The Arctic is undergoing increased warming compared to the global mean, with major implications for the mass balance of glaciers. Direct observations of mass balance in the Russian Arctic are sparse and remotely sensed volume changes do not provide information about climatic drivers. Here, we present simulations of the climatic mass balance and meltwater runoff from glaciers in Franz Josef Land and Novaya Zemlya from 1991 to 2022. Based on simulations of glacier climatic mass balance over the period 1991–2022, we present a first detailed view of mass balance evolution in Franz Josef Land and Novaya Zemlya. The simulations are conducted at a 2.5 km resolution using the CryoGrid model forced by the Copernicus Arctic Regional ReAnalysis (CARRA) product. Over the 30 year simulation period, the climatic mass balance of both Franz Josef Land (0.21 m w.e. a−1) and Novaya Zemlya (0.07 m w.e. a−1) is positive on average without a significant trend in annual climatic mass balance. There is still a tendency towards more frequent high-melt years after 2010 and the associated glacier runoff has intensified with record melt years occurring during the model period.

The term ‘water pocket’ describes invisible en- and subglacial water reservoirs that can cause sudden glacial outburst floods. However, there is currently no consensus on its definition and the formation and rupture mechanisms of water pockets remain poorly understood. This study aims to understand the mechanisms behind water pocket outburst floods (WPOFs) from alpine glaciers by analyzing their spatial and temporal distribution, pre-event meteorological conditions and the glacio-geomorphic features of the glaciers from which the floods originate. To this end, we updated an inventory of known WPOFs in the Swiss Alps to 91 events from 37 individual glaciers. Most WPOFs occurred between June and September, likely linked to meltwater input. Meteorological data indicate anomalously high temperatures during the days preceding most events and heavy precipitation on 25% of days for which WPOFs occur, indicating that water pockets typically rupture during periods of high water input. We propose four mechanisms of water pocket formation: temporary subglacial channel blockage (which is the mechanism suggested most often for our inventory), hydraulic barriers, water-filled crevasses and accumulation of liquid water behind barriers of cold ice (thermal barriers). Overall, our analysis highlights the challenge of understanding WPOFs due to the subsurface nature of water pockets, emphasizing the need for field-based research to improve their detection and monitoring.

Submarine melting is one of the major mechanisms of ice loss from marine-terminating glaciers and ice shelves, but its contribution is yet to be fully understood. Here, we demonstrate the feasibility of monitoring melting using passive underwater acoustics, by sensing the loud crackling sound produced during melting due to the release of pressurised ice-trapped bubbles. We profile the acoustic field in glacial bays in Svalbard using a hydrophone array and show that the sound level in the bay contains clues on the melt activity. The sound level’s interpretation is hindered by its spatial variability, which we suppress using a model of melt-induced acoustic activity. Thereby, we show that the sound generated at the glacier terminus is correlated with the ablation rate at the calving glacier front and the water temperature and thus linked to the melt rate. This marks a step forward in using passive acoustics to monitor submarine melt, paving the way for an autonomous, long-term, large-scale monitoring tool providing data that can inform assessments and simulations of ice sheet loss and sea level rise.

The evolution of the temperature and mass balance of first-year (FYI: Site S1) and second-year (SYI: Site S2) land-fast sea ice (LFSI) in May–November were investigated using high-resolution thermistor-string-based ice mass balance buoys, borehole measurements and a numerical sea ice model. In May, the growth rate of a 0.55 m FYI ice floe (9.2 mm day−1) was twice that of 1.08 m SYI (4.7 mm day−1) in snow-free conditions. After snow accumulation on 10 June, the growth slowed down and both reached 3.5 mm day−1 by 20 July. The observed/modelled ice thicknesses were 1.38/1.47 m for S1 (26 November) and 1.70/1.84 m for S2 (30 November). The correlation coefficients between the modelled and observed average ice temperature profiles were 0.8(vertical)/0.9(temporal) for S1 and 0.89/0.97 for S2. SYI had a higher winter cold content (32.78 MJ m−2) than FYI (21.01 MJ m−2). The modelled and observed snow depths were comparable when 50% ERA5 precipitation was used as the forcing. Snow–ice and superimposed ice formation were most sensitive to the precipitation pattern, followed by the initial snow depth and initial ice thickness. The net ice growth of both FYI and SYI were inversely related to the initial ice thickness and snow depth.

The driving mechanisms of glacier fast flow and the cyclical instability inherent in ice streams and surging glaciers are not fully understood. Current theories suggest fast flow is driven by glacier sliding and basal deformation facilitated by water at the ice–bed interface and/or the presence of weak till. However, the wettability of sediments and the physics driving these sediment–water interactions have yet to be fully explored. Here, we review recent work on superhydrophobicity, hydrophobic soils and lubricated surfaces, and bring together aspects of materials science, biophysics and geoscience, to propose three modes by which a subglacial environment could become super slippery. Those modes are via (i) hydrophobic chemistry, (ii) microbial biofilms or (iii) the incorporation of oil. We then hypothesise how ice flow on super slippery sediments would result in enhanced sliding and deformation by introducing or increasing a lubricated interface and/or creating zones of sediment weakness and instability. We propose that future research should further explore this potential paradigm to soft bed deformation and sliding.

Obtaining high-resolution, autonomous and continuous measurements of internal and interfacial convection at the ice–ocean interface is important to understand sea-ice desalination, compare the effects of gravity drainage and salt segregation, and give insight into the behaviour of the sublayer beneath the ice. We present the first digital image processing method that can be applied to Schlieren images from a quasi-2D Hele-Shaw cell to provide continuous high-frequency measurements of fingers and streamers, which are linked to interfacial and internal convection, respectively. Previous studies lack the ability to provide a temporal evolution of this dynamic system at a high enough resolution to investigate these interactions. The improved algorithm confirms previous results, while providing a more detailed and statistically acceptable description of the processes during artificial sea-ice growth. We demonstrate that internal convection exhibits a highly variable behaviour that changes in time. As the ice growth rate decreases to its minimum value, internal convection becomes periodically inactive while interfacial convection remains active throughout the experiments. This temporal change suggests a dominant, shorter time-period for gravity drainage to occur and a longer time-period over which salt segregation occurs, while the oscillation in expulsion behaviour suggests that the sublayer is more turbulent than diffusive.

Motivated by the ponding refreezing of meltwater in firn, we analyze the interaction of liquid water and nonreactive gas with porous ice by developing a unified kinematic wave theory. The wave theory is based on the conservation of composition and enthalpy, coupling advective heat and mass transport in firn, and encompasses cases of meltwater perching where the conventional kinematic wave approximation fails. For simple initial conditions (Riemann problems), this model allows for self-similar solutions that reveal the structure of melting/refreezing fronts, with analytical solutions provided for 12 basic cases of physical relevance encountered in the literature. These solutions offer insights into processes such as the formation of frozen fringes, the perching of meltwater on low porosity layers and conditions for impermeable ice layer formation. This theoretical framework can enhance our understanding of the partitioning between meltwater infiltration and surface runoff, which influences surface mass loss from ice sheets and contributes to sea level rise. Furthermore, these analytic solutions serve as benchmarks for numerical models and can aid in the improvement and comparison of firn hydrology, ice-sheet and Earth system models.

The systematic investigation of individual glacier surges across a large statistical sample is key to a better understanding of surge mechanisms. This study introduces a consistent framework for identifying glacier surges from diverse remotely sensed datasets: NASA ITS_LIVE velocity fields, glacier thickness changes digital elevation models and surface roughness from SAR backscatter. We combined these diverse datasets using Gaussian process modelling and signal processing approaches to generate the first worldwide inventory of glaciers with active surges between 2000 and 2024, identifying 261 surge events on 246 glaciers. We performed validation against reference data and conducted a quantitative analysis of key surge metrics - surge duration and peak surface velocity. Our results confirm 12 surge-type glaciers in the Randolph Glacier Inventory (v7). We further evaluated climatological influences on the distribution of surge-type glaciers and assessed the predictive capabilities of existing theories for surges, including hydrological and thermal controls as well as the enthalpy balance theory. In addition, we present the first global analysis of velocity time series from individual surge events and discuss terminus-type dependent dynamics. Our findings strongly support the unified enthalpy balance theory in explaining the breadth of observed surge behaviours. Finally, we report new surge onsets in glaciers quiescent since the 19th century.

We analyse seismic time series collected during experimental campaigns in the area of the David Glacier, Victoria Land, Antarctica, between 2003 and 2016. We observe hundreds of repeating seismic events, characterized by highly correlated waveforms (cross-correlation > 0.95), which mainly occur in the grounding zone, i.e. the region where the ice transitions from grounded ice sheet to freely floating ice shelf. The joint analysis of seismic events and observed local tidal measurements suggests that seismicity is not only triggered by a regular, periodic driver such as the ocean tides but also more likely by transient pulses. We consider potential environmental processes and their impact on the coupling between the glacier flow and the bedrock brittle failure. Among the environmental variables examined, our findings suggest that clustered and repeated seismic events may be related to transient episodes of ice-mass discharge correlated to a change in the subglacial hydrographic system that originates upstream of the glacier, lubricating the interface with the bedrock. This hypothesis is supported by the gravity variation observations provided by the GRACE satellite mission, which observed mass variations during periods characterized by seismic clustering.

New experiments have revealed that a thin layer of granular ice bonded to salty and to salt-free columnar-grained ice increases flexural strength when the composite material is rapidly bent to the point of failure through brittle fracture. When bent slowly within the regime of ductile behavior, the layer has no detectable effect. Strengthening is attributed to the suppression of cracking; its absence, to dislocation creep.

Large-scale glacier mass-balance models often rely on positive degree-day (PDD) melt models, which have known limitations. This study evaluates a relatively simple, elevation-dependent surface energy balance (SEB) model that requires minimal downscaling of climate input data to simulate glacier melt. Using ECMWF Reanalysis v5 (ERA5) reanalysis data and multi-year mass-balance observations from 23 glaciers across Canada, we compare mass-balance models incorporating SEB and PDD components under various calibration scenarios. Initial tests with the uncalibrated SEB model highlight the importance of accurate ERA5 inputs, particularly lapse-rate corrections for 2 m air temperature. Mass-balance simulations with the SEB model that includes calibrated corrections for precipitation and albedo match or outperform those with the PDD model, especially when using a machine learning-derived albedo trained on remote sensing data, which tends to underestimate summer albedo in accumulation zones. Seasonal calibration further improves accuracy of the mass-balance simulations by addressing biases in summer melt and winter accumulation. Despite its simplicity, the SEB model provides a good balance of performance and computational efficiency, emphasizing its utility for regional-scale applications when calibrated appropriately.

Greenland’s peripheral glaciers and ice caps contribute disproportionately to sea-level rise relative to their small area. Winter snow accumulation directly influences glacier mass balance and downstream hydrology, but spatially extensive observations of this important mass balance component remain sparse. In this study, we present a unique multi-year (2008–2024) dataset of winter snow accumulation over A.P. Olsen Ice Cap, Northeast Greenland, from ground-penetrating radar surveys covering an average of 47 km per survey year. Our results reveal strong spatial heterogeneity that is likely influenced by wind redistribution and local topography, especially in the ablation zone. We compare our findings with automatic weather station data from three sites and outputs from the Copernicus Arctic Regional Reanalysis (CARRA). Governed by the high spatial variability, the automatic weather station point-based observations significantly underestimate regional accumulation by 40–45%. Despite the high spatial variability, the CARRA accumulated precipitation variable provides a reasonable overall mean winter snow accumulation (RMSE of 0.07 m w.e.); however, it fails to reproduce the complex non-linear relationship between snow depth and elevation observed in the radar data. Our findings emphasize the need for high-resolution, spatially extensive measurements to better understand snow accumulation on ice caps and glaciers and improve reanalysis assessments.

Predicting calving in glacier models is challenging, as observations of diverse calving styles appear to contradict a universal calving law. Here, we generalize and apply the analytical Horizontal Force-Balance fracture model from ice shelves to land- and marine-terminating glaciers. We consider different combinations of “crack configurations” including surface crevasses with or without meltwater above saltwater- or meltwater-filled basal crevasses. Our generalized crevasse-depth model analytically reveals that, in the absence of meltwater, the calving criterion depends on two dimensionless variables: buttressing B and dimensionless water level λ. Using a calving regime diagram, we quantitatively demonstrate that glaciers are generally more prone to calving with reduced buttressing B and lower water level λ. For a specified set of $B, \lambda$ and crack configuration, an analytical calving law can be derived. For example, the calving law for an ice shelf, land-, or marine-terminating glacier with a dry surface crevasse above a saltwater basal crevasse reduces to a state with no buttressing (B = 0). With climate warming, glaciers are expected to become more vulnerable to calving due to meltwater-driven surface and basal crevassing. Our findings provide a framework for understanding diverse calving styles.

Glacier motion, retreat and glacier hazards such as surges and glacial lake outburst floods (GLOFs) are likely underpinned by subglacial hydrology. Recent advances in subglacial hydrological modeling allow us to shed light on subglacial processes that lead to changes in ice mass balance in High Mountain Asia. We present the first application of the Subglacial Hydrology And Kinetic, Transient Interactions (SHAKTI) model on an alpine glacier. Shishper Glacier, our study site, is a mountain glacier in northern Pakistan that exhibits concurrent surges and GLOFs, which endanger local communities and infrastructure. Without coupling to ice velocity, the modeled subglacial hydrological system undergoes transitions between inefficient to efficient drainage and back during spring and fall, supporting previous observations of spring and fall speedups of glaciers in the region. We compare modeled effective pressures from the years 2017-19 with previously observed velocities, suggesting that while subglacial hydrology may explain seasonal sliding dynamics, our model is unable to provide an explanation for surge-scale behavior, implicating a need for coupled hydrological and ice dynamics modeling of surge conditions. This work demonstrates the potential of using ice sheet models for alpine glaciology and provides a new nucleus for modeling of glacial hazards in alpine environments.

Glacial lakes in the Himalayas have expanded significantly in recent decades, increasing the potential risk of outburst floods. However, limited field surveys and systematic assessments leave downstream communities vulnerable. Accurate volume estimation of glacial lakes is essential for modelling flood dynamics, yet in-situ bathymetric data remain scarce. In this study, we surveyed four glacial lakes—Kya Tso Lake, Panchi Nala Lake, Gepang Gath Lake and Samudra Tapu Lake—in the Chandrabhaga basin, western Himalayas. Depth measurements were conducted using a portable inflatable kayak in August 2022 and an echo sounder mounted on an uncrewed surface vehicle in August 2024. Bathymetric modelling revealed maximum depths of 16 m, 10 m, 46 m, and 59 m, with corresponding storage capacities of 0.89, 0.44, 24.12, and 24.69 × 10⁶ m3, respectively. Volume estimates derived from empirical equations showed substantial discrepancies of ± 36–1736% compared to in-situ measurements. Despite several operational challenges, this study provides valuable in-situ bathymetric data for future modelling and hazard assessment of rapidly expanding glacial lakes in the region. The findings emphasise the need for robust field-based bathymetric datasets to refine empirical volume estimation models for Himalayan glacial lakes.

A key challenge in advancing slushflow management is the limited record of past incidents. Identifying their starting points and enhancing the quality of slushflow documentation are important in order to improve the regional early warning and develop slushflow numerical runout models and susceptibility maps. Here we investigate three major slushflow events at Kistrandfjellet, northern Norway and quantify the differences between registered slushflows in the national rapid mass movement database and the actual events. We use unique image datasets from the events in February 2021, January 2023 and January 2024, and identify slushflow starting points and flow paths. The curvature of the starting point locations is examined to assess how local topography influences slushflow release at the field site. Our mapping reveals 25 slushflows across the three events, whereas only five were registered in the database. For the 2021 event, we found six times as many slushflows as were officially registered. Comparison of our mapped slushflows to modeled drainage pathways and FKB-Vann (the official surface water dataset of Norway), yielded an average overlap of 35%. To improve slushflow management, we recommend establishing a standardized protocol for future data collection.

In this study, we established an annually resolved chronology for the upper 98.5 m of a 210.5 m deep ice core (Styx-M core) drilled at the Styx Glacier plateau (SGP) in northern Victoria Land, East Antarctica, to reconstruct the multi-centennial variations of the snow accumulation rate (SAR). The core was dated via the annual layer counting of highly resolved impurities exhibiting seasonal cycles. The layer counting result was constrained using multiple temporal markers, including the 239Pu peaks that resulted from atmospheric weapon tests as well as five large volcanic eruptions in recorded history. These approaches show that the Styx-M core chronology covered 755 years (1259–2014 CE), with the estimated dating uncertainties of ±8 years. The annual accumulation record was derived using the depth-age scale and depth-density relationships of the core. This record revealed a long-term trend of a ∼30% increase in the SARs over the past 755 years, overlapping the pronounced inter-decadal and multi-decadal fluctuations. Further study will be needed to reveal the complex interaction of oceanic and atmospheric processes controlling the temporal fluctuations of SARs in the coastal areas of northern Victoria Land, combining multiple proxy records in the Styx-M core.

This work aims to address two main scientific objectives. First, it seeks to rigorously compare ice thickness estimates from GPR datasets with those derived from various modelling approaches. Second, it examines warm and cold ice areas identified by GPR in relation to 2D thermal modelling performed along selected profiles. The analyses focus on two nearby glaciers in Greenland, surveyed in different years (2014 and 2024) and seasons (August and February) and with different GPR antennas, namely 50 MHz unshielded and 100 MHz shielded. We found that global-scale ice thickness models provide relatively accurate volume estimates at regional scale, while they have limitations in local accuracy, as well as the ice thickness models, especially when the bedrock topography derived from GPR data is complex. 2D thermal modelling results were only partially consistent with warm and cold ice occurrence derived from GPR data, indicating the unique and complex thermal structures of polythermal glaciers with irregular shape and geometry. Due to the differences between the two surveys, we believe that the results are relevant not only to the specific test site, but also to a wider range of geographical and climatic conditions and may provide useful guidance for similar applications.

Sít’ Tlein (Malaspina Glacier), located in Southeast Alaska, has a complex flow history. This piedmont glacier, the largest in the world, is fed by three main tributaries that all exhibit similar flow patterns, yet with varying surge cycles. The piedmont lobe is dramatically reshaped by surges that occur at approximately decadal timescales. By combining historical accounts with modern remote sensing data, we derive a surge history over the past century. We leverage the Stochastic Matrix Factorization, a novel data analysis and interpolation technique, to process and interpret large datasets of glacier surface velocities. A variant of the Principal Component Analysis allows us to uncover spatial and temporal patterns in ice dynamics. We show that Sít’ Tlein displays a wide range of behaviors, spanning quiescence to surge with seasonal to decadal variations of ice flow direction and magnitude. We find that in the lobe, surges dominate the velocity dataset’s variance (spanning 1984–2021), while seasonal variations represent a much smaller part of the variance. However, despite the regular surge pulses, the glacier lobe is far from equilibrium, and widespread retreat of the glacier is inevitable, even without further climate warming.

Remotely sensed datasets indicate that Fisher Glacier underwent two surges since 1948: during approximately 1969–72 and 2013–16. These were characterized by an advanced terminus position (terminus-wide average advance 571 ± 143 m from 1963 to 1972 and 868 ± 8 m from 2014 to 2017), intense surface crevassing (up to >30 km up-glacier from the terminus during both surges), high surface velocities and a down-glacier transfer of mass. The intervening quiescent phase lasted for 40 years, during which velocities were generally low (<50 m a−1), but underwent a slow multidecadal increase starting around 1985, spreading from the middle of the glacier. A pre-surge buildup phase beginning around 2008 resulted in velocities of up to ∼200 m a−1. The active phase of the surge initiated in winter 2013/14, with velocities of up to 1500 m a−1 propagating both up- and down-glacier from the mid-glacier region. In July 2016, the surge rapidly terminated within a period of ∼1 month. Characterized by a rapid onset and termination, but also displaying a multidecadal acceleration prior to the surge, the cause of Fisher Glacier’s surges may be best explained by a unifying framework such as the enthalpy balance theory.