The discovery of long-term accumulations of snow petrel stomach-oil deposits in Antarctica have provided an excellent opportunity to reconstruct changes in climate, ice-sheet thickness and sea ice. However, providing age constraints on the deposition of these biological accumulations can be challenging, particularly when they extend beyond the radiocarbon age limit (ca. 55 ka). Luminescence dating is successfully used here to provide accurate ages for rocks underlying and incorporated into snow petrel stomach-oil deposits in East Antarctica. The agreement between the different luminescence signals measured from K-feldspars, in addition to the independent age control (radiocarbon dating) gives confidence in the results. We show the potential for reconstructing ice-sheet histories from multiple burial events with prior exposure durations recorded in the luminescence depth profiles of the rocks. Our study extends beyond the traditional sedimentary contexts usually used for luminescence dating, and into biological accumulations, which has not previously been done. We show that rock luminescence dating can overcome some challenges of using radiocarbon dating for biological accumulations (e.g. young carbon contamination, marine reservoir uncertainty) and can potentially extend the dateable age range to at least Marine Isotope Stage 5 according to the saturation limit of the luminescence signal measured for these samples. This is key for using these stomach-oil deposits to quantify the contribution to sea-level rise provided by Antarctic Ice Sheet retreat, and changes in sea ice during the last warm interglacial period experienced on Earth.

The Foundation-Patuxent-Academy system (FPAS) is a major Antarctic ice stream system, draining both East and West Antarctica, with a global sea level potential of ∼3 m. We provide a holistic catchment-scale overview of the FPAS reviewing its glaciological and hydrological systems, its glacial history, and its modelled response to past and future climate change. FPAS may be vulnerable to future change because of: (i) a deep (∼2.4 km below sea level) low-gradient retrograde bed that encourages grounding-zone retreat; (ii) a low-gradient ice surface and high tidal range, which are likely to promote flotation of grounded ice and seawater intrusion; (iii) an active and dynamic subglacial hydrological system; (iv) complex ice-meltwater-ocean interactions at the grounding zone; (v) potential for substantive expansion of the across-flow length – and cross sectional area – of the grounding zone; and (vi) susceptibility to ice flow-switching and water piracy (e.g. via the adjacent Support Force Glacier). Despite such potential vulnerabilities, existing numerical model simulations of FPAS grounding-zone retreat produce a wide and divergent range of past and future scenarios. Uncertainties in the future response of the FPAS to a warming climate result from poor constraints on its topography and hydrology, processes of ice-ocean interaction, interlinkages with the surrounding ice sheet and ice shelf, and a shortage of FPAS-specific modelling experiments. This review outlines and evaluates these critical gaps in our knowledge of the FPAS and develops a strategy to address them. This strategy would provide: (i) the first robust and comprehensive evaluation of the FPAS's vulnerability to current and near-future climate forcing; and (ii) improved constraints on projections of the future contribution of the Antarctic Ice Sheet to sea-level rise.

Vincennes Bay provides a unique opportunity to understand the role of bed topography on modulating deglaciation in East Antarctica. Here, one of the deepest troughs on the margin (Vanderford Trough), lies adjacent to a terrestrially grounded, independent ice dome (Law Dome). Thus, we contrast the deglacial history of these systems and provide insights into future ice loss in parts of the continent underlain by large subglacial basins. We use multibeam bathymetry to map the ice retreat of these systems and cosmogenic nuclide dating onshore, to constrain timing. Bedforms suggest at least two phases of retreat across the continental shelf, separated by a large mid-shelf ridge. Seaward of the ridge, bedforms evidence ice sheet expansion to the continental shelf break. Landward of the ridge distinct bedforms, combined with synchronous exposure of the Windmill Islands and Snyder Rocks similar to 10 ka, are consistent with a Marine Ice Sheet Instability style retreat into the overdeepened troughs. This timing evidences a distinct difference in deglacial histories in East Antarctica, with regions east of 60 degrees E stabilising several thousand years earlier than to the west. We explore drivers of this divergence, including the potential for continental shelf geometry to limit warm water incursion to overdeepened grounding lines. Lastly, a gap in exposure age distribution and the reworking of marine material into modern day shear moraines suggest the western margin of Law Dome was retreated further than present similar to 5.7 to 2.3 ka, with re-advance potentially driven by a strengthening of easterly winds after similar to 4 ka.

Making accurate measurements and predictions of the West Antarctic Ice Sheet's (WAIS) contribution to present and future sea-level rise fundamentally depends on knowing its trajectory over the last few thousand years. We present new in situ 14C concentrations from subglacial bedrock cores collected from the southern Weddell Sea sector of the WAIS. Critically, these concentrations are above levels that can be produced under present-day ice thicknesses at the core sites. The cosmogenic nuclide inventories provide clear evidence for the ice sheet being thinner-than present at some point during the Holocene following initial thinning from its Last Glacial Maximum configuration. Forward modelling of nuclide concentrations indicates that our results are best explained by ice-surface lowering of at least 20 m. This period of thinner ice persisted for 300-3800 years and occurred after 6-4 ka. We suggest that thinning at our core sites is most likely to reflect a regional, dynamic response to grounding-line retreat rather than a localised change in ice-surface elevation. Our data are the first direct geological evidence for a thinner-than-present WAIS in the Weddell Sea sector and are consistent with Holocene retreat that culminated inboard of present-day limits. Glacio-isostatic adjustment has been inferred as a driving mechanism, causing re-grounding of floating ice and increased buttressing allowing the grounding line to stabilise and readvance. These data allow dynamic retreat-readvance behaviour of this nature to be tested in ice-sheet models, improving predictions of future sea-level rise in this critical sector of West Antarctica.

ABSTRACT An understanding of the terrestrial extent, retreat dynamics and climate–glacier coupling of ice masses during the Last Glacial Termination (LGT, ~18–11 ka) is often limited by a fragmentary geomorphological record and is dependent on precise, accurate and robust dating frameworks. For the first time, we successfully apply Schmidt hammer exposure‐age dating (SHD) to Torridonian sandstone surfaces (Applecross Formation) at 31 sites in NW Scotland. Field results from a 2000 km 2 area of Wester Ross demonstrate that application of the Schmidt hammer can detect statistically significant differences in R (rebound)‐values between surfaces exposed since the Wester Ross Readvance (~15.3 ± 0.7 ka) and the Loch Lomond Readvance (~12.9–11.7 ka). Based on 48 existing 10 Be ages from 18 landforms, we generate calibration equations for the LGT period for two 10 Be production rates, which are used to estimate SHD ages for nine previously undated landforms. Our findings are broadly consistent with current theory and field evidence, allow regional ice‐cover reconstructions to be tested and support the view that on selected lithologies and with rigorous adherence to, and careful consideration of field procedure and the wider evidence, SHD can represent a valuable, cost‐effective and reliable tool for obtaining large numerical dating samples for landforms in formerly glaciated terrain.

The East Antarctic Ice Sheet (EAIS) formed circa 34 million years ago and now contains an ice volume equivalent to similar to 52 m of global sea-level rise. Although the EAIS is approximately in balance today, there is substantial uncertainty regarding the sensitivity of sectors underlain by low-lying bed topography to future climate and ocean warming. This is especially pertinent for Coats Land (eastern Weddell Sea), where geological records of past ice-sheet changes are sparse. Here, we use airborne radio-echo sounding and magnetic data, satellite imagery, and isostatic modeling to map the subglacial geomorphology of Coats Land for the first time and constrain the regional geological and ice-sheet history. Our mapping reveals topographic features such as tilted highlands and deep, asymmetric depressions, which likely formed via regional extension associated with Gondwana breakup, concomitant with early Jurassic magmatism. We also document low-relief, seaward-dipping surfaces that we infer to be remnants of coastal plains formed by fluvial erosion after continental breakup. Subglacial troughs that were incised into (i.e., post-date) these pre-glacial erosion surfaces were selectively eroded by ice flowing south-to-north. The ice within these troughs is stagnant today, indicating that they did not form beneath the modern (east-to-west-flowing) EAIS. Based on local geomorphological and geochronological evidence, we infer that these troughs were most likely incised during an interval of the Oligocene-Miocene (ca. 34-14 Ma) when the regional ice configuration and bed topography were significantly different from today. Subsequent EAIS reconfiguration switched off these early outlets and facilitated widespread landscape preservation beneath regionally non-erosive ice.

A glacial trimline at high elevations in West Antarctica informs on previous warm-based glaciation that occurred during an earlier stage of Antarctic Ice Sheet evolution. A multi-million-year history of theses landscapes has previously been evidenced in a few disparate locations. Here we present new cosmogenic nuclide analyses (Be-10 and Al-26) from a total of 60 samples (clasts and bedrock) at high elevations in several hard-to-access locations across the interior of West Antarctica. In the Sentinel Range of the Ellsworth Mountains this trimline occurs at the highest elevations of any sites in West Antarctica (similar to 3000 m asl). These new data reveal that clasts and bedrock, both above and below the trimline, have long exposure histories with minimum exposure-burial histories of 0.9-2.6 Ma. Accounting for low rates of erosion extends these exposure-burial histories to 2.7-4.8 Ma. Under the assumption of cyclical exposure-burial for proportions of glacial-interglacial cycles we show that some of our samples have exposure-burial histories extending back to the Miocene. We also present new data from the nearby Heritage Range where our new data supports previous work potentially extends the inferred persistence of the location of the West Antarctic ice sheet divide to >2.1 Ma. Finally, we present new data from two isolated nunataks (Mount Woollard and Mount Johns) located deep in the interior of the West Antarctic Ice Sheet near the main ice divide. Paired nuclide analyses of samples from these nunataks also shows long exposure histories and unambiguous evidence of past burial within the last similar to 100 ka. Such a thickening is not currently represented in ice-sheet models.

Satellite and airborne synthetic aperture radar (SAR) systems are frequently used for topographic mapping. However, their limited scene aspects lead to reduced angular coverage, making them less effective in environments with complex surface structures and tall objects. This limitation can be overcome by drone-based SAR systems, which are becoming increasingly advanced, but their potential for three-dimensional (3-D) imaging remains largely unexplored. In this article, we utilize multiaspect SAR data acquired with a K-band drone system with 700 MHz bandwidth and investigate the potential 3-D point cloud retrievals in high resolution. Through a series of experiments with increasingly complex 3-D structures, we evaluate the accuracy of the derived point clouds. Independent references—based on light detection and ranging (LiDAR) and 3-D construction models—are used to validate our results. Our findings demonstrate that the drone SAR system can produce accurate and complete point clouds, with average Chamfer distances on the order of 1 m compared to reference data, highlighting the significance of multiple aspect acquisitions for 3-D mapping applications.

3-D urban maps from optical, LiDAR, or synthetic aperture radar (SAR) data are crucial for urban planning, solar panel installation, visibility analysis, and shadow estimation. Digital surface models (DSMs) from airborne laser scanning (ALS) serve as high-quality references but often lack wall information and exhibit gaps in vertical structures. This study explores the effectiveness of airborne SAR in mapping complex urban geometries and compares the results to ALS data, including point clouds and DSMs. We also propose a framework for fusing 3-D SAR and ALS data to enhance the accuracy of 3-D city models. This fusion approach ensures precise alignment, reduces outliers near walls, rooftops, and ground surface (commonly caused by SAR phase noise) and preserves valuable information about walls and vertical structures absent in ALS data. Given the diversity of urban areas, we performed class-specific analyses (ground, trees, buildings, and power lines). Multiaspect SAR was found to be critical for addressing radar shadows and gaps caused by nonbackscattering objects. Using six SAR aspects covering 270(degrees) provided comprehensive 3-D data, minimizing the need to consider building orientation. While SAR and LiDAR provided similar scene information, only 30% of voxels contained the same information from both sources, highlighting their complementary nature. Datasets with more SAR aspects proved more informative than those with fewer aspects and more baselines. Ground and tree reconstructions benefited from multiple baselines due to the resolution of low-backscattering objects, whereas building and power line reconstruction showed minimal improvement. The findings suggest that a combination of ALS and SAR data is essential for a complete understanding of urban environments.

Satellite and airborne synthetic aperture radar (SAR) systems are frequently used for topographic mapping. However, their limited scene aspects lead to reduced angular coverage, making them less effective in environments with complex surface structures and tall objects. This limitation can be overcome by drone-based SAR systems, which are becoming increasingly advanced, but their potential for three-dimensional (3D) imaging remains largely unexplored. In this paper we utilize multi-aspect SAR data acquired with a K-band drone system with $700\; \text{MHz}$ bandwidth and investigate the potential 3D point cloud retrievals in high-resolution. Through a series of experiments with increasingly complex 3D structures, we evaluate the accuracy of the derived point clouds. Independent references—based on light detection and ranging (LiDAR) and 3D construction models—are used to validate our results. Our findings demonstrate that the drone SAR system can produce accurate and complete point clouds, with average Chamfer distances on the order of $700\; \text{MHz}$ compared to reference data, highlighting the significance of multiple aspect acquisitions for 3D mapping applications.

Records of relative sea-level (RSL) change shed light on mechanisms that control ice-sheet evolution and are used to improve estimates of current mass loss. Despite being the largest potential contributor to future sea-level change there are relatively few records of RSL from the margin of the East Antarctic Ice Sheet. We provide new geological data that define the timing of deglaciation and the pattern and rates of subsequent RSL change in the Windmill Islands in Wilkes Land, East Antarctica. Our new data constrain deglaciation by 10.0-9.5 ka. Combining our new data with previously unused sea-level indicators from penguin remains redefines understanding of RSL changes after deglaciation. A high-stand at c. 8.0 ka was followed by rapid sea-level fall with RSL dropping to <15 m at 6.0 ka at a rate of similar to 10 m ka(-1), more than double that inferred previously. A reinterpretation of an existing marine core provides circumstantial evidence that RSL fell below 5 m ASL at c. 3.6-2.8 ka which would be coincident with a previously inferred retreat-readvance of the ice margin at this time. Overall, the timing of the Holocene sea-level high stand in the Windmill Islands is similar to other sites around East Antarctica. However, the greater magnitude of this high stand and the rapid fall during the period 8 - 6 ka suggests that interactions between the ice sheet and solid Earth in this sector of East Antarctica may be influenced by relatively lower mantle viscosities.

The prevalence of saturated azacycles within pharmaceuticals, natural products, and agrochemicals has prompted the development of many methods that modify their periphery. In contrast, technologies that interconvert distinct saturated azacyclic frameworks, which would uniquely facilitate access to underexplored chemical space, are highly limited. Existing approaches for modifying the core of azacycles usually require either the installation of reactive functionality, which must later be removed in subsequent steps, or the use of tailored substrates, limiting applicability to drug discovery. Herein, we report a borane-catalyzed contraction of saturated N-hydroxy azacycles. This transformation is uniquely enabling, allowing reorganization of the connectivity of the substrate without altering the molecular formula and generating products without vestigial functionality derived from auxiliary groups. The outcome of the reductive Stieglitz-type contraction can be attributed to a key stereoelectronic interaction enforced by geometric constraints, the mechanism of which we investigate using density functional theory. The method developed here enables the rapid late-stage reorganization of bioactive molecules featuring cyclic and linear amines. Overall, a general platform for saturated amine constitutional isomerization has been achieved.

Predicting future change to the Antarctic Ice Sheets requires high quality data to constrain numerical ice sheet models. A major uncertainty stems from a lack of knowledge regarding the late Holocene trajectory of the West Antarctic Ice Sheet (WAIS). There are two hypotheses regarding the late Holocene behaviour of the WAIS. A) Steady retreat throughout the Holocene with stabilisation at or near the present-day position (ice relaxation hypothesis) or, B) retreat to a smaller-than-present configuration with subsequent readvance to the present-day position (the retreat-readvance hypothesis). The two hypotheses represent profoundly different ice sheet trajectories. These hypotheses have been discussed with particular reference to the Amundsen, Ross and Weddell Sea sectors of the WAIS. Initial studies proposing the retreat-readvance model suggested that GIA related uplift caused re-grounding of ice rises in the Weddell Sea, increasing ice shelf buttressing and leading to grounding line re-advance. In the southern Weddell Sea major ice streams are currently at threshold positions on reverse bed slopes where they are vulnerable to Marine Ice Sheet/Cliff Instabilities. As this region drains ~22% of Antarctica the lack of geological constraint on the current ice sheet trajectory contributes significant uncertainty to future predictions. Any groundling line retreat beyond present day limits would be accompanied by up-stream ice sheet thinning thus retreat to a smaller-than-present configuration would be accompanied by thinning of the ice sheet surface below the present-day level. Consequently, determining whether sub-glacial rock samples from the Weddell Sea sector have been exposed in the recent past can robustly test for a smaller-than-present ice sheet configuration. We present an update on two field seasons where, using a modified Winkie Drill, we recovered sub-glacial rock samples from the Ellsworth Mountains and Pensacola Mountains. These mountain ranges bracket the proposed zone of retreat and can thus provide limiting data points on the extent and duration of any retreat. The subglacial cores are to be analysed using in situ 14C and luminescence to test for any past exposure to cosmic rays and sunlight respectively. We will present a summary of the field season outcomes and preliminary analytical data along with initial interpretations.

The demand for drone-based synthetic aperture radar (SAR) systems is growing, especially for applications in cases where satellites or airborne systems are not sufficiently flexible. However, the combination of a long operating range and high spatial resolution causes the atmosphere to pose challenges for these systems. In this article, we present our $K$-band drone system that has a long range sensibility through modification to a commercially available radar. In addition, a moving baseline configuration has been integrated to ensure accurate attitude data, especially the heading. The desired spatial resolution is achieved by our proposed autofocus algorithm based on image sharpness. It is designed to also work in challenging cases of nonlinear flight paths and can be integrated into a processing framework based on back-projection. Several experiments were conducted to demonstrate the drone system's capabilities. These included a comparison with an established airborne radar: MIRANDA35. The obtained results demonstrate the ability of the drone SAR system to map wide areas at high spatial resolution.

This paper presents the efforts of the European Space Agency (ESA) to define a harmonised family of SAR Analysis Ready Data (ARD) products for the Sentinel-1, ERS-1/2, ENVISAT, ROSE-L and BIOMASS missions. This family of new SAR products is specifically aimed at users who are interestet in exploring the potential of SAR but may lack the expertise of facilities for SAR processing. It will allow immediate analysis with minimum additional user effort, and interoperability between sets of past and future ESA missions.

We review successes and challenges from five recent subglacial bedrock drilling campaigns intended to find evidence for Antarctic Ice Sheet retreat during warm periods in the geologic past. Insights into times when the polar ice sheets were smaller than present serve as guiding information for modeling efforts that aim to predict the rate and magnitude of future sea level rise that would accompany major retreat of the Antarctic Ice Sheet. One method to provide direct evidence for the timing of deglaciations and minimum extent of prior ice sheets is to extract subglacial bedrock cores for cosmogenic nuclide analysis from beneath the modern ice sheet surface. Here we summarize the lessons learned from five field seasons tasked with obtaining bedrock cores from shallow depths (<120 m beneath ice surface) across West Antarctica since 2016. We focus our findings on drilling efforts and technology and geophysical surveys with ground-penetrating radar. Shallow subglacial drilling provides a high risk, high reward means to test for past instabilities of the Antarctic Ice Sheet, and we highlight key challenges and solutions to increase the likelihood of success for future subglacial drilling efforts in polar regions.

Radiometric Terrain Corrected (RTC) gamma nought backscatter, which was introduced around a decade ago, has evolved into the standard for analysis-ready Synthetic Aperture Radar (SAR) data. While working with RTC backscatter data is particularly advantageous over undulated terrain, it requires substantial computing resources given that the terrain flattening is more computationally demanding than simple orthorectification. The extra computation may become problematic when working with large SAR datasets such as the one provided by the Sentinel-1 mission. In this study, we examine existing Sentinel-1 RTC pre-processing workflows and assess ways to reduce processing and storage overheads by considering the satellite’s high orbital stability. By propagating Sentinel-1’s orbital deviations through the complete pre-processing chain, we show that the local contributing area and the shadow mask can be assumed to be static for each relative orbit. Providing them as a combined external static layer to the pre-processing workflow, and streamlining the transformations between ground and orbit geometry, reduces the overall processing times by half. We conducted our experiments with our in-house developed toolbox named wizsard, which allowed us to analyse various aspects of RTC, specifically run time performance, oversampling, and radiometric quality. Compared to the Sentinel Application Platform (SNAP) this implementation allowed speeding up processing by factors of 10–50. The findings of this study are not just relevant for Sentinel-1 but for all SAR missions with high spatio-temporal coverage and orbital stability.

The rational design of electrolytes has been a long-standing challenge in chemistry and materials science. In this work, we demonstrate a computational rationale for improving the performance of weakly coordinating electrolytes in currently challenging multivalent-ion battery applications, based on enhanced thermodynamic and kinetic stability against reductive decomposition. A series of fluorinated alkoxyborate and alkoxyaluminate salts are systematically examined based on their reduction and oxidation potentials and, motivated by NMR spectroscopy, detailed reductive decomposition pathways involv-ing the breaking of Al/B-O, C-O, or C-F bonds are obtained. Based on the decomposition kinetics, the hexafluoro-tert-isopropoxy (hfip) ligand for borates and the trifluoro-tert-butoxy (tftb) ligand for aluminates are identified as promising ligands for constructing the salt anions. This borate prediction corroborates previous experimental work on Mg[B(hfip)4]2 and Ca[B(hfip)4]2, in which excellent electrochemical properties were reported. We find that steric factors govern the B-O bond-breaking decomposition kinetics while electronic factors are more important for aluminate salts. There is more charge transfer character in the aluminate transition states compared with borates for Al/B-O bond-breaking decomposition and thus electron-withdrawing ligands tend to stabilize the aluminate transition states. Such molecular-level understandings allow for better design principles for developing new electrolytes with improved stability and performance.