Search

Direct geological information in Antarctica is limited to ice free regions along the coast, high mountain ranges, or isolated nunataks. Therefore, indirect methods are required to reveal subglacial geology and heterogeneities in crustal properties, which are critical steps toward interpreting geological history. We present a 3D crustal model of density and susceptibility distribution in the Wilkes Subglacial Basin (WSB) and the Transantarctic Mountains (TAM) based on joint inversion of airborne gravity and magnetic data. The applied "variation of information" technique enforces a coupling between inferred susceptibility and density, relating these quantities to the same gravity and magnetic sources to give an enhanced inversion result. Our model reveals a large body located in the interior of the WSB interpreted as a batholithic intrusive structure, as well as a linear dense body at the margin of the Terre Adélie Craton. Density and susceptibility relationships are used to inform the interpretation of petrophysical properties and the reconstruction of the origin of those crustal bodies. The petrophysical relationship indicates that the postulated batholitic intrusion is granitic, but independent from the Granite Harbor Igneous Complex described previously in the TAM area. Emplacement of a large volume of intrusive granites can potentially elevate local geothermal heat flow significantly. Finally, we present a new conceptual tectonic model based on the inversion results, which includes development of a passive continental margin with seaward dipping basalt horizons and magmatic underplating followed by two distinct intrusive events associated with the protracted Ross Orogen. Plain Language Summary: Most rocks in Antarctica are hidden beneath a thick ice sheet. Therefore, indirect techniques are required to reveal rock provinces within Earth's crust below the ice. Rocks simultaneously influence the gravity and magnetic fields through their physical properties (density and susceptibility). Here we use both the gravity and magnetic fields to reveal rock provinces beneath the ice and use the relationship between density and susceptibility of the rocks to interpret the distribution of granitic rocks of the Transantarctic Mountains and the Wilkes Subglacial Basin region in East Antarctica. Granitic rocks can lead to elevated heat flow due to radiogenic decay of minerals within the rock and thus influence the overlying ice sheet. Based on our subsurface model of rock provinces we speculate on the tectonic evolution of the region. Key Points: We present a new 3D crustal density and susceptibility distribution model based on joint inversion of gravity and magnetic dataDensity and susceptibility data are used to identify crustal level intrusions and the craton marginOur new conceptual tectonic model identifies a earlier intrusive event in the interior of the Wilkes Subglacial Basin, separate from those exposed in the Transantarctic Mountains [ABSTRACT FROM AUTHOR]

Bedrock geology from Antarctica remains largely unknown since it is hidden beneath thick ice sheets. Geophysical methods such as gravity and magnetic inverse modelling provide a framework to infer crustal rock properties indirectly in Antarctica. However, due to limited availability of rock samples, validation against direct geological information is challenging. We present a new rock property catalogue containing density and susceptibility measurements on 320 rock samples from northern Victoria Land. This catalogue is used to assess the reliability of local and regional scale inverse results, including a new local high resolution magnetic inversion in the Mesa Range region and a previously published regional scale joint inversion of gravity and magnetic data in northern Victoria Land and the Wilkes Subglacial Basin. We compare our density and susceptibility measurements to global and local measurements from the literature to access the correlation to rock types and geological units. Furthermore, the measured values are compared against inverted values. The close correspondence between inverted and measured rock properties allows us to predict locations of rock types where currently such information is missing. The utility of measured susceptibility and density relationships for interpreting inversion output provides a strong incentive to incorporate local rock samples into geophysical studies of subglacial geology across Antarctica. [ABSTRACT FROM AUTHOR]

The subglacial landscape of Antarctica records and influences the behaviour of its overlying ice sheet. However, in many places, the evolution of the landscape and its control on ice sheet behaviour have not been investigated in detail. Using recently released radio-echo sounding data, we investigate the subglacial landscape of the Evans–Rutford region of West Antarctica. Following quantitative analysis of the landscape morphology under ice-loaded and ice-unloaded conditions, we identify 10 flat surfaces distributed across the region. Across these 10 surfaces, we identify two distinct populations based on clustering of elevations, which potentially represent remnants of regionally coherent pre-glacial surfaces underlying the West Antarctic Ice Sheet (WAIS). The surfaces are bounded by deeply incised glacial troughs, some of which have potential tectonic controls. We assess two hypotheses for the evolution of the regional landscape: (1) passive-margin evolution associated with the break-up of the Gondwana supercontinent or (2) an extensive planation surface that may have been uplifted in association with either the West Antarctic Rift System or cessation of subduction at the base of the Antarctic Peninsula. We suggest that passive-margin evolution is the most likely of these two mechanisms, with the erosion of glacial troughs adjacent to, and incising, the flat surfaces likely having coincided with the growth of the WAIS. These flat surfaces also demonstrate similarities to other identified surfaces, indicating that a similar formational process may have been acting more widely around the Weddell Sea embayment. The subsequent fluctuations of ice flow, basal thermal regime, and erosion patterns of the WAIS are therefore controlled by the regional tectonic structures. [ABSTRACT FROM AUTHOR]

The subglacial landscape of Antarctica records and influences the behaviour of its overlying ice sheet. However, in many places, the evolution of the landscape and its control on ice sheet behaviour has not been investigated in detail. Using recently released radio-echo sounding data, we investigate the subglacial landscape of the Evans-Rutford region of West Antarctica. Following quantitative analysis of the landscape morphology under ice-loaded and unloaded conditions, we identify ten flat surfaces distributed across the region. Across these ten surfaces, we identify two distinct populations based on clustering of elevations, which potentially represent remnants of regionally coherent pre-glacial surfaces underlying the West Antarctic Ice Sheet (WAIS). The surfaces are bounded by deeply incised glacial troughs, some of which have potential tectonic controls. We assess two hypotheses for the evolution of the regional landscape: (1) passive margin evolution associated with the breakup of the Gondwana supercontinent, or (2) an extensive planation surface that may have been uplifted either in association with the West Antarctic Rift System or cessation of subduction at the base of the Antarctic Peninsula. We suggest that passive margin evolution is most likely of these two mechanisms, with the erosion of glacial troughs adjacent to, and incising, the flat surfaces likely having coincided with the growth of the WAIS. These flat surfaces also demonstrate similarities to other identified surfaces, indicating that a similar formational process may have been acting more widely around the Weddell Sea Embayment. The subsequent fluctuations of ice flow, basal thermal regime and erosion patterns of the WAIS are therefore controlled by the regional tectonic structures. [ABSTRACT FROM AUTHOR]

The analysis of englacial layers using radio-echo sounding data enables the characterisation and reconstruction of current and past ice-sheet flow. Despite the Lambert Glacier catchment being one of the largest in Antarctica, discharging ∼16% of East Antarctica's ice, its englacial architecture has been little analysed. Here, we present a comprehensive analysis of Lambert Glacier's englacial architecture using radio-echo sounding data collected by Antarctica's Gamburtsev Province Project (AGAP) North survey. We used an internal layering continuity index (ILCI) to characterise the internal architecture of the ice and identify four macro-scale ILCI zones with distinct glaciological contexts. Whilst the catchment is dominated by continuous englacial layering, disrupted or discontinuous layering is highlighted by the ILCI at both the onset of enhanced ice flow (defined here as >15 m a -1) and along the shear margin, suggesting a transition in englacial deformation conditions and converging ice flow. These zones are characterised by buckled and folded englacial layers which have fold axes aligned with the current ice-flow regime. These folds suggest that the flow direction of the Lambert Glacier trunk has changed little, if at all, during the Holocene. Disturbed englacial layers that do not correspond to modern ice-flow routing found within a deep subglacial channel, however, suggest that ice-flow change has occurred in a former tributary that fed Lambert Glacier from grid north. As large outlet systems such as Lambert Glacier are likely to play a vital role in the future drainage of the East Antarctic Ice Sheet, constraining their englacial architecture to reconstruct their past ice flow and determine basal conditions is important for refining projections of future sea-level change. [ABSTRACT FROM AUTHOR]

Polarimetric Airborne Scientific INstrument, mark 2 (PASIN2) is a 150 MHz coherent pulsed radar with the purpose of deep ice sounding for bedrock, subglacial channels and ice‐water interface detection in Antarctica. It is designed and operated by the British Antarctic Survey from 2014. With multiple antennas, oriented along and across‐track, for transmission and reception, it enables polarimetric 3D estimation of the ice base with a single pass, reducing the gridding density of the survey paths. The off‐line data processing stream consists of channel calibration; 2D synthetic aperture radar (SAR) imaging based on back‐projection, for along‐track and range dimensions; and finally, a direction of arrival estimation (DoA) of the remaining across‐track angle, by modifying the non‐linear MUSIC algorithm. Calibration flights, during the Antarctic Summer campaigns in 16/17 and 19/20 seasons, assessed and validated the instrument and processing performances. Imaging flights over ice streams and ice shelves close to grounding lines demonstrate the 3D sensing capabilities. By resolving directional ambiguities and accounting for reflector across‐track location, the true ice thickness and bed elevation are obtained, thereby removing the error of the usual assumption of vertical DoA, that greatly influence the output of flow models of ice dynamics. [ABSTRACT FROM AUTHOR]

The article focuses on the geological sketch map and implications for ice flow of Thwaites Glacier in West Antarctica. The topics include the unknown geology beneath the glacier, the importance of understanding the underlying geology for predicting ice sheet change and studying West Antarctic tectonics, and the geological and tectonic setting of Thwaites Glacier within the West Antarctic Rift System/Marie Byrd Land province.

Process improvement and organizational development go hand-in-hand. Building out your organizational process infrastructure will provide the tools necessary to build and maintain effective processes. It takes time, effort, and persistence to get through the initial stages, but the foundational steps of process awareness set the stage for later achievements. This is hard work, and much of it will fall on the management team. Much like establishing a technical infrastructure, however, it is necessary to enable your organization to reach its potential. By doing this work, you will become process-savvy and ensure that your organization amplifies rather than mutes the talents of your individuals and teams. (Contains 2 figures and 4 endnotes.)

The Transantarctic Mountains (TAMs) separate the warmer lithosphere of the Cretaceous‐Tertiary West Antarctic rift system and the colder and older provinces of East Antarctica. Low velocity zones beneath the TAM imaged in recent seismological studies have been interpreted as warm low‐density mantle material, suggesting a strong contribution of thermal support to the uplift of the TAM. We present new Curie Point Depth (CPD) and geothermal heat flow (GHF) maps of the northern TAM and adjacent Wilkes Subglacial Basin (WSB) based exclusively on high resolution magnetic airborne measurements. We find shallow CPD and high GHF beneath the northern TAM, reinforcing the hypothesis of thermal support of the topography of the mountain range. Additionally, this study demonstrates, that limiting spectral analysis to areas with a high density of aeromagnetic measurements increases the resolution of CPD estimates revealing localized shallow CPD and associated high heat flow in the Central Basin of the WSB and the Rennick Graben (RG). Across the study area the CPD ranges from 15 to 35 km and the GHF values range from 30 to 110 mW/m2. The recovered CPD range is compatible with recent Moho depth estimates, as the CPD predominantly lies within the crust, rather than in the magnetite‐poor mantle. GHF estimates, based on the CPD estimates, show a good agreement to sparse in situ GHF measurements and the location of active volcanoes. Comparison to existing continent‐wide GHF estimates shows strong differences from magnetically‐derived heat flow estimates, while seismologically‐derived heat flow estimates show the best agreement to our results. Plain Language Summary: The Transantarctic Mountains (TAMs) separating the ancient East Antarctic region from the younger West Antarctic region. Recent studies found regions where acoustic waves move slowly beneath the TAM. Slow wave speeds are considered to be caused by warmer rocks at depth, which provide thermal support for the TAM. We present heat flow maps for this region. The estimated heat flow is based on "Curie Point Depths" (CPDs), which describes the depth at which magnetic rocks lose their magnetic properties due to increasing temperature. This temperature is called the Curie temperature (∼580°C for magnetite, the most common magnetic mineral in the Earth's crust). The heat flow at the surface is estimated from the depth at which this temperature is reached. We use for the first time for a CPD study in Antarctica exclusively high‐resolution magnetic data measured from aircraft. We demonstrated that limiting this method to airborne data improves the resolution of CPD variation, and thus heat flow estimates, substantially. We find shallow CPD and high heat flow beneath the TAM, which supports the suggestion that warmer rocks provide thermal support for the TAM. Additionally, we find high heat flow in the adjacent Wilkes Subglacial Basin and Rennick Graben. Key Points: Spectral analysis of exclusively aeromagnetic data over East Antarctica provides new Curie Point Depth and geothermal heat flow estimatesHigh heat flow imaged beneath the Transantarctic Mountains reinforces the hypothesis that the topography is thermally supportedUsing exclusively airborne data improves the resolution of Curie depth estimation, revealing heat flow correlated to geological features [ABSTRACT FROM AUTHOR]

The presence of subglacial lakes and subglacial hydrological networks under the East and West Antarctic ice sheets is now relatively well understood, whilst their influence on ice dynamics is the subject of ongoing research. In contrast, little is known about subglacial lakes and hydrological networks under the Antarctic Peninsula Ice Sheet and how these are influencing glacier behaviour. Here we describe the rapid drainage and slow refill of a subglacial lake under Mars Glacier using remote sensing and aerogeophysics. Results suggest drainage of the subglacial lake occurred prior to 2011, resulting in the collapse of the overlying ice into the newly formed subglacial cavity. The cavity has been refilling since this time, with peak rates of infilling associated with seasonal surface meltwater activity. We review evidence for similar features elsewhere in the Antarctic Peninsula and discuss whether their appearance marks a threshold shift in glacier thermal regimes and the activation or enhancement of their subglacial hydrological networks by surface meltwater. Collectively, these features show coupling of climate processes and the bed of the region's glaciers highlighting their ongoing vulnerability to climate change. [ABSTRACT FROM AUTHOR]

The Gamburtsev Subglacial Mountains are the least understood tectonic feature on Earth, because they are completely hidden beneath the East Antarctic Ice Sheet. Their high elevation and youthful Alpine topography, combined with their location on the East Antarctic craton, creates a paradox that has puzzled researchers since the mountains were discovered in 1958 (1). The preservation of Alpine topography in the Gamburtsevs (2) may reflect extremely low long-term erosion rates beneath the ice sheet (3), but the mountains' origin remains problematic. Here we present the first comprehensive view of the crustal architecture and uplift mechanisms for the Gamburtsevs, derived from radar, gravity and magnetic data. The geophysical data define a 2,500-km-long rift system in East Antarctica surrounding the Gamburtsevs, and a thick crustal root (4) beneath the range. We propose that the root formed during the Proterozoic assembly of interior East Antarctica (possibly about 1 Gyr ago), was preserved as in some old orogens (5,6) and was rejuvenated during much later Permian (roughly 250 Myr ago) and Cretaceous (roughly 100 Myr ago) rifting. Much like East Africa (7), the interior of East Antarctica is a mosaic of Precambrian provinces affected by rifting processes. Our models show that the combination of rift-flank uplift, root buoyancy and the isostatic response to fluvial and glacial erosion explains the high elevation and relief of the Gamburtsevs. The evolution of the Gamburtsevs demonstrates that rifting and preserved orogenic roots can produce broad regions of high topography in continental interiors without significantly modifying the underlying Precambrian lithosphere., Although the Gamburtsevs have been identified as a site of early Antarctic ice-sheet growth (2), their age and origin remain a matter of considerable speculation. A Precambrian basement for the [...]

Over the past 50 years, the British Antarctic Survey (BAS) has been one of the major acquirers of aerogeophysical data over Antarctica, providing scientists with gravity, magnetic, and radar datasets that have been central to many studies of the past, present, and future evolution of the Antarctic Ice Sheet. Until recently, many of these datasets were not openly available, restricting further usage of the data for different glaciological and geophysical applications. Starting in 2020, scientists and data managers at BAS have worked on standardizing and releasing large swaths of aerogeophysical data acquired during the period 1994–2020, including a total of 64 datasets from 24 different surveys, amounting to ∼ 450 000 line-km (or 5.3 million km 2) of data across West Antarctica, East Antarctica, and the Antarctic Peninsula. Amongst these are the extensive surveys over the fast-changing Pine Island (BBAS 2004–2005) and Thwaites (ITGC 2018–2019 & 2019–2020) glacier catchments, and the first ever surveys of the Wilkes Subglacial Basin (WISE-ISODYN 2005–2006) and Gamburtsev Subglacial Mountains (AGAP 2007–2009). Considerable effort has been made to standardize these datasets to comply with the FAIR (findable, accessible, interoperable and re-usable) data principles, as well as to create the Polar Airborne Geophysics Data Portal (https://www.bas.ac.uk/project/nagdp/ , last access: 18 July 2022), which serves as a user-friendly interface to interact with and download the newly published data. This paper reviews how these datasets were acquired and processed, presents the methods used to standardize them, and introduces the new data portal and interactive tutorials that were created to improve the accessibility of the data. Lastly, we exemplify future potential uses of the aerogeophysical datasets by extracting information on the continuity of englacial layering from the fully published airborne radar data. We believe these newly released data will be a valuable asset to future glaciological and geophysical studies over Antarctica and will significantly extend the life cycle of the data. All datasets included in this data release are now fully accessible at https://data.bas.ac.uk (British Antarctic Survey, 2022). [ABSTRACT FROM AUTHOR]

We present measurements of the proton-induced secondary particle environment in the vicinity of an infrared focal plane array. Measurements were made of the energy depositions from secondary electrons and scattered protons from the interior of a cryogenic test dewar using an infrared detector array. The results are compared with model predictions and analyzed for implications to space-based infrared sensors. Index Terms--Delta electrons, infrared detectors, proton testing, secondary electrons, secondary particles.

George VI Sound is an ~600 km‐long curvilinear channel on the west coast of the southern Antarctic Peninsula separating Alexander Island from Palmer Land. The Sound is a geologically complex region presently covered by the George VI Ice Shelf. Here we model the bathymetry using aerogravity data. Our model is constrained by water depths from seismic measurements. We present a crustal density model for the region, propose a relocation for a major fault in the Sound, and reveal a dense body, ~200 km long, flanking the Palmer Land side. The southern half of the Sound consists of two distinct basins ~1,100 m deep, separated by a −650 m‐deep ridge. This constricting ridge presents a potential barrier to ocean circulation beneath the ice shelf and may account for observed differences in temperature‐salinity (T‐S) profiles. Plain Language Summary: Knowing the seafloor depth beneath ice shelves is crucial for understanding the interaction between the ocean and the overlying ice, as the shape of the sea floor influences water circulation pathways. We present a new bathymetric model of the seafloor beneath George VI Ice Shelf on the Antarctica Peninsula. The data for our model were collected from airborne surveys, including the ice surface elevation, ice thickness, and gravity field measurements. We first present a new geological model of the Sound and use our improved data coverage to relocate a previously interpreted geological fault. The new bathymetry model shows that in the southern segment of the Sound, an area with shallow bathymetry and deep ice might be acting as a barrier to the water flow. This information can change our understanding of the circulation between the northern and southern segments of the Sound and can be used in models of how this impacts the melt in the base of the ice shelf. Key Points: We present an improved resolution of bathymetry over George VI Sound from airborne gravity inversionNew crustal density model across the Sound allows relocation of a major fault and reveals a dense body on the Palmer Land side of the SoundA newly identified ridge appears to act as a constriction to ocean circulation between the southern and northern segments of the Sound [ABSTRACT FROM AUTHOR]

Ice shelves play a critical role in the long-term stability of ice sheets through their buttressing effect. The underlying bathymetry and cavity thickness are key inputs for modelling future ice sheet evolution. However, direct observation of sub-ice-shelf bathymetry is time-consuming, logistically risky, and in some areas simply not possible. Here we use new compilations of airborne and marine gravity, radar depth sounding, and swath bathymetry to provide new estimates of sub-ice-shelf bathymetry outboard of the rapidly changing West Antarctic Thwaites Glacier and beneath the adjacent Dotson and Crosson ice shelves. This region is of special interest, as the low-lying inland reverse slope of the Thwaites Glacier system makes it vulnerable to marine ice sheet instability, with rapid grounding line retreat observed since 1993 suggesting this process may be underway. Our results confirm a major marine channel >800 m deep extends tens of kilometres to the front of Thwaites Glacier, while the adjacent ice shelves are underlain by more complex bathymetry. Comparison of our new bathymetry with ice shelf draft reveals that ice shelves formed since 1993 comprise a distinct population where the draft conforms closely to the underlying bathymetry, unlike the older ice shelves, which show a more uniform depth of the ice base. This indicates that despite rapid basal melting in some areas, these recently floated parts of the ice shelf are not yet in dynamic equilibrium with their retreated grounding line positions and the underlying ocean system, a factor which must be included in future models of this region's evolution. [ABSTRACT FROM AUTHOR]

The geometry of the sea floor immediately beyond Antarctica's marine-terminating glaciers is a fundamental control on warm-water routing, but it also describes former topographic pinning points that have been important for ice-shelf buttressing. Unfortunately, this information is often lacking due to the inaccessibility of these areas for survey, leading to modelled or interpolated bathymetries being used as boundary conditions in numerical modelling simulations. At Thwaites Glacier (TG) this critical data gap was addressed in 2019 during the first cruise of the International Thwaites Glacier Collaboration (ITGC) project. We present more than 2000 km 2 of new multibeam echo-sounder (MBES) data acquired in exceptional sea-ice conditions immediately offshore TG, and we update existing bathymetric compilations. The cross-sectional areas of sea-floor troughs are under-predicted by up to 40 % or are not resolved at all where MBES data are missing, suggesting that calculations of trough capacity, and thus oceanic heat flux, may be significantly underestimated. Spatial variations in the morphology of topographic highs, known to be former pinning points for the floating ice shelf of TG, indicate differences in bed composition that are supported by landform evidence. We discuss links to ice dynamics for an overriding ice mass including a potential positive feedback mechanism where erosion of soft erodible highs may lead to ice-shelf ungrounding even with little or no ice thinning. Analyses of bed roughnesses and basal drag contributions show that the sea-floor bathymetry in front of TG is an analogue for extant bed areas. Ice flow over the sea-floor troughs and ridges would have been affected by similarly high basal drag to that acting at the grounding zone today. We conclude that more can certainly be gleaned from these 3D bathymetric datasets regarding the likely spatial variability of bed roughness and bed composition types underneath TG. This work also addresses the requirements of recent numerical ice-sheet and ocean modelling studies that have recognised the need for accurate and high-resolution bathymetry to determine warm-water routing to the grounding zone and, ultimately, for predicting glacier retreat behaviour. [ABSTRACT FROM AUTHOR]

The englacial stratigraphic architecture of internal reflection horizons (IRHs) as imaged by ice‐penetrating radar (IPR) across ice sheets reflects the cumulative effects of surface mass balance, basal melt, and ice flow. IRHs, considered isochrones, have typically been traced in interior, slow‐flowing regions. Here, we identify three distinctive IRHs spanning the Institute and Möller catchments that cover 50% of West Antarctica's Weddell Sea Sector and are characterized by a complex system of ice stream tributaries. We place age constraints on IRHs through their intersections with previous geophysical surveys tied to Byrd Ice Core and by age‐depth modeling. We further show where the oldest ice likely exists within the region and that Holocene ice‐dynamic changes were limited to the catchment's lower reaches. The traced IRHs from this study have clear potential to nucleate a wider continental‐scale IRH database for validating ice sheet models. Plain Language Summary: Ice‐penetrating radar is widely used to measure the thickness of ice sheets, critical to assessments of global sea level rise potential. This technique also captures reflections from chemical contrasts within the ice sheet, caused by the atmospheric deposition of conductive impurities, known as "internal reflection horizons" (IRHs) that can be traced over large distances. As these deposits are laid down in distinct events, most IRHs are isochronous age tracers and contain valuable information on past ice sheet processes. In this paper we trace and place age constraints on stratigraphic horizons across a large portion of the West Antarctic Ice Sheet, including regions where fast ice flow has disrupted the ice sheet stratigraphy. The resulting data set allows us to identify where the oldest ice is buried in the study region and provides evidence that flow of the ice sheet interior has been stable during the Holocene. Our results can be used to test the performance of ice sheet models, which seek to simulate the response of ice sheets to long‐term environmental change. Key Points: We measure and date individual isochronal radar internal reflection horizons across the Weddell Sea sector of the West Antarctic Ice SheetHorizons dated to 1.9–3.2, 3.5–6.0, and 4.6–8.1 ka are widespread and linked to previous radar surveys of the Ross and Amundsen Sea sectorsThese form the basis for a wider database of ice sheet architecture for validating and calibrating ice sheet models of West Antarctica [ABSTRACT FROM AUTHOR]

The East Antarctic Ice Sheet (EAIS) is underlain by a series of low‐lying subglacial sedimentary basins. The extent, geology, and basal topography of these sedimentary basins are important boundary conditions governing the dynamics of the overlying ice sheet. This is particularly pertinent for basins close to the grounding line wherein the EAIS is grounded below sea level and therefore potentially vulnerable to rapid retreat. Here we analyze newly acquired airborne geophysical data over the Pensacola‐Pole Basin (PPB), a previously unexplored sector of the EAIS. Using a combination of gravity and magnetic and ice‐penetrating radar data, we present the first detailed subglacial sedimentary basin model for the PPB. Radar data reveal that the PPB is defined by a topographic depression situated ~500 m below sea level. Gravity and magnetic depth‐to‐source modeling indicate that the southern part of the basin is underlain by a sedimentary succession 2–3 km thick. This is interpreted as an equivalent of the Beacon Supergroup and associated Ferrar dolerites that are exposed along the margin of East Antarctica. However, we find that similar rocks appear to be largely absent from the northern part of the basin, close to the present‐day grounding line. In addition, the eastern margin of the basin is characterized by a major geological boundary and a system of overdeepened subglacial troughs. We suggest that these characteristics of the basin may reflect the behavior of past ice sheets and/or exert an influence on the present‐day dynamics of the overlying EAIS. Key Points: We present new compilations of ice thickness, bedrock topography, and gravity anomalies for the Pensacola‐Pole BasinA significant sedimentary succession, 2–3 km in thickness, is preserved beneath the southern part of the basinBasin topography and geology may have influenced the dynamics of past and present‐day ice sheets [ABSTRACT FROM AUTHOR]

The recent rapid growth of rifts in the Brunt Ice Shelf appears to signal the onset of its largest calving event since records began in 1915. The aim of this study is to determine whether this calving event will lead to a new steady state in which the Brunt Ice Shelf remains in contact with the bed, or an unpinning from the bed, which could predispose it to accelerated flow or possible break-up. We use a range of geophysical data to reconstruct the sea-floor bathymetry and ice shelf geometry, to examine past ice sheet configurations in the Brunt Basin, and to define the present-day geometry of the contact between the Brunt Ice Shelf and the bed. Results show that during past ice advances grounded ice streams likely converged in the Brunt Basin from the south and east. As the ice retreated, it was likely pinned on at least three former grounding lines marked by topographic highs, and transverse ridges on the flanks of the basin. These may have subsequently formed pinning points for developing ice shelves. The ice shelf geometry and bathymetry measurements show that the base of the Brunt Ice Shelf now only makes contact with one of these topographic highs. This contact is limited to an area of less than 1.3 to 3 km 2 and results in a compressive regime that helps to maintain the ice shelf's integrity. The maximum overlap between ice shelf draft and the bathymetric high is 2–25 m and is contingent on the presence of incorporated iceberg keels, which protrude beneath the base of the ice shelf. The future of the ice shelf depends on whether the expected calving event causes full or partial loss of contact with the bed and whether the subsequent response causes re-grounding within a predictable period or a loss of structural integrity resulting from properties inherited at the grounding line. [ABSTRACT FROM AUTHOR]

The Recovery subglacial basin, with its largest glacier Recovery Glacier, has been identified as potentially the biggest contributor to future sea level rise from East Antarctica. Subglacial lakes along the main trunk have been detected from satellite data, with four giant lakes (Recovery Lakes A, B, C, and D) located at the onset of the fast ice flow (≥15 m/yr) and multiple smaller lakes along the glacier. The presence of subglacial water potentially plays a key role in the control of fast ice flow of Recovery Glacier. We present new insights on the Recovery Lakes from airborne radar data collected in 2013 and 2015. Using an adjusted classification scheme, we show that a single large area consisting of smaller lakes connected by likely saturated sediment, referred to as Lake AB, exists in the originally proposed area of the Recovery Lakes A and B. We estimate that the current size of Lake AB is ∼4,320 km2. Water likely leaks from the western shore of Lake AB lubricating the bed initiating fast ice flow at this location. The difference in the outlines of Lake AB and the Lakes A and B previously derived from surface features suggested that a larger paleolake existed here in the past. From our data, we find Recovery Lake C to be dry; we attribute fast ice flow originating from this area to be due to a topographic step and thus an increase in ice thickness rather than enhanced lubrication at the bed. Plain Language Summary: Lakes of liquid water exist under the Antarctic ice sheet. The lake surface is very smooth, and the ice can easily slide over it. This is reflected in a very smooth ice surface, which can be detected in satellite images. To gain more detailed information about subglacial lakes, we need to look below the ice. This is possible with radar waves that travel through the ice where they are reflected at the interface between ice and bedrock or ice and water. Analyzing the reflected signal strength, we derive information about the conditions at the bed and can detect water. Four giant lakes (Recovery Lakes A–D) were identified from satellite data at the onset of fast ice flow of Recovery Glacier. Analyzing a 10‐km grid of radar data over these lakes, we now show that Lakes C and D are dry and only one lake exists in the area of the proposed Lakes A and B. This one lake likely regulates the fast ice flow of Recovery Glacier by water leakage from the lake shore. Key Points: Automatic classification reveals patchy lake area at onset of Recovery GlacierThe main ice flow branch of Recovery Glacier is likely initiated through leakage of water from the lake areaFast ice flow originating at the dry Lakes C and D is triggered by a topographic step [ABSTRACT FROM AUTHOR]