Differential synthetic aperture radar interferometry (DInSAR) of COSMO-SkyMed (CSK) SAR 1-day tandem pairs was used to map the 2020-2021 grounding line (GL) of the Cook Ice Shelf, East Antarctica, and to assess the observed retreat relative to the 1996 GL and 2018 grounding zone (GZ). To interpret the dynamics of the retreat, we combined annual ice velocities, ice-thickness change rates, and bed topography. Agreement between tidal predictions and DInSAR-derived vertical displacements within the hydrostatic-equilibrium zone indicates that the GL mapping is robust. The CSK-DInSAR GL shows inland retreat of ~ 5.8km relative to the 2018 upstream GZ boundary in the western Cook East Ice Shelf and ~ 8.8km relative to the 1996 GL across Cook West Ice Shelf, while other sectors remain stationary. In the retreating sector of western Cook East Ice Shelf, ice flow slowed in 2017-2018 and then increased by ~ 60m/yr in 2018-2019, returning to prior speeds with no further acceleration. The retreat occurred where the 2018 upstream GZ already lay on a retrograde bed. The 2020-2021 GL occupies either a local prograde bed or a retrograde segment immediately seaward of a prograde transition, suggesting threshold-like retreat controlled by bed geometry.

Despite its importance and being commonly accepted in other regions, meltwater influence on the Antarctic ice sheet dynamics continues to be debated and questioned. To investigate the possible impact of surface melt on subglacial water pressure and ice dynamics, we performed hot-water drilling ~1 km upglacier from the grounding line of Langhovde Glacier in East Antarctica. Borehole measurements revealed that the subglacial water pressure exceeded 90% of the ice overburden and the pressure elevated during periods of intensive melting and rain. Coinciding with these events, ice speed increased by 10-20% and the surface rose by ~0.1 m. Subglacial water was freshwater, but hydraulically connected to the sub-shelf cavity, where sessile animals were distributed in a thin seawater layer. Our in-situ measurements confirm meltwater-driven acceleration of grounded ice in Antarctica. Since meltwater is ubiquitous along the Antarctic coast, its impact on outlet glacier dynamics should be considered when projecting Antarctic ice sheet evolution.

Despite decades of effort to map bed elevation under the Antarctic Ice Sheet, significant gaps remain in this geometric boundary, controlling ice sheet flow and grounding line dynamics. The impact of such uncertainties on ice flow simulations of the Antarctic evolution, however, has received little attention. Here, we investigate their impact on the Antarctic evolution at the continental scale as well as the regional scale for the Bellingshausen and Aurora basins and compare them to the impact of climate forcing scenarios. Using error estimates reported in BedMachine Antarctica, our simulations show that bed topography affects the Antarctic contribution to sea level by more than 40 cm in 2150 and 1 m by 2300, comparable to changes caused by different emission scenarios. Variations in grounding line retreat and mass loss are especially important in the Amundsen Sea, Ross and Filchner-Ronne basins. The impact of bedrock uncertainties is even larger on regional- and glacier-scale simulations with a higher spatial resolution, resulting in more variations in grounding line positions and mass change. Overall, these results suggest that errors in bedrock elevation under the Antarctic Ice Sheet are a critical but underexplored source of uncertainty. Additional observations in critical regions are needed to help reduce these systemic uncertainties. This article is part of the Theo Murphy meeting issue 'Next generation ice-sheet bed measurements'.

Grounding zones have long been recognized as critical for understanding the past, present and future evolution of ice sheets. The ice mass flux through the grounding line contributes to global sea-level rise, and the freshwater flux impacts ocean salinity. This narrow zone-where the grounded ice sheet transitions into a floating shelf-is challenging to observe and model because of the remoteness of ice sheet beds and ice shelf cavities and is thus poorly understood. However, our understanding of grounding zones has changed as we collect new observations, which are revealing a far more complex system than previously thought. These observations serve as the foundation for mathematical and numerical models of ice sheets. Models have progressed from simply representing the grounding line as hydrostatic equilibrium and treating ice flow as a viscous fluid to solving visco-elastic problems, including coupled ice sheet-subglacial hydrological models and complex grounding zones. What all these models, however, have in common is the need to know the shape of the bedrock and basal conditions beneath the grounded ice, making a targeted observational campaign of bedrock in current and future possible grounding zones key to fully understanding the Antarctic ice sheet. This article is part of the Theo Murphy meeting issue 'Next generation ice-sheet bed measurements'.

As new airborne surveys of the Antarctic ice sheet are completed, the ever-enlarging survey dataset provides an opportunity for generating new 'Bedmaps' of ice thickness, surface and bed topography. These surveys are fundamental to improving our ability to predict the future of Antarctica, but other data-analysis challenges emerge because surveys often do not agree, large data gaps remain, the ice thickness changes or interpolation works well for one landscape but not another. Similar problems afflict other key Bedmap components: the coastline, the grounding line, rock outcrops, the ice shelves and the bathymetry. The process of merging the interpolated ice sheets and shelves and the grounded bed with the sea floor can also inject spurious cliffs and bumps in the grounding zone-exactly where ice-sheet models are most sensitive to flaws in their boundary conditions. In each case, unintended errors and artefacts that arise in the Bedmap grids require careful checking, correction and sometimes bespoke, local approaches to interpolation, slowing the process further. Here, I highlight the key challenges to overcome and address the question of how future Bedmaps can be automated to speed up the supply of new datasets demanded by the ice-sheet modelling community. This article is part of the Theo Murphy meeting issue 'Next generation ice-sheet bed measurements'.

The resilience of the East Antarctic Ice Sheet (EAIS) to anthropogenic climate change has critical implications for future global sea level. Constraining how the ice sheet has responded to past periods of naturally elevated carbon dioxide and global warmth can provide vital clues as to its future stability. Relic fluvial landscapes preserved beneath the EAIS have been used to place limits on retreat into the Aurora Subglacial Basin (ASB) in the warm Pliocene (approx. 3 million years ago). Here, we use high-resolution ice sheet model (ISM) simulations to better understand if the preservation of this landscape precludes significant glacial retreat in this sector in at least the past 3 million years. We apply a subglacial topography map that resolves mesoscale landscape features within the model and create an ensemble of simulations with varying retreat into the ASB. Nearly all simulations feature predominantly cold-based ice caps on the landforms through warm interglacial periods of the Pliocene, meaning the fluvial landscape could have been preserved, even with significant grounding line retreat into the ASB. This study highlights the utility of well-resolved subglacial landscapes when paired with numerical model simulations in informing past ice sheet retreat. This article is part of the Theo Murphy meeting issue 'Next generation ice-sheet bed measurements'.

Accurate bed topography is critical for predicting Antarctica's future ice discharge and sea-level contribution, yet large portions of the coastal ice sheet remain poorly mapped. We assessed radar-derived ice-thickness data coverage along the ice-sheet margin zone, focusing on dynamically sensitive sectors, using a 0.5 km grid and distance-to-data metrics. The study area encompassed a 100 km buffer from a simplified grounding line, including fast-flowing ice and regions where ISMIP6 experiments project grounding-line retreat by 2100. After filtering for GPS-quality data, over 41 million Bedmap3 measurements were analysed. Coverage varies widely across the 27 GSFC drainage basins: rapidly changing regions such as Thwaites and Pine Island glaciers are well sampled, whereas Enderby Land, Oates Land and the eastern Antarctic Peninsula exhibit gaps of 40-100 km. Ice rises and rumples are broadly undersampled despite their role in ice-shelf stability. These results provide an initial prioritization of targets for future airborne and helicopter-borne surveys. This prioritization is based primarily on existing data distribution and will be further refined through SCAR's RINGS Action Group regional efforts, ultimately supporting the development of next-generation Bedmap products. This article is part of the Theo Murphy meeting issue 'Next generation ice-sheet bed measurements'.

Subglacial topography and basal conditions form critical controls on ice-sheet dynamics and ice-flow pathways. These controls modulate basal shear stress, affect grounding-line stability and allow the potential for marine ice-sheet instability. Deep troughs and reverse slopes facilitate rapid retreat driven by ocean warming, while topographic ridges and bumps can anchor ice margins. However, substantial data gaps in ice-sheet bed measurements limit the accuracy of sea-level rise projections from numerical ice-sheet models that require such information as inputs. Interpolation techniques often smooth over key features, creating digital elevation models (DEMs) that do not replicate 'real' glacierized systems. This causes uncertainty in simulations of ice-sheet evolution. Advances in physics-informed methods, which use surface velocity and mass conservation to infer bed elevation, have improved reconstructions of bed topography. Nonetheless, important details that characterize glacierized surfaces remain to be resolved in the DEMs and bed topography grids that models rely on. Future priorities to improve these data products involve dense, targeted surveys in key areas such as grounding zones. Machine learning (ML) offers promising tools for optimizing interpolation, prioritizing survey targets and planning future surveys. As ice-sheet model projections extend to 2300 CE and beyond, survey strategies must anticipate migrating grounding lines. Automation and repeat observations, including swath radar and unmanned aerial vehicle (UAV)-based campaigns, will be vital for maintaining up-to-date, high-resolution bed datasets. Ultimately, significant advancements in subglacial mapping are possible within the next 10-20 years, which could greatly improve model accuracy and better inform sea-level rise mitigation and adaptation strategies. This article is part of the Theo Murphy meeting issue 'Next generation ice-sheet bed measurements'.

Bed topography is a key control on the evolution of the Antarctic Ice Sheet, influencing ice flow, grounding line retreat and the rate and timing of ice mass loss. To assess the sensitivity of ice sheet evolution to bed variability in ice sheet models, synthetic gridded bed topography datasets are often used. Here, we review methods commonly used to generate synthetic beds, their associated uncertainties and the influence of the approach on the characteristics of the resulting bed. Using the Aurora Subglacial Basin in East Antarctica as a case study, we evaluate the impact of five synthetic bed generation methods on projected ice mass loss under a high emission scenario. Sea-level rise estimates vary by up to 11% (SSP5-8.5 forcing scenario) and 32% (RCP2.6) at 2300 CE when basal friction coefficients from the friction law are optimized for each bed, and by up to 23% (SSP5-8.5) and 51% (RCP2.6) at 2300 CE when using non-optimized coefficients. Our results highlight the importance of relatively small bed variations on the timing and extent of grounding line retreat and the need for process-informed representation of the basal friction in decadal- to centennial-scale sea-level projections. This article is part of the Theo Murphy meeting issue 'Next generation ice-sheet bed measurements'.

We consider the axisymmetric, radial extrusion of Newtonian and shear-thinning, power-law fluids from a cylindrical source, which displace an ambient inviscid fluid of equal density. In unconfined geometries, the upper and lower fluid interfaces are stress free, and the flow is dominated by extensional stresses everywhere. In a layer of extruded shear-thinning fluid, a radially growing viscosity field, associated with a radially decaying velocity field, causes the current to bulge near the cylindrical source, with the thickness of the layer growing without bound over time. In contrast, with a Newtonian fluid, the thickness of the fluid layer never exceeds the height of the cylindrical source. We compute numerical solutions to this system, and find similarity solutions describing its late-time behaviour for values of the rheological power-law exponent $1\leqslant n\leqslant 3/2$ . We also consider extrusion between parallel plates, in which the shear-thinning fluid displaces the inviscid fluid and fills the cell completely up to a grounding line, beyond which it separates from the boundaries to extend freely. In this case, we find similarity solutions for values of the power-law exponent $n \geqslant 1$ .

Abstract. Constraining the dynamic evolution of past ice sheets is critical for unravelling their responses to external forcing and feedbacks over long timescales. This is particularly true in the context of marine ice sheet collapse, as this is one of the largest sources of uncertainty for future sea-level rise projections. The Iceland Ice Sheet (IIS) provides an empirically constrained case study for investigating such an instability, having retreated from a predominantly marine-based ice sheet to isolated mountain ice caps during the last deglaciation. However, previous reconstructions of the IIS have been limited by either sparse data or a restricted exploration of model parameter space, lacking a robust quantification of uncertainties. Here, we address this gap by performing a truncated history matching of the last glacial cycle of the IIS. We use the Glacial Systems Model (GSM) constrained by a curated set of geochronological data to generate an envelope of not-ruled-out-yet(NROY) ice sheet histories. Our results indicate that numerous asynchronous ice streams effectively drain ice from the interior to the margins, resulting in an extensive yet relatively thin ice sheet. During its local Last Glacial Maximum (23.6–20.9 ka), the IIS reaches the continental shelf edge in most sectors with a total volume of 0.41 to 0.76 metres equivalent sea level (m e.s.l.). In the most extreme NROY glaciation scenarios, our model reveals an ice bridge connecting the Iceland and Greenland ice over Denmark Strait. We find that accelerated ice discharge (at the grounding line) dominates mass loss during deglaciation. This acceleration is primarily driven by atmospheric warming through a cascade of mechanisms: surface meltwater induces hydrofracturing, leading to both ice shelf disintegration and tidewater calving, which in turn reduces buttressing and triggers rapid ice stream acceleration. The critical role of hydrofracturing in enabling model capture of deglacial data constraints is shown by explicit sensitivity experiments. This thereby supports inclusion of hydrofracturing for modelling of ongoing ice sheet response to climate change.

Abstract. 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.

This article introduces an intelligent framework using deep learning to recognize and classify different faults through the real-time detection of multiple faults in power distribution systems. A collection of data representing normal operating conditions, alongside various fault scenarios including line-to-ground (LG), line-to-line (LL), double line-to-ground (LLG), and three-phase line (LLL) faults, was created using three phase current signals obtained from the Real-Time Digital Simulator (RTDS) microgrid test system. To properly model the system dynamics, a feature extraction method that integrates phase currents, differential currents, summation currents and magnitude results was developed. The temporal features of the fault signals were identified by using a sliding window approach to fit the data. A one-dimensional convolutional neural network (CNN) was developed to identify different types of faults. This model performed well, obtaining nearly 96.15% accuracy while testing. In order to evaluate the feasibility of the approach, the trained model was loaded on Raspberry Pi 5, NodeMCU, ESP32 and existing sensing devices. The fault classification performed in real-time was time-sensitive. The proposed intelligent framework is applicable to low-scale operation for smart grid fault monitoring and protection and it is an economically viable solution.

Radiographic assessment of the sagittal inclination of the first metatarsal (1M) is essential for evaluating foot disorders. However, 1M varus deviation may influence these measurements. This study aimed to determine whether hallux valgus (HV) varus deformity influences the sagittal radiographic inclination of the 1M by comparing weightbearing radiography (WBR) and weightbearing computed tomography (WBCT) images. Eighty-four feet were analyzed, including HV cases with intermetatarsal angle (IMA) >15° and control feet without HV. The sagittal inclination of the 1M, its base height, and ground lines form a rectangular scalene triangle, in which perspective changes can modify the lengths and angles of its sides. The first metatarsal declination angle (FMDA) and length of the first metatarsal (L1M) were used to assess the influence of 1M varus on sagittal alignment differences between WBR and WBCT. FMDA values showed no significant differences within or between groups, with a mean difference of 0.39° (P = .98). In contrast, L1M measurements differed significantly between imaging modalities and between HV and control groups, with a mean difference of 2.48 mm (P < .05). Agreement analysis demonstrated strong concordance between WBR and WBCT measurements, indicating comparable values with minimal systematic bias. In patients with IMA >15°, forefoot geometric changes were reflected with modest L1M differences, although their clinical impact should be interpreted cautiously. Importantly, these changes did not affect FMDA, which remained stable across imaging modalities. The strong agreement between WBR and WBCT supports FMDA as a reliable parameter for assessing 1M sagittal alignment and planning realignment procedures, irrespective of HV severity. Level IV, cross-sectional study.

Abstract. Knowledge of Antarctic glacier grounding lines, which mark the transition between grounded and floating ice, is a vital parameter in determining the stability of major ice shelves and hence the ice sheet. Rapid grounding line retreat and associated mass loss has been documented at numerous Antarctic glaciers, particularly in the Amundsen Sea Embayment. However, few comprehensive grounding line mappings exist, particularly from recent years. Here, we utilize a unique record of Sentinel-1 Synthetic Aperture Radar 1 d repeat-pass imagery to generate a comprehensive retrieval of grounding line location in the Amundsen Sea Embayment in 2025 and evaluate recent changes.

Considering the drastic variations in the surface elevation of the piedmont region in the Bai Cheng West Area, there is no reference point within the Reference Ground Line (RG line) of the starting point of the synthetic seismic records in the process of calibration of the horizon. Through the analysis of the process and properties of the production of the RG line, in the processing of seismic data, it is indicated that the position of the synthetic data of seismic records is not located at the beginning of the RG line. Rather, it must be at the time point of the seismic profile at the elevation of a datum position of the static value of less than the datum plane. Both the RG line and the elevation static correction value line can easily be seen by computerizing the calculated value of the elevation static correction of the datum plane relating to the seismic section and plotting it on the seismic section. To achieve a good calibration with the synthetic seismogram, it is possible to set the starting point of the synthetic seismogram on the elevation static correction value line that is situated at the place of the Common Mid-Point (CMP). In the current paper, a systematic overview of methods and safety procedures for establishing the seismic interpretation work area and horizon calibration in seismic interpretation has been reviewed, which will form an effective guide towards seismic interpretation under the complicated surface conditions in the Bai Cheng west region.

The Grounding Line (GL)-the transition from ice grounded on the continent and ice afloat in the ocean-is a sensitive indicator of glacier stability and mass balance. Using differential synthetic aperture radar interferometry from ERS-1/2, Sentinel-1, RADARSAT-1/2, RADARSAT Constellation Mission, ALOS PALSAR-2, COSMO-SkyMed, and ICEYE, we assemble a continental scale record of grounding line migration from 1992 to 2025. Over 77 ± 10% of Antarctic coastal length, we detect no GL migration. Retreat is concentrated in i) the Antarctic Peninsula-2 to 18 km along Larsen A-B and 2 to 6 km along parts of George VI; ii) Wilkes and George V lands-6 to 10 km on Denman, Totten, Moscow, Frost, Holmes, Mertz, Ninnis, and Cook, and 26 km on Vanderford; and iii) West Antarctica-5 to 7-km on Ferrigno, Fox, and Venable, with extreme retreat in the Amundsen and Getz sectors (Pine Island 33 km, Thwaites 26 km, Haynes 20 km, Pope 23 km, Smith 42 km, Kohler 12 km, East Getz 9 km toward Berry 18 km, Hull 14 km, and Land 5 km). The ice sheet lost 12,820 ± 1,873 km2 of grounded ice in 1996-2025, or 442 ± 64 km2/y, with 62% from West Antarctica and 28% from East Antarctica. Retreat clusters in areas where bathymetry channelizes warm Circumpolar Deep Water toward deep grounding zones where beds are retrograde, except in the northeastern Antarctic Peninsula. The results provide a harmonized benchmark for ice grounding zone-based ice sheet models and identifies gateways where future retreat is likely to accelerate.

Abstract. Previous studies do not agree on the magnitude of the influence of basal friction laws in sea-level projections. We use the Community Ice Sheet Model (CISM) to show that the sensitivity of the projected sea level rise to the choice of basal friction law depends on the specific geometric setting and the initial state of the ice sheet model. We find a geometry-driven connection between buttressing and basal sliding in the Amundsen Sea Embayment when performing multi-century future simulations based on the present-day observed imbalance of the Antarctic Ice Sheet, in which Thwaites and Pine Island glaciers eventually collapse. We perform two initializations which differ in their value of a free parameter that governs the effective pressure of ice grounded on bedrock below sea level. Both initializations lead to a modelled Antarctic Ice Sheet that well resembles present-day conditions (ice thickness, ice surface velocities and mass changes rates). Following each initialization, we run the model forward with present-day climate forcing. In one simulation, Thwaites Glacier collapses first, and in the other, Pine Island Glacier collapses first. When Thwaites Glacier collapses first, it creates a grounding line flux large enough to sustain an ice shelf that provides buttressing which largely balances the basal friction differences when using different basal friction parameterizations. A collapsing Pine Island Glacier, however, is sensitive to the choice of basal friction law. Thus, the regional evolution and its sensitivity to friction laws depend on initialization choices that are poorly constrained by observations. In both simulations, present-day ocean thermal forcing, which is a product of the inversion using the present-day imbalance, is sufficient to drive Thwaites and Pine Island collapse, but small differences introduce an uncertainty of about 500 years in the collapse timing.

The Linfen–Yuncheng Basin is located on the southern edge of the Fenwei Fault Zone, influenced by intense tectonic activity, thick Quaternary sedimentation, and anthropogenic disturbance, it exhibits prominent characteristics of ground subsidence and fissure development. However, uncertainties still exist regarding the primary controlling factors of subsidence. This study employs multi-temporal InSAR data, combined with small baseline subset (SBAS–InSAR) technology to invert the high-precision ground line of sight deformation fields, and conducts time-series decomposition analysis using the Seasonal Trend Decomposition (STL) method. The results show that from 2017 to 2025, subsidence was mainly concentrated in the central and southern regions of the basin, with a maximum cumulative subsidence exceeding 200 mm and an average annual subsidence rate of −40 mm/year. Its spatial distribution is highly consistent with major structural zones such as the Zhongtiao Mountain Front Fault and the Linyi Fault, indicating that fault activity exerts a significant controlling effect on subsidence patterns. Groundwater level fluctuations are positively correlated with overall ground subsidence, and the response rate of different monitoring points is constrained by differences in aquifer depth and permeability. Groundwater aquifer points exhibit rapid and reversible subsidence response, while confined aquifer points are affected by low-permeability or compressible layers, showing a significant lag effect. The research results indicate that time-series analysis based on InSAR can not only effectively reveal the subsidence evolution process at different scales, but also provide a scientific basis for groundwater resource regulation, geological disaster prevention and control, and sustainable regional land utilization.

Abstract Melting of floating ice shelves is one of the key processes determining the mass balance of the Antarctic ice sheet. Freshwater discharge at the grounding line provides an additional buoyancy source, causing local melt enhancement near the grounding line and possibly faster grounding line retreat. The impact of freshwater discharge has been studied extensively for the Greenland ice sheet, but it is only beginning to be assessed for Antarctic ice shelves. In this study, a basal melt parameterization that incorporates both the effects of freshwater discharge and the ocean heat is derived. Based on a simplified melt expression, convergence solutions of a meltwater plume model are used to approximate the plume thermal forcing and velocity for the region near the grounding line. Deviations of the plume solutions from the convergence solutions occur due to nonlinearities associated with the effect of freshwater influx in combination with that of basal geometries and ambient conditions. Those nonlinearities are described based on power-law dependencies in the limit of small heat advection within the plume. This yields a new melt formulation that can be applicable to warm ice shelf cavities. Close agreements are observed when comparing the parameterization with solutions of the plume model for a wide range of freshwater influxes and oceanic conditions. The two-dimensional extension of the parameterization captures the local melt enhancement up to ∼140 m yr −1 observed near the grounding line of Pine Island Glacier. Significance Statement This study provides an improved representation of basal melting under ice shelves including freshwater discharge. Our results reveal nonlinear correlation between the freshwater discharge and meltwater plumes. This interaction plays an important role on determining spatial melt distributions and thus has potential implications on ice sheet stability. The parameterization developed here is a useful tool to improve the simulations of basal melting in the West Antarctic ice sheet where both the effects of warm ambient ocean and freshwater discharge are important.