altimetry data, as well as electromagnetic waveform modeling to characterize the properties of the ice base and the evolution of the subglacial morphology of the Jutulstraumen drainage basin (western Dronning Maud Land, Antarctica). Based on the classification of the bed topography, we reconstruct the step-by-step modifications the subglacial landscape has experienced since the beginning of the glaciation of Antarctica, 34 million years ago. Between 2017 and 2020, we find evidence of active episodic cascade-like subglacial water transport along the subglacial valley network. In addition, our high-resolution radio-echo sounding data reveal a cluster of anomalous basal ice units whose material properties we constrain by electromagnetic waveform modeling. Through this, we aim to derive the physical conditions at the ice base, and establish a link to the subglacial hydrology system. The combination of these observations will represent an important step towards a better understanding of large-scale ice-sheet dynamics in western Dronning Maud Land.

Topographic data sets in and around Antarctica have covered increasingly more ground over recent years and decades. While shipborne hydroacoustic data deliver seafloor information at and beyond the ice shelves’ calving fronts, ice penetrating radar data provide bedrock information beneath grounded ice sheets. The seafloor beneath the interjacent ice shelves, however, is largely unexplored and its unveiling by seismic reflection data is linked with tremendous logistical efforts. A lack of knowledge regarding topographic boundary conditions in these crucial coastal regions has not only hindered proper assessments of water mass and heat exchange between the open ocean and ice shelf cavities, but also an interpretation of glaciodynamic and geomorphological processes in their entirety. We have modelled the subglacial bathymetry for the majority of ice shelves at the coast of Dronning Maud Land in East Antarctica from 10º W to 35º E by inverting topographic signals in airborne gravity data and tying them to existing acoustic and radar soundings. Our models cover the Ekström, Atka, Jelbart, Fimbul, Vigrid, Nivl, Borchgrevink, and Roi Baudouin ice shelves. Recurring bathymetric patterns beneath the ice shelves are linked back to their shared regional setting. Deep troughs that mimic present-day ice flow are confined landward by grounding lines and seaward by shallow bathymetric sills at or close to the continental shelf break. These sills and further minor ridges crossing the troughs and continental shelves run perpendicular to current ice flow and were likely formed at paleo-grounding lines over previous glacial cycles. The shallow bathymetric sills along the shelf breaks are crossed by narrow gateways. Although deeper than the sill crests, the floors of these gateways mostly still lie above or at the average depth of the Warm Deep Water thermocline off coastal Dronning Maud Land. Hence, warm and deep water intrusion into the ice shelf cavities of Dronning Maud Land is currently likely to be limited and sporadic. The depths of the gateways are, however, critical for an understanding of future risk to ice shelf stability in Dronning Maud Land in response to thermocline shallowing during oceanographic change.

Sub-ice-bathymetry is an important boundary condition when modelling the evolution of ice shelves and ice sheets. Radar sounding is a proven method to reveal the sub-ice-topography beneath grounded ice. However, it fails to image the bathymetry beneath the floating ice shelves due to the strong radar reflectivity of sea water. As an alternative, the inversion of gravity measurements has been used increasingly frequently in recent years. To overcome the ambiguity of inverse modelling, this method benefits from independent depth constraints derived from direct measurements distributed throughout the model area, such as by active seismic, hydroacoustic, and radar methods. Here, we present a novel geostatistical approach to gravity inversion and compare it to the classical and more commonly used FFT approach. Instead of only fitting individual points, we also include the spatial continuity of the sub-ice morphology. To do so, we calculate a variogram that fits the available depth measurements and derive a covariance matrix from it. The covariance matrix and an initial bathymetry model obtained by kriging together describe an a-priori probability density. For the inversion, the model bathymetry is related to the measured gravity using a quasi-Newton method, for which the derived probability density serves as the inversion’s regularization term. We successfully apply the algorithm to airborne gravity data across the Ekström ice shelf (Antarctica) and compare our results with those of previous studies based on the classical approach. The simplified addition of constraints both for the geometry and the density structure in our approach proves to be advantageous.

The stability of ice shelves and drainage of ice sheets they buttress is largely determined by melting at their atmospheric and oceanic interfaces. Subglacial bathymetry can impact ice shelf stability because it influences the onset and the pattern of warm ocean water incursions into the cavities between them and the seafloor. Bathymetry is further important at pinning points, which significantly retard the flow of ice shelves. This effect can be lost instantaneously if basal and surface melting cause an ice sheet to thin and lift off its pinning points. With all this in mind, we have developed a model of bathymetry beneath the western Roi Baudouin and central and eastern Borchgrevink ice shelves in Dronning Maud Land based on inversion from gravity data and tied to available depth references offshore and subglacial topography inland of the grounding line. The model shows deep glacial troughs beneath the ice shelves and bathymetric sills close to the continental shelf. The central Borchgrevink Ice Shelf overhangs the continental slope by around 50 km, exposing its northern parts to the open ocean and higher ocean temperatures. Continuous troughs traverse the central Borchgrevink and western Roi Baudouin ice shelves at depths greater than the offshore thermocline and thus present a risk of Warm Deep Water intrusions into their cavities under the current and future oceanographic regimes. Differing bathymetric characteristics might explain the ice shelves' contrasting dominant mass loss processes.

The landscape of Antarctica, hidden beneath kilometre-thick ice in most places, has been shaped by the interactions between tectonic and erosional processes. The flow dynamics of the thick ice cover deepened pre-formed topographic depressions by glacial erosion, but also preserved the subglacial landscapes in regions with moderate to slow ice flow. Mapping the spatial variability of these structures provides the basis for reconstruction of the evolution of subglacial morphology. This study focuses on the Jutulstraumen Glacier drainage system in Dronning Maud Land, East Antarctica. The Jutulstraumen Glacier reaches the ocean via the Jutulstraumen Graben, which is the only significant passage for draining the East Antarctic Ice Sheet through the western part of the Dronning Maud Land mountain chain. We acquired new bed topography data during an airborne radar campaign in the region upstream of the Jutulstraumen Graben to characterise the source area of the glacier. The new data show a deep relief to be generally under-represented in available bed topography compilations. Our analysis of the bed topography, valley characteristics and bed roughness leads to the conclusion that much more of the alpine landscape that would have formed prior to the Antarctic Ice Sheet is preserved than previously anticipated. We identify an active and deeply eroded U-shaped valley network next to largely preserved passive fluvial and glacial modified landscapes. Based on the landscape classification, we reconstruct the temporal sequence by which ice flow modified the topography since the beginning of the glaciation of Antarctica.

Antarctica's ice shelves play a key role in stabilizing the ice streams that feed them. Since basal melting largely depends on ice‐ocean interactions, it is vital to attain consistent bathymetry models to estimate water and heat exchange beneath ice shelves. We have constructed bathymetry models beneath the ice shelves of western Dronning Maud Land by inverting airborne gravity data and incorporating seismic, multibeam, and radar depth references. Our models reveal deep glacial troughs beneath the ice shelves and terminal moraines close to the continental shelf breaks, which currently limit the entry of Warm Deep Water from the Southern Ocean. The ice shelves buttress a catchment that comprises an ice volume equivalent to nearly 1 m of eustatic sea level rise, partly susceptible to ocean forcing. Changes in water temperature and thermocline depth may accelerate marine‐based ice sheet drainage and constitute an underestimated contribution to future global sea level rise.

The direct contact of warm ocean water with the front and base of ice shelves is the main driver for accelerated mass loss of the Antarctic ice sheet. We present a compilation of observations from various projects and methodological approaches applied over the last decade along the Dronning Maud Land coast and highlight their importance for understanding the ice-ocean interactions. With a focus on the Ekstrom ice shelf, these include spatially continuous seismic observations in combination with airborne gravity inversion to yield sub-shelf bathymetry and geomorphological evidence of past ice-flow activity; ice-dynamic numerical modelling to investigate the role of seafloor/subglacial substrate characteristics to enhance or reduce ice-sheet extent and advance/retreat rates; sub-shelf CTD measurements to determine ocean properties driving basal melting; satellitebased remote sensing to determine ice-shelf height changes and spatially-distributed basal melting; and point measurements of basal melt with surface-based phase-sensitive radar to determine ocean-driven melt and validate remote-sensing products. As the Dronning Maud Land coast plays a critical role in preconditioning the water mass of the coastal current before it enters the Filcher ice-shelf cavity, we argue that a coordinated inter- and transdisciplinary observational network is required to facilitate monitoring a potential ice-sheet mass loss in this part of Antarctica.

Antarctica’s ice shelves play a key role in stabilizing their related ice sheets. The ice shelves of western Dronning Maud Land – including the Ekström, Atka, Jelbart, Fimbul and Vigrid ice shelves – currently buttress a catchment that comprises an ice volume equivalent to 0.95 meters of sea level. Any future increase in ice shelf mass loss, with basal melting likely being the main cause, will inevitably accelerate ice sheet drainage and contribute to global sea level rise. Since basal melting largely depends on ice-ocean interactions, it is crucial to attain reliable and consistent bathymetry models to estimate water and heat exchange beneath these ice shelves. We have constructed bathymetry models for an area of about 63,000 km2 beneath the ice shelves of western Dronning Maud Land by inverting airborne gravity data, tied to radar, seismic, and offshore depth reference points. New high-resolution airborne magnetic data across the ice shelves point to Jurassic intrusions and seaward-dipping reflectors originating from Gondwana breakup; enabling us to consider geological density variations as part of the bathymetry modelling process. Our bathymetric models reveal deep glacial troughs beneath the ice shelves, and sills close to the continental shelf breaks which currently limit the possible entry of Warm Deep Water from the Southern Ocean. The present-day average thermocline depth is comparable to the average depths of saddles along the sills, which present gateways into the sub-ice cavities. This leads us to suggest a high sensitivity for these ice shelves to changes in ocean temperature and especially thermocline depth in the future. Once a significant amount of warm water overtops the sills, the deep troughs will allow for fast access to the grounding line, after which it seems there may be little to stop basal melting from rapidly eroding the ice shelves of western Dronning Maud Land.