Swiss Permafrost Monitoring

The Swiss Permafrost Monitoring initiative PERMOS (http://www.permos.ch) maintains a network of 28 high alpine sites in order to document the state and changes of permafrost in Switzerland based on three main observation elements (ground temperatures, changes in subsurface ice and water content, and permafrost creep velocities). PERMOS is funded by the Federal Office for the Environment (FOEN), the Swiss GCOS Office at MeteoSwiss, and the Swiss Academy of Sciences (SCNAT). The PERMOS Office (at the University of Zurich) coordinates observation and reporting activities undertaken by the six partner institutions ETH Zurich (ETHZ), the Universities of Fribourg (UNIFR), Lausanne (UNIL), Zurich (UZH), the WSL Institute for Snow and Avalanche Research (SLF) and the University of Applied Sciences and Arts of Southern Switzerland (SUPSI). 2014 is the end of a 4-year contract period and a renewed organization of the PERMOS Office will be set up in 2015 for the next 4 years.

Ongoing research projects and activities

In parallel to its long-term monitoring of borehole temperatures and deformation together with PERMOS, the WSL Institute for Snow and Avalanche Research SLF is investigating the impact of the snow cover on the thermal regime and stability of steep rock walls (A. Haberkorn, M. Phillips) at three sites in the Swiss Alps. Rock wall dynamics are also being monitored using various remote sensing techniques including terrestrial laser scanning and interferometric radar at Pizzo Cengalo (Bregaglia) and Piz Kesch (Albula Alps), in collaboration with different Swiss and Italian partners in the context of an ARGE Alp project. The stability and thermal regime of high mountain infrastructure is monitored (M. Phillips) with various engineers and operators, and in-situ GPS is being tested with the ETHZ (J. Beutel, S. Weber) to monitor creeping permafrost terrain causing damage to snow nets (Fig. 1). The dynamics of rock glaciers are being investigated in the context of the SNF Sinergia project TEMPS and in collaboration with Italian partners in the Interreg project SloMove (R. Kenner) using in-situ and remote sensing techniques. The influence of taliks and lateral liquid water fluxes on the thermal regime of rock glaciers is being simulated using the SNOWPACK model (R. Lüthi).

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Figure 1. GPS mounted on a rock between snow nets which are damaged by downslope creep and subsidence in permafrost terrain at Wisse Schijen (Randa, Switzerland).

Permafrost research activities at the Institute of Earth Sciences of the University of Applied Sciences and Arts of Southern Switzerland (SUPSI) (C. Scapozza, C. Ambrosi) continued after their beginning in 2013 in affiliation with the PERMOS network. Research focused mainly on the assessment of rock glacier kinematics, with a project conducted in collaboration with the Swiss Federal Research Institute WSL in Bellinzona (M. Conedera, C. Bozzini), the University of Lausanne (C. Lambiel), and the University of Fribourg (S. Mari). In this project, the (palaeo)climatic variations of the Stabbio di Largario rock glacier, in the southern Swiss Alps, were assessed using three different timescales thanks to the Schmidt hammer exposure-age dating (SHD), the georeferentiation and orthorectification of six historical photographs of the rock glacier taken between ad 1910 and 2012 and differential global positioning system (dGPS) monitoring data available since 2009. The results show a link between periods of increase in mean air temperature on different time scales and variations in rock glacier kinematics, and provide important new insights into rock glacier development and evolution on the long-term scale. In September 2014, the quantification of movements and deformation process of rock glaciers in the Southern Swiss Alps was improved by the installation of two permanent GPS (fig. 2), in collaboration with the Federal Office for the Environment FOEN (H. Raetzo) and the ETH Zurich (J. Beutel), and by the realization of very-high resolution digital elevation models thanks to the use of drones, in collaboration with Studio di Geomatica Lehmann–Visconti (R. Visconti and D. Righetti).

Switzerland_Fig.2Figure 2. Permanent GPS installed on the right lobe of the Stabbio di Largario rock glacier, in the Eastern Ticino Alps (Photo: C. Scapozza).

At the University of Lausanne, the high mountain geomorphology group of the Institute of Earth Surface Dynamics (C. Lambiel, J.-B. Bosson, N. Deluigi, N. Micheletti) focuses its research on ground ice detection, mapping and characterization, on ground ice related movements and on permafrost monitoring and modelling.

Final field investigations in debris-covered glacier systems in permafrost environments have been carried out this year, resulting in a 4-year dataset. The characterization of internal structure and current surface kinematics highlights their strong relation in these complex systems. Strictly glacial zones, where the debris-cover overlies a pure sedimentary ice body are largely more dynamic and sensitive to climate signal than the marginal ice-debris mixtures, where slow surface lowering and downslope motions are observed.

The decadal and current evolution of surface movements of these small high mountain debris-covered glaciers and of active rock glaciers is carried out with several techniques, such as digital photogrammetry, Lidar and GPS measurements and monitoring with automatic cameras (Fig. 3). The decadal evolution of sediment transfer in steep valley sides is another topic on which we currently work.

As grain size in sedimentary materials is considered one of the main factors controlling the ground (surface) temperature, a new procedure was developed to automatically detect this feature and improve the dataset employed in our modelling project on the spatial distribution of mountain permafrost using machine learning algorithms. In parallel, an exploratory spatial data analysis was performed to reveal underlying structures/anomalies in the data.

Finally, a part of our activities concern the monitoring of rock glacier velocities, of ground (surface) temperatures and of electrical resistivity at several sites, mainly located in the Valais Alps. In summer 2014, a new borehole was drilled at the top of the Mont Fort (Verbier-Nendaz) at 3300 m a.s.l. The first data revealed the presence of permafrost at temperatures around -2°C. A part of these measurements are included in the PERMOS network and are used in the TEMPS project.

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Figure 3. Permanent GPS installed in October 2014 on La Roussette rock glacier (Arolla, VS).

At the Institute for Geotechnical Engineering of ETH Zurich, the project Furggwanghorn has been successful and is coming towards an end. Thanks to geophysical surveys and 7 boreholes - the latter having temperature distributions at various depths until the cables were cut by the movements -, an excellent ground model has been created for the Furggwanghorn rock glacier. The deformations at the surface and in the boreholes are fascinating and constitute an excellent set of data for a degrading rock glacier that will be published next year. The internal structure was also explored with a 60 MHz helicopter-borne ground-penetrating radar (GPR) (fig.4) and a flight height of 15-20 m. A transition from an upper high reflective zone to an underlying layer of lower reflectivity at about 17 – 20 m depth (blue line in fig. 5). According to three inclinometer survey stations within boreholes there is at least one major shear zone at the same depth, which shows average displacement up to 1cm / day. The pore ice content is significantly lower below this transition zone. Therefore it is concluded that the deformations measured on the boreholes occurs at the transition between ice - rich and ice poor parts of the rock glacier. Xiaohai Zhou successfully finished her PhD thesis titled "Experimental and Numerical Study of Coupled Water and Heat Transport in the Freezing Ground" combining thermal modelling with controlled lab experiments. Kaspar Merz (geophysics) and Thomas Buchli will defend theirs in 2015.

Switzerland_Fig.4Figure 4. Ground penetrating radar (GPR) system mounted under the helicopter (Photo: Kaspar Merz)

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Figure 5. Processed and depth-converted helicopter GPR section showing the main geologic units of the Furggwanhorn rock glacier. Red arrows indicate depth and direction of shear zones observed in the boreholes.

At ETH Zurich, the Geodesy and Geodynamics Lab (GGL) of the Institute of Geodesy and Photogrammetry is involved in several interdisciplinary projects and activities related to mountain permafrost (e.g. X-Sense, X-Sense2, PermaSense, PERMOS). Its major field of activities is the monitoring of displacements and deformations with continuously operated GPS stations, and especially the geodetic processing of the GPS data (P. Limpach, A. Geiger, S. Su, R. Hohensinn). At present, the data of more than 30 permafrost-related GPS stations from various projects in Switzerland are operationally processed at GGL. A large number of these stations were deployed by X-Sense (ETHZ, UZH, FOEN, GAMMA, J. Beutel, T. Gsell, S. Gruber, V. Wirz, P. Limpach). GPS techniques for real-time processing, near real-time processing and post-processing are applied, depending on the application. The GPS data allows the precise monitoring of rock glaciers, slope instabilities and rock instabilities with a high temporal resolution. With continuous observations over several years, it was possible to analyse the temporal variations of the displacements and the displacement rates. In collaboration with the Federal Office for the Environment (FOEN), GPS data was used to validate results from interferometric radar observations. In the framework of the X-Sense project, GGL has developed algorithms for automated image processing from digital cameras (F. Neyer, A.Geiger). Two cameras (ETHZ, TIK, J. Beutel, T. Gsell) have been installed at the Grabengufer rock glacier to monitor the displacement field. The advantage of areal displacement information is tested in terms of resolution and accuracy to complement the GPS data (Fig. 6).

Switzerland_Fig.6Figure 6. Imaged based estimates of displacements at the upper part of Grabengufer rock glacier. The steep front area shows displacements of 1.4m in 10 months (1.7m/year) (Photo: F. Neyer, T. Gsell).

In 2014 the Institute of Geography of the University of Bern continued the solifluction study at the North slope of Blauberg close to Furkapass. 250 points were surveyed by tachymeter and dGPS, infrared-photogrammetry was applied, soil water content and temperature sensors were installed, meteorological parameters were measured and the spatial disappearance of the snow cover was recorded (fig. 7). The WSL-institute for Snow and Avalanche Research SLF performed terrestrial laser-scanning and the Institute of Geography of the University of Würzburg conducted 3D-geoelectric measurements. New insights in alpine solifluction processes and controls are expected in 2015.

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Figure 7. Picture from the Blauberg taken by an automatic camera showing the situation in mid June 2014 when the slope started to become snow-free.

At the University of Fribourg, the SNSF-Sinergia project «The evolution of Mountain Permafrost in Switzerland» (TEMPS, 2011-2015), which is regrouping scientists from several institutions (ETH Zurich, Universities of Fribourg, Lausanne, and Zurich, SLF) closely related with PERMOS, is entering into its final phase. A particular aim of this project was combining observation and model-based research approaches to obtain an integrative view of the current state of mountain permafrost in the Swiss Alps and the governing processes for its recent and future evolution. The work done in 2014 focused on methodological improvements of the various modelling and observation techniques, which are required for the synergetic data analysis, scenario generation and impact assessment of the TEMPS project. On the Becs-de-Bosson rock glacier in the Valais Alps (Fig. 8) an automated ERT device was installed for the first time in a remote location and first measurements have been conducted in autumn 2014.

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Figure 8. Installing the new A-ERT system on the Becs-de-Bosson (Réchy) rock glacier in autumn 2014. (Photo: D. Sciboz).

Within the SNSF-Project SOMOMOUNT (soil moisture in mountainous terrain and its influence on the thermal regime in seasonal and permanently frozen terrain), six entirely automatized soil moisture monitoring stations were installed between summer 2013 and autumn 2014 at Frétaz, Moléson, Dreveneuse (Fig. 9), Gemmi, Schilthorn and Stockhorn, that is along a NW-SE transect throughout Switzerland, with altitude ranging from 1200 m.a.s.l. to 3400 m.a.s.l. They cover several landform types (talus slope, rock plateau, solifluxion lobe, etc.) as well as different thermal regimes of the ground (unfrozen, seasonally frozen and permanently frozen). In parallel extensive geophysical surveys were conducted in the vicinity of each station with ERT and RST methods to expand the one dimensional soil moisture measurements to a 2D repartition of water (and ice) content in the ground.

In addition to the already mentioned projects the University of Fribourg has currently a large research group (Hauck, Hoelzle, Delaloye, Salzmann, Hilbich, Hasler, Scherler, Schneider, Barboux, Mari, Marmy, Pellet, Staub, Kummert, Braillard, Rick)focusing on a wide range of topics including the analysis of rock mechanics and rock glacier dynamics, sediment transport, geomorphology, geophysics, subsurface modelling and remote sensing related to permafrost. In 2014 Sina Schneider and Chloé Barboux finished their PhDs on the heterogeneity of mountain permafrost and the detection, mapping and monitoring of slope movements in the Alpine environment using DInSAR, respectively.

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Figure 9. Permafrost is also investigated on forested sites in Switzerland: new combined PERMOS/SOMOMOUNT on-line logging station on a low elevation cold talus slope at Dreveneuse (Photo: D. Sciboz).

At the Geography department at the University of Zurich (UZH) the kinematic monitoring of several high mountain permafrost landforms has been continued. Terrestrial and airborne instruments such as terrestrial laser scanning and drone-based photogrammetry have been used to acquire multi-temporal datasets of rock glaciers which are used to assess landform kinematics and geometrical/volumetric changes (Figs. 10-11). The above mentioned datasets help to establish a model which shows rock glacier evolution in relation to rock wall properties and climatic forcing. The goal is to focus on a holistic approach to assess landform evolution on a catchment area bases.

The PermaSense project has continued the existing measurements (temperature, cleft dynamics, high-precision L1-DGPS) at Matterhorn, Mattervalley, Jungfraujoch and Aiguille du Midi to investigate kinematics of alpine rock faces and slopes. A number of improvements with regard to the data management and processing have been achieved. The PermaSense L1-DGPS technology enabling detailed surface kinematic analysis at spatial scale and high temporal resolution has been made available to PERMOS partners in a technology transfer effort. Furthermore, a new field campaign to capture micro-seismic activity as an indicator for damage in steep bedrock has been initiated and is planned to be continued over the next two years.

Switzerland_Fig.10Figure 10. RGB colored 3D LAS Pointcloud derived from drone-based photogrammetry.

Switzerland_Fig.11Figure 11. NIR Orthophoto of rock glacier Muragl at a GSD 6.5cm.

Report prepared by Reynald Delaloye ( reynald.delaloye@unifr.ch)