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We applied an interdisciplinary approach to capture the sediment dynamics and evolution of the channel system in the transition zone from glacial ice to pro-glacial areas of a partially debris-covered glacier. Historical land cover based reconstructed based on maps dating as far back as the early 19th century. Modern terrain information from orthophotos and elevation models formed the basis for the interpretation of such historical maps. Historical landscape evolution shows a 126% increase in fluvially influenced sediment areas between the years of 1820 and 2015 as a result of the retreating glacier tongue. In turn, a 196% increase in alpine grassland indicates the adaptation of vegetation to the changing climate, as well as a long-term stabilisation of proglacial wasteland. In the recent past, however, the process of deglaciation has been faster than colonisation by alpine vegetation.A detailed analysis of the landscape changes in the glacier forefield of the Jamtalferner based on laser-scanning and photogrammetric data reveals the dynamics of the geomorphological processes and their sediment input into the channel of the glacial stream. The intensity of slope dynamics in the lateral moraines, as indicated by elevation changes, decreases noticeably with distance from the present glacier tongue position. The dynamics of the channel in the glacier forefield are generally very high. However, there is only minor direct sediment contribution from the debris cover of the glacier to the total sediment transport.The data and documentation of hydro-morphological processes form the basis for hydraulic modelling of sediment transport in these highly variable areas., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The emergence of glacial lakes is a significant consequence of global climate change in high mountain regions. Recent developments in ice thickness modelling combined with high-resolution glacier surface data led to the generation of modelling approaches to simulate the ice-free bedrock topography below current glaciers and to detect potential glacier bed overdeepenings (GBO) that may form into future lakes. We simulated the subglacial topography in the Austrian Alps using two different ice thickness models. Glaciers in the study area differ significantly from glaciers investigated in previous studies on potential future lakes because of their in general small size and location often restricted to cirques. The aim of this study is to estimate the number and location of potential future lakes in Austria. We tested the performance of ice thickness models for modelling of potential future lakes in an environment dominated by mountain glaciers that are under high stress of climate change. Modelling results are compared with lakes that evolved since the modelling periods and with data on subglacial topography derived from geophysical surveys. Results show significant differences in model performance concerning the total ice volume and the number of simulated GBOs. The number and total area of the modelled GBOs is overestimated, compared with the number of lakes that have evolved in the past. Most GBOs are simulated for valley type glaciers, even though most glaciers are mountain types. This does not match with the location of existing glacial lakes that are dominantly found in cirques. We ascertain that this modelling approach performs better on large valley type glaciers and less well on mountain glaciers. Intersecting the modelling runs indicates that up to 42 new lakes may form within 23 glaciers in Austria covering a total area of 2 km2.

Die Schneebedeckung ist ein entscheidender Parameter für den Energiehaushalt der Erde, da Schneeoberflächen einen großen Teil der einfallenden Globalstrahlung reflektieren. Die Ausprägung der Schneedecke hängt dabei besonders stark von der Temperatur während des Niederschlages und darüber hinaus von der Niederschlagsmenge sowie den Witterungsbedingungen vor und nach einem Schneefallereignis ab. Mit dem Temperaturanstieg über die vergangenen Jahrzehnte wurde global eine Abnahme der Schneebedeckung vor allem in sehr temperatursensitiven Höhenlagen um den Bereich der Schneefallgrenze beobachtet. Signifikante Langfristtrends in der Schneedeckendauer sowie der Schneehöhe sind in den meisten Gebirgen der Welt zu finden, auch wenn diese von einer großen natürlichen Variabilität der Schneebedeckung von Jahr zu Jahr sowie dekadischen Schwankungen überlagert sind. Climate change impacts on snow cover: The snow cover is an important parameter in the energy balance of the Earth, since snow surfaces reflect a large part of the incident global radiation. The state of the snow cover is particularly dependent on the temperature during precipitation events, but also on the amount of precipitation and the prevailing weather conditions before and after a snowfall. As a consequence of rising temperatures over the past decades, a decrease in snow cover has been observed worldwide, especially at very temperature-sensitive altitudes around the snow line. Significant long-term trends in snow cover duration and snow depth can be found in most mountain regions of the world. These trends are overlaid by a high natural year-to-year and decadal variability.

Knowledge on ice thickness distribution and total ice volume is a prerequisite for computing future glacier change for both glaciological and hydrological applications. Various ice thickness estimation methods have been developed but regional differences in fundamental model parameters are substantial. Parameters calibrated with measured data at specific points in time and space can vary when glacier geometry and dynamics change. This study contributes to a better understanding of accuracies and limitations of modelled ice thicknesses by taking advantage of a comprehensive data set of in-situ ice thickness measurements from 58 glaciers in the Austrian Alps and observed glacier geometries of three Austrian glacier inventories between 1969 and 2006. The field data are used to calibrate an established ice thickness model to calculate an improved ice thickness data set for the Austrian Alps. A cross-validation between modelled and measured point ice thickness indicates a model uncertainty of 25-31% of the measured point ice thickness. The comparison of the modelled and measured average glacier ice thickness revealed an underestimation of 5% with a mean standard deviation of 15% for the glaciers with calibration data. The apparent mass balance gradient, the primary model parameter accounting for the effects of surface mass balance distribution as well as ice flux, substantially decreases over time and has to be adjusted for each temporal increment to correctly reproduce observed ice thickness. This reflects the general stagnation of glaciers in Austria. We applied optimized apparent mass balance gradients to all glaciers of the latest Austrian glacier inventory and found a volume of 15.9 km for the year 2006. The ten largest glaciers account for 25% of area and 35% of total ice volume. An estimate based on mass balance measurements from nine glaciers indicates an additional volume loss of 3.5 0.4 km (i.e. 22 2.5%) until 2016. Relative changes in area and volume were largest at glaciers smaller than 1 km, and relative volume changes appear to be higher than relative area changes for all considered time periods. FUTURELAKES (VLID)3596959

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.

Hydrological sciences journal, 64 (10), ISSN:0262-6667, ISSN:2150-3435

The Cryosphere Discussions, ISSN:1994-0432, ISSN:1994-0440

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.

Knowledge of the ice thickness distribution of glaciers and ice caps is an important prerequisite for many glaciological and hydrological investigations. A wealth of approaches has recently been presented for inferring ice thickness from characteristics of the surface. With the Ice Thickness Models Intercomparison eXperiment (ITMIX) we performed the first coordinated assessment quantifying individual model performance. A set of 17 different models showed that individual ice thickness estimates can differ considerably – locally by a spread comparable to the observed thickness. Averaging the results of multiple models, however, significantly improved the results: on average over the 21 considered test cases, comparison against direct ice thickness measurements revealed deviations on the order of 10 ± 24 % of the mean ice thickness (1σ estimate). Models relying on multiple data sets – such as surface ice velocity fields, surface mass balance, or rates of ice thickness change – showed high sensitivity to input data quality. Together with the requirement of being able to handle large regions in an automated fashion, the capacity of better accounting for uncertainties in the input data will be a key for an improved next generation of ice thickness estimation approaches., The Cryosphere, 11 (2), ISSN:1994-0416, ISSN:1994-0424

Snow deposition and redistribution are major drivers of snow cover dynamics in mountainous terrain and contribute to the mass balance of alpine glaciers. The quantitative understanding of inhomogeneous snow distribution in mountains has recently benefited from advances in measuring technologies, such as airborne laser scanning (ALS). This contribution further advances the quantitative understanding of snow distribution by analysing the areas of maximum surface elevation changes in a mountain catchment with large and small glaciers. Using multi-annual ALS observations, we found extreme surface elevation changes on rather thin borders along the glacier margins. While snow depth distribution patterns in less extreme terrain have presented high inter-annual persistence, there is little persistence of those extreme glacier accumulations between winters. We therefore interpret the lack of persistence as the result of a predominance of gravity-driven redistribution, which has an inherently higher random component because it does not occur with all conditions in all winters. In highly crevassed zones, the lidar-derived surface elevation changes are caused by a complex interaction of ice flux divergence, the propagation of crevasses and snow accumulation. In general, the relative contribution of gravitational mass transport to glacier snow cover volume was found to decrease for glaciers larger than 5 km(2) in the investigated region. We therefore suggest that extreme accumulations caused by gravitational snow transport play a significant role in the glacier mass balance of small to medium-size glaciers and that they may be successfully parameterized by simple mass redistribution algorithms, which have been presented in the literature.