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Over the last million years, cyclical changes in Earth's orbital parameters have been responsible for climate fluctuations and ice ages that have shaped our landscape. Current climate change, on the other hand, is caused by human greenhouse gas emissions and the CO2 content in the atmosphere exceeds the maximum value of the last 800,000 years by far. This is the main cause of current global climate change, which will affect human beings, and the whole ecosystem far into the future.While public awareness of climate change has increased massively over the last years, many misconceptions are still widespread. In order to increase awareness about the human impact versus natural processes, we are designing an interactive «Ice Age Machine», which will be placed at popular vantage points in Switzerland from September 2023 onwards. These interactive stations will allow groups of users to actively experience past ice ages as well as the corresponding environmental changes thanks to an innovative design and new visualization techniques based on artificial intelligence. The visitors will learn about the history of glaciations in the Alps, the extreme impact of human being on climate and what the future effects could be. The users have the opportunity to retrieve a photo showing them in action at the station in front of the panoramic ice age view to share via social media. To increase the visibility of the machine beyond the vantage points, communication activities on site and in the digital space (website, social media) will accompany the project., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Accurate knowledge of the ice thickness distribution and glacier bed topography is essential for predicting dynamic glacier changes and the future developments of downstream hydrology, which are impacting the energy sector, tourism industry and natural hazard management. Using AIR-ETH, a new helicopter-borne ground-penetrating radar (GPR) platform, we measured the ice thickness of all large and most medium-sized glaciers in the Swiss Alps during the years 2016–20. Most of these had either never or only partially been surveyed before. With this new dataset, 251 glaciers – making up 81% of the glacierized area – are now covered by GPR surveys. For obtaining a comprehensive estimate of the overall glacier ice volume, ice thickness distribution and glacier bed topography, we combined this large amount of data with two independent modeling algorithms. This resulted in new maps of the glacier bed topography with unprecedented accuracy. The total glacier volume in the Swiss Alps was determined to be 58.7 ± 2.5 km3 in the year 2016. By projecting these results based on mass-balance data, we estimated a total ice volume of 52.9 ± 2.7 km3 for the year 2020. Data and modeling results are accessible in the form of the SwissGlacierThickness-R2020 data package.

Glacier mass-balance observations at seasonal resolution have been performed since 1914 at two sites on Claridenfirn, Switzerland. The measurements are the longest uninterrupted records of glacier mass balance worldwide. Here, we provide a complete re-analysis of the 106-year series (1914–2020), focusing on both point and glacier-wide mass balance. The approaches to evaluate and homogenize the direct observations are described in detail. Based on conservative assumptions, average uncertainties of$\pm$0.25 m w.e. are estimated for glacier-wide mass balances at the annual scale. It is demonstrated that long-term variations in mass balance are clearly driven by melting, whereas decadal changes in accumulation are uncorrelated with mass balance and can only be relevant in short periods. Mass change of Claridenfirn is impacted by dry calving at a frontal ice cliff. Considerations of ice volume flux at a cross-profile reveal long-term variations in frontal ice loss accounting for$\sim$9% of total annual ablation on average. The effect of changes in frontal ablation mostly explains$\lt$10% of the mass-balance difference relative to the period 1960–1990, but accounts for$\sim$20% in 2010–2020. Glacier mass changes are discussed in the context of observations throughout the European Alps indicating that Claridenfirn is regionally representative.

Accurate knowledge of the ice thickness distribution and glacier bed topography is essential for predicting dynamic glacier changes and the future developments of downstream hydrology, which are impacting the energy sector, tourism industry and natural hazard management. Using AIR-ETH, a new helicopter-borne ground-penetrating radar (GPR) platform, we measured the ice thickness of all large and most medium-sized glaciers in the Swiss Alps during the years 2016–20. Most of these had either never or only partially been surveyed before. With this new dataset, 251 glaciers – making up 81% of the glacierized area – are now covered by GPR surveys. For obtaining a comprehensive estimate of the overall glacier ice volume, ice thickness distribution and glacier bed topography, we combined this large amount of data with two independent modeling algorithms. This resulted in new maps of the glacier bed topography with unprecedented accuracy. The total glacier volume in the Swiss Alps was determined to be 58.7 ± 2.5 km3 in the year 2016. By projecting these results based on mass-balance data, we estimated a total ice volume of 52.9 ± 2.7 km3 for the year 2020. Data and modeling results are accessible in the form of the SwissGlacierThickness-R2020 data package., Journal of Glaciology, 67 (266), ISSN:0022-1430, ISSN:1727-5652

International audience

Glacier retreat results in major landscape changes including the formation of new lakes in Glacier-Bed Overdeepenings (GBOs) that can provoke catastrophic Glacial Lake Outburst Flood (GLOF) hazards, but could also provide economic opportunities. This study aims to identify and characterize the location of potential GBOs in the French Alps as possible sites for future lakes. We first ran GlabTop (Glacier-bed Topography) and GlabTop2 models, two GIS schemes calculating glacier ice thickness and mapping potential GBOs. Their level of confidence is estimated using morphological analysis based on slope angle, crevasse fields and lateral narrowing at bedrock thresholds. 139 GBOs (>0.01km²) were predicted among which 59 have medium to very high confidence. 20 lakes are already forming at the snout of retreating glaciers, including four lakes at predicted GBOs 0,01 km²) ont été détectés, dont 59 qui ont un niveau de confiance moyen à très élevé. L’approche utilisée est limitée pour les calottes glaciaires, ce qui explique certains faibles niveaux de confiance en Vanoise. 19 lacs se forment déjà au front de certains glaciers, dont deux dans des surcreusements dont la superficie estimée est

With increasing anthropogenic greenhouse gas emissions and corresponding global warming, glaciers in Switzerland are shrinking rapidly as in many mountain ranges on Earth. Repeated glacier inventories are a key task to monitor such glacier changes and provide detailed information on the extent of glaciation, and important parameters such as area, elevation range, slope, aspect etc. for a given point or a period in time. Here we present the new Swiss Glacier Inventory (SGI2016) that has been acquired based on high-resolution aerial imagery and digital elevation models in cooperation with the Federal Office of Topography (swisstopo) and Glacier Monitoring in Switzerland (GLAMOS), bringing together topological and glaciological knowhow. We define the process, workflow and required glaciological adaptations to compile a highly accurate glacier inventory based on the digital Swiss topographic landscape model (swissTLM3D).The SGI2016 provides glacier outlines (areas), supraglacial debris cover, ice divides and location points of all glaciers in Switzerland referring to the years 2013-2018, whereas most of the glacier outlines have been mapped based on aerial images acquired between 2015-2017 (75% in number and 87% in area), with the centre year 2016. The SGI2016 maps 1400 individual glacier entities with a total glacier surface area of 961 km2 (whereof 11% / 104 km2 are debris-covered) and constitutes the so far most detailed cartographic representation of glacier extent in Switzerland. Analysing the dependencies between topographic parameters and debris-cover fraction on the basis of individual glaciers reveals that short glaciers with a moderate mean slope and glaciers with a low median elevation tend to have high debris fractions. A change assessment between the SGI1973 and SGI2016 based on individual glacier entities affirms the largest relative area changes for small glaciers and for low-elevation glaciers, whereas the largest glaciers show small relative area changes, though large absolute changes. The analysis further indicates a tendency for glaciers with a high share of supraglacial debris to show larger relative area changes.Despite of an observed strong glacier volume loss between 2010 and 2016, the total glacier surface area of the SGI2016 is somewhat larger than reported in the last Swiss glacier inventory SGI2010. Even though both inventories were created based on swisstopo aerial photographs, the additional data, tools, resources and methodologies used by the professional cartographers digitizing glacier outlines in 3D for the SGI2016, are able to explain the counter-intuitive difference between SGI2010 and SGI2016. A direct comparison of these two datasets is thus not meaningful, but an experiment where a representative glacier sample of the SGI2010 was re-assessed based on the approaches of the SGI2016 led to an upscaled total glacier surface area of 1010 km2 for the Swiss Alps around 2010. This indicates an area loss of 49 km2 between the two last Swiss glacier inventories. As swisstopo data products are and will be regularly updated, the SGI2016 is the first step towards a consistent and accurate data product of repeated glacier inventories in six-year time intervals that promises a high comparability for individual glaciers and glacier samples.

Glacier mass-balance observations at seasonal resolution have been performed since 1914 at two sites on Claridenfirn, Switzerland. The measurements are the longest uninterrupted records of glacier mass balance worldwide. Here, we provide a complete re-analysis of the 106-year series (1914–2020), focusing on both point and glacier-wide mass balance. The approaches to evaluate and homogenize the direct observations are described in detail. Based on conservative assumptions, average uncertainties of 0.25 m w.e. are estimated for glacier-wide mass balances at the annual scale. It is demonstrated that long-term variations in mass balance are clearly driven by melting, whereas decadal changes in accumulation are uncorrelated with mass balance and can only be relevant in short periods. Mass change of Claridenfirn is impacted by dry calving at a frontal ice cliff. Considerations of ice volume flux at a cross-profile reveal long-term variations in frontal ice loss accounting for 9% of total annual ablation on average. The effect of changes in frontal ablation mostly explains 10% of the mass-balance difference relative to the period 1960–1990, but accounts for 20% in 2010–2020. Glacier mass changes are discussed in the context of observations throughout the European Alps indicating that Claridenfirn is regionally representative., Journal of Glaciology, 67 (264), ISSN:0022-1430, ISSN:1727-5652

Numerous models to project the future evolution of mountain glaciers in response to ongoing climate change are available, both at the local and the global scale. However, a suite of partly major simplifications is necessary in these models given the restrictions in data availability. Whereas most models account for the primary feedbacks, such as the snow-ice albedo feedback and the dynamic glacier response in some way, a considerable number of yet poorly understood or less investigated feedbacks is present that might significantly hamper the reliability of current glaciological projections. Here, we present results of a detailed modelling study for the example of Vadret da Morteratsch, Swiss Alps. A surface mass balance model accounting for ice dynamics is forced with downscaled regional climate model output (68 scenarios, CH2018) for the period 2015 to 2100. Various processes are either parameterized or explicitly accounted for. We focus on the use of a fully distributed surface energy-balance approach in comparison to simplified degree-day methods. The relevance of projected changes in different components of the energy balance is assessed using model experiments. In particular, the importance of feedback effects due to (1) the spatio-temporal evolution of supraglacial debris, (2) the formation of new proglacial lakes, and (3) changes in bare-ice albedo and local direct solar irradiance is investigated. We find that the above feedback effects all have a rather small potential to substantially impact on the rates of expected glacier retreat. In some cases, this is unexpected (e.g. for debris coverage and proglacial lakes) but can be explained by compensating processes. We also discuss and visualize the future wastage of Vadret da Morteratsch under the newest generation of climate scenarios, and put these results into context with previous studies, as well as with plans to artificially reduce the rate of glacier mass loss.

Alpine glacier retreat due to global warming generates major landscape changes in high mountain environments. New lakes can potentially form in Glaciers Bed Overdeepenings (GBOs). Those new water bodies, sometimes located near potentially instable slopes or behind unstable moraine dams, can increase outburst flood hazards, generating risks for valley floors. Such GLOF events (Glacial Lake Outbrust Floods) can result from displacement waves triggered by rock fall into lakes and/or sudden dam breaching. Those events can travel far down to low altitude areas and turning into high magnitude debris flows. Beyond the threats, those lakes can also represent opportunities for tourism, hydropower production or fresh water supply. Anticipating location and formation of potential future lakes is thus essential for risk mitigation and seizing the opportunities. In the French Alps so far, potential future lakes have only been investigated in the Mont Blanc massif, while several other glaciated high mountain ranges may also yield water bodies in the near future. This study aims to identify and characterize the location of potential future lakes for each mountain massif of the French Alps (mainly the Mont Blanc, Grandes Rousses, Vanoise and Écrins massifs). To do so, we first ran GlabTop model, a GIS scheme calculating ice thickness from surface slope via basal shear stress, to map potential GBOs. We also ran GlabTOP 2, which is based on the same concept but is fully automated. In this study, we compared the results between GlabTop and GlabTop 2. We then estimated the level of confidence of the predicted GBOs using morphometric analysis (slope angle at GBOs and downstream, presence/absence of crevasse fields, presence/absence of bedrock threshold) and classification of lakes according to their susceptibility of formation. GlabTOP output thus revealed 89 GBOs (>1ha) which can potentially be sites for future lakes. 20 lakes are predicted in Écrins, 2 in Grandes Rousses, 39 in Vanoise and 30 on the French side of the Mont Blanc massif. The lakes with the highest surfaces/thicknesses are situated in the latter. Among the 89 predicted water bodies, 41 are highly susceptible to be formed. Some can already be observed in GBOs in recently deglaciated areas like at the Bionnassay and Tré la Tête glaciers (Mont Blanc massif). This communication will present the approach, the detailed results and possible implications for landscape management at the French Alps scale.

De-glaciating high mountain areas result in new landscapes of bedrock and debris where permafrost can degrade, persist or even newly form in cases, and of new lakes in glacier bed overdeepenings (GBOs) becoming ice-free. These landscapes with new lakes in close neighborhood to over-steepened and perennially frozen slopes are prone to chain reaction processes (e.g. rock-ice avalanches into lakes triggering impact waves, dam breach or overtopping, and debris flows) with potentially far-reaching run-out distances causing valley floors devastation. The frequency, magnitude and zonation of hazards are shifting, requiring integrative approaches combining comprehensive information about landscape evolution and related processes to support stakeholders in their adaptation strategies. In this study, we intend to setup an essential baseline for such an integrative approach in the Mont Blanc massif (MBM), which is a typical high-mountain range affected by de-glaciation processes. We first (i) predict and (ii) detect potential GBOs by combining the GlabTop model with a visual analysis based on morphological indications of glacier flow through over- deepened bed parts. We then (iii) determine the level of confidence concerning the resulting information, and (iv) estimate the approximate time range under which potential lakes could form. The location of the predicted GBOs and the shape of glacier beds are evaluated against currently forming water bodies at retreating glacier snouts, and seismic and ice penetrating radar measurements on the Argentière glacier. This comparison shows that the location of predicted GBOs is quite robust whereas their morphometric characteristics (depth, volume) are highly uncertain and tend to be underestimated. In total, 48/80 of the predicted or detected GBOs have a high level of confidence. In addition to five recently formed water bodies at glacier snouts, one of the high confidence GBOs (Talèfre glacier) which is also the most voluminous one could form imminently (during coming years), if not partially or totally drained through deeply incised gorges at the rock threshold. Twelve other lakes could form within the first half of the century under a constant or accelerated scenario of continued glacier retreat. Some of them are located below high and permanently frozen rock walls prone to destabilization and high-energy mass movements, hinting at possible hot spots in terms of hazards in the coming decades, where more detailed analysis would be required.

International audience

This study was supported by grants from the Natural Science Foundation of China (41871056, 21661132003, 41571068, 41571061 and 41771088), the Strategic Priority Research Program (A) of the Chinese Academy of Sciences (XDA20060201), the Swiss National Science Foundation (project: “Recent and future EVOlution of Glacial LAkes in China (EVOGLAC)”, IZLCZ2_169979/1) and the Dragon 4 project funded by ESA (4000121469/17/I-NB). G. Zhang thanks the China Scholarship Council for supporting his visit to University of Zurich from December 2017 to December 2018 (no. 201704910339). TanDEM-X CoSSC data were provided by German Aerospace Center (DLR) with proposal ATI_HYDR7290. Despite previous studies, glacier–lake interactions and future lake development in the Poiqu River basin, central Himalaya, are still not well understood. We mapped glacial lakes, glaciers, their frontal positions and ice flow from optical remote sensing data, and calculated glacier surface elevation change from digital terrain models. During 1964–2017, the total glacial-lake area increased by ~110%. Glaciers retreated with an average rate of ~1.4 km2 a−1 between 1975 and 2015. Based on rapid area expansion (>150%), and information from previous studies, eight lakes were considered to be potentially dangerous glacial lakes. Corresponding lake-terminating glaciers showed an overall retreat of 6.0 ± 1.4 to 26.6 ± 1.1 m a−1 and accompanying lake expansion. The regional mean glacier elevation change was −0.39 ± 0.13 m a−1 while the glaciers associated with the eight potentially dangerous lakes lowered by −0.71 ± 0.05 m a−1 from 1974 to 2017. The mean ice flow speed of these glaciers was ~10 m a−1 from 2013 to 2017; about double the mean for the entire study area. Analysis of these data along with climate observations suggests that ice melting and calving processes play the dominant role in driving lake enlargement. Modelling of future lake development shows where new lakes might emerge and existing lakes could expand with projected glacial recession. Publisher PDF

Filiacion institucional de autor: Alejo Cochachin Rapre /Autoridad Nacional del Agua - Unidad de Glaciologia y Recursos Hidricos (ANA-UGRH), Huaraz, Peru

Glacial lake outburst floods (GLOFs) are a serious and potentially increasing threat to livelihoods and infrastructure in most high-mountain regions of the world. Here, we integrate modelling approaches that capture both current and future potential for GLOF triggering, quantification of affected downstream areas, and assessment of the underlying societal vulnerability to such climate-related disasters, to implement a first-order assessment of GLOF risk across the Himalayan state of Himachal Pradesh (HP), Northern India. The assessment thereby considers both current glacial lakes and modelled future lakes that are expected to form as glaciers retreat. Current hazard, vulnerability, and exposure indices are combined to reveal several risk ‘hotspots’, illustrating that significant GLOF risk may in some instances occur far downstream from the glaciated headwaters where the threats originate. In particular, trans-national GLOFs originating in the upper Satluj River Basin (China) are a threat to downstream areas of eastern HP. For the future deglaciated scenario, a significant increase in GLOF hazard levels is projected across most administrative units, as lakes expand or form closer towards steep headwalls from which impacts of falling ice and rock may trigger outburst events. For example, in the central area of Kullu, a 7-fold increase in the probability of GLOF triggering and a 3-fold increase in the downstream area affected by potential GLOF paths can be anticipated, leading to an overall increase in the assigned GLOF hazard level from ‘high’ to ‘very high’. In such instances, strengthening resilience and capacities to reduce the current GLOF risk will provide an important first step towards adapting to future challenges.

The potential contribution of glaciers and ice caps to sea level rise is usually calculated by comparing the estimated total ice volume with the surface area of the ocean. Part of this total ice volume, however, does not contribute to sea level rise because it is below the surface of the ocean or below the levels of future lakes on land. The present communication points to this so far overlooked phenomenon and provides a first order-of-magnitude estimate. It is shown that the effect is small (most likely about 1 to 6 cm sea level equivalent) but systematic, could primarily affect earlier stages of global glacier vanishing, and should therefore be adequately considered. Now-available techniques of slope-related high-resolution glacier bed modelling have the potential to provide more detailed assessments in the future.

In the course of glacier retreat, new glacier lakes can develop. As such lakes can be a source of natural hazards, strategies for predicting future glacier lake formation are important for an early planning of safety measures. In this article, a multi-level strategy for the identification of overdeepened parts of the glacier beds and, hence, sites with potential future lake formation, is presented. At the first two of the four levels of this strategy, glacier bed overdeepenings are estimated qualitatively and over large regions based on a digital elevation model (DEM) and digital glacier outlines. On level 3, more detailed and laborious models are applied for modeling the glacier bed topography over smaller regions; and on level 4, special situations must be investigated in-situ with detailed measurements such as geophysical soundings. The approaches of the strategy are validated using historical data from Trift Glacier, where a lake formed over the past decade. Scenarios of future glacier lakes are shown for the two test regions Aletsch and Bernina in the Swiss Alps. In the Bernina region, potential future lake outbursts are modeled, using a GIS-based hydrological flow routing model. As shown by a corresponding test, the ASTER GDEM and the SRTM DEM are both suitable to be used within the proposed strategy. Application of this strategy in other mountain regions of the world is therefore possible as well.

International audience; The rapid transformation of glacial into periglacial mountain landscapes under conditions of continued global warming can cause new and locally severe changes in hazard and risk conditions. A special focus must be on systematically increasing risks due to far-reaching flood waves or debris flows caused by rock/ice avalanches into new lakes at the foot of steep slopes with decreasing stability due to permafrost degradation and/or glacial de-buttressing. Modeling permafrost occurrence and glacier-bed topography provides important information for anticipating critical future situations.

The Swiss Glaciers. Glaciological Report, 137/138, ISSN:1424-2222, ISSN:1423-2820

Overdeepenings, i.e. closed topographic depressions with adverse slopes in the direction of flow, are characteristic for glacier beds and glacially sculpted landscapes. Quantitative information about their morphological characteristics, however, has so far hardly been available. The present study provides such information by combining the analysis of (a) numerous bed overdeepenings below still existing glaciers of the Swiss Alps and the Himalaya-Karakoram region modelled with a robust shear stress approximation and (b) detailed bathymetries from recently exposed lakes in the Peruvian Andes. The investigated overdeepenings exist where glacier surface slopes are low (< 5°–10°), occur in bedrock or morainic material and are most commonly a fraction of a kilometre squared in surface area, hundreds of metres long, about half the length in width and tens of metres deep. They form under conditions of low to high basal shear stresses, at cirque, confluence, trunk valley and terminus positions. The most striking phenomenon, however, is the high variability of their geometries: Depths, surface areas, lengths and widths of the overdeepenings vary over orders of magnitude and are only weakly – if at all – interrelated. Inclinations of adverse slopes do not differ significantly from those of forward slopes and are in many cases higher than so far assumed theoretical limits for supercooling of ascending water and corresponding closure of sub-glacial channels. Such steep adverse slopes are a robust observation and in support of recently developed new concepts concerning the question about where supercooling of sub-glacial water and closure of ice channels can or must occur. However, the question of when and under what climatic, topographic and ice conditions the overdeepenings had formed remains unanswered. This open question constitutes a key problem concerning the interpretation of observed overdeepenings, the understanding of the involved glacio-hydraulic processes and the possibility of realistic predictive modelling of overdeepening formation.

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 in the order of 10 &pm; 24% of the mean ice thickness (1-sigma estimate). For models relying on multiple data sets -- such as surface ice velocity fields, surface mass balance, or rates of ice thickness change – the results highlighted the sensitivity to input data consistency. 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.

Ice volume estimates are crucial for assessing water reserves stored in glaciers. Due to its large glacier coverage, such estimates are of particular interest for the Himalayan–Karakoram (HK) region. In this study, different existing methodologies are used to estimate the ice reserves: three area–volume relations, one slope-dependent volume estimation method, and two ice-thickness distribution models are applied to a recent, detailed, and complete glacier inventory of the HK region, spanning over the period 2000–2010 and revealing an ice coverage of 40 775 km2. An uncertainty and sensitivity assessment is performed to investigate the influence of the observed glacier area and important model parameters on the resulting total ice volume. Results of the two ice-thickness distribution models are validated with local ice-thickness measurements at six glaciers. The resulting ice volumes for the entire HK region range from 2955 to 4737 km3, depending on the approach. This range is lower than most previous estimates. Results from the ice thickness distribution models and the slope-dependent thickness estimations agree well with measured local ice thicknesses. However, total volume estimates from area-related relations are larger than those from other approaches. The study provides evidence on the significant effect of the selected method on results and underlines the importance of a careful and critical evaluation.