Numerous supraglacial lakes form on the Greenland Ice Sheet (GrIS) during the summer, and accurately estimating their depth is crucial for understanding GrIS water storage. In this study, we estimate the depth of 35 representative GrIS supraglacial lakes using ICESat-2, Sentinel-2 imagery and ArcticDEM data. ICESat-2-derived lake depth is used to validate the performance of three remote sensing methods, namely empirical formula method (EFM), radiative transfer method (RTM) and depression topography method (DTM). EFM relies on ICESat-2-derived lake depth to construct empirical formulas, while RTM and DTM do not. The results show that (1) the green band EFM performs best; the DTM performs secondarily but tends to consistently underestimate depths; the green-band RTM has lower accuracy and overestimates depths, while the red-band RTM also has lower accuracy but underestimates depths. (2) Temporal changes of depression topography have limited impacts on the performance of DTM, whereas the uncertainties caused by lake shoreline height estimates should be considered. (3) The performance of RTM is significantly influenced by the spectral attenuation coefficient. We further identify the factors that affect spatiotemporal extrapolation of these methods and recommend prioritizing the use of the EFM when near-simultaneous ICESat-2 data are available; otherwise, DTM is recommended, yet an underestimation ratio should be used.

Glacier ice flux is a key indicator of mass balance; therefore, accurate monitoring of ice dynamics is essential. Satellite-based methods are widely used for glacier velocity measurements but are limited by satellite revisit frequency. This study explores using seismic station internal GPS data to track glacier movement. While less accurate than differential GPS, this method offers high-temporal resolution as a by-product where seismic stations are deployed. Using a seismic station on Borebreen, Svalbard, we show that internal GPS provides reliable surface velocity measurements. When compared with satellite-inferred velocities, the results show a strong correlation, suggesting that the internal GPS, despite its inherent uncertainty, can serve as an efficient tool for glacier velocity monitoring. The high-temporal sampling reveals short-term dynamics of speed-up events and underscores the role of meltwater in driving these processes. This approach augments glacier observation networks at no additional cost.

Runoff contributions from glacierized catchments are changing in response to accelerating mass loss. We reconstruct the 1980–2022 mass balance, runoff and water budget of the ∼70% glacierized Kaskawulsh River headwaters in Yukon, Canada, using an enhanced temperature-index model driven by downscaled and bias-corrected reanalysis data. Debris is treated using melt-scaling factors based on site-specific measurements of the critical debris thickness. Accumulation is estimated from downscaled precipitation bias corrected based on in situ measurements. Model tuning incorporates observations of the 2007–18 geodetic mass balance and seasonal snowline positions on the Kaskawulsh Glacier. We assess model sensitivity to the representation of supraglacial debris and accumulation, including treatments of these processes that can be applied in the absence of in situ data. Different representations of debris produce <1% variation in the catchment-wide runoff and water budget. In contrast, accumulation estimates that omit in situ data produce 33–40% variations in modelled runoff relative to those that use these data. This work identifies site-specific measurements of accumulation as critical to accurate estimates of mass balance and runoff for the Kaskawulsh Glacier, in contrast to site-specific characterization of the effects of debris which influence estimated thinning rates at the glacier terminus but have little impact on the glacier-wide runoff.

We present a practically simple methodology for tracking glacier surge onset and evolution using interferometric synthetic aperture radar (InSAR) coherence. Detecting surges early and monitoring their build-up is interesting for a multitude of scientific and safety-related aspects. We show that InSAR coherence maps allow the detection of surge-related instability on Svalbard many years before being detectable by, for instance, feature tracking or crevasse detection. Furthermore, we present derived data for two types of surges; down- and up-glacier propagating, with interestingly consistent surge propagation and post-surge relaxation rates. The method works well on Svalbard glaciers, and the data and core principle suggest a global applicability.

The ice shelves buttressing the Antarctic ice sheet determine the rate of ice-discharge into the surrounding oceans. Their geometry and buttressing strength are influenced by the local surface accumulation and basal melt rates, governed by atmospheric and oceanic conditions. Contemporary methods quantify one of these rates, but typically not both. Moreover, information about these rates is only available for recent time periods, reaching at most a few decades back since measurements are available. We present a new method to simultaneously infer the surface accumulation and basal melt rates averaged over decadal and centennial timescales. We infer the spatial dependence of these rates along flow line transects using internal stratigraphy observed by radars, using a kinematic forward model of internal stratigraphy. We solve the inverse problem using simulation-based inference (SBI). SBI performs Bayesian inference by training neural networks on simulations of the forward model to approximate the posterior distribution, therefore also quantifying uncertainties over the inferred parameters. We validate our method on a synthetic example, and apply it to Ekström Ice Shelf, Antarctica, for which independent validation data are available. We obtain posterior distributions of surface accumulation and basal melt averaging over up to 200 years before 2022.

The conditions under which ice fractures and calves icebergs from Antarctic ice shelves are poorly understood due largely to a lack of relevant observations. Though previous studies have estimated the stresses at which ice fractures in the laboratory and through sparse observations, there remains significant uncertainty in the applicability of these results to naturally deforming glacier ice on larger scales. Here, we aim to better constrain the stresses under which ice fractures using remote sensing data by identifying large-scale fractures on Antarctic ice shelves, calculating the principal stresses from the observed strain rates and comparing the stresses of unfractured and fractured areas. Using the inferred stresses, we evaluate five common fracture criteria: Mohr–Coulomb, von Mises, strain energy, Drucker–Prager and Hayhurst. We find the tensile strength of ice ranges from 202 to 263 $\mathrm{kPa}$ assuming the viscous stress exponent n = 3, narrowing the range produced by previous observational studies. For n = 4, we find tensile strengths of 423–565 $\mathrm{kPa}$, bringing our inferences closer to alignment with laboratory experiments. Importantly, we show that crevassed and uncrevassed areas in the four largest ice shelves are distinct in principal stress space, suggesting our results apply to all ice shelves and the broader ice sheet.

In 2015, a continuous 15.4 m snow/firn core was recovered from central South Georgia Island at ∼850 m a.s.l. All firn core samples were analyzed for major (Al, Ca, Mg, Na, K, Ti and Fe) and trace element concentrations (Sr, Cd, Cs, Ba, La, Ce, Pr, Pb, Bi, U, As, Li, S, V, Cr, Mn, Co, Cu and Zn) and stable water isotopes. The chemical and isotopic signal is well preserved in the top 6.2 m of the core. Below this depth, down to the bottom of the core, signal dampening is observed in the majority of the elemental species making it difficult to distinguish a seasonal signal. Thirteen elements (As, Bi, Ca, Cd, Cu, K, Li, Mg, Na, Pb, S, Sr and Zn) have crustal enrichment factor values higher than 10 suggesting sources in addition to those found naturally in the crust. While this study shows that 850 m a.s.l. is not high enough to preserve a record including recent years, higher-elevation (>1250 m a.s.l.) glaciers may be likely candidates for ice core drilling to recover better-preserved, continuous, recent to past glaciochemical records.

The Fedchenko Glacier in central Pamir is one of Asia’s longest glaciers and has been a focal point for scientific investigation spanning the 20th and 21st centuries. This study explores a time series of elevation changes from 1928 to 2021 using diverse data sources: historical maps, optical digital elevation models from various sensors (KH-9, SPOT5 and Pléiades), ICESat laser altimetry and GNSS surveys. The mean rate of elevation change along the glacier center line over this period of 93 years is $-0.46\ \mathrm{m\ yr}^{-1}$. The different sub-periods of elevation changes are investigated together with Fedchenko meteorological station data (1936–91) and ERA5 reanalysis (1950–2021). The most moderate thinning is observed during the earliest and coldest period (1928–58). The 1958–80 period is characterized by large thinning rates that can be partially explained by a dry anomaly and, locally, by a dynamic thinning related to a probable, but not directly observed, surge-like event. A wet anomaly in 1980–2010 potentially mitigated temperature-induced mass losses for this warm period, which is consistent with the observed moderate thinning. From 2010 to 2021, substantial thinning of $-0.31\,\mathrm{m\ yr}^{-1}$ was recorded in the accumulation area (>4800 m a.s.l.), in line with a broader trend of generalized mass losses in the Pamir region.

Thermal imagery was collected for 26 hours over a crevassed region within the accumulation zone of the Haupapa/Tasman Glacier, New Zealand. During the night, the imaged snow surfaces associated with crevasses cooled slower than non-crevassed surfaces resulting in temperature differences of several degrees. Night surface temperature varied across the non-crevassed areas to a smaller degree, primarily in relation to slope. The surface temperature difference between crevassed and non-crevassed surfaces is primarily attributed to the reduced sky-view of crevasses so that a large proportion of longwave radiation is not emitted away from the glacier but is received by opposing crevasse walls. Possible additional causes are that crevasses trap warm air which enables greater sensible heat transfer, crevasses have greater conduction of heat from isothermal glacier ice as a result of limited insulating snow, and crevasse walls have greater amounts of liquid water which delays the onset of surface freezing.

Two-dimensional (2D) views dominate the application of linear elastic fracture mechanics to problems in ice-shelf rift propagation, yet from the perspective of fracture mechanics, processes at the rift front are inherently three-dimensional (3D). 2D simplifications are nevertheless desirable for their efficiency and apparent compatibility with shallow-shelf approximation (SSA) ice flow models. Here, the implications of flattening the ice-shelf rift problem are investigated and a theoretical foundation is established to support using a plane stress approximation. In this way, we verify compatibility between 2D simplifications for rifts and for ice-shelf flow, which is a requirement for situations in which SSA-derived stresses are used to study rift propagation. Comparing the plane problem to a 3D counterpart, we show that the 2D results at rift tips are a good estimate for mean rift front stress conditions. Mode I (opening mode) stress intensity factors exhibit a depth-dependence that implies that rifts should be longer at the ice base than at sea level. Other minor 3D effects, which also involve Modes II and III, arise where the rift front intersects the upper and lower ice surfaces.

The shallow ice approximation (SIA) model in strong form is commonly used for inferring the flow dynamics of grounded ice sheets. The solution to the SIA model is a closed-form expression for the velocity field. When that velocity field is used to advance the ice surface in time, the time steps have to take small values due to quadratic scaling in the horizontal mesh size. In this paper, we write the SIA model in weak form and add in the free-surface stabilization algorithm (FSSA) terms. We find numerically that the time-step restriction scaling is improved from quadratic to linear, but only for large horizontal mesh sizes. We then modify the weak form by adding the initially neglected normal stress terms. This allows for a linear time-step restriction across the whole range of horizontal mesh sizes, leading to improve efficiency. Theoretical analysis demonstrates that the inclusion of FSSA stabilization terms transitions the explicit time-stepping treatment of second derivative surface terms to an implicit approach. Moreover, a computational cost analysis, combined with numerical results on stability and accuracy, advocates for preferring the SIA models written in weak form over the standard SIA model.

Brine migration from sea ice into the overlying snowpack is relatively understudied yet can significantly modify thermodynamic and electromagnetic properties of the snow. In this study, we investigate the impact of snow properties on brine wicking and runoff by producing samples of four distinctly different snow types (soft wind slab, hard wind slab, faceted grains and melt-freeze clusters) and monitor changes in snow properties after adding brine. The results illustrate that snow grain type and density have a pronounced effect on the height of brine wicking and runoff, snow compaction rates and salt concentrations. In all samples, we observed separation of the initial brine-saturated slush layer into two sublayers with distinctly different properties: solid saline snow-ice at the bottom and less saline brine-wetted snow above it. The maximum height of brine wicking ranged from 6.5 cm in faceted snow to 8.9 cm in hard wind slab samples, which was equivalent of 40 to 50% of total samples’ height. The volume and timing of brine runoff varied between samples, occurring later and in smaller volumes in hard wind slab compared to soft wind slab and coarse-grained samples.

We summarise 15 years of field and remote monitoring of Tapado Glacier in north-central Chile (30° S). Observations include meteorological records, direct mass balance measurements, uncrewed aerial vehicle surveys and tri-stereo satellite imagery for deriving high-resolution elevation changes. Frequent droughts and a significant warming trend of 0.29°C decade−1 since 1974 have caused a decrease in glacier surface albedo and an accelerated loss of glacier area and mass, particularly since the onset of the Chilean Megadrought in 2010, associated here with a 43% winter precipitation deficit. Geodetic estimates indicate increasingly more negative mass balance, varying from slightly negative before 2000 to −0.18 ± 0.35 m w.e. a−1 in 2000–12, −0.44 ± 0.11 m w.e. a−1 in 2012–20 and −0.75 ± 0.12 m w.e. a−1 after 2020. Glacier mass loss is associated with several morphological changes, such as increased penitente height, a larger total surface area of ice cliffs and supraglacial ponds over the debris-covered section and more frequent falls of snow and ice from marginal ice surrounding a steep area of exposed bedrock. Tapado Glacier exemplifies how glacier mass loss is driven by various processes, requiring multiple monitoring techniques, and highlights the accelerated changes of the Andes cryosphere.

Fast glacier motion is facilitated by slip at the ice-bed interface. For slip over rigid beds, areas of ice-bed separation (cavities) can exert significant control on slip dynamics. Analytic models of these systems assume that cavities instantaneously adjust to changes in slip and effective pressure forcings, but recent studies indicate transient forcings violate this—and other—underlying assumptions. To assess these incongruities, we conducted novel experiments emulating hard-bedded slip with ice-bed separation under periodic effective pressure transients. We slid an ice-ring over a sinusoidal bed while varying the applied overburden stress to emulate subglacial effective pressure cycles observed in nature and continuously recorded mechanical and geometric system responses. We observed characteristic lags and nonlinearities in system responses that were sensitive to forcing periodicity and trajectory. This gave rise to hysteresis not predicted in analytic theory, which we ascribed to a combination of geometric, thermal and rheologic processes. This framework corroborates other studies of transient glacier slip and we used it to place new constraints on transient phenomena observed in the field. Despite these divergences, average system responses converged toward model predictions, suggesting that analytic theory remains applicable for modeling longer-term behaviors of transiently forced slip with ice-bed separation.

We determined the compressive strength of weak layers of faceted crystals and depth hoar using artificially grown samples with a wide range of microstructural morphologies in a cold laboratory setup. Micro-computed tomography (µCT) imaging showed that the microstructures of the artificial samples were comparable to that of natural depth hoar. We performed compression experiments in a displacement controlled testing machine on 92 depth hoar samples with densities ranging from 150 kg m−3 to 350 kg m−3. The compressive strength spanned two orders of magnitude (1–150 kPa) at strain rates of about 10−3 s−1 at $-5^{\circ}\mathrm{C}$ and followed a power law as a function of density. Several microstructural metrics such as the specific surface area, connectivity density and correlation lengths obtained from µCT measurements exhibited a statistically significant relationship with compressive strength. Analysis of the residuals of the power law fit showed that in addition to density, horizontal correlation lengths also correlated with strength. However, in this study, density remained the dominant predictor of the compressive strength of depth hoar.

Peru hosts a significant portion of the world’s tropical glaciers, which are undergoing rapid mass loss due to climate change. Knowledge of the ice volume and bedrock topography of these glaciers is important for predicting changes in glacier dynamics, runoff, and interpreting ice-core records. This study presents results from glaciological and geophysical surveys conducted during a 2019 expedition to Nevado Huascarán, Peru’s highest mountain when four ice cores were extracted from the col and summit. Ground-penetrating radar measurements provided detailed ice thickness and snow accumulation data, highlighting complex internal glacier structure and indicated that the climatic records obtained from ice cores recovered in 2019 were continuous and extended past the Holocene. Ice flow modeling enabled investigation of glacier dynamics. It was shown that the upstream effect on ice-core record is minimal. Comparison with ice thickness modeling data for Huascarán from various sources revealed significant discrepancies with measured ice thicknesses, suggesting that the inversion methods underestimate ice thickness for the accumulation zones of mountain glaciers. This research contributes data for understanding glacier behavior in the context of climate change and for modeling efforts for better assessments of water resources, potential geohazards and paleoclimatic interpretations.

In situ glaciological observations in the Himalaya–Karakoram (HK) region mostly come from small glaciers. Drang Drung (69.6 km2, Zanskar, Ladakh) is the largest glacier in the HK monitored for in situ glacier-wide mass balances applying the traditional glaciological method. During 2021–23, point ablation varies from –1.8 to –8.3 meter water equivalent (m w.e. a–1) in the ablation area, and from 0.15 to 1.70 m w.e. a–1 in the accumulation area. The mean glacier-wide mass balance is −0.74 ± 0.43 m w.e. a−1 over 2021‒2023, corresponding to a mean equilibrium line altitude of 5134 m a.s.l. and accumulation area ratio of 0.53. The mean annual vertical mass-balance gradient of 0.62 m w.e. (100 m)–1 on Drang Drung Glacier resembles that observed on other Himalayan glaciers. These initial investigations on Drang Drung Glacier address the gap for glacier monitoring in the Zanskar Range and will be continued in the long term.

Firn can store glacial meltwater and delay contribution to sea level rise, but ice layers and ice slabs within the shallow firn layer can impede the downward percolation of melt. Here we report firn conditions along a transect on southwest Devon Ice Cap (DIC), Nunavut, and explore its response to air temperature variability over a decadal period. We present results from two field campaigns, during which six shallow firn cores were extracted along the same transect in spring 2012 and 2022. At all sites, the ice fraction (IF) was less in 2022 than in 2012, and the firn content increased. Between 2012 and 2022, the IF of the firn layer changed by −30% at the lowest elevation site (1400 m a.s.l.) and by −11% at the highest elevation site (1800 m a.s.l.) and by an average of −26% across all sites. Despite higher annual positive degree day sums during 2012–22 compared to 2002–12, cooler summers in 2013, 2018 and 2021 resulted in less ice content in the shallow firn layer. This demonstrates that the shallow firn layer can regenerate from several cooler years and highlights the nuanced response of the DIC shallow firn layer to climate warming.

This study provides a comprehensive analysis of the snow and avalanche climate of the Chic-Chocs region of the Gaspé Peninsula, located in the northeastern Appalachians of eastern Canada. The data revealed two major components of the snow and avalanche climate: a cold snow cover combined with a maritime influence causing melt/ice layers through rain-on-snow events. The CRCM6-SNOWPACK model chain was good at representing the seasonal mean of climatic indicators, snow grain type and an avalanche problem type that well represented the investigated snow and avalanche climate of the study region. The global comparison shows that the snow and avalanche climate is different from other areas in western North America, but similar to Mount Washington (New Hampshire, USA) and central Japan. We show a clustering based solely on avalanche problem types, which showed that the onset date of wet snow problems divided most of the winters into three clusters. We compare these clusters with the French Alps and show some similarities, moving away from a traditional snow and avalanche climate description. The paper concludes that the use of advanced snow cover modeling combined with avalanche problem type characterization represents a suitable method to improve our understanding and classification of snow and avalanche climates for avalanche related problems, ultimately contributing to improved forecasting and risk management in similar regions.

Variations in stable oxygen isotopic compositions in sea ice provide information on environmental conditions during sea ice formation and also are important in understanding the regional and temporal aspects of the fresh water budget of the Arctic Ocean. We analyzed the oxygen isotope fractionation between sea ice and sea water using ice core and surface ocean samples obtained in a field study in the Lincoln Sea/Switchyard region of the Arctic Ocean. Using the Sea Ice Tracking Utility, we track the sea ice backward in time along drift trajectories, and use a simple model to calculate ice growth rates. Our results indicate that sea ice at the bottom of the floes that we sampled in the Switchyard Region grew within the past winter along a trajectory extending back to the North Pole. The effective fractionation coefficients from the bottom ice layers and the parent water mass are close to 2.11‰ with a standard error of ±0.06‰. Knowing this sea-ice oxygen isotope fractionation coefficient for high Arctic drifting ice is critical for use of equations for mass balance, salinity, oxygen isotopes and nutrients to calculate water mass fractions and sources to understand freshwater balance.