In alpine regions, snow avalanches endanger infrastructure such as roads, ski slopes and buildings. While permanent protection measures minimize avalanche impact, local experts must implement additional safety measures such as road or ski slope closures during critical situations. To support this demanding decision-making process, we propose a framework that can be used on a daily basis to calculate avalanche probability indication maps of potential avalanche runout extents and intensities. The probability indication maps are generated by running multiple avalanche simulations, based on an ensemble of estimations of input parameters derived from weather station measurements and weather forecasts, to assess a range of possible scenarios, e.g. for fracture depth, maximum erosion depth and snow temperature. We aim to identify the minimum number of input parameters needed to meaningfully represent daily snowpack conditions. We focus on cold snow conditions that produce powder snow avalanches. To evaluate the quality of the proposed probability indication maps, we conduct a hindcast for four well-documented avalanche events around Davos, Switzerland, using meteorological station data from the day before the avalanches released, weather forecast and SNOWPACK simulations. For validation we compare the resulting predictions to the measured outlines of the avalanche cores. This study demonstrates how real-time weather and snowpack data can be utilized effectively to provide practitioners with an overview of the current avalanche situation to support their decision-making process. In the future, such approaches could be implemented into more data-based decision-making processes to better protect traffic infrastructure in high-risk avalanche hazard areas.
The Pine Island Ice Shelf can be analysed within three distinct sectors: northern, southern, and central. Dynamics within the Northern Pine Island Ice Shelf (N-PIIS) remain less understood than those of the Central Pine Island Ice Shelf. Using satellite imagery and data, we investigate changes in the N-PIIS, including ice-front position and pinning-point evolution since 1973, annual ice velocity since 2014, surface elevation since 2018, rift propagation events in 2022 and 2025, and polynya activity from 1986 to 2026. Our results show an overall reduction in ice-shelf area, with increased calving following the loss of pinning points and reduced protection by landfast sea ice against ocean swell. Velocities of grounded and floating ice have increased. Polynya formation within the ice shelf may promote disconnection from the ice sheet and reduce lateral buttressing. Surface elevation changes and the redistribution of pinning points indicate ongoing thinning. Newly formed rifts are likely to promote further calving events. Our observations document continued thinning, frontal retreat, pinning-point loss, and rift propagation at the N-PIIS. This study provides critical new insights into the evolving stability of the N-PIIS and highlights the importance of continued monitoring to anticipate potential disintegration.
Most hydrological models underestimate snow water equivalent (SWE) in the mountainous western US. Key limitations may include inadequate representation of spatial variability due to coarse-resolution precipitation input and inadequate representations of snow-vegetation interactions. Vegetation affects snow dynamics through snow interception, throughfall/unloading, and energy transfer through the canopy, yet basin-scale studies on the vegetation effects are limited. To address this issue, we applied Noah-MP version 5.0 with a dynamic vegetation module over the Sacramento and San Joaquin River Basins in California at 1 km resolution. The model was driven by the Analysis of Record for Calibration (AORC) forcing at its native 1 km resolution and by the NLDAS-2 forcing downscaled from ∼ 12 to 1 km using the WRF-Hydro Meteorological Forcing Engine. We carried out eight model experiments driven by the two forcing datasets and two vegetation schemes over the two Basins. Compared to the 4 km PRISM and 1 km AORC, the downscaled 1 km NLDAS-2 forcing data shows higher precipitation and lower temperatures over the mountains, resulting in more snowfall and SWE, which is more consistent with in-situ SWE observations. Using the 1 km NLDAS-2 forcing, the default vegetation scheme that prescribes leaf area index (LAI) and vegetation cover fraction, produces excessive SWE on the ground, mainly because the strong canopy shading (too high LAI) reduces snowmelt, even though more snowfall is intercepted by the canopy. The dynamic vegetation module produces smaller LAI than the prescribed (more consistent with MODIS LAI) and thus leads to more shortwave radiation reaching the snow surface, thereby enhancing episodic melting during the accumulation season. Validation against in-situ snow data suggests that the use of dynamic vegetation model and the downscaled NLDAS-2 data perform the best. These findings highlight the importance of vegetation effects and downscaling of atmospheric forcing to improve the accuracy of snow modeling over the Southwest US.
Proglacial lakes can accelerate terminus retreat and dynamic thinning of lake-terminating glaciers. However, glacier responses to abrupt lake disconnection following glacial lake outburst floods (GLOFs) remain poorly quantified. Here, we investigate the dynamic evolution of Jinwu Glacier in southeastern Tibet, China, whose proglacial lake (Jinwuco) drained during a GLOF on 26 June 2020, shifting the glacier from lake- to land-terminating conditions. Following this loss of lake contact, the downstream glacier tongue showed clear changes in ice flow and frontal morphology. Mean ice-flow velocity within 100–200 m of the terminus decreased from 42.97 ± 4.38 m a−1 during 2017–2020 to 24.09 ± 6.71 m a−1 during 2021–2025, corresponding to a reduction of approximately 44 %. During 2020–2021, the glacier front was characterized by ice-cliff degradation and collapse, together with a slight terminus advance of approximately 23 m. In contrast, the glacier tongue upstream of the icefall showed no pronounced velocity change, with mean velocity in the 650–1600 m section changing from 37.55 ± 9.56 m a−1 during 2017–2020 to 35.24 ± 9.37 m a−1 during 2021–2025. The icefall may limit dynamic coupling between the upstream section and the terminus. These results show that GLOF-induced lake disconnection can substantially alter ice flow and frontal morphology near the glacier terminus. This study provides the first quantitative evidence of glacier dynamic adjustment following a GLOF driven transition from lake- to land-terminating conditions.
Supraglacial drainage systems represent critical components of the surface hydrology on Antarctic ice shelves, facilitating the redistribution of meltwater, including into and out of supraglacial lakes, potentially influencing ice-shelf stability. However, the seasonal and interannual variability in their spatial extent, structural evolution, and climatic sensitivity remain poorly quantified, particularly compared to observations of supraglacial lakes. In this study, we investigate the interannual evolution of supraglacial drainage systems on Nivlisen Ice Shelf in East Antarctica between 2017 and 2024 using Sentinel-2 and Landsat-8 satellite imagery, with a detailed seasonal analysis during the 2018–2019 melt season. Key metrics including surface water area, total channel length, number of supraglacial drainage components, and the number of individual channels were derived to quantify the drainage evolution, system connectivity and complexity. We find significant interannual variability in the number of drainage components (from 34–186) and total channel length (from 345–1275 km), with peak length of channels observed in 2018. During the 2018–2019 melt season, channels progressively integrated and connected to form a very well-connected drainage system, which then fragmented towards the end of the melt season. We find that drainage systems are strongly influenced by ice shelf surface structures and undulations at a range of scales, with larger channels reforming in the same location. Correlation analysis shows that the evolution of drainage systems is tightly coupled to regional air temperature, with surface water extent and drainage connectivity strongly linked to reanalysis-based temperature outputs (r>0.9, p<0.05). Snow had variable effects, depending on its timing and how readily it could be melted. Our findings underscore the important dynamic nature of supraglacial channels in redistributing meltwater on Antarctic ice shelves.
