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Arctic rivers transport water, sediment and carbon, playing a central role in coastal stability and biogeochemical cycling. Although freshwater discharge to the Arctic Ocean has increased in recent decades, limited observations have hindered system-wide assessment of long-term, reach-level sediment dynamics. Here we develop a pan-Arctic-specific, satellite- and machine learning-based framework to reconstruct four decades of suspended sediment concentration dynamics for 4,331 river reaches. Our analysis reveals a significant increase in suspended sediment concentration in 40% of river reaches (858 out of 2,158) draining continuous permafrost zone, primarily driven by increasing discharge, intensified thermokarst disturbances and fires. The pan-Arctic land–ocean sediment flux averages 315 ± 33 Mt yr⁻¹, with 198 ± 35 Mt yr⁻¹ (63%) from the six major rivers (Yenisey, Lena, Ob’, Kolyma, Yukon and Mackenzie) and 117 ± 13 Mt yr⁻¹ (37%) from 263 previously overlooked small- and medium-sized coastal rivers. The total land–ocean sediment flux has increased by ~15%, from ~299 ± 28 Mt yr⁻¹ in the 1980s to 344 ± 29 Mt yr⁻¹ in the 2010s. These results provide a baseline for pan-Arctic river sediment dynamics and underscore the essential yet underappreciated contribution of small- and medium-sized coastal rivers to Arctic landscape and carbon cycle changes. A copy of the paper is freely available here.

Hydrological dynamics in glacierized catchments of the Alps are shaped by temperature-driven processes, including snow and ice melt as well as precipitation, leading to diel streamflow cycles that vary in intensity within- and among-the seasons. During the summer melt period, the amplitude of these diel cycles increases due to diminished snow storage and the emergence of efficient subglacial drainage systems. Accurately modeling these sub-daily cycles remains difficult, due to a lack of high-resolution meteorological input data for melt simulations and due to challenges in parameterizing meltwater routing through dynamic glacial systems. This research develops an approach for downscaling daily streamflow timeseries to sub-daily timescales (daily flow duration curves) in alpine glacierized catchments influenced by snow and ice melt runoff. We adapt a maximum entropy framework (POME) to the specificities of glacial systems, that we calibrate on a 45-year data set of 15-min discharge records from seven glacier-fed catchments in the southwestern Swiss Alps. The calibrated method is then applied to the outputs of a semi-lumped hydrological model that simulates daily discharge and provides hydrological variables such as snow depth and ice melt to inform the downscaling, and the results are evaluated against observed discharge. Our results reveal that a sigmoid function effectively represents seasonally varying daily flow duration curves in glacierized catchments and highlight the influence of climate warming on sub-daily flow dynamics over recent decades. This downscaling method offers a robust tool for reconstructing sub-daily discharge in catchments with limited data, opening new perspectives for hydrological modeling at finer scales. A copy of the paper is freely available here.

Congratulations to Gilles Antoniazza who has been selected as one of the 2025 Outstanding Reviewers for the American Geophysical Union journal JGR: Earth Surface. More details are available here.

Storage hydropower alters the natural flow regime of rivers through reservoir impoundment, modified residual flows, and hydropeaking operations. These hydrological changes may also affect river temperatures and so aquatic ecosystems. Hydropower mitigation has primarily focused on hydrological impacts; thermal consequences and interactions with climate change remain poorly understood. To address this gap, this study evaluates the thermal effects of three hydropeaking mitigation strategies for a peri-Alpine river strongly affected by hydropower regulation; regulation basin, diversion tunnel, and residual flow increase; under current and future climate conditions. Under current climate conditions, both regulation basins and residual flow increases significantly reduce short-term thermal rates of change (from approximately 7 to 4 °C/h), though values remain above those observed in natural rivers (around 1.5 °C/h). Only residual flow increases markedly reduce the number of days exceeding critical thermal thresholds (15 °C here), by up to 35 days. In contrast, diversion tunnels show negligible effect on thermal indicators and may increase vulnerability to temperature extremes. Under future climate scenarios, mitigation strategies maintain their relative effectiveness in limiting thermal gradients, but their ability to reduce threshold exceedances declines under the most severe climate scenarios, due to rising reservoir temperatures. These findings illustrate how ecologically relevant thermal indicators can be integrated into mitigation assessment within a modelling framework that accounts for the combined effects of hydropower operations and climate change under current and future conditions. The work shows the limitations of current approaches to assessment, which are often restricted to short-term thermal indicators or rely on idealized reference conditions. A copy of the paper is freely available here.

The retreat of glaciers and ice sheets since the end of the Little Ice Age has exposed proglacial margins that rapidly develop new ecosystems. These areas are quickly colonized by soil microbes (Bacteria, Archaea), which are less constrained by nutrient scarcity and disturbance than higher organisms. Microbial communities drive biogeochemical changes that initiate pedogenesis, and glacier-forefield ecosystem development is commonly examined through chronosequences. However, the ecological trajectory of the soil microbiome and the influence of local environmental factors on community composition remain unclear. We investigated bacterial community composition along a 180-year glacier-forefield chronosequence in southwestern Switzerland, focusing on links between sediment microbiology, geochemistry, and environmental context. Taxonomic diversity decreased over the first 115 years after exposure, driven by declining psychrophilic autotrophs and increasing psychrotolerant heterotrophs. Species turnover corresponded to changing abiotic conditions, including rising carbon and nitrogen content, soil acidification, and warming. Local context (topography, seasonality) exerted only minor effects on the soil microbiome, likely contributing to the rapid ecological convergence observed among sites farther from the current glacier front. Our results show that soil bacterial communities and soil development follow a shared geoecological trajectory after deglaciation. Considering environmental context improves understanding of proglacial-margin ecology amid accelerating twenty-first-century glacier retreat. A copy of the paper is freely available here.

Glacial erosion and sediment evacuation are key in shaping polar and mountain landscapes and influencing downstream ecological and social systems. The glacier dynamics and hydrology responsible for these processes are closely linked to hydrological and climatic (hydro-climatic) conditions. Recent studies indicate that sediment export and glacier erosion respond strongly to hydro-climatic variations across millennia to individual events lasting hours to weeks. (a) Sedimentary records and numerical ice flow models indicate increased erosion during glacier retreat following climate warming. (b) Rising equilibrium line altitudes due to climate change enhance meltwater access to subglacial sediment, increasing sediment export markedly. (c) Changing meltwater dynamics over hydrological events, particularly daily variations in melt or precipitation events, strongly impact sediment transport capacity. We propose that hydro-climatic changes from millennia to hours, along with the climatic conditions themselves, provide a useful framework for examining glacier erosion. The sensitivity of glacier erosion and sediment export to hydro-climatic conditions likely introduces timescale biases when averaging glacier erosion over long or short periods. Major uncertainties in interactions amongst processes and their relevant timescales underscore the need to better understand climate change impacts on glacierized landscapes. Emerging observational methodologies combined with numerical models may provide new insights into the complex and interacting dynamics controlling glaciers’ impact on sediment export. A copy of the paper is freely available here.

It is well established that changes in climatic conditions across Alpine environments have influenced tree-growth at altitudes close to the tree line. Less well known is the impact that increasing proportions of glacial melt water, which may accompany increasing temperatures and otherwise drier conditions during warmer summers, have on the tree growth along the glacial outwash rivers within the basin. In many Alpine basins in Switzerland, hydropower development further alters natural hydrological regimes by modifying runoff timing and flow composition. This study investigates the combined effects of climate variability and hydropower regulation on tree growth and isotopic compositions in the Turtmann River Basin in south-west Switzerland, where an upstream hydropower dam (2200 m a.m.s.l.) stores almost all glacial meltwater, and therefore, the riverine flow below the dam becomes increasingly dependent on snowmelt and rainfall from the unglaciated and unexploited basins. We analysed 75 years (1946–2020) of δ¹⁸O and the δ²H values in earlywood (EW) and latewood (LW) Larix decidua growing proximal and distal to the river at two sites within the Turtmann basin. The results show that tree ring growth was primarily temperature-limited at both sites, with a tendency for precipitation becoming a growth-limiting factor particularly at the downstream Site 2 in recent decades. The LW showed stronger climatic sensitivity than EW, reflecting increasingly dry summer conditions. Both δ¹⁸O and δ²H values of proximal trees are lower compared with those of the distal trees, reflecting snowmelt and summer precipitation but are not influenced by the glacial meltwaters draining from the upper catchment and/or released by the dam. These results demonstrate that tree-ring stable isotopic compositions can effectively trace changes in Alpine hydrologic regimes and provide valuable insights into how climate change and hydropower operations combine to influence water availability and tree growth dynamics in glaciated basins. A copy of the paper is freely-available here.

Areas of serpentine in ophiolitic mélange zones often trigger large rock avalanches and exhibit strong movement. However, how the mechanism under which they post-failure hypermobility and long runout are unclear. Here, we identify and analyze a representative prehistoric rock avalanche, the Basu rock avalanche, with a large volume and a high mobility, which developed in the Nu River ophiolitic mélange zone of the Tibetan Plateau. Based on field investigations, experimental, and Numerical simulation analyses we determined its development background and thus explained why it was hypermobile. This rock avalanche, with a volume of approximately 3.15 × 10⁹ m³, occurred around ∼187 ka before present (B·P.). It developed on a marble nappe, with serpentine soft rock exposed locally at its base. It may have ultimately been triggered under seismic action, resulting in intense movement. The lubrication effect of fine-grained serpentine particles within the slip zone facilitated the hypermobility of the rock avalanche, resulting in both a large volume and an extended runout distance. This demonstrates that serpentine soft fine particles widely distributed in the suture zone are a typical lubricating material. The hypermobility of this large rock avalanche are striking and emphasizes the need to determine where, how and when these rare but high-magnitude rock avalanche events may occur. We proposed a new perspective on the triggering mechanisms of the rock avalanches and further verified the hypothesis of powder lubrication control effects. The paper may be accessed here.

The retreat of glaciers opens up large proglacial areas which become available for colonization and primary succession. Yet, factors that contribute to habitability during early succession in proglacial areas remain poorly understood. In proglacial streams, biofilms, which are matrix-enclosed microbial communities, colonize the streambed and grow into millimeter thick mats. Particularly in proglacial streams draining relatively flat and stable lateral terraces, these biofilms may augment habitability by reducing water scarcity through clogging of the streambed. To quantitatively address this phenomenon, we performed streamside flume experiments and conceived the idealized terrace model, which models stream length elongation as a function of microbially induced clogging, sediment hydraulic properties, stream roughness, slope, width and inflow. Significant stream elongation, and hence habitabilization, occurs when clogging suffices to induce unsaturated conditions below the streambed. Considering multiple terrace configurations with educated parameter bounds, we found a wide range of possible elongation, ranging from none to 100-fold. Sensitivity analysis suggests that sediment hydraulic properties mostly contribute to variability in stream elongation due to biofilm induced clogging. Taken together, we here show that microbial communities can significantly extend the habitability of proglacial stream ecosystems by inducing streambed clogging and retaining water. This is relevant in light of the rapid glacier retreat. A copy of the paper is freely available here.

Climate change is driving an increase in river water temperatures, presenting challenges for aquatic ecosystems and water management. Many rivers are regulated by hydropower production, which alters their thermal regimes, causes short-term temperature fluctuations (thermopeaking) linked to flow variations, and whose future evolution under climate change remains uncertain. This study examines how the thermal regime of a peri-alpine regulated river could evolve under future climate scenarios using a high-resolution process-based model. Projections indicate that mean annual water temperatures may rise by up to 4 °C by 2080–2090 under RCP 8.5, with daily mean temperatures exceeding 15 °C for nearly half the year, raising ecological concerns. While these trends are comparable to those in unregulated rivers, river regulation introduces distinct spatial and seasonal patterns in climate change impacts. The reach with only a residual flow is particularly susceptible to warming due to limited discharge, whereas deep reservoir releases help moderate climate change impacts downstream of the dam and the hydropower plant. Furthermore, unlike in unregulated rivers where the strongest warming typically occurs in summer, climate change impacts in this regulated system are projected to be most pronounced in autumn and winter due to the thermal inertia of the reservoir. Indicators used to assess thermopeaking impacts remain largely unaffected by climate change, provided that hydropower operation remains unchanged. This study highlights that while regulation can exacerbate vulnerabilities to climate change, it also mitigates climate change impacts by influencing river temperature dynamics beyond thermopeaking alone. A copy of the paper is freely available here.