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Ice shelf dynamics and morphology play an important role in the stability of floating bodies of ice by driving fracturing that can lead to calving, in turn impacting the ability of the ice shelf to buttress upstream grounded ice. Following a 2016 calving event at the Nansen Ice Shelf (NIS), East Antarctica, we collected airborne and ground-based radar data to map ice thickness across the shelf. We combine these data with published satellite-derived data to examine the spatial variations in ice shelf draft, the cause and effects of ice shelf strain rates, and the possibility that a suture zone may be channelizing ocean water and altering patterns of sub-ice-shelf melt and freeze-on. We also use our datasets to assess limitations that may arise from relying on hydrostatic-balance equations applied to ice surface elevation to determine ice draft morphology. We find that the Nansen Ice Shelf has a highly variable basal morphology driven primarily by the formation of basal fractures near the onset of the ice shelf suture zone. This morphology is reflected in the ice shelf strain rates but not in the calculated hydrostatic-balance thickness, which underestimates the scale of variability at the ice shelf base. Enhanced melt rates near the ice shelf terminus and in steep regions of the channelized suture zone, along with relatively thin ice in the suture zone, appear to represent vulnerable areas in the NIS. This morphology, combined with ice dynamics, induce strain that has led to the formation of transverse fractures within the suture zone, resulting in large-scale calving events. Similar transverse fractures at other Antarctic ice shelves may also be driven by highly variable morphology, and predicting their formation and evolution could aid projections of ice shelf stability. [ABSTRACT FROM AUTHOR]

The East Antarctic Ice Sheet (EAIS) has its origins ca. 34 million years ago. Since then, the impact of climate change and past fluctuations in the EAIS margin has been reflected in periods of extensive vs. restricted ice cover and the modification of much of the Antarctic landscape. Resolving processes of landscape evolution is therefore critical for establishing ice sheet history, but it is rare to find unmodified landscapes that record past ice conditions. Here, we discover an extensive relic pre-glacial landscape preserved beneath the central EAIS despite millions of years of ice cover. The landscape was formed by rivers prior to ice sheet build-up but later modified by local glaciation before being dissected by outlet glaciers at the margin of a restricted ice sheet. Preservation of the relic surfaces indicates an absence of significant warm-based ice throughout their history, suggesting any transitions between restricted and expanded ice were rapid. Using satellite and survey data, an ancient river landscape 300 km wide has been discovered buried and preserved beneath the ice in East Antarctica. It has likely survived largely intact for up to 34 million years since before ice sheet growth. [ABSTRACT FROM AUTHOR]

The recent discovery of warm ocean water near the Totten Ice Shelf (TIS) has increased attention to the Sabrina Coast in East Antarctica. We report the result of 6‐day helicopter‐based observations conducted during the 61st Japanese Antarctic Research Expedition (JARE61), revealing warm ocean water (0.5–1°C) occupying a large previously unsampled area of the Sabrina Coast (116.5°E−120°E) below 550–600 m. Along the TIS front, we observe modified Circumpolar Deep Water (mCDW) well above freezing (∼−0.7°C), consistent with previous work. We identify glacial meltwater outflow from the TIS cavity west of 116°E. No signs of mCDW intrusions toward the Moscow University Ice Shelf cavity are observed; however, those observations were limited to only two shallow (∼330 m) profiles. We also highlight the advantages of helicopter‐based observations for accessibility, speed, maneuverability, and cost‐efficiency. The combination of ship‐ and helicopter‐based observations using the JARE61 approach will increase the potential of future polar oceanographic observations. Plain Language Summary: Totten Glacier hosts the most rapidly thinning ice in East Antarctica. This record of thinning is due to rapid melt along the grounding line of the Totten Ice Shelf (TIS), where warm ocean water from the open ocean flows into ice shelf cavities. To understand the pathways and mechanisms of warm water inflow, ocean observations for entire continental shelf regions are necessary. This has historically not been possible due to intense sea ice and icebergs in the region. To overcome this problem, we conducted a 6‐day helicopter‐based oceanographic campaign during the 61st Japanese Antarctic Research Expedition. Our measurements show that warm ocean water occupies a large area of the continental shelf off the TIS. We identify glacial meltwater outflow from the TIS cavity west of 116°E, which provides direct evidence of TIS melting. We also show that helicopter‐based measurements are better for the following aspects; (a) helicopter operations are insensitive to sea ice conditions, (b) helicopter travels faster than a ship, (c) helicopter can conduct measurement in a small ice crack, and (d) helicopter is cheaper to operate than an ice breaker. By combining ship‐based and helicopter‐based approaches, we may be able to enhance the efficiency of future polar oceanographic observations. Key Points: Six‐day helicopter‐based observations retrieved 67 temperature profiles covering the entire continental shelf region off the Totten Ice Shelf (TIS)Between 116.5°E and 120°E, modified Circumpolar Deep Water can be found uniformly over the continental shelf region below 550–600 mGlacial meltwater outflow from the TIS cavity is identified west of 116°E [ABSTRACT FROM AUTHOR]

The Totten Glacier in East Antarctica, with an ice volume equivalent to >3.5 m of global sea-level rise, is grounded below sea level and, therefore, vulnerable to ocean forcing. Here, we use bathymetric and oceanographic observations from previously unsampled parts of the Totten continental shelf to reveal on-shelf warm water pathways defined by deep topographic features. Access of warm water to the Totten Ice Shelf (TIS) cavity is facilitated by a deep shelf break, a broad and deep depression on the shelf, a cyclonic circulation that carries warm water to the inner shelf, and deep troughs that provide direct access to the TIS cavity. The temperature of the warmest water reaching the TIS cavity varies by ~0.8 °C on an interannual timescale. Numerical simulations constrained by the updated bathymetry demonstrate that the deep troughs play a critical role in regulating ocean heat transport to the TIS cavity and the subsequent basal melt of the ice shelf. The Totten Glacier in East Antarctica is grounded below sea level and vulnerable to ocean forcing. Observations and simulations demonstrate warm water access from offshore to the glacier, facilitated by deep topography off the Sabrina Coast. [ABSTRACT FROM AUTHOR]

The discovery of Antarctica's deepest subglacial trough beneath the Denman Glacier, combined with high rates of basal melt at the grounding line, has caused significant concern over its vulnerability to retreat. Recent attention has therefore been focusing on understanding the controls driving Denman Glacier's dynamic evolution. Here we consider the Shackleton system, comprised of the Shackleton Ice Shelf, Denman Glacier, and the adjacent Scott, Northcliff, Roscoe and Apfel glaciers, about which almost nothing is known. We widen the context of previously observed dynamic changes in the Denman Glacier to the wider region of the Shackleton system, with a multi-decadal time frame and an improved biannual temporal frequency of observations in the last 7 years (2015–2022). We integrate new satellite observations of ice structure and airborne radar data with changes in ice front position and ice flow velocities to investigate changes in the system. Over the 60-year period of observation we find significant rift propagation on the Shackleton Ice Shelf and Scott Glacier and notable structural changes in the floating shear margins between the ice shelf and the outlet glaciers, as well as features indicative of ice with elevated salt concentration and brine infiltration in regions of the system. Over the period 2017–2022 we observe a significant increase in ice flow speed (up to 50 %) on the floating part of Scott Glacier, coincident with small-scale calving and rift propagation close to the ice front. We do not observe any seasonal variation or significant change in ice flow speed across the rest of the Shackleton system. Given the potential vulnerability of the system to accelerating retreat into the overdeepened, potentially sediment-filled bedrock trough, an improved understanding of the glaciological, oceanographic and geological conditions in the Shackleton system are required to improve the certainty of numerical model predictions, and we identify a number of priorities for future research. With access to these remote coastal regions a major challenge, coordinated internationally collaborative efforts are required to quantify how much the Shackleton region is likely to contribute to sea level rise in the coming centuries. [ABSTRACT FROM AUTHOR]

The bathymetry under the Amery Ice Shelf steers the flow of ocean currents transporting ocean heat, and thus is a prerequisite for precise modeling of ice‐ocean interactions. However, hampered by thick ice, direct observations of sub‐ice‐shelf bathymetry are rare, limiting our ability to quantify the evolution of this sector and its future contribution to global mean sea level rise. We estimated the bathymetry of this region from airborne gravity anomaly using simulated annealing. Unlike the current model which shows a comparatively flat seafloor beneath the calving front, our estimation results reveal a 255‐m‐deep shoal at the western side and a 1,050‐m‐deep trough at the eastern side, which are important topographic features controlling the ocean heat transport into the sub‐ice cavity. The new model also reveals previously unknown depressions and sills that are critical to an improved modeling of the sub‐ice‐shelf ocean circulation and induced basal melting. Plain Language Summary: The ocean currents are strongly steered by the seafloor topography. Therefore, the seafloor topography should be represented at fine resolution to study how the warm water melts the ice shelf from below. However, the seafloor beneath the largest ice shelf in East Antarctica remains poorly known, because the thick floating ice blocks direct bathymetric observations. We used gravity measured by airplane to infer the shape of the seafloor beneath the floating ice. The gravity‐inferred seafloor topography model is substantially improved over the existing BedMachine Antarctica model, and reveals previously unknown topographic features. The newly identified seafloor topographic features could improve our knowledge about how much ocean heat enters the sub‐ice cavity and how the ocean currents flow beneath the ice shelf. With this knowledge, scientists could more accurately project the response of the Amery Ice Shelf to ocean forcing and this region's future contribution to global mean sea level rise. Key Points: The seafloor topography beneath the Amery Ice Shelf, East Antarctica, is estimated from airborne gravity using simulated annealingEstimation results present updated ice front geometry, an important factor controlling the ocean heat transport into sub‐ice cavityThe model reveals previously unknown depressions at the western flank that are critical to an improved modeling of ocean circulation [ABSTRACT FROM AUTHOR]

The Totten ice shelf (TIS) in East Antarctica has received increasing attention in recent years due to high basal melt rates, which have been linked to a presence of warm modified Circumpolar Deep Water (mCDW) observed at the ice front. We show that mCDW on‐shelf intrusions towards the TIS strengthen when the Antarctic Slope Current (ASC) weakens. This demonstrates that the ASC has a blocking effect and ASC weakening leads to on‐shelf intrusions, as proposed by previous observational studies. The interannual variability of the ASC is controlled primarily by atmospheric and oceanic conditions beyond our regional model domain. We further show that heat intrusions onto the continental shelf off the TIS are not influenced by off‐shelf warming but are enhanced with coastal freshening, suggesting positive feedback whereby ice melt and freshening upstream could start a chain reaction, leading to increased melt, and further coastal freshening. Plain Language Summary: East Antarctica's Totten Glacier holds enough ice to raise global sea levels by more than 4 m, and it has recently been melting at an alarming rate. To understand what causes high melt rates at the base of Totten's floating ice shelf, we developed an ocean model that shows how warm water masses circulate throughout the region. We find that the westward‐moving Antarctic Slope Current (ASC) has the ability to block warm water from flowing toward the Totten ice shelf. The warm ocean heat intrusions towards the Totten ice shelf are simulated in 1993–1994, 2004–2006, and 2015–2016 together with extreme ASC weakening events. The ASC strength in the interannual time scale, which caused these weakening events, is controlled primarily by atmospheric and oceanic processes that originate more than 1,000 km away. We also find that as upstream ocean freshens, the blocking effect of the slope current could weaken, setting up a feedback mechanism in which a weaker slope current and on‐shelf freshening allows more warm water to access Totten, leading to increased melt, more on‐shelf intrusions of warm water, and yet more melt, ad infinitum. Key Points: On‐shelf intrusions of ocean heat peak when the Antarctic Slope Current (ASC) weakensSynoptic scale ocean circulation dominantly controls the interannual variability of ASC strengthHeat intrusions towards the Totten ice shelf are enhanced with upstream coastal freshening [ABSTRACT FROM AUTHOR]

Based on sparse data, Titan Dome has been identified as having a higher probability of containing ice that would capture the middle Pleistocene transition (1.25 to 0.7 Ma). New aerogeophysical observations (radar and laser altimetry) collected over Titan Dome, located about 200 km from the South Pole within the East Antarctic Ice Sheet, were used to characterize the region (e.g., geometry, internal structure, bed reflectivity, and flow history) and assess its suitability as a paleoclimate ice core site. The radar coupled with an available ice core chronology enabled the tracing of dated internal reflecting horizons throughout the region, which also served as constraints on basal ice age modeling. The results of the survey revealed new basal topographic detail and better constrain the ice topographical location of Titan Dome, which differs between community datasets. Titan Dome is not expected to be relevant to the study of the middle Pleistocene transition due to a combination of past fast flow dynamics, the basal ice likely being too young, and the temporal resolution likely being too coarse if 1 Ma ice were to exist. [ABSTRACT FROM AUTHOR]

The Drygalski Ice Tongue in East Antarctica stretches 90 km into the Ross Sea and influences the local ocean circulation, and persistence of the Terra Nova Bay Polynya. We examine the controls on the size of this floating ice body by comparing the propagation of six large fractures on the ice tongue's northern side using 21 years of Landsat imagery with hydrostatic ice thickness maps and strain rate calculations. We also apply a subglacial hydrology model to estimate the location and discharge from subglacial channels over the grounding line and compare these with basal channels identified along the ice tongue using remote sensing and airborne radar data. Our results suggest that large fractures are inhibited from full-width propagation by thicker ice between basal channels. We hypothesize that only once the ice tongue thins towards the terminus, can fractures propagate and cause large calving events. This suggests an important relationship between the melting of floating ice from subglacial and ocean sources and the expansion of fractures that lead to ice tongue calving. [ABSTRACT FROM AUTHOR]

Using frequency-modulated continuous wave radar data from the 32nd Chinese Antarctic Research Expedition in 2015/16, subsurface profiles were obtained along an East Antarctic inland traverse from Zhongshan station to Dome A, and four distinct regions were selected to analyze the spatiotemporal variability in historical surface mass balance (SMB). Based on depth, density, and age data from ice cores along the traverse, the radar data were calibrated to yield average SMB data. The zone 49–195 km from the coast has the highest SMB (235 kg m−2 a−1). The 780–892 km zone was most affected by the Medieval Warm Period and the Little Ice Age, and the SMB during ad 1454–1836 (71 kg m−2 a−1) was only one-quarter of that in the 20th century. The SMB in the 1080–1157 km zone fluctuates the most, possibly due to erosion or irregular deposition of snow by katabatic winds in low SMB areas with surface elevation fluctuations. Dome A (1157–1236 km) has the lowest SMB (29 kg m−2 a−1) and did not decrease during Little Ice Age. Understanding the spatiotemporal variability of SMB in a larger space can help us understand the complex climate history of Antarctica. [ABSTRACT FROM AUTHOR]

High‐quality aeromagnetic data are important in guiding new knowledge of the solid earth in frontier regions, such as Antarctica, where these data are often among the first data collected. The difficulties of data collection in remote regions often lead to less than ideal data collection, leading to data that are sparse and four‐dimensional in nature. Standard aeromagnetic data collection procedures are optimized for the (nearly) 2‐D data that are collected in industry standard surveys. In this work we define and apply a robust magnetic data correction approach that is optimized to these four‐dimensional data. Data are corrected in three phases, with phase 1 operations on point data, correcting for spatiotemporal geomagnetic conditions, then phase 2 operations on line data, adjusting for elevation differences along and between lines and in phase 3, a line‐based leveling approach to bring lines into agreement while preserving data integrity. For a large‐scale East Antarctic survey, the overall median cross‐tie error reduction error reduction is 93%, reaching a final median error of 5 nT. Error reduction is spread evenly between phases 1 and 3. Phase 2 does not reduce error directly but permits a stronger error reduction in phase 3. Residual errors are attributed to limitations in the ability to model 4‐D geomagnetic conditions and also some limitations of the inversion process used in phase 2. Data have improved utility for geological interpretation and modeling, in particular quantitative approaches, which are enabled with less bias and more confidence. Plain Language Summary: Observations of the Earth's magnetic field underpin our knowledge of geology and tectonics and are often among the first data collected in frontier regions. This work focuses on the problems experienced in remote surveys, including observation periods extending over years, and flying heights that vary over kilometers. Conventional approaches are designed for more tightly constrained survey collection and can be inappropriate for these data. A new way to process airborne observations of magnetic field intensity is developed and tested. Applied to a data set in East Antarctica, the data quality is substantially improved and the data better reveals the geology hidden beneath the ice of Antarctica. Key Points: A new approach to correcting four‐dimensional aeromagnetic data is developed and tested with the large‐scale ICECAP data set from East AntarcticaSubstantial improvements in data quality and reliability are seen and error thresholds are well definedThese improvements in data quality support the investigation of subglacial geology and tectonics in magnetic data [ABSTRACT FROM AUTHOR]

We present a topographic digital elevation model (DEM) for Princess Elizabeth Land (PEL), East Antarctica. The DEM covers an area of ∼900000 km2 and was built from radio-echo sounding data collected during four campaigns since 2015. Previously, to generate the Bedmap2 topographic product, PEL's bed was characterized from low-resolution satellite gravity data across an otherwise large (>200 km wide) data-free zone. We use the mass conservation (MC) method to produce an ice thickness grid across faster flowing (>30 myr-1) regions of the ice sheet and streamline diffusion in slower flowing areas. The resulting ice thickness model is integrated with an ice surface model to build the bed DEM. Together with BedMachine Antarctica and Bedmap2, this new bed DEM completes the first-order measurement of subglacial continental Antarctica – an international mission that began around 70 years ago. The ice thickness data and bed DEMs of PEL (resolved horizontally at 500 m relative to ice surface elevations obtained from the Reference Elevation Model of Antarctica – REMA) are accessible from 10.5281/zenodo.4023343 (Cui et al., 2020a) and 10.5281/zenodo.4023393 (Cui et al., 2020b). [ABSTRACT FROM AUTHOR]

Antarctica's Getz Ice Shelf has been rapidly thinning in recent years, producing more meltwater than any other ice shelf in the world. The influx of fresh water is known to substantially influence ocean circulation and biological productivity, but relatively little is known about the factors controlling basal melt rate or how basal melt is spatially distributed beneath the ice shelf. Also unknown is the relative importance of subglacial discharge from the grounded ice sheet in contributing to the export of fresh water from the ice shelf cavity. Here we compare the observed spatial distribution of basal melt rate to a new sub-ice-shelf bathymetry map inferred from airborne gravity surveys and to locations of subglacial discharge from the grounded ice sheet. We find that melt rates are high where bathymetric troughs provide a pathway for warm Circumpolar Deep Water to enter the ice shelf cavity and that melting is enhanced where subglacial discharge fresh water flows across the grounding line. This is the first study to address the relative importance of meltwater production of the Getz Ice Shelf from both ocean and subglacial sources. [ABSTRACT FROM AUTHOR]

We derive the surface and basal radar reflectance and backscatter coefficients of the southern McMurdo Ice Shelf (SMIS) and part of the nearby Ross Ice Shelf (RIS), Antarctica, from radar statistical reconnaissance using a 60-MHZ airborne survey. The surface coefficients are further inverted in terms of snow density and roughness, providing a spatial distribution of the processes contributing to the surface boundary conditions. We disentangle the basal coefficients from surface transmission losses, and we provide the basal coherent content, an indicator of the boundary geometric disorder that is also self-corrected from englacial attenuation. The basal radar properties exhibit sharp gradients along specific iso-depths, suggesting an abrupt modification of the ice composition and geometric structure. We interpret this behavior as locations where the pressure-melting point is reached, outlining fields of freezing and melting ice. Basal steps are observed at both SMIS and RIS, suggesting a common geometric expression of widespread basal processes. This technique offers a simultaneous view of both the surface and basal boundary conditions to help investigate the ice-shelf stability, while its application to airborne data significantly improves coverage of the difficult-to-observe ice–ocean boundary. It also provides constraints on thermohaline circulation in ice shelves cavities, which are analogs for ice-covered ocean worlds. [ABSTRACT FROM AUTHOR]

Satellite altimetric time series allow high-precision monitoring of ice-sheet mass balance. Understanding elevation changes in these regions is important because outlet glaciers along ice-sheet margins are critical in controlling flow of inland ice. Here we discuss a new airborne altimetry dataset collected as part of the ICECAP (International Collaborative Exploration of the Cryosphere by Airborne Profiling) project over East Antarctica. Using the ALAMO (Airborne Laser Altimeter with Mapping Optics) system of a scanning photon-counting lidar combined with a laser altimeter, we extend the 2003-09 surface elevation record of NASA's ICESat satellite, by determining cross-track slope and thus independently correcting for ICESat's cross-track pointing errors. In areas of high slope, cross-track errors result in measured elevation change that combines surface slope and the actual ∆z=∆t signal. Slope corrections are particularly important in coastal ice streams, which often exhibit both rapidly changing elevations and high surface slopes. As a test case (assuming that surface slopes do not change significantly) we observe a lack of ice dynamic change at Cook Ice Shelf, while significant thinning occurred at Totten and Denman Glaciers during 2003-09. [ABSTRACT FROM AUTHOR]

Geckos with a leaf-toed morphology (digits with a single pair of enlarged adhesive pads located terminally) occur on six continents and many islands. Although most leaf-toed gecko genera belong to independently derived lineages, recent studies support the monophyly of a circum-Indian Ocean group including four genera from disparate regions: the southern African generaAfrogeckoandCryptactites, the Malagasy genusMatoatoa, and the Australian genusChristinus. We obtained molecular and/or morphological data for most species in these genera to estimate phylogenetic relationships among constituent species and infer broad historical biogeographic patterns. Our results confirm thatAfrogeckois not monophyletic, and thatChristinusis embedded among African taxa.Afrogeckois comprised of three lineages, each of which is distinct in external features and osteology. Based on these results, we partitionAfrogeckoand recognize two new genera. Molecular clock analyses suggest divergences within the circum-Indian Ocean group are too recent for Gondwanan vicariance or hypothesized land bridges (e.g. Kerguelen Plateau) to account for the observed Africa/Madagascar/Australia distributional pattern. Ancestral area analyses support an origin of the clade in mainland Africa or Madagascar, and imply a dispersal event from southern Africa to Australia, similar to those observed in some plant and arthropod taxa, but otherwise unknown among non-volant terrestrial vertebrates. Dispersal was likely via a southern route and may have been facilitated by island hopping using Antarctica or other southern landmasses available in the mid-Cainozoic. http://zoobank.org/urn:lsid:zoobank.org:pub:7706B624-CD49-45CC-9DA3-FAB370BEE12B). [ABSTRACT FROM PUBLISHER]

The first Cenozoic ice sheets initiated in Antarctica from the Gamburtsev Subglacial Mountains and other highlands as a result of rapid global cooling ∼34 million years ago. In the subsequent 20 million years, at a time of declining atmospheric carbon dioxide concentrations and an evolving Antarctic circumpolar current, sedimentary sequence interpretation and numerical modelling suggest that cyclical periods of ice-sheet expansion to the continental margin, followed by retreat to the subglacial highlands, occurred up to thirty times. These fluctuations were paced by orbital changes and were a major influence on global sea levels. Ice-sheet models show that the nature of such oscillations is critically dependent on the pattern and extent of Antarctic topographic lowlands. Here we show that the basal topography of the Aurora Subglacial Basin of East Antarctica, at present overlain by 2-4.5 km of ice, is characterized by a series of well-defined topographic channels within a mountain block landscape. The identification of this fjord landscape, based on new data from ice-penetrating radar, provides an improved understanding of the topography of the Aurora Subglacial Basin and its surroundings, and reveals a complex surface sculpted by a succession of ice-sheet configurations substantially different from today's. At different stages during its fluctuations, the edge of the East Antarctic Ice Sheet lay pinned along the margins of the Aurora Subglacial Basin, the upland boundaries of which are currently above sea level and the deepest parts of which are more than 1 km below sea level. Although the timing of the channel incision remains uncertain, our results suggest that the fjord landscape was carved by at least two iceflow regimes of different scales and directions, each of which would have over-deepened existing topographic depressions, reversing valley floor slopes. [ABSTRACT FROM AUTHOR]

The Princess Elizabeth Land sector of the East Antarctic Ice Sheet is a significant reservoir of grounded ice and is adjacent to regions that experienced great change during Quaternary glacial cycles and Pliocene warm episodes. The existence of an extensive subglacial water system in Princess Elizabeth Land (to date only inferred from satellite imagery) bears the potential to significantly impact the thermal and kinematic conditions of the overlying ice sheet. We confirm the existence of a major subglacial lake, herein referred to as Lake Snow Eagle (LSE), for the first time using recently acquired aerogeophysical data. We systematically investigated LSE's geological characteristics and bathymetry from two-dimensional geophysical inversion models. The inversion results suggest that LSE is located along a compressional geologic boundary, which provides reference for future characterization of the geologic and tectonic context of this region. We estimate LSE to be ~42 km in length and 370 km² in area, making it one of the largest subglacial lakes in Antarctica. Additionally, the airborne ice-penetrating radar observations and geophysical inversions reveal a layer of unconsolidated water-saturated sediment around and at the bottom of LSE, which--given the ultralow rates of sedimentation expected in such environments--may archive valuable records of paleoenvironmental changes and the early history of East Antarctic Ice Sheet evolution in Princess Elizabeth Land. [ABSTRACT FROM AUTHOR]

The Antarctic ice sheet and the continent both play critical roles in global sea level rise and climate change but they remain poorly understood because data collection is greatly limited by the remote location and hostile conditions there. Airborne platforms have been extensively used in Antarctica due to their capabilities and flexibility and have contributed a great deal of knowledge to both the ice sheet and the continent. The Snow Eagle 601 fixed-wing airborne platform has been deployed by China for Antarctic expeditions since 2015. Scientific instruments on the airplane include an ice-penetrating radar, a gravimeter, a magnetometer, a laser altimeter, a camera and a Global Navigation Satellite System (GNSS). In the past five austral seasons, the airborne platform has been used to survey Princess Elizabeth Land, the largest data gap in Antarctica, as well as other critical areas. This paper reviews the scientific operations of Snow Eagle 601 including airborne and ground-based scientific instrumentation, aviation logistics, field data acquisition and processing and data quality control. We summarize the progress of airborne surveys to date, focusing on scientific motivations, data coverage and national and international collaborations. Finally, we discuss potential regions for applications of the airborne platform in Antarctica and developments of the airborne scientific system for future work. [ABSTRACT FROM AUTHOR]

Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica - CORRIGENDUM. [Extracted from the article]

Understanding the trend and main causes of the formation and distribution of Blue ice areas (BIAs) in Antarctica may help the search for areas (BIAs) suitable for ice runways for heavy aircraft. Two districts were explored on the glacier within a 50 km radius around the Larsemann Hills. They were isolated as blue ice areas based on the analysis of satellite images. According to the results of surface studies, one of the areas (about 500x5,000 m in size), though initially identified as a BIA based on the analysis of satellite images, has a high density firn covered with sun crust. The second area is indeed a blue ice area of significant size (about 5,000x5,000 m). Similarities and differences have been determined in the formation conditions of the glacier surface in the two areas of assumed BIAs, and an analysis was carried out to identify dominant, necessary and "sufficient" reasons for the sustained existence of BIAs. An obvious link has been found between the distribution of BIAs and the morphology of the subglacial mountain relief and the ice dynamics. [ABSTRACT FROM AUTHOR]

The article cities a research study that describes a mechanism for preventing the thinning and weakening of Ross ice shelves in Antarctica. It has been found that this thinning and weakening is primarily driven by warm ocean water entering into the shelf cavities. Basal channels underneath the shelves cause ice thinning.

• Validity of the hydrology model determined from comparison with geophysical data. • Correspondence between modeled high water pressure and specularity content data. • Large channels drain into Totten Ice Shelf cavity and may impact melt rates. • Regions of observed faster ice flow are coincident with modeled regions of high basal water pressure. Aurora Subglacial Basin (ASB), which feeds Totten Glacier, is a marine basin lying below sea level and contains up to 3.5 m of global sea level equivalent. Rates of future sea level rise from this area are primarily dependent on the stability of Totten Ice Shelf and the controls on ice flow dynamics upstream of the grounding line, both of which may be influenced by subglacial hydrology. We apply the GlaDS subglacial hydrology model to ASB to examine whether the spatial patterns of distributed and efficient drainage systems impact the dynamics of Totten Glacier. We determine the most appropriate model configuration from our series of sensitivity tests by comparing the modeled basal water pressure and water depth results with specularity content data. Those data are derived from ICECAP radar surveys over the same region and represent regions of basal water accumulation. The best match between simulated basal hydrology properties and specularity content shows a strong correspondence in regions of distributed water in the ASB troughs for both water depth and water pressure, but weak correspondence between water depth and specularity content near the grounding line. This may be due to the presence of several large channels draining over the grounding line into the head of Totten Ice Shelf, which are likely not as well represented in the specularity content data as distributed systems. These channels may have a significant impact on melt, and therefore the stability, of Totten Ice Shelf. Within ASB, regions of high water pressure and greater water accumulation correspond well with regions of faster ice flow, suggesting some control of basal hydrology on ice dynamics in this region. [ABSTRACT FROM AUTHOR]

The Drygalski Ice Tongue is one of the largest ice tongues in Antarctica, extending 140 km into the Ross Sea. The ice tongue prevents the break up of sea ice within the Ross Sea and may also impact polynya formation within Terra Nova Bay to the North. We use a combination of remote sensing techniques and numerical modelling to examine the stability of the ice tongue.In 2005, iceberg B15-A collided with the tongue terminus, breaking off a large section of ice. In 2006, iceberg C-16 collided with the terminus, resulting in a total loss of 11 km in length from both calving events. These events have been captured in Landsat 7, MODIS, and ENVISAT ASAR imagery and provide an opportunity to examine pre- and post-calving properties of the ice tongue to determine how the tongue reacts after large mass loss. We use Landsat GoLIVE products from 2014 to 2017 to calculate ice strain, which we compare with the location of basal channels identified from aerial ice penetrating radar surveys and inversion of surface DEMs. We also apply feature tracking to four large crevasses using Landsat imagery from 1988 to 2017 to determine velocity along the tongue and rate of change of the frontal position. Water flux rates and subglacial channel location over the grounding line are determined by applying the Glacier Drainage System (GlaDS) model to the David Glacier catchment, which feeds into Drygalski Ice Tongue. Preliminary results suggest that there is a relationship between calving events, ice tongue velocity, and formation of new crevasses. These crevasses in turn control the location of future calving. There is also a relationship between basal channel location and ice surface strain rates, which may impact the transverse propagation distance of the marginal crevasses. [ABSTRACT FROM AUTHOR]