Frontal ablation is a major component of ice loss in Patagonia but remains uncertain outside the Patagonian icefields. We present a multiple fluxgate method to quantify frontal ablation near the calving front, capturing spatial heterogeneity and complex tongue geometries. We apply the method to Manso Glacier (Monte Tronador, Northern Patagonia), providing the first frontal ablation estimates for a Patagonian glacier outside the icefields. Subseasonal frontal ablation time series were reconstructed for 2017–24 and annual values for 2013–23. Mean annual frontal ablation was ∼3.6 Mm3 a−1, totaling 39.5 ± 1.8 Mm3 (0.036 ± 0.002 Gt, assuming 917 kg m−3) over 2013–23. Frontal ablation shows marked seasonality and strong spatiotemporal variability, with hotspots migrating irregularly along the calving front, whereas ice velocity at the glacier terminus exhibits a stable spatial pattern. Frontal ablation correlates strongly with air temperature (r = 0.71) and lake level (r = 0.71), moderately with lake surface temperature (r = 0.63) and negatively with precipitation (r = −0.56). The method is particularly suited for high-resolution studies of mountain glaciers, where spatial variability and transient frontal processes dominate terminus dynamics.

In recent decades, Greenland’s marine-terminating glaciers have retreated and accelerated, contributing significantly to sea level rise. The presence of an ice mélange and its associated buttressing force on a glacier terminus has a significant impact on glacier advance and retreat. The buttressing force is modulated by mélange thickness, which is influenced by mélange melt rate, but our understanding of mélange melting remains limited. We model the melting of ice mélange by the ocean using MITgcm, focusing on the relationship between melt rate and mélange thickness. Melt rates generally increase with mélange thickness (thicker mélange reaches further into deep warm water) and are particularly sensitive at thicknesses shallower than 100 metres. We test three ways of incorporating the mélange thickness into a parameterisation of mélange melt rates with additional inputs of subglacial discharge and oceanic thermal forcing. We apply the most general parameterisation to 27 instances of ice mélange around Greenland, estimating summertime melt rates of 0.01–0.62 m/d. Melt rates are primarily controlled by oceanic thermal forcing, followed by mélange thickness. The development of these parameterisations represents a key step in advancing our understanding of ice mélange dynamics and enabling a representation of mélange in climate and ice sheet models.

Water at glacier beds has been repeatedly linked to short term ice-velocity fluctuations and plays a key role in theoretical models of glacier surging. However, the details of water storage in the surge cycle, including where and when water accumulates and drains, remain unclear. Here, we use seismic noise interferometry to monitor changes in water volume near the glacier bed through the surge cycle at Sít’ Kusá, Alaska, and infer evolution in the structure of the drainage system. Within the reservoir zone, we identify multi-year water accumulation during quiescence in a poorly connected basal drainage system, followed by a rapid decrease in basal water volume driven by a reorganization toward a better-connected system that coincides with surge termination. This multi-year cycle is overlain by similar dynamics at the seasonal timescale that modulate annual increases in ice velocity within the reservoir zone. We speculate that reorganization of subglacial drainage and increases in connectivity between previously isolated water volumes can play a central role in the onset of high ice velocities during both seasonal speedups and surges. Our findings regarding the long-term evolution of water storage near the bed fit well within enthalpy-based models of glacier surging.

Glaciers actively store and release meltwater with significant impacts on glacier flow velocity and downstream environments. The evolution of this drainage system is a key component in understanding glacier dynamics. In temperate alpine glaciers, the change of the subglacial drainage network from distributed to channelised is theoretically known, but lacks empirical documentation. As subglacial channels are extremely difficult to access, it is important to test innovative methods for locating them. Here, we use surface seismic monitoring, which enables us to identify the location of multiple subglacial channels below Glacier d’Otemma, Valais, Switzerland. We calculate time delays between pairs of seismic sensors and backtrack source locations. Using matched field processing and beamforming analysis, we obtain spatial and temporal patterns of seismic noise produced by the glacier. This allows us to interpret a possible evolution of the subglacial drainage network from a distributed to an efficient one and locate three distinct subglacial channels in close proximity.

We use all 27 years of airborne laser altimetry from the University of Alaska Fairbanks to quantify changes in surface elevation across 205 large glaciers that together represent 56% of the glacier area in Alaska and adjacent Canada, including 71% of the ice cover in Alaska’s National Parks. We reprocessed lidar point clouds into a homogenized publicly available 2.5 m digital elevation model (DEM) archive, implemented a new double-differencing approach to incorporate partially overlapping surveys and derived elevation change in 10 m elevation bins to assess glacier-wide mass balance for all surveyed epochs on each glacier. The resulting mean balance rate for all measured glaciers shows statistically significant acceleration of mass loss, ranging from $-0.83 \pm{0.13} \,\, \text{m}\,\, \text{w.e.}\ \text{a}^{-1}$ before 2008 to $-1.16 \pm{0.08} \,\, \text{m}\,\, \text{w.e.}\ \text{a}^{-1}$ thereafter. Extrapolating measured thinning rates from the latter period (2008–22) to unsurveyed glaciers suggests that Alaskan National Parks are losing 33.74 $\text{Gt a}^{-1}$ of ice, approximately one third of all estimated losses in the region. We use case studies of several prominent glaciers to show how this sustained acceleration of mass loss, which is consistent with recent global assessments, is having direct impacts on visitors, land managers, ecosystems and geohazards in the National Parks.

Supraglacial lakes on the Greenland Ice Sheet are becoming increasingly abundant, impacting the distribution and routing of surface runoff with implications for drainage system evolution and ice flow. Their dynamics are well understood in summer when optical satellite imagery provides effective monitoring; however, their distribution and impact are less clear in winter when monitoring is restricted by the 24-hour darkness of the polar night. Using Sentinel-1 C-band Synthetic Aperture Radar (SAR) time series from 2018 to 2019, we assess whether an unsupervised time series clustering approach can be used to identify dynamic lake processes in winter. Our results show that: 1) winter lakes can be detected with an 87.6% accuracy; 2) SAR backscatter time series can be used to automatically and accurately (75.0%) classify winter lake behaviour (freeze-through, buried, no winter lake presence) without training data; 3) the temporal backscatter pattern of winter lake behaviour is consistent across regions and years and therefore generalisable; and 4) individual lakes can exhibit multiple behaviours over winter. Our work underscores the need for methods that capture spatio-temporal complexities in SAR backscatter, and provides insights into how C-band backscatter can be used to contribute towards year-round monitoring of lake dynamics across Greenland.

This study presents the first chemical characterization of the seasonal snowpack on the Godwin-Austen Glacier (central Karakoram), based on two snow pits sampled during winter 2018–19. Major ions were quantified and complemented by trace element measurements to investigate source contributions. The main snow pit (SP1), deeper and more sheltered, preserves a continuous record of seasonal atmospheric deposition, with ionic variability reflecting alternating crustal and anthropogenic aerosol inputs. Mineral dust is identified as the dominant source of Ca2+, Mg2+, SO42−, Sr and Ba, consistent with carbonate- and evaporite-rich regional inputs. In contrast, distinct NO3− enrichments indicate episodic anthropogenic pollution inputs. Ten-day back trajectories reveal both temporal and elevation-dependent shifts in source regions during the accumulation season, linking mineral dust deposition to arid and semi-arid regional sources and anthropogenic signals to local human activities on and near the glacier, as well as to inputs from the Indo-Gangetic Plain, with both source types additionally influenced by long-range westerly transport. The second snow pit (SP2), more exposed to post-depositional alteration, shows patterns consistent with sublimation, wind erosion and downward ion redistribution driven by partial melting. Overall, this study provides a new reference dataset for snow chemistry in the western sector of High Mountain Asia.

Mountain glaciers are melting at an accelerated rate due to global warming, thereby significantly altering proglacial and downstream hydrology. However, the biogeochemical transformation of dissolved organic matter (DOM) along the glacier-lake-stream continuum remains unclear. We investigated DOM dynamics within a typical continuum on the Dagu Glacier (eastern Tibetan Plateau) by analyzing samples from supraglacial snow, surface ice, a proglacial lake and a downstream glacier-fed stream during the mid (July) and late (October) melting seasons of 2021, coupled with in situ incubation experiments at the glacier terminus. Optical spectroscopy revealed that protein-like components dominated the supraglacial snow, ice and proglacial lake samples (72.2–95.3%), whereas stream samples exhibited higher proportions of humic-like components (23.1–44.1%), indicating an increasing terrestrial influence downstream. Ultrahigh-resolution mass spectrometry (Fourier transform ion cyclotron resonance mass spectrometry [FT-ICR MS]) analysis further revealed a 12.8–35.8% decrease in aliphatic and peptide-like compounds, alongside a 12.7–36.2% increase in lignin, polyphenolic compounds and polycyclic aromatic compounds along the continuum. The bio-incubation experiment, conducted under ambient field conditions with acknowledged methodological constraints (e.g. non-sterile filtration, fluctuating temperatures), provided evidence consistent with microbial degradation being a key driver of DOM transformation, showing a 26.3% net loss of aliphatic and peptide-like compounds over 30 days. These findings advance our understanding of glacial DOM biogeochemistry and its seasonal evolution.

Sea ice motion in marginal ice zones is inherently multi-scale, influenced by the relationship between the floe size distribution and the temporal and spatial scales of winds and ocean currents. Joint observations of the floe size distribution and motion are necessary to develop and validate models of the marginal ice zone. However, such observations are rare. We present observations of floe-scale Lagrangian sea ice translation and rotation in the East Greenland seasonal and marginal ice zones spanning the spring-to-summer transition for the years 2003–20. The observations are derived from moderate-resolution optical imagery using the Ice Floe Tracker algorithm and consist of floe shapes, geometric properties, reflectance and trajectories. We investigate sea ice seasonality, links between floe size, translation and rotation, and length scale dependence of horizontal deformation. The floe size distribution evolves from April to July, with increasing prevalence of small floes. Variability of both drift speed and rotation depends on the floe size. Deviations from the mean drift are exponentially distributed, suggesting a dominant role for ocean turbulence in observed sea ice dynamics. Deformation rates show strong length scale dependence and vary seasonally. These observations provide new information for sea ice model development and validation in marginal ice zones.

Supraglacial lakes on Northeast Greenland Ice Stream glaciers (79N and Zachariæ Isstrøm) store and route meltwater to the bed, yet controls on their evolution and cascading drainage remain poorly understood. We mapped the lakes across contrasting 2019 (warm) and 2020 (normal) melt seasons using Sentinel-2 imagery, ArcticDEM and ICESat-2 altimetry with an empirically calibrated reflectance-depth model. Sustained warming in 2019 produced 10% larger peak lake area despite similar lake counts, showing cumulative temperature control on growth. The $ \lt 800\,\mathrm{m}$ elevation range hosted most number of lakes while gentle slopes ($ \lt 0.3^\circ$) stored largest volumes despite shallower depths. Of $\sim$600 rapid drainages detected, cascades (with $ \lt 3$ lakes per cluster over a spatial extent $ \lt 2.5\,\mathrm{km}$) dropped from 31% to 20% between years. Overall, our results demonstrate that variations in melt-season intensity could be a factor in modulating supraglacial lake persistence, drainage behaviour and cascading dynamics. These findings emphasize the importance of mid-elevation lakes as critical nodes in meltwater transfer and provide new insights into the understanding of surface water storage and surface-to-bed hydrological connectivity across the northeast Greenland ice margin.

There is a growing collection of ice-penetrating radar systems being used in a variety of glaciological settings to collect a body of data that is expanding in its scale, diversity and information richness. While there are nuanced differences among particular instruments, there are four main classes of radar systems used to observe the subsurface of ice sheets and glaciers: monotone pulse airborne sounders, chirped airborne sounders, ground-traversed impulsive systems and stationary continuous-wave systems. While these classes are often treated as fundamentally different instruments with distinct communities and literature, we seek to reframe them as choices on a continuum of potential waveforms. In particular, we focus on the tradeoff between achieving large coherent processing gains and mitigating interference from the matched-filter response of strong echoes at shorter delays as the key limiting factors for subsurface target detection. We also discuss the glaciological settings in which different waveform choices perform best, as well as potential avenues this raises for new instrument and experiment designs.

Water pressures in conduit networks (e.g. linked cavities, R-channels, subglacial water sheets) support a fraction of glacier weight; the remainder is carried by elevated normal stresses where basal ice is separated from the bed by extremely thin water films. We show how the requirements for melt flow toward conduits constrain film water pressure regimes. Where permeable bed materials facilitate efficient drainage, film pressures approach conduit water pressures, and deficits below the ice normal stress require the direct ice–bed stress transfer, termed thermomolecular pressure, that accompanies interfacial premelting. Beneath warm-based regions of the Greenland Ice Sheet, premelting is likely wherever meter-scale till depths are present; bulk melting conditions, with film water pressures balancing ice normal stresses, are anticipated where the ice and bed are both effectively impermeable. Englacial transport through vein networks can facilitate premelting over small film areas on impermeable beds; absent significant vein transport, such locations are prone to the formation of basal crevasses, which can buffer water pressures near the minimum compressive stress. Interfacial premelting is important for the preservation of unconsolidated bedforms, the strengthening of debris–bed frictional contacts and the enhancement of basal temperature fluctuations; anticorrelations between nearby borehole pressure records are expected when bulk melting prevails.

Wilkes Subglacial Basin (WSB) stores enough ice to raise global sea levels by three to four metres, and comprises a region of East Antarctica potentially vulnerable to climate-induced ice loss. We investigate WSB’s glacial history back to just after the Last Interglacial ($\sim$130–115 ka) using its englacial stratigraphy. We trace eight radio-echo-sounded internal reflection horizons (IRHs) across WSB, dating them at intersections with Talos Dome and EPICA Dome C ice cores, with one IRH englacially connecting the ice cores. The WSB IRHs span ages from 13.1 $\pm$ 0.5 to 90.3 $\pm$ 2.3 ka, with an older 122.5 $\pm$ 2.0 ka IRH traced across the Dome C plateau. With these IRHs, we make regional inferences about past and present ice behaviour, including identifying areas of IRH drawdown relating to ice velocity, accumulation and geothermal heat flow. Approximately 300 km upstream of the WSB grounding line, 20$\%$ of the ice lies below and hence is older than 90.3 $\pm$ 2.3 ka, suggesting ice presence across this region throughout the Last Interglacial. Several of our IRHs have been mapped extensively elsewhere across the East Antarctic Ice Sheet, and this study therefore contributes to the wider objective of mapping Antarctica-wide englacial stratigraphy.

Accurate knowledge of glacier bed geometry and flow parameters is essential for glaciological modeling and can be inferred from surface data and theoretical principles. This study evaluates the performance of the Instructed Glacier Model (IGM) v2.2.1 in estimating glacier ice thickness using the protocol from Phase II of the Ice Thickness Models Intercomparison eXperiment (ITMIX II). Results show that IGM ranks among the best-performing models, producing largely unbiased ice-thickness fields. Compensating errors, where underestimations of ice thickness in some glacier regions are offset by overestimations in others, are generally small, indicating robust overall performance. Extreme deviations from observed thicknesses are less frequent in IGM than in the ITMIX II model ensemble. We also examine the ability of IGM to reproduce glacier dynamics by comparing modeled and observed surface velocities. While IGM is generally capable of reproducing the surface velocities well, our analysis reveals a trade-off between matching ice thickness and surface velocity, possibly due to inconsistencies or biases in the observational datasets. Generally, the overall good performance of IGM in reproducing glacier geometry and dynamics supports its potential for initializing glacier evolution simulations.

Field data suggest that Thwaites Glacier’s bed is composed of alternating areas of hard and soft material with correlated topographic variations. Prior modeling shows that forced response differs strongly for simulations on endmember beds, suggesting that under some circumstances, a mosaicked bed can exhibit a response that falls outside endmembers. We explore the impact of spatially variable bed rheology draped on the measured topography beneath Thwaites under sustained sub-ice shelf melting. Experiments utilize the Ice-sheet and Sea-Level System Model to assign the basal sliding law exponent and associated friction coefficient on an element-wise basis. In mixed-rheology models, thinning is localized over harder basal topographic ridges (bedrock), with widespread drawdown over flatter areas comprising a softer material (deforming till). This dual dynamic signature creates rapid retreat under sustained forcing, as enhanced driving stresses over ridges upstream of extended areas of retrograde bed allow faster retreat across a more thinned catchment. For more moderate forcing that allows this pattern to develop, retreat can be faster than for either endmember bed. Findings indicate a need for additional data and more-informed inversions for basal friction in order to constrain and simulate basal conditions beneath Thwaites, thereby reducing uncertainty in predictive models of sea-level rise from the West Antarctic Ice Sheet.

The beds of many fast-flowing glaciers are underlain by sediment (till) whose physical properties regulate the mechanical and hydrological controls on glacier slip. Despite the importance of the till’s physical properties in affecting slip and hydrology, they are often ill-constrained, in part due to the inaccessible nature of glacier beds. Here, we assess a range of till properties for 11 different till samples, 10 of which were acquired from the Byrd Polar Rock Repository, collected from a range of locations along the Transantarctic Mountain Range, and one till sample collected from the paleo-grounding zone of Bindschadler Ice Stream (Ice Stream D). Using these sediment samples, we assess their coefficient of consolidation, friction angle, cohesion value, hydraulic conductivity, mineralogy, density and grain-size distribution. We provide an overview of the methods used and the resulting measurements but refrain from wide-scale interpretations of the results. In general, we find that some physical properties have a relatively small variance among the samples (e.g. friction angle, cohesion and grain-size maturity), whereas other properties vary more widely (e.g. hydraulic conductivity and coefficient of consolidation).

Antarctic sea ice frequently undergoes seawater flooding, initiating the upward wicking of saline water into the snowpack and leading to the formation of slush, brine-wetted and snow-ice layers near the snow–ice interface. This study investigates how variations in liquid volume, salinity and snow stratigraphy affect upward liquid migration in the snowpack. Results indicate that liquid volume exerts the strongest control on wicking height, runoff onset and total runoff volume. While salinity is also important, its effect is secondary. Notably, even when both liquid volume and salinity are doubled, the increase in snow-ice and brine-wetted layer thickness is modest. We further examine the role of snow stratigraphy using samples with three distinct layering structures. Capillary barriers at fine- and coarse-grained layer interfaces promote liquid pooling and the formation of ice lenses, likely altering snowpack thermophysical and electromagnetic properties.

Antarctic ice cores provide highly detailed climate histories; yet, the existing proxy record is limited by uneven spatial and temporal coverage. Collecting new ice cores will improve our understanding of climate processes in Antarctica, but the cost of drilling new records demands careful site selection. Here, we present a data-driven optimal sensor approach to select ice core sites that best constrain a chosen climate metric by iteratively applying an Ensemble Kalman Filter. We demonstrate the method by choosing two Antarctic-wide metrics: average annually resolved temperature and annual accumulation since the Industrial Era. Our approach accounts for proxy uncertainty based on the site accumulation rate; we discuss logistical constraints for specific case studies. We find that the southern Ross Ice Shelf and western Dronning Maud Land are optimal regions to reconstruct Antarctic-wide total accumulation and average temperature, respectively. We describe three case studies: 1) drilling a new core at Crary Ice Rise on the Ross Ice Shelf; 2) drilling a new core at Lyddan Ice Rise in Dronning Maud Land; and 3) redrilling the US-ITASE cores in West Antarctica. Our data-driven methodology can guide future community drilling efforts to maximize the value of new ice cores for climate reconstruction.

Basal sliding is an important component of ice motion that is integrated into ice flow models via the use of a friction law, which relates basal shear stress to basal sliding speed and effective pressure. Recent two-way model coupling has utilized temporally changing effective pressure from subglacial hydrology models to drive ice dynamics models. However, there is still significant work required to understand how the friction law impacts such two-way coupled models. Here, we use the Siple Coast, West Antarctica, as a case study to examine these impacts. We compare the Budd and Schoof friction laws, as well as two new regularized Coulomb friction laws that we propose, which respond to changes in ice speed and effective pressure in a way that is consistent with subglacial conditions predicted from subglacial hydrology modeling. We find that the Budd and Schoof friction laws struggle to operate with two-way coupled modeling, leading to a non-physically large speedup of ice in the interior of the ice sheet. Instead, the new friction laws that we propose do not lead to such instabilities in ice motion, producing more physically realistic ice flow outputs.