AlpWISE : ALPine Water, Ice, Sediment and Ecology

The recordings of the David Linton Award and Medal Lecture are now available on-line, including additional recordings of the two topics that did not win the public vote for being presented. They are accessible here.

Glacial lake outburst floods (GLOFs) pose a growing risk in high mountain regions as climate-driven glacier retreat accelerates lake expansion and new lake formation. In the Hindu Kush Himalaya, particularly in Afghanistan, triggering processes and GLOF propagation downstream are largely unstudied. This study evaluates two Afghanistan GLOFs (Peshghor 2018; Bam-Tanab 2021) using field observations and satellite imagery, and applies two-dimensional hydrodynamic simulation (BASEMENT-MD with BASEbreach) to the Kunj-Peshghor lake event to assess flood propagation, dam-breach dynamics, and downstream hazards under different scenarios. Both lakes formed and expanded over 33–42 days before catastrophic drainage, triggered by extreme temperatures, rapid-melt, ice-cliff collapse, and englacial tunnel failure. Both impacted Peshghor village downstream. The Kunj-Peshghor lake flood wave produced estimated peak velocities of 9 ms⁻¹ and depths >10 m in confined valleys, associated with peak discharges >170 m³s⁻¹, high turbidity >800 NTU, and channel widening of up to 250 m. Secondary surges caused by temporary river blockages prolonged flooding and amplified downstream impacts. Hazard mapping indicates that ~46% of inundated zones in the Peshghor village fell within high to very high hazard levels, threatening settlements, roads, markets, and agricultural land. These findings provide the first quantitative GLOF propagation modeling for Afghanistan and highlight the need for site-specific monitoring, early warning systems, and mitigation measures. Both GLOFs were caused by the rapid formation and expansion of new lakes. This raises the question about whether current approaches to identifying dangerous lakes, based on remote-sensing of existing lakes are sufficient to detect all dangerous lakes and the associated hazards. A copy of the paper is freely available here.

Glaciers actively store and release meltwater with significant impacts on glacier flow velocity and downstream environments. The evolution of this drainage system is a key component in understanding glacier dynamics. In temperate alpine glaciers, the change of the subglacial drainage network from distributed to channelised is theoretically known, but lacks empirical documentation. As subglacial channels are extremely difficult to access, it is important to test innovative methods for locating them. Here, we use surface seismic monitoring, which enables us to identify the location of multiple subglacial channels below Glacier d’Otemma, Valais, Switzerland. We calculate time delays between pairs of seismic sensors and backtrack source locations. Using matched field processing and beamforming analysis, we obtain spatial and temporal patterns of seismic noise produced by the glacier. This allows us to interpret a possible evolution of the subglacial drainage network from a distributed to an efficient one and locate three distinct subglacial channels in close proximity. A copy is freely available here.

We present the first large-sample, spatially resolved measurements of coarse sediment transport within a subglacial meltwater channel. We released 324 radio-tagged pebbles into a near-terminus channel of Glacier d’Otemma, Switzerland, and monitored their positions through 10–50 m of ice during the mid to late melt season. Concurrently, proglacial discharge and bedload flux were monitored at the terminus. Particles moved infrequently: more than half never moved, most remained near their release location, and only 25% were exported to the proglacial river. Particle export was more consistently related to recent movement history than to proglacial discharge or bedload export, whereas virtual velocity showed no consistent relationship with these predictors. These observations indicate substantial coarse sediment retention within an active near-terminus subglacial channel, potentially weakening short-term correspondence between coarse subglacial transport and proglacial sediment export. A copy of the paper is freely available here.

Predicting bedload fluxes in Alpine river systems is extremely challenging because of the complexity of sediment dynamics and the difficulty of quantifying bedload to support model development. Traditional methods to predict bedload rates and volumes rely on the calculation of bedload transport capacity at individual river sections, assuming unlimited sediment supply. This often leads to large overestimations of transported volumes and an inability to capture actual network-scale dynamics. To overcome these caveats, we have adapted the network-scale sediment transport model D-CASCADE for application to steep, coarse-bedded mountain river systems. We introduced different approaches to estimate flow hydraulics and sediment transport capacity. We evaluated the model at a single cross-section using 6 years of continuous bedload measurements at the outlet of the Sulden/Solda River basin (Italian Alps). The model was run using two different assumed channel widths—mean-flow and bankfull—resulting in overestimation and underestimation of measured bedload, respectively. Despite this, the adapted model predicted annual bedload volumes at the catchment outlet within one order of magnitude of the measured values, consistently better than using the traditional approach. We then used the model to assess longitudinal connectivity, transport rates, sediment storage dynamics and bedload budgets along the whole Sulden river network, comparing model predictions qualitatively against the available information on channel dynamics for the same period. These comparisons highlight the model’s ability to reproduce key geomorphic processes, supporting its value as a novel approach for estimating sediment fluxes in Alpine river systems. Data suggest that the adapted D-CASCADE model can provide realistic spatial and temporal patterns of sediment transport and storage, aligning well with observations across the network. A copy of the paper is freely available here.

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.