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.