Martin Hölzle
martin.hoelzle@unifr.ch
+41 26 300 9022
https://orcid.org/0000-0002-3591-4377
Géographie physique
Cryosphère
Professeur·e ordinaire
Département de géosciences
PER 14, 3.335
Recherche et publications
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Publications
152 publications
Six decades of satellite remote sensing reveal widespread glacier pulsations in the Hissar-Alay (Central Asia)
Enrico Mattea, Martina Barandun, Atanu Bhattacharya, Amaury Dehecq, Sajid Ghuffar, Martin Hoelzle, (2025) | PrépublicationTesting time-lapse gravimetry on Murtèl rock glacier (Swiss Alps) to quantify subsurface water/ice storage changes
Dominik Amschwand, Landon Halloran, Daniel Vonder Mühll, Martin Hoelzle, Jan Beutel, (2025) | PrépublicationPermafrost boreholes and geophysical observations in Central Asia
Martin Hoelzle, (2025) | PrépublicationModelling Cold Firn Evolution at Colle Gnifetti, Swiss/Italian Alps
Marcus Gastaldello, Enrico Mattea, Martin Hoelzle, Horst Machguth, (2025) | PrépublicationPermafrost in talus slopes: what are the main drivers of low temperatures and ice content ?
Christian Hauck, Dominik Amschwand, Tomasz Gluzinski, Christin Hilbich, Martin Hoelzle, Tamara Mathys, Coline Mollaret, Sarah Morard, (2025) | PrépublicationCorrelation between environmental variables and slope movements in the Ala Archa catchment, Kyrgyzstan
Rainer Gardeweg, Tamara Mathys, Martin Hoelzle, Simon Allen, (2025) | PrépublicationMulti-seasonal land cover changes of South Peruvian Highland Andean ecosystems
Catriona L. Fyffe, Vinisha Varghese, Evan Miles, Martin Hoelzle, Francesca Pellicciotti, Joshua Castro, (2025) | PrépublicationFive decades of Abramov glacier dynamics reconstructed with multi-sensor optical remote sensing
The Cryosphere (2025) | Article -
Projets de recherche
Strengthening the resilience of Central Asian countries by enabling regional cooperation to assess glacio-nival systems to develop integrated methods for sustainable development and adaptation to climate change
Statut: En coursCROMO-ADAPT: Cryospheric Observation and Modelling for improved Adaptation in Central Asia
Statut: En coursFrom ice to microorganisms and humans:Toward an interdisciplinary understanding of climate change impacts on the Third Pole (PAMIR)
Statut: En coursPermafrost Meltwater Assessment eXpert Tool - PERMA-XT
Statut: TerminéArtificial Ice Reservoirs (2019-2022)
Statut: TerminéThe 2°C target in the Alps - An experience in virtual reality
Statut: TerminéThe 2°C target in the Alps – An Experience in Virtual Reality
Statut: TerminéDébut 01.05.2018 Fin 31.07.2020 Financement FNS Voir la fiche du projet This AGORA project aims to make climate change tangible and produce an emotional involvement by means of Virtual Reality (VR). A VR-Experience will simulate the alpine environment to let the target audience, mainly young people, experience scenarios of a future world at and beyond the 2°C target. The VR-Experience and the possibility of interaction will demonstrate that every individual can contribute by changing personal behaviour and political activism. In addition, the audience will come to understand that a collective effort is required to control climate change. Users will learn that a social-ecological transformation is needed for a sustainable future with a more stable climate, a transformation that requires public debate and political consciousness. Since the Industrial Revolution, anthropogenic emissions of greenhouse gases, has changed the climate drastically and global temperatures have risen sharply. At the climate conference COP21 in Paris, in December 2015, the United Nations agreed on the 2°C target, to limit the maximum temperature increase well below 2°C. The goal is easy to formulate, but what does it mean? For the most people an average increase of 2°C in global temperature is hard to grasp. Even with a limited increase of 2°C, serious impacts are expected worldwide (e.g. Sea level rise, droughts, floods). By staying below 2°C, however, there is at least the chance that the Earth’s system dynamics would remain largely intact and gives society the ability to react and adapt. Should the global average temperature increase reach 3-5°C, it would seriously harm the ecosystem, altering the planet in extreme and unprecedented ways. The alpine environment, with its high sensitivity to changes in air temperature, provides an ideal environment to visualize such changes. Scientific knowledge on climate change has rapidly accumulated over the past decade and we are now able to communicate the economic, social and ecological impacts of rising temperature on the alpine environment as a whole. The main objective of the 2°C-VR project is to let the target audience interactively experience the impacts of climate change in VR. This new medium allows to view past, current and future alpine environments and to experience expected changes. Current research in climate change communication shows clearly that emotional involvement alone has its limits and does not necessarily lead to long-term sustainable actions. A better approach is to combine emotional involvement with a space for debate about the causes and possible actions to take. Therefore, we will base our communication strategy on a combination of the VR-Experience and the development of opportunities for action. VR technology will allow us to integrate different forms of scientific knowledge and communicate very complex processes in an easily understandable manner. The impacts of different climate change scenarios will enable an emotional, individual and unique experience. The interactive set-up of the installations will create the sense of being dependent upon each other’s’ actions and transmit the idea that only a collective effort of all individuals within a society can address the root causes of climate change. Later, school classes can debate and reflect on their experiences and on future actions. A web platform will provide a 360° video of the virtual experience and material for classroom discussion after the museum visit. Hyperlinks will lead students to other websites describing concrete actions for a sustainable way of living. For the development and the implementation of the VR-Experience, we commit to a close partnership with two museums, the World Nature Forum (UNESCO World Heritage Swiss Alps Jungfrau-Aletsch) in Naters and the visitor centre of the Swiss National Park in Zernez. The project team consists of the group "Alpine Cryosphere and Geomorphology" from the Department of Geosciences at the University of Fribourg, which is responsible for the scientific content, the communication concept and the project management, the discipline "Knowledge Visualization" at the Zurich University of the Arts, which develops and creates the Virtual Reality experience, and the College of Education Grisons, which is responsible for pedagogical implementation and project evaluation. The project is supported by a broad coalition of institutions and partners (BAFU, EKK, SCNAT, ETH, UZH, GLAMOS, PERMOS, WGMS, Eclim, swisstopo) and other museums (Gletschergarten Luzern, Alpines Museum Bern). At the end of the project, the know-how, installations and VR-Experiences may be used not only for education and mediation in schools and museums, but also for showing to decision makers and the general public. Cryospheric Climate Services for improved Adaptation (CICADA)
Statut: TerminéDébut 01.05.2017 Fin 31.12.2020 Financement Europe Voir la fiche du projet Climate change poses a major challenge for humanity and the related global implications will influence and threaten future economies and livelihood of coming generations, especially in developing countries (IPCC 2013). The UN General Assembly agreed upon 17 Sustainable Development Goals (SDGs) and related Targets, which represent an overarching framework for the implementation of the Paris Agreement at the 21st Conference of the Parties of the UN Framework Convention on Climate Change (UNFCCC). However, large efforts are needed to reach the SDGs and the 2°C (or 1.5°C)-atmospheric warming target within a time frame that prevents major drawbacks for humanity. Therefore, monitoring and strategies to enforce climate resilience, mitigation as well as adaptation must be based on sound baseline information, such as climate observations, and in particular, the Essential Climate Variables (ECVs) defined by the Global Climate Observing System (GCOS) (GCOS 2010). As stated by the World Meteorological Organization (WMO), large gaps currently exist in the global climate observing system. Especially in developing and emerging countries such baseline data are missing but fundamental to plan and mitigate future developments. One region, where climate change has major impacts, is Central Asia (SDC 2012). With the Tien Shan and Pamir, the region contains two of the largest mountain systems of the world, which serve as water towers in arid and continental region (Immerzeel et al. 2010, Kaser et al. 2010). They store enormous amounts of water in form of glacier ice and ice embedded in permafrost. These resources will play an important role for future water availability under the ongoing climate warming influencing future water resource management. Several recent studies (Hagg et al. 2006, 2007, 2013, Braun and Hagg 2009, Kaser et al. 2010, Huss et al. 2008, Huss 2011) point out clearly that a) in arid regions like Central Asia, water release by glaciers is fundamental to keep runoff sufficient during the dry summer months and b) at the end of this century the water contribution of glaciers will be drastically reduced and certain catchment will completely dry-out. However, water resources are unevenly distributed and mainly controlled by upstream countries, - Kyrgyzstan and Tajikistan. At the same time, downstream Kazakhstan, Uzbekistan and Turkmenistan are the main consumers of water resources (UNDP 2011). Since the collapse of the Soviet Union in the early 1990s this setting causes political tensions and creates a complex set of future challenges in the areas of water management, energy production, irrigation, agriculture, environment, disaster risk reduction, security and public health. Notably this also poses challenges in the field of climate services, as, on one hand, each project target country underlines the necessity in sharing the baseline data and elaboration of the complex regional climate mitigation strategies, but on the other hand, the lack of reliable data and commitment of the governments to fully integrate their observatory systems inhibits the sustainable development of the region. To improve the complex cooperation on climate data between stakeholders in Central Asia, sound and high-quality information on the climate and hydrological system are needed in order to provide climate scenarios and services for water runoff and natural hazards (e.g. GLOFs, debris flows and landslides). This is a prerequisite to allow early planning and adaptation measures within the water resource management (WRM) and disaster risk reduction (DRR) sectors. These scenarios and services have to be based on calibrated models linked to high quality baseline data. Therefore, baseline data has to be made available, especially for the most important alpine cryospheric variables such as snow, glaciers and permafrost as they are major controlling factors of the hydrological cycle in the region. Changing glacier firn in Central Asia and its impact on glacier mass balance
Statut: TerminéDébut 01.04.2017 Fin 31.03.2021 Financement FNS Voir la fiche du projet The glaciers of the Central Asian Pamir-Alay and Tien Shan are key to water availability in the surrounding lowlands and glacier monitoring is essential to anticipate future water resources. Most monitoring programs, however, were discontinued after the end of the Soviet Union and in-situ observations became sparse and discontinuous. Selected glacier monitoring sites in Kyrgyzstan have recently been reactivated by the University of Fribourg (UNIFR) and collaborators. Simultaneously, glacier volume changes based on subtracting surface elevations measured at different points in time became available for several regions of Central Asia. These so called geodetic glacier mass balances indicated substantial differences in glacier change among the different mountain ranges which are, tentatively, attributed to changes in precipitation pattern. However, direct comparisons of geodetic and in-situ mass balance of Kyrgyzstan glaciers also show disagreement between the two approaches. It is unclear whether the disagreement roots in the in-situ data, the geodetic data or both. Major uncertainties in both geodetic and in-situ glacier mass balance measurements relate to the little explored changes in the firn cover, i.e. the porous and up to a few dozen meter thick near-surface layer of a glacier where snow densifies into glacier ice. Unmeasured meltwater percolation and retention, and associated changes in firn density and/or temperature, are likely explanations for the differences between in-situ and geodetic mass balances. However, few of Central Asia glacier mass balance studies involved in-situ firn observations. Given its key role, measuring, analysing and modelling firn evolution is a necessity to understand and reconcile the mass balance estimates. It is the aim of the present research project to measure the current state of the firn, to reconstruct its evolution over the last century and to develop the respective modelling tools to simulate firn evolution. The project outcome is threefold, namely (i) establishing a century long accumulation time series, (ii) the design of a firn model, calibrated with the measurements and applied to simulate and understand the processes in firn evolution and (iii), the application of measurements and model to reconcile geodetic and in-situ glacier mass balances. On Abramov glacier, Pamir-Alay range, Kyrgyzstan, a series of firn cores will be drilled to measure accumulation rates and quantify the amount of refrozen meltwater at different elevations of the glacier’s firn area. Analysis of the cores focuses on stratigraphy, density profiles as well as stable isotopes, major ions and dust constituents. The measurements and comprehensive legacy firn and ice core data will be merged into a century long record of accumulation, dust deposition and meltwater retention. An existing firn and glacier mass balance model is subsequently applied to model, analyse and quantify the processes driving observed firn evolution. Thereby model evaluation using Sentinel-1 snow melt products is pioneered. Firn density changes over the entire glacier is calculated using the calibrated model with the help of extensive GPR measurements and the output is applied to understand the reasons behind differing geodetic and in-situ glacier mass balances. Carried out on the extensively studied Abramov glacier, probably one of the best investigated glaciers within the Global Terrestrial Network for Glaciers (GTN-G), this project pioneers methods to be subsequently applied in reconciling mass balance measurements at the High Mountain Asia scale and to address changing accumulation patterns as well as melt water retention in estimates of future glacier meltwater resources. Changing glacier firn in Central Asia and its impact on glacier mass balance
Statut: TerminéEKK-Webportal
Statut: TerminéSnowline observations to remotely derive seasonal to sub-seasonal glacier mass balance in the Tien Shan and Pamir Mountains
Statut: TerminéDébut 01.01.2015 Fin 31.08.2018 Financement FNS Voir la fiche du projet The monitoring of glacier mass balance in remote regions is challenging but vital for understanding the response of glaciers to climate change. Glacier mass balance observations are sparse and inhomogeneously distributed, in particular for the target regions of the proposed project: the Tien Shan and the Pamir. In these regions glacier ice represents an important source of runoff, but glacier monitoring has only recently been re-established for selected glaciers. The under-sampling problem of glacier change assessments limits change predictions and impact projections. In this study, we plan to elaborate novel approaches to derive sub-seasonal glacier mass balance at a regional scale based on remote snowline monitoring. The proposed methodology is predicated on the information content of short-term changes in snowline elevation detected with repeated remote sensing imagery for both the quantities of winter accumulation and summer ablation. A relation between the observed snowline position, the glacier geometry and the glacier-wide mass balance is created by backward modelling. We will first apply and validate the methodology for Central Asian glaciers using terrestrial photography and mass balance measurements on three to four carefully selected study sites, and then incorporate snow depletion observations throughout the summer season provided by satellite images at the regional scale. Finally, satellite images of a larger part of the Tien Shan and Pamir mountain ranges will be compiled for the period 2000 to present and the validated approach will be used to evaluate the seasonal to sub-seasonal mass balance for several dozens of selected glaciers. We intend to combine these remote mass balance estimates with measurements of regional ice volume changes derived from repeat digital elevation models. In combination, this will provide glacier mass changes at high temporal and spatial resolution for a region about which so far only little is known about. The sub-seasonal mass balance calculations will provide an important input for runoff models allowing more accurate estimation of future water availability for Central Asian countries. Snowline observations to remotely derive seasonal to sub-seasonal glacier mass balance in the Tien Shan and Pamir Mountains
Statut: TerminéCapacity Buliding and Twinning for Climate Observing Systems Phase 2
Statut: TerminéSwiss Earth Observatory Network (SEON)
Statut: TerminéDébut 01.01.2013 Fin 31.12.2016 Financement Autre Voir la fiche du projet The Swiss Earth Observatory Network (SEON) is a competence centre to monitor status and functioning of Swiss ecosystems in a changing environment. An increasing demand for natural resources impacts important biotic and physical processes within the Earth system and causes complex interactions within terrestrial ecosystems. SEON pursues a holistic Earth system science approach to assess environmental change impacts on ecosystem functioning and considers complex feedback mechanisms between the Earth spheres, including the human impact. The contribution of the University of Fribourg focuses on the use of albedo products from the air-borne multispectral imagery for glacier melt modelling and process understanding. In particular, the reasons for the presently observed darkening of alpine glacier surfaces, i.e. its components and drivers, will be investigated. New monitoring techniques for understanding the response of very small glaciers to climate change
Statut: TerminéDébut 01.03.2012 Fin 29.02.2016 Financement FNS Voir la fiche du projet With the rapid climate change observed in recent years, there is increasing interest in the retreat of mountain glaciers as they are important fresh water reservoirs, represent an economic factor (tourism, hydropower production), and can be the origin of natural hazards. Alpine glaciers are expected to retreat considerably in the 21st century, and smaller glaciers are even likely to disappear completely over the next decades. Presently glaciological research in the European Alps is focussed on the medium and large valley glaciers. However, there is an important knowledge gap concerning the response of very small glaciers (here defined as <0.5 km2) to climate change. Very small glaciers, however often account for 80-90% of the number of glaciers within a mountain range. Although their total area and ice volume is comparably small, the hydrological cycle can be significantly affected by the presence of small glaciers in poorly glacierized basins, as e.g. in many sub-basins of the Rhine River headwaters. As very few glaciological measurements have so far been achieved on very small glaciers, there is a large uncertainty regarding their mass balance response to atmospheric warming. Furthermore, important processes governing the mass balance of very small glaciers, as e.g. wind-driven snow accumulation, are poorly understood and can not be sufficiently well captured by current glacier mass balance models. The typical ice thickness, the dynamics and thermal conditions of very small glaciers are widely unknown as well. Therefore, projections of the future lifetime of very small glaciers are highly uncertain. Moreover, small glaciers might be valuable and well accessible climate archives that have not yet been exploited due to the limited understanding of the processes that determine their distribution, their thermal conditions and flow dynamics. This project aims at addressing the response of very small glaciers in the Swiss Alps to climate change. New monitoring techniques will be tested and applied. The potential of terrestrial LiDAR for the determination of annual ice volume change of small glaciers will be analyzed in detail. These surveys will be accompanied by different types of field measurements: On selected, well accessible glaciers the ice thickness will be measured using Ground Penetrating Radar and the seasonal surface mass balance will be determined with the glaciological method. In addition, surface ice movement and englacial temperatures will be monitored. The combination of these comprehensive field studies will provide a strengthened process understanding of the response of very small glaciers to climate change. The knowledge gained from the field surveys will be applied for enhancing existing models for predicting the future glacier evolution and for assessing the impact of the likely disappearance of small glaciers on alpine environments. Thus, this project is expected to yield an important piece of the puzzle for understanding rates and trends in mountain glacier mass loss due to atmospheric warming. Very small glaciers have – in spite of their overwhelming majority in number – always received little attention in glaciological research. This project will attempt to close this important gap. The mountain cryosphere - a holistic view on processes and their interactions
Statut: TerminéDébut 01.01.2012 Fin 30.06.2012 Financement FNS Voir la fiche du projet The mountain cryosphere - a holistic view on processes and their interactions The evolution of mountain permafrost in Switzerland
Statut: TerminéDébut 01.11.2011 Fin 30.04.2015 Financement FNS Voir la fiche du projet Permafrost, defined as lithospheric material whose temperature remains below 0 °C for two or more consecutive years, occurs in many high-mountain regions of the European Alps. In the context of anticipated climatic changes, permafrost degradation and associated ground deformation and instabilities could occur. To evaluate the sensitivity of mountain permafrost to climatic changes and to assess its future evolution, not only climatic variables such as air temperature, radiation and timing and duration of snow cover have to be considered, but also subsurface characteristics such as ground temperature, ice content, porosity or hydraulic properties. Permafrost monitoring in the Swiss Alps started only 1-2 decades ago, but currently comprises a large set of meteorological, geophysical, kinematic and ground thermal parameters at a large variety of field sites, e.g. within the national permafrost monitoring network PERMOS. The project TEMPS will analyse and integrate these high-mountain observations with model simulations using a dynamic process-oriented permafrost model. In combination with results from Regional Climate Model simulations, TEMPS aims to create plausible evolution scenarios of mountain permafrost at specific sites and will investigate the interactions between atmosphere and permafrost focusing on the evolution of ground temperature, ice content and related degradation and creep processes. The overall objective of the new Sinergia project TEMPS is to improve the understanding of the vulnerability of mountain permafrost regions to climate changes and assess the potential impact at different field sites in the Swiss Alps. The project includes collaborating scientists from a variety of different fields, such as atmospheric and cryospheric sciences, geomorphology, geophysics, geography and remote sensing. Capacity Building and Twinning for Climate Observing Systems Phase 1
Statut: TerminéDébut 01.08.2011 Fin 31.12.2013 Financement Autre Voir la fiche du projet CATCOS (Capacity Building and Twinning for Climate Observing Systems) is supported by the Swiss Agency for Development and Cooperation (SDC) with MeteoSwiss as the coordinating partner. In the context of the Global Climate Observing System (GCOS) and WMO Global Atmosphere Watch (GAW), the project addresses the need to improve climate observations world-wide, but particularly in developing countries and countries in transition. The University of Fribourg as well as the University of Zurich have their main focus on glacier monitoring. Our University is responsible for re-establishing glacier monitoring in Central Asia focusing on the countries Kyrgyzstan and Uzbekistan. Helicopter-borne GPR for mapping snow accumulation distribution
Statut: TerminéDébut 01.04.2011 Fin 30.04.2015 Financement FNS Voir la fiche du projet The Alpine cryosphere system consisting mainly of snow, glaciers and permafrost is particularly vulnerable to ongoing and future atmospheric warming. Important impacts on snow, glaciers and permafrost have increasingly been observed in recent years. The warming is leading to pronounced disequilibria in the Alpine geomorphological and hydrological process systems, such as the water cycle, mass-wasting processes, natural hazards and sediment flux. Major industries, tourism and agriculture based in Alpine regions will be strongly affected. However, the assessment of projected impacts in these environments is complicated by many feedback mechanisms. As a consequence, public authorities on the communal, cantonal or federal level, and private companies, urgently need specialized know-how and tools for making reliable projections how climate change will affect their economic basis over the next 10 to 30 years. Snow accumulation, its spatial distribution and its water equivalent are highly important. This factor has a strong impact on the future management of water resources and tourism in the Alps, but also directly affects important cryospheric processes, such as snow avalanche hazards, glacier mass balance and permafrost degradation. In high-Alpine terrain snow depth can vary by one order of magnitude over distances of a few meters. Measurements are laborious and only possible with direct surveys in the field. No easily applicable models for the spatial snow accumulation distribution are available to date. Therefore, tools to identify the spatial distribution of snow are an urgent need and would contribute to a much better understanding of the highly variable spatial distribution of snow. Ground-penetrating radar (GPR) is an already well-established tool in geosciences and is frequently used in snow and glacier research. Developments in recent years by performing GPR surveys from helicopters have shown a considerable potential to solve some of the above mentioned problems. The proposed project will apply and further develop the new technology for monitoring and determining the spatial distribution of snow in high alpine terrain by the application of innovative helicopter-borne GPR techniques. This technology will be used to accurately map the pattern of spatial variability in the snow cover in high-Alpine terrain. We propose two field objectives to establish the method. First, the technology will be applied at two glacierized test sites (Findelengletscher and Grenzgletscher/Colle Gnifetti, Valais) in order to evaluate and make use of its potential for glacier mass-balance monitoring and detection of different firn facies (recrystallisation-infiltration, cold infiltration and warm infiltration zones) and their possible future changes. Second, we will test the method at a well established snow research test site (Wannengrat, Davos), where already a wealth of data and model results from previous and ongoing projects exist, allowing careful validation of estimated snow thickness, snow water equivalent and possible internal layering delivering information about formation and release of avalanches. At all test sites, the helicopter-borne GPR soundings will be performed in combination with extensive ground based measurements (snow probing, snow/firn coring, ground-based GPR reference measurements, pits, etc.) to assess the uncertainties. Existing models for calculating the spatial distribution of snow accumulation (Alpine3D) will be applied and new methods will be developed based on an enhanced process understanding that will result from the high-resolution field data. Sensitivity of mountain permafrost to climate change (SPCC)
Statut: TerminéGlacier Monitoring Switzerland (GLAMOS)
Statut: TerminéWorld Glacier Monitoring Service (WGMS)
Statut: TerminéDébut 01.09.2008 Fin 01.09.2018 Financement Autre Voir la fiche du projet Worldwide collection of information about ongoing glacier changes was initiated in 1894 with the foundation of the International Glacier Commission at the 6th International Geological Congress in Zurich, Switzerland. It was hoped that long-term glacier observations would give insight into processes of climatic change such as the formation of ice ages. Since then, the goals of international glacier monitoring have evolved and multiplied. Since this beginning of internationally coordinated systematic observations on glacier variations in 1894, a valuable and increasingly important data basis on glacier changes has been built up. In 1986 the World Glacier Monitoring Service (WGMS) started to maintain and continue the collection of information on ongoing glacier changes, when the two former ICSI services PSFG (Permanent Service on Fluctuations of Glaciers) and TTS/WGI (Temporal Technical Secretary/World Glacier Inventory) were combined. Today, the World Glacier Monitoring Service (WGMS) collects standardised observations on changes in mass, volume, area and length of glaciers with time (glacier fluctuations), as well as statistical information on the distribution of perennial surface ice in space (glacier inventories). Such glacier fluctuation and inventory data are high priority key variables in climate system monitoring; they form a basis for hydrological modelling with respect to possible effects of atmospheric warming, and provide fundamental information in glaciology, glacial geomorphology and quaternary geology. The WGMS is located at the University of Zurich and the University of Fribourg is related as an associated partner. PERMOS : Permafrost monitoring Switzerland
Statut: Terminé