Glacier albedo is a key driver of snow and ice melt through the absorption of solar radiation. The albedo strongly depends on the amount of light-absorbing particles deposited on the surface. In the European Alps, Saharan dust particles are frequently deposited and highly contribute to lower snow albedo. However, the role of dust in the currently accelerated melt of Alpine glaciers remains unknown. Here, we show that dust promotes the accelerated wastage of Alpine glaciers in the context of climate change. Using process-based surface mass balance modeling and 60-year-long simulations, we demonstrate that dust increases the current sensitivity of Alpine glaciers to air temperature by 11 %, even in the absence of increasing dust deposition. The magnitude of the impact of dust is controlled by the snow and ice-albedo feedbacks, as well as the exposure of old firn layers. Such feedbacks are amplified by the current warming leading to longer exposure of darker surfaces to solar radiation. Dust thus induces increasingly negative mass balances not because of higher deposition fluxes but because of longer exposure. Our study hence emphasizes the crucial role of indirect positive feedbacks at play in the current accelerated decline of Alpine glaciers.

Observing glacier mass changes is essential for understanding and projecting the impacts of climate change on sea-level rise, water resources and natural hazards, as well as providing data for developing, calibrating and validating glacier evolution models. The principal methods used to measure glacier mass changes - glaciological, geodetic (surface elevation differencing) and gravimetric - differ in the spatial and temporal scales at which they are most effectively applied. Here, we review these methods in the context of challenges that arise when comparing published mass-balance estimates. Compatibility can be hampered by (1) inconsistent reporting and lack of relevant information; (2) discrepancies in which mass-balance components are included; (3) differences in the time span analyzed; and (4) variations in the spatial domain of the reported mass balance. We provide recommendations for more rigorous and comprehensive reporting of mass-balance estimates to improve comparability and synthesis of reported glacier mass changes, and we emphasize open data and code sharing to enable full reproducibility and future reinterpretation. Our recommendations apply equally to both glacier and ice-sheet mass-balance reporting, and they are generally valid for mass balances simulated by numerical models.

Abstract. Understanding whether the current decline of Alpine glaciers is unprecedented requires direct evidence of ice persistence through past warm periods. While maximum glacier extents are well constrained, for example through landmarks (moraines), minimum Holocene ice extents—particularly at high elevations—remain poorly documented. Cold, low-accumulation summit glaciers can preserve very old ice, yet these archives are increasingly threatened by recent atmospheric warming. Here we present the first ice core record from the summit glacier of Tödi at 3565 m a.s.l. (Swiss Alps). Two ice cores drilled to bedrock (~20 m) were absolute dated with multiple radionuclides (210Pb, 3H, 39Ar, 14C) complemented by glaciological observations and age–depth modelling. Based on evidence for recent surface ablation, we determined that the ice surface at the time of drilling (2023) dates to 1960 ± 1 CE. An exceptionally high-resolution radiocarbon dataset reveals stratigraphically consistent preservation of basal ice dating to ~10 ka cal BP, confirming the persistence of early Holocene ice. The Tödi basal age questions the previously suggested relationship in timing of Alpine ice-free conditions around 6 ka ago at altitudes of about 3500 m a.s.l.. Instead, our results indicate that long-term ice persistence is not controlled by elevation alone, but rather dependent on local glaciological factors. Further, our results imply that other cold-based high-altitude glaciers in the Alps may preserve older ice than currently recognized and underscore both the scientific value and increasing vulnerability of these disappearing climate archives.

Glacier ice flow not only transports eroded rock material, but can also mobilize remnants of previous touristic activities, linking physical environment with human exploitation of mountains. Here, we investigate the transport and deposition of bottles and cans on a small, rapidly shrinking glacier in the Southeastern Swiss Alps. Object positions were documented using the global positioning system (GPS), and for several items, age estimates from literature and manufacturers suggest production dates between about 1900 and 1980. Field observations were combined with glaciological data and the results from a higherorder iceflow model to reconstruct their likely origin, transport pathways, and deposition period. The results indicate that the objects originated from the summit area of Piz Murtèl and were transported downslope by ice flow or by sliding over the surface, leading to the deposition of several hundred objects along the former glacier margin. We therefore conclude that bottles and cans were discarded near the summit of Piz Murtèl between more than a century and 50 years ago, and were then transported to form a morainelike shape. These findings demonstrate that glacierscale reconstructions of surface and englacial debris transport are feasible and highlight the role of glaciers as longterm archives of human activity in alpine environments.

Glaciers in the Tien Shan mountains of Central Asia are a crucial source of freshwater for agriculture and local communities, sustaining over 100 million people in the region. Here, we project future water availability for this region by dynamically modeling the evolution of all glaciers and merging their runoff with hydrological runoff simulations from three global hydrological models. We compare this hybrid estimate of water availability with water demand simulations to assess potential risks of water scarcity. Our findings show that Tien Shan glaciers are projected to lose around one-third of their 2020 ice mass before 2040, and between 69% and 93% by 2100, depending on the climate scenario. Compared to a 2000-2020 baseline, the runoff from glacier areas initially increases by 15%-24%, reaching its peak before 2050, followed by a decrease of 14%-20% by 2100. This reduction is particularly pronounced in summer, when glacier areas currently supply up to 45% of total summer runoff, coinciding with peak water demand. A gradual shift in glacier-area runoff toward spring further intensifies the risk of summer water shortages. By the late 21st century, the probability of unmet water demand in summer is projected to increase significantly, especially in heavily glaciated basins, where the increase ranges from 30% to 70% depending on the emissions scenario. These findings highlight the urgent need for adaptive water management strategies and climate mitigation efforts to preserve long-term water security for millions of people reliant on glacier-fed rivers for their water supply.

Recognising the global importance and vulnerability of mountain glaciers, the United Nations General Assembly declared 2025 the International Year of Glaciers’ Preservation, highlighting the critical role of glaciers in the hydrological cycle and the growing societal risks associated with their rapid decline. These concerns are well founded: glaciers worldwide are retreating rapidly, yet projections have traditionally focused on changes in mass and area rather than on the fate of individual glaciers.Here, we quantify the future evolution of the global number of glaciers and introduce the concept of peak glacier extinction: the year in which the largest number of individual glaciers is projected to disappear. Using three global glacier models and the Randolph Glacier Inventory v6.0, we project the fate of more than 200,000 glaciers worldwide under four policy-relevant global warming scenarios by 2100 (+1.5 °C, +2.0 °C, +2.7 °C and +4.0 °C relative to pre-industrial levels). A glacier is classified as extinct when its area falls below 0.01 km² or its remaining volume declines to less than 1% of its initial value.Across all scenarios, we identify a pronounced mid-century peak in glacier extinction. Under a +1.5 °C pathway, this peak occurs around 2041, with approximately 2,000 glaciers disappearing per year, whereas under a +4.0 °C scenario it shifts to the mid-2050s and intensifies to nearly 4,000 glacier extinctions annually. Regional differences reflect contrasts in glacier size distributions and climatic conditions. Our results highlight the urgency of ambitious climate action. Whether the world faces the loss of 2,000 or 4,000 glaciers per year by mid-century, and whether roughly 20,000 or 100,000 glaciers remain by the end of the century, will be determined by near-term policy and societal choices made today.

We summarize and reflect on the nearly 30 studies that form this Collection on Vanishing Glaciers as a contribution to the 2025 International Year of Glaciers' Preservation. Some of the studies in this Collection are extensions of the stories told in the Global Glacier Casualty List, a collaboration between social and physical scientists. They document glaciers in various states of demise in regions across six continents, including Svalbard, Iceland, Norway, Germany, France, Italy, Spain, Austria, Switzerland, New Zealand, Indonesia, USA, Canada, Peru, Bolivia and Chile. Vanishing glaciers affect archaeology, biodiversity, water resources, tourism, culture and glaciology itself, as we grapple with more precise definitions of dwindling ice masses and the loss of long-term monitoring sites. Landscapes are being transformed by rapid deglaciation, serving as a call to action and introducing numerous challenges for those engaged in measuring, monitoring and documenting glacier change.

Abstract. Englacial temperature measurements in the Alps remain sparse and biased toward high-elevation accumulation areas, leaving the thermal state of ablation zones poorly constrained. Here, we present borehole thermometry and ground-penetrating radar surveys from six small Swiss glaciers (< 0.5 km², 2700–3800 m a.s.l.). Polythermal conditions are confirmed in three glaciers, with the cold-temperate transition surface at depths of 17–38 m and ice temperatures ranging from temperate to −2.1 °C. A fourth site, Glacier du Sex Rouge, likely retains its historically documented polythermal structure, but borehole measurements were limited to the near-surface cold layer and do not reach the temperate ice below. A consistent spatial pattern emerges, with temperate ice at higher elevations transitioning into fully or partially cold-based glacier termini. Ground-penetrating radar retrievals are generally consistent with borehole-derived thermal conditions, with low scattering in cold ice and enhanced scattering in temperate zones. The observed thermal structures are closely linked to the history of firn cover loss, reconstructed from long-term mass balance records, with sites that lost their firn cover earliest showing the most advanced cooling. Our findings suggest that polythermal conditions among small Alpine glaciers may be more widespread than previously recognised, with important implications for glacial hazard assessments and highlighting the need for systematic regional-scale thermal observations and modelling.

The year 2025, designated by the United Nations as the 'International Year of Glaciers' Preservation', ironically became the most negative glacier mass-balance year on record in Central Asia. In situ observations reveal exceptionally strong and spatially coherent ice losses across the region, although not all individual glaciers experienced record losses. Regional simulations with the Global Glacier Evolution Model support these findings, indicating that 64% of glaciers larger than 1 km2 (similar to 4000 glaciers) reached their most negative annual mass balance within the study period. Within a single year, glaciers in Central Asia lost an estimated 30 +/- 6 km3 of ice (26 +/- 9 Gt), corresponding to similar to 2% of their present-day total mass. Mass loss was strongest in the western Tien Shan and western Pamir (-2% to -4%) and more moderate in the eastern Tien Shan and eastern Pamir (-1% to -1.5%). Climate reanalysis attributes the extreme 2025 losses to persistently above-average spring and summer temperatures, an unusually early onset of the melt season, and reduced snowfall frequency during late spring and summer. Together, these conditions enhanced melt-amplifying feedbacks by accelerating snow loss, leading to earlier exposure of low-albedo ice surfaces. The 2025 losses mark an alarming milestone for Central Asian glaciers and may become the new normal in the future.

Visitors are increasingly drawn to disappearing glacier landscapes for their beauty and scientific value. This Comment examines the paradoxes reshaping relationships among glaciers, people and communities, and highlights research needed to avoid maladaptation harming local communities.

Glacier thermal conditions directly influence ice mechanics, meltwater storage, and drainage, thereby governing glacier stability and hazard potential. Polythermal glaciers, in particular, can create conditions that promote ice break-offs, ice avalanches, water pocket outbursts, and even large-scale glacier detachments. Understanding their distribution is therefore critical for hazard assessment. Yet englacial temperature measurements in the Alps remain sparse and are biased toward high-elevation accumulation areas, while the thermal state of mid- and lower-elevation ablation areas is largely unknown. Extended melt seasons and refreezing of meltwater in cold firn have been associated with warming at high elevations, whereas firn loss at lower elevations may reduce meltwater retention and latent heat input. Modeling studies suggest that this imbalance can lead to cooling in ablation areas, an effect that may be particularly pronounced for very small glaciers, where internal heat production from glacier dynamics is minimal.Here, we present a new englacial temperature dataset from six small Swiss Alpine glaciers (3000–3800 m a.s.l.), directly addressing the lack of observations in mid- to lower-elevation ablation areas that are poorly constrained by existing measurements. The dataset combines borehole thermometry with ground-penetrating radar surveys. Polythermal conditions were identified in three glaciers, with the cold–temperate transition surface (CTS) occurring at depths of 14–25 m. Below the seasonal surface layer, ice temperatures generally ranged from temperate conditions to –2.1 °C. Two of the glaciers exhibit a recurring pattern in which temperate ice at higher elevations transitions downslope into fully or partially frozen glacier tongues. At the third polythermal site, the CTS was detected at several locations between 17 and 22 m depth, while basal thermal conditions remain partly unresolved. One glacier appears predominantly cold, and at two additional sites, shallow thermistors recorded year-round cold conditions within the seasonal layer, while temperate ice at depth cannot be ruled out. Ground-penetrating radar reflectivity is generally consistent with borehole-derived thermal conditions, characterized by low reflectivity in cold ice and enhanced reflectivity in temperate zones. Our findings suggest that polythermal-type glaciers in the European Alps may be more widespread than previously recognized, with important implications for glacial hazard assessment and for understanding climate-driven changes in smaller Alpine glaciers.

Glacier Equilibrium Line Altitudes (ELAs) are substantially influenced by topography through processes such as preferential shading, avalanching, or snow redistribution by wind. Here, we present a novel framework with which these topographic controls can be better assessed. The approach involves (1) estimating the ELA from glacier outlines and surface geometries, (2) separating the ELA into a regional climatic average (regELA) and a local topographic residual (ΔELA) via spatial autocorrelation, and (3) correlating ΔELA to terrain parameters characterizing the shape and orientation of glaciers and their catchments. The framework is developed and calibrated using the Swiss Glacier Inventory (SGI) 2016. In the SGI2016, the average absolute ΔELA is around 200 m, and shows significant correlations with potential solar radiation, topographic openness, ice surface curvature, and the relative size of a glacier’s catchment. These terrain parameters are then used to train a random forest-based regression model, which accurately predicts ΔELA for each Swiss glacier (R2 = 0.95) but can also be successfully transferred to earlier inventories within the Swiss Alps (R2 = 0.59 to 0.73). A spatial transfer, on the other hand, works only for regions with similar topographic and glaciological characteristics like New Zealand (R2 = 0.59), while a transfer from Switzerland to Icelandic glaciers proved unsuccessful (R2 = 0.11) and requires local recalibration. The framework developed in this study allows for a better quantification of topographic controls on present-day glaciers but can eventually also be transferred to a palaeoclimatic context, leading to improved temperature and precipitation reconstructions for past glaciations.

The year 2022 was extremely warm and dry in Europe, resulting in a severe hydrological drought. In Switzerland, part of Europe's water tower, streamflow in glacier-fed rivers could have been even more reduced if the situation had not led simultaneously to extreme glacier melt. Here we analyze the role of glaciers during the 2022 drought for 88 glacierized catchments by combining streamflow and meteorological observations with estimations of snow water equivalent, actual evapotranspiration and daily glacier storage changes. We also compare the year 2022 to earlier exceptionally warm and dry years (1921, 1928, 1947, 1998, 2003 and 2018) to assess if the ongoing glacier retreat has already caused a declining meltwater supply in such extreme conditions. Results show that 60 %-80 % of the total glacier melt in 2022 came from net mass loss (imbalanced melt). During summer, the increased glacier melt could completely offset the precipitation and snowmelt deficits for catchments with around 15 % glacierization. Further downstream, the extra glacier melt in summer alleviated water input deficits by up to 5 % at Basel (Rhine) and 70 % at Porte du Scex (Rhone). Compared to past extreme years, total glacier meltwater volume has declined due to strong glacier area loss, despite higher melt rates per unit area. In 2022 versus 2003 - the most comparable recent extreme summer - total glacier meltwater supply decreased in two thirds of the catchments over the entire summer, and in one third in July. In the remaining catchments, the more intense specific melt of 2022 could offset the 21 % glacier area loss since 2003. Despite these declines, relative glacier melt contributions to streamflow stayed rather constant, or even rose in some months, highlighting its ongoing importance during droughts while simultaneously raising concerns for future drought situations.

Abstract Glacier mass balance (MB) is a key indicator of climate change and a central driver of glacier evolution, yet most glaciers worldwide lack long‐term in situ measurements. For estimating glacier MB, data‐driven models provide a complementary alternative to traditional numerical approaches by learning empirical relationships between climate forcing, topography, and MB from observations. Here, we develop a recurrent neural network (RNN) based on a Long Short‐Term Memory (LSTM) architecture within the Mass Balance Machine (MBM) framework to predict winter and annual point surface MB across the Swiss Alps. MBM is trained on 30,000 observations from 30 glaciers and tested on eight glaciers excluded from training to assess spatial generalization. MBM predicts winter and annual MB with high accuracy on unseen glaciers (root mean squared error of 0.35 and 0.78 m w.e.). Its recurrent structure enables learning temporal dependencies, improving the representation of seasons with strong accumulation or ablation. Beyond point predictions, MBM generates spatially distributed MB maps that capture MB gradients, and produce glacier‐wide mass changes consistent with geodetic estimates. Monthly outputs further show that MBM reproduces the seasonal transition from winter accumulation to summer ablation with realistic timing and magnitude. These results show that a RNN can recover key characteristics of glacier MB dynamics and that the learned relationships transfer effectively across the climatic and topographic settings of the Swiss Alps. The demonstrated generalization skill highlights the potential of MBM for application in regions with limited direct measurements, though transferability to glaciers with fundamentally different climatic and topographic settings remains to be established.

Glacier retreat drives the expansion of glacier-contact lakes until topographic constraints trigger their detachment from parent glaciers. While the expansion phase is well-documented, the post-detachment evolution and its driving mechanisms remain poorly understood, limiting future glacier-related water resource and hazard assessments. Here, we investigated the spatio-temporal evolution of recently glacier-detached lakes across the Third Pole from 1990 to 2023 by combining multi-temporal lake inventories, climate and glacier mass-balance datasets, glacier runoff simulations, and geomorphic proxies for erosion and sediment supply. We identified 882 glacier-contact lakes that became detached during the study period, equivalent in number to 29% of the 3024 glacier-contact lakes mapped in 2023. Contrary to the widely documented expansion of glacier-contact lakes, detached lakes decreased in total area from 45.11 ± 0.02 to 42.63 ± 0.02 km2, corresponding to an estimated water-volume loss of ∼0.04 Gt, despite an increase in modeled glacier runoff of ∼0.37 Gt. Moraine-dammed lakes accounted for the larger absolute area loss, whereas bedrock-dammed lakes showed greater relative shrinkage. Shrinking detached lakes exhibited a median proglacial erosion potential about two times higher than non-shrinking lakes and preferentially occurred in areas with higher abrasion potential, suggesting an important role of proglacial erosion and sediment infilling in post-detachment lake shrinkage. These results indicate that detached lake evolution cannot be explained by meltwater supply alone. Instead, glacier detachment may mark a shift from meltwater-dominated lake expansion toward sediment-influenced lake shrinkage, reflecting an ongoing proglacial-to-paraglacial transition in high mountain glacial lake systems. Accounting for this transition can improve future assessments of glacial lake evolution, alpine water storage, and GLOF-related hazards under continued glacier retreat.

Reliable estimates of glacier mass balance for an entire mountain range provide valuable insights into the impact of glacier melt on regional water resources. Here, we derive daily mass balance estimates for every glacier in the Swiss Alps over the period 2010-2024. To do so, we leverage two simplified surface energy-balance models and remote sensing observations, i.e. geodetic volume changes and observations of the snow-covered area fraction (SCAF) of glaciers during summer, together with machine-learning techniques for extrapolation purposes. This allows reproducing the seasonal variability of glacier mass balance for glaciers without in situ observations and determining daily glacier mass balance across Switzerland. Over the study period, the Swiss glaciers lost almost 25 % of their 2010 ice volume, which corresponds to a wastage of -15.2 +/- 1.6 km3 of ice. The highest winter snow accumulation is inferred to occur in central and western Switzerland, with up to 1.5-1.9 mw.e. by the end of April, whereas the lowest winter accumulation is detected in Valais and ranges between 0.9 and 1.2 mw.e. Furthermore, winter balances are found to show better correlation in space compared to long-term annual balances, which range between -0.6 and -1.5 mw.e., indicating different dominating mechanisms. Finally, we assessed the spatio-temporal variability of seasonal mass balance to gain in-depth insights into the relation between glacier mass balance and the driving climatic factors in the Swiss Alps.