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Monitoring of the periglacial environment is relevant for many disciplines including glaciology, natural hazard management, geomorphology, and geodesy. Since October 2022, Rock Glacier Velocity (RGV) is a new Essential Climate Variable (ECV) product within the Global Climate Observing System (GCOS). However, geodetic surveys at high elevation remain very challenging due to environmental and logistical reasons. During the past decades, the introduction of low-cost global navigation satellite system (GNSS) technologies has allowed us to increase the accuracy and frequency of the observations. Today, permanent GNSS instruments enable continuous surface displacement observations at millimetre accuracy with a sub-daily resolution. In this paper, we describe decennial time series of GNSS observables as well as accompanying meteorological data. The observations comprise 54 positions located on different periglacial landforms (rock glaciers, landslides, and steep rock walls) at altitudes ranging from 2304 to 4003 ma.s.l. and spread across the Swiss Alps. The primary data products consist of raw GNSS observables in RINEX format, inclinometers, and weather station data. Additionally, cleaned and aggregated time series of the primary data products are provided, including daily GNSS positions derived through two independent processing tool chains. The observations documented here extend beyond the dataset presented in the paper and are currently continued with the intention of long-term monitoring. An annual update of the dataset, available at https://doi.org/10.1594/PANGAEA.948334 (Beutel et al., 2022),​​​​​​​ is planned. With its future continuation, the dataset holds potential for advancing fundamental process understanding and for the development of applied methods in support of e.g. natural hazard management.

Permafrost warming is coinciding with accelerated mass movements, talking place especially in steep, mountainous topography. While this observation is backed up by evidence and analysis of both remote sensing as well as repeat terrestrial surveys undertaken since decades much knowledge is to be gained about the specific details, the variability and the processes governing these mass movements in the mountain cryosphere. This dataset collates data of continuously acquired kinematic observations obtained through in-situ Global Navigation Satellite Systems (GNSS) instruments that have been designed and implemented in a large-scale multi field-site monitoring campaign across the whole Swiss Alps. The landforms covered include rock glaciers, high-alpine steep bedrock bedrock as well as landslide sites, most of which are situated in permafrost areas. The dataset was acquired at 54 different stations situated at locations from 2304 to 4003 m a.s.l and comprises 209’948 daily positions derived through double-differential GNSS post-processing. Apart from these, the dataset contains down-sampled and cleaned time series of weather station and inclinometer data as well as the full set of GNSS observables in RINEX format. Furthermore the dataset is accompanied by tools for processing and data management in order to facilitate reuse, open alternate usage opportunities and support the life-long living data process with updates. To date this dataset has seen numerous use cases in research as well as natural-hazard mitigation and adaptation due to climate change., Earth System Science Data Discussions, ISSN:1866-3591

The PermaSense project is an ongoing interdisciplinary effort between geo-science and engineering disciplines started in 2006 with the goals to make observations possible that previously have not been possible. Specifically the aims are to obtain measurements data in unprecedented quantity and quality based on technological advances. This paper describes a unique ten+ year data record obtained from in-situ measurements in steep bedrock permafrost in an Alpine environment on the Matterhorn Hörnligrat, Zermatt Switzerland at 3500 m a.s.l. Through the utilization of state-of-the-art wireless sensor technology it was possible to obtain more data of higher quality, make this data available in near real-time and tightly monitor and control the running experiments. This data set (DOI: https://doi.org/10.1594/PANGAEA.897640, Weber et al., 2019a) constitutes the longest, densest and most diverse data record in the history of mountain permafrost research worldwide with 17 different sensor types used at 29 distinct sensor locations consisting of over 114.5 million data points captured over a period of ten+ years. By documenting and sharing this data in this form we contribute to making our past research reproducible and facilitate future research based on this data e.g. in the area of analysis methodology, comparative studies, assessment of change in the environment, natural hazard warning and the development of process models.

We present a review of the changing state of European permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of Svalbard and the discontinuous high altitude mountain permafrost of Iceland, Fennoscandia and the Alps. The paper focuses on methodological developments and data collection over the last decade or so, including research associated with the continent-scale network of instrumented permafrost boreholes established between 1998 and 2001 under the European Union PACE project. Data indicate recent warming trends, with greatest warming at higher latitudes. Equally important are the impacts of shorter-term extreme climatic events, most immediately reflected in changes in active layer thickness. A large number of complex variables, including altitude, topography, insolation and snow distribution, determine permafrost temperatures. The development of regionally calibrated empirical-statistical models, and physically based process-oriented models, is described, and it is shown that, though more complex and data dependent, process-oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography. Mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed. We report on recent research into ground ice formation, including ice segregation within bedrock and vein ice formation within ice wedge systems. The potential impacts of climate change on rock weathering, permafrost creep, landslides, rock falls, debris flows and slow mass movements are also discussed. Recent engineering responses to the potentially damaging effects of climate warming are outlined, and risk assessment strategies to minimise geological hazards are described. We conclude that forecasting changes in hazard occurrence, magnitude and frequency is likely to depend on process-based modelling, demanding improved understanding of geomorphological process-response systems and their impacts on human activity.

This review paper examines thermal conditions (active layer and permafrost), internal composition (rock and ice components), kinematics and rheology of creeping perennially frozen slopes in cold mountain areas. The aim is to assemble current information about creep in permafrost and rock glaciers from diverse published sources into a single paper that will be useful in studies of the flow and deformation of subsurface ice and their surface manifestations not only on Earth, but also on Mars. Emphasis is placed on quantitative information from drilling, borehole measurements, geophysical soundings, photogrammetry, laboratory experiments, etc. It is evident that quantitative holistic treatment of permafrost creep and rock glaciers requires consideration of: (a) rock weathering, snow avalanches and rockfall, with grain-size sorting on scree slopes; (b) freezing processes and ice formation in scree at sub-zero temperatures containing abundant fine material as well as coarse-grained blocks; (c) coupled thermohydro-mechanical aspects of creep and failure processes in frozen rock debris; (d) kinematics of non-isotropic, heterogeneous and layered, ice-rich permafrost on slopes with long transport paths for coarse surface material from the headwall to the front and, in some cases, subsequent re-incorporation into an advancing rock glacier causing corresponding age inversion at

Direct-current (DC) resistivity tomography has been applied to different mountain permafrost regions. Despite problems with the very high resistivities of the frozen material, plausible results were obtained. Inversions with synthetic data revealed that an appropriate choice of regularization constraints was important, and that a joint analysis of several tomograms computed with different constraints was required to judge the reliability of individual features. The theoretical results were verified with three field experiments conducted in the Swiss and the Italian Alps. At the first site, near Zermatt, Switzerland, the location and the approximate lateral and vertical extent of an ice core within a moraine could be delineated. On the Murtel rock glacier, eastern Swiss Alps, a steeply dipping boundary at its frontal part was observed, and extremely high resistivities of several MΩ indicated a high ice content. The base of the rock glacier remained unresolved by the DC resistivity measurements, but it could be constrained with transient EM soundings. On another rock glacier near the Stelvio Pass, eastern Italian Alps, DC resistivity tomography allowed delineation of the rock glacier base, and the only moderately high resistivities within the rock glacier body indicated that the ice content must be lower compared with the Murtel rock glacier.

Permafrost distribution in nonpolar mountain areas is strongly influenced by topo-graphical effects. Conditions therefore change within short distances and consequently the permafrost pattern is often very complex. Warm permafrost with temperatures between -2°C and 0°C is sensitive in terms of slope failures. It is also crucial to determine the lower permafrost boundary by geophysical means in order to calibrate models. Various geophysical methods have been applied to the mapping of mountain permafrost, including bottom temperature of the snow cover (BTS), refraction seismics, DC resistivity, ground penetrating radar (GPR), electromagnetic induction and radiometry. This paper gives an overview of investigations to map mountain permafrost distribution showing the potential of the modern use of geophysical methods. The two-dimensional DC resistivity tomography makes it possible to get an impression of internal structures. Electromagnetic induction methods showed good results, in particular the EM-31 for determining the permafrost distribution and the PROTEM to assess the overall permafrost thickness. Using passive microwave (11.4 GHz), the BTS, which is used as an indicator for the presence of permafrost, was measured. After ground surveys, an airborne test measurement from a helicopter was made. Traditional BTS measurements agreed very well with the BTS determined by radiometry.

To map the internal structure and lower boundary of an alpine rock glacier, we recorded three shallow seismic profiles and drilled four ∼70‐m‐deep holes through to the underlying bedrock. Although analysis of the seismic data using standard reflection processing schemes did not yield conclusive results because of the dominantly low‐frequency returned signals and the presence of strong source‐generated noise, tomographic inversions of first‐arrival times were successful in mapping several critical subsurface features. A thin, low‐velocity layer of loose boulders, air voids, and snow was found to extend across the entire surveyed area. Below this layer, two distinct velocity regimes superimposed on a general increase in velocity with depth were identified. A broad regime of high velocities was interpreted to contain boulders with numerous ice‐filled voids, whereas an adjacent regime of relatively low velocities was explained in terms of boulders with air‐ and water‐filled voids. This latter region of degraded permafrost, which was unexpected, may be an early result of global warming. The transition from rock glacier to gneissic bedrock was delineated approximately by the 4300‐m/s isovelocity line. Although poorly resolved, its depth varied from ∼35 to ∼70 m beneath the surface of the rock glacier. The tomographic inversion results also provided an explanation for the occurrence of strong source‐generated noise in our data. Using the derived velocity distributions as input, synthetic shot gathers were calculated using a finite‐difference viscoelastic scheme that accounted for surface topography. The resultant synthetic data were dominated by the overwhelming effects of back‐ and side‐scattered waves from shallow heterogeneities and high‐amplitude guided phases that originated from the thin, surficial low‐velocity zone. Had the guided phases not been correctly identified and eliminated during processing, they would have appeared as reflections in the stacked sections. Since low‐velocity layers overlying heterogeneous media are common features of the shallow subsurface, our findings may have implications for a broad range of engineering‐scale seismic investigations (e.g., studies of landfills, rockslides, moraines, talus slopes, alluvial fans).

During the past 30 years, intensive permafrost research has been performed in the area of Corvatsch-Furtschellas, Eastern Swiss Alps. Main progress has been achieved by borehole observations in creeping permafrost, geophysical soundings, energy flux measurements above and within permafrost, photogrammetric determination of surface kinematics of creeping permafrost and permafrost distribution pattern modelling. The paper gives a review of principle results during the 30 years' research period.

This paper introduces the structure and organization of permafrost monitoring within global climate-related monitoring programmes. The five-tiered principle proposed for the Global Hierarchical Observing Strategy (GHOST) is applied to the Global Terrestrial Network for Permafrost (GTN-P) monitoring system, and the European network of mountain permafrost boreholes established by the PACE project is discussed in the context of GTN-P. Borehole design and standard PACE instrumentation are described and some preliminary data from selected boreholes are presented. The broader research aims of the PACE programme include geophysical investigations, mapping and GIS strategies, numerical distribution modelling, physical modelling of thaw-related slope processes and mountain permafrost hazard assessment. Copyright © 2001 John Wiley & Sons, Ltd. RESUME Le present article decrit la structure et l'organisation du programme de surveillance du pergelisol et son integration dans les programmes de surveillance du climat. Le principe a 5 niveaux propose pour la strategie d'observation hierarchique (GHOST) est appliquee au reseau global de surveillance terrestre du pergelisol (GTN-P). Le reseau europeen de sondages dans le pergelisol etabli par le projet PACE est discute dans le contexte du GTN-P. La localisation des sondages et l'instrumentation standard de PACE sont decrites et quelques donnees preliminaires de certains sondages selectionnes sont presentees. Les recherches du programme PACE comprennent des recherches geophysiques, des strategies de cartographie et de systemes d'information geographique, des modeles de distribution numerique, des modeles physiques des processus de versants en relation avec le degel et enfin des estimations des risques lies au pergelisol de montagne. Copyright © 2001 John Wiley & Sons, Ltd.

A series of geophysical surveys were undertaken within the PACE geophysical work package. Various methods were applied including refraction seismics, DC resistivity, ground penetrating radar (GPR), electromagnetic induction, radiometry and bottom temperature of snow cover (BTS). The focus of the surveys was to determine the internal structures and distribution of mountain permafrost. This paper gives a preliminary overview of progress. The two-dimensional DC resistivity tomography combines the geoelectrical sounding and mapping and makes it possible to model internal structures. This method was applied at all PACE drill sites. Electromagnetic induction methods showed good results, in particular the EM-31 for determining the permafrost distribution and the PROTEM to assess the overall permafrost thickness. A major new development discussed here is the use of passive microwave (11.4 GHz) for airborne remote measurement of the bottom temperature of snow cover (BTS). Manual BTS measurements agreed very well with the BTS determined by radiometry. To reduce ambiguity, several geophysical methods should be deployed at the same locality. As a further step, such measurements could be interpreted using joint inversions. Copyright © 2001 John Wiley & Sons, Ltd. RESUME Une serie de leves geophysiques a ete realise dans le cadre des travaux de PACE. Differentes methodes ont ete utilisees y compris la seismique refraction, la resistivite DC, le radar penetrant le sol (GPR), l'induction electro-magnetique, la radiometrie et la temperature a la base de la couverture nelgeuse (BTS). Le but de ces leves etait de determiner les structures internes et la distribution du pergelisol de montagne. Le present article donne une vue generale preliminaire des progres realises. La tomographie en deux dimensionns par resistivite. DC qui combine le sondage geoelectrique et la cartographie, rend possible la reconnaissance des structures internes. Cette methode a ete appliquee dans tous les sites de sondage. Les methodes par induction electromagnetique ont donne de bons resultats, en particulier la methode par EM-31 pour determiner la distribution du pergellisol, tandis que la methode PROTEM a ete utile pour estimer l'epaisseur totale du pergelisol. Un imporant nouveau developpement discute ici est l'emploi de micro-ondes passives (11.4 GHz) dans des mesures aeroportees de la temperature de la base de la converture de neige (BTS). Des mesures manuelles BTS se sont revelees bien en accord avec les donnees BTS obtenues par radiometrie. Pour diminuer les ambiguites, plusieurs methodes geophysiques devraient toujours etre utilisees. Copyright © 2001 John Wiley & Sons, Ltd.

This paper reviews the principles related to the mapping and modelling of the occurrence and distribution of mountain permafrost. It gives a state-of-the art report about this topic and defines future research needs.

In the Bever Valley, Upper Engadine, eastern Swiss Alps, one-dimensional DC resistivity soundings and two-dimensional DC resistivity tomography were performed at a site where both GIS-based modelling and measurements of the bottom temperature of the winter snow cover (BTS) suggest a potential permafrost occurrence at low altitude (1840 m ASL). The results of the geoelectric measurements indeed point to a permafrost occurrence below the timberline which consists of several thin permafrost lenses. In comparison with other Alpine permafrost sites the resistivities are fairly low which might be expected at a low altitude location with permafrost temperatures probably close to 0 °C. The active layer appears to be fairly thin which is surprising for a permafrost occurrence at mean annual air temperatures well above 0 °C. Here, the reduced radiation due to the topography as well as the organic layers are considered to play an important role in insulating the subsurface and controlling the ground thermal regime. The permafrost occurrence is assumed to be a result of the interaction of climatic conditions and topography as well as surface and subsurface factors. The application of resistivity measurements is shown to be a useful geophysical method as the organic layers provide good ground contact for the electrodes. Furthermore, the application of one-dimensional DC resistivity soundings in combination with two-dimensional DC resistivity tomography proves to be a useful tool for mapping and characterizing isolated permafrost occurrences on a small scale. Copyright © 2000 John Wiley & Sons, Ltd. RESUME Dans la vallee de la Bevers en Haute Engadine, a l'est des Alpes suisses, des sondages par resistivite DC a une dimension et des tomographies par resistivite DC a deux dimensions ont ete realisees a faible altitude (1840∼m) en un endroit ou, a la fois des modeles obtenus par SIG et des measures de temperature a la base de la couverture de neige (BTS), ont suggere l'occurrence probable d'un pergelisol. Les resultats des mesures geoelectriques ont indique la presence de plusieurs lentilles fines de pergelisol alors que on se trouve sous la limite des arbres. En comparaison avec d'autres sites ou existe un pergelisol, les resistivites sont basses, ce qui pouvait etre attendu en cet endroit ou les temperatures du pergelisol sont probablement proches de 0 °C. La couche active parait mince, ce qui est surprenant en ces endroits ou la temperature moyenne annuelle est bien superieure a 0 °C. Une radiation thermique reduite, due a la topographie, ainsi que la presence de couches organiques, sont probablement les facteurs importants qui isolent la surface et controlent le regime thermique du sol. La presence du pergelisol en cet endroit resulte de l'interaction entre les conditions climatiques, la topographie et plusieurs autres facteurs de surface et de faible profondeur. Les mesures de resistivite ont ete ici excellentes parce que les couches organiques fournissent de bons contacts pour les electrodes. L'utilisation simultanee des sondages par resistivite DC a une dimension en combinaison avec des tomographies DC en deux dimensions constitute un outil utile pour cartographier et caracteriser de petits ilots isoles de pergelisol. Copyright © 2000 John Wiley & Sons, Ltd.

Analyses of the geothermal gradient in permafrost areas constitute a key signal of the ground-surface temperature history. Permafrost temperatures in selected areas are particularly well suited to reconstructing past surface-temperature changes, mainly because there is no thermal disturbance due to circulating groundwater. One year of temperature data from an instrumented 102 m deep borehole in permafrost on Janssonhaugen, Svalbard, is presented. Ground thermal properties are calculated. The average value for the thermal conductivity is 1.85 ±0.05 W m–1 K–1 , and the average value for the thermal diffusivity is 1.1m2 s–1, which gives a phase speed for the annual wave of 5.65 × KT2 m d–1. The depth of zero annual amplitude is 18 m The permafrost thickness is estimated as approximately 220 m. Analysis of the temperatures reveals an increasing temperature gradient with depth. Using a heat-conduction inversion model, a palaeoclimatic reconstruction is presented, showing a warming of the surface temperature over the last 60–80 years. The temperature profile represents a regional signal on Svalbard, which shows an inflection associated with near-surface warming of 1.5 ± 0.5°C in the 20th century.

At two permafrost sites in the Swiss Alps a range of geophysical methods were applied to model the structure of the subsurface. At both sites, borehole information was used to verify the quality of the model results. On the Murtèl-Corvatsch rock glacier (2700 m a.s.L; upper Engadine) a 58 m deep core drilling was performed in 1987. D. c resistivity measurements, refraction seismics, ground-penetrating radar (GPR) and gravimetric surveys allowed the shape of the permafrost table beneath the marked surface microtopography to be determined and the lateral extent of a deeper shear horizon to be established The validity of each method was verified by the borehole information (cores, density log and temperature). A coherent model of the rock-glacier structure was developed. At the Schilthorn (2970 m a.s.L; Bernese Oberland), it was not clear whether permafrost is in fact present. Various geophysical surveys (d.c. resistivity tomography, refraction seismics, GPR and EM-31) gave results that were not typical of permafrost environments. A 14 m percussion drilling revealed warm permafrost and a very low ice content. These geotechnical and geothermal data allowed reinterpretation of the geophysical results, improving modelling of ground conditions. The paper demonstrates that in the difficult terrain of Alpine permafrost, boreholes may be critical in calibration and verification of the results of geophysical methods. The most useful combinations of geophysical techniques proved to be (a) seismics with d.c. resistivity, and (b) gravimetry with GPR.

Within the framework of core-drilling through the permafrost of the active rock glacier Murtèl–Corvatsch in the Swiss Alps, subfossil stem remains of seven different bryophyte species were found at a depth of 6 m below surface and about 3 m below the permafrost table in samples from massive ice. The composition of the moss species points to the former growth of the recovered mosses in the nearest surroundings of the drill site. A total of 127 pollen and spores captured by the mosses and representing 23 taxa were determined. The local vegetation during deposition time must be characterized as a moss-rich alpine grassland meadow rich in Cyperaceae, Poaceae, Chenopodiaceae and Asteraceae, comparable to today’s flora present around the study site. For l4C analysis, accelerator mass spectrometry had to be used due to the small sample mass (about 0.5 mg Carbon content). The mean conventional 14C age of 2250 ± 100 years (1σ variability) corresponds to ranges in the calibrated calendar age of 470–170 BC and 800 BC to AD 0 at statistical probabilities of 68% and 95%, respectively. This result is compared with the present-day flow field as determined by high-precision photogrammetry and with information about the thickness, vertical structure and flow of the permafrost from borehole measurements. Total age of the rock glacier as a landform is on the order of 104 years; the development of the rock glacier most probably started around the onset of the Holocene, when the area it now occupies became definitely deglaciated. The bulk of the ice/rock mixture within the creeping permafrost must be several thousand years old. Characteristic average values are estimated for (1) surface velocities through time (cm a-1), (2) long-term ice and sediment accretion rates (mm a-1) on the debris cone from which the rock glacier develops, (3) retreat rates (1–2 mm a-1) of the cliff which supplies the debris to the debris cone and rock glacier, and (4) ice content of the creeping ice/rock mixture (50–90% by volume). The pronounced supersaturation of the permafrost explains the steady-state creep mode of the rock glacier.

Permafrost is not directly visible. It can be inferred from geomorphological forms such as rock glaciers, patterned ground, pingos, and so on. Another possibility is to perform geophysical soundings: BTS, refraction seismics, D C resistivity soundings or gravimetry are appropriate methods. The most reliable way to prove the occurrence of permafrost is to dig a pit (a major disturbance and hence not to be recommended) o r to drill a borehole. This makes it possible to measure the ground temperature below the surface for more than a year and thus to confirm the presence of permafrost.

A gravimetrical study was carried out in the area of the Murtel-Corvatsch rock glacier in order to check the applicability of this method in alpine permafrost. The residual anomaly observed after removal of the linear regional trend is up to −1.5 mgal. Cores of borehole 2/1987 through this rock glacier showed a very high ice content in the uppermost 30 m. Borehole geophysical measurements furnished the density distribution with depth at the drill site showing values of less than 1000 kg m−3. According to the core stratigraphy and the density log at the drill site four layers were distinguished: an active layer to 3 m depth; massive ice (3–20 m); an ice-silt-sand layer (20–30 m); and a layer with ice-saturated blocks (30–50 m). The extension of the four distinguished layers is modelled in three dimensions for the entire rock glacier according to the gravity data. The bedrock underneath the creeping permafrost is bowl-shaped. Une etude gravimetrique a ete entreprise sur le glacier rocheux de Murtel-Corvatsch (Haute Engadine, Suisse) pour etudier l'applicabilite de la methode sur le pergelisol alpin. L'anomalie de Bouguer residuelle, obtenue apres soustraction d'un champ regional lineaire, atteint une amplitude maximale de −1.5 mgal. Des carottes du sondage 2/1987, traversant le glacier rocheux, montrent un contenu tres eleve en glace dans les premiers 30 m. Des mesures geophysiques faites dans le sondage ont fournis une distribution verticale des densites sur le site, donnant des valeurs inferieures a 1000 kg m−3. A partir de la stratigraphie des carottes et des densites obtenues par geophysique du sondage (density log), quatre couches ont ete identifiees: une couche active s'etendant jusqu'a 3 m; une couche de glace massive de 3 a 20 m; une couche mixte glace-limon-sable de 20 a 30 m; et enfin une couche de bloc saturee en glace de 30 a 50 m. Les extensions de ces quatres couches ont ete modellees en trois dimensions en accord avec les donnees gravimetriques. La modelisation montre un soubassement du pergelisol en mouvement ayant la forme d'une cuillere.

In two boreholes through Alpine permafrost, borehole geophysical measurements were performed. At the borehole through rock glacier Murtel-Corvatsch, where cores were taken, the main difficulty was to fill up the hole with water. Consequently, only some of the logging methods could be applied. Nevertheless, gamma-gamma log (and qualitatively also gamma-ray) made it possible to obtain density and to calculate ice content. At the Pontresina-Schafberg drill site, a complete set of logs was run in a water-filled hole. The bedrock was reached at a depth of approximately 16 m. No cores were obtained by the air-lift percussion technique. Logging measurements were done to determine thickness of the perennially frozen debris layer above the bedrock and to investigate P-wave velocity, resistivity and ice content of the whole permafrost body. The boreholes at both drill sites show a high ice content layer (80–95 % by volume), although temperature characteristics are quite different. Des mesures geophysiques (diagraphies) ont ete faites dans deux forages du pergelisol alpin. La principale difficulte rencontree au forage Murtel-Corvatsch, ou des carottes ont ete prises, fut de le remplir d'eau. De ce fait, seulement une partie des methodes de logging a pu etre employee. Cependant avec le gamma-gamma ‘log’ (ainsi qu'avec le gamma-ray) on a pu determiner la densite et calculer la teneur en glace. Dans le forage Pontresina-Schafberg, une serie complete de mesures de ‘logging’ a pu etre effectuee dans le trou rempli d'eau. Le bedrock a ete atteint a une profondeur approximative de 16 m. Avec la technique de forage employee, il n'a pas ete possible d'extraire des carottes. Des mesures de logging ont ete effectuees dans le but de determiner l'epaisseur de la couche gelee de roches detriques ainsi que la vitesse des ondes-P, la resistivite, la densite et la teneur en glace dans le pergelisol. Dans les deux trous de forages examines, une couche avec une importante teneur en glace (80–95 % par volume) a pu etre observee. Les conditions thermiques sont, quant a elles, differentes dans les deux trous.

Temperature measurements in borehole 2/1987 through rock glacier Murtel Corvatsch revealed a very high mean heat flow of 150 mW/m2. Between 52 m and 56 m depth, seasonal variations are observed; above and underneath this zone temperatures have remained negative during the last 4 years. In addition, a zero curtain effect at the same depth hints at the existence of a water aquifer which is active mainly in summer. This phenomenon is interpreted as a talik at about 55 m depth. The permafrost may have a total thickness of approximately 100 m. The high heat flow is a result of the boundary conditions at the surface (mean annual temperature: −3 °C) and at the aquifer (at a depth of about 50 m), where the temperature is close to 0 °C. Les mesures de temperature dans les trous de forage dans le glacier rocheux Murtel-Corvatsch presentent une tres grande valeur moyenne pour le flux de chaleur (150 m W/m2). Entre 52 m et 56 m de profondeur, il y a des variations saisonnieres de temperature; au dessus et en dessous les temperatures etaient toujours negatives durant les quatres annees passees. Dans cette zone un effet de ‘zero curtain’ a pu ětre observe, indiquant un aquifere d'eau actif en ete. Le phenomene est interprete comme un talik a une profondeur d'environ 55 m, entoure de pergelisol, qui peut atteindre une profondeur de 100 m. La grande valeur de flux de chaleur est due aux conditions a la surface (temperature moyenne de −3 °C) et a l'aquifere (situe a environ 50 m de profondeur) ou la temperature est proche de 0 °C.

Temperatures from a bore hole through an active rock glacier in the eastern Swiss Alps are presented and thermal conditions within the slowly creeping permafrost are analyzed. Present mean annual temperature in the uppermost part of the permafrost is −3°C. Permafrost is 52 m thick and reaches heavily fissured bedrock. Thermal conductivity as determined in situ from seasonal temperature variations and measured in a cold laboratory using frozen samples is close to 2.5–3.0 W m−1 °C−1. Vertical heat flow is anomalously high (around 150 mW m-2), probably due to heat advection from circulating ground water or air within the fissured bedrock zone. Beneath this zone, which could in fact represent a non-frozen intra-permafrost layer or “talik”, relic permafrost from past centuries may possibly exist as indicated by a corresponding heat-flow inversion. Given the current temperature condition at the surface of the rock glacier and the fact that the twentieth century is among the warmest in post-glacial time, permafrost conditions may be assumed to have existed during the whole of the Holocene and, hence, during the entire time of rock-glacier formation.

Here we present the first systematic measurements of European mountain permafrost temperatures from a latitudinal transect of six boreholes extending from the Alps, through Scandinavia to Svalbard. Boreholes were drilled in bedrock to depths of at least 100 m between May 1998 and September 2000. Geothermal profiles provide evidence for regional-scale secular warming, since all are nonlinear, with near-surface warm-side temperature deviations from the deeper thermal gradient. Topographic effects lead to variability between Alpine sites. First approximation estimates, based on curvature within the borehole thermal profiles, indicate a maximum ground surface warming of +1 °C in Svalbard, considered to relate to thermal changes in the last 100 years. In addition, a 15-year time series of thermal data from the 58-m-deep Murtel–Corvatsch permafrost borehole in Switzerland, drilled in creeping frozen ice-rich rock debris, shows an overall warming trend, but with high-amplitude interannual fluctuations that reflect early winter snow cover more strongly than air temperatures. Thus interpretation of the deeper borehole thermal histories must clearly take account of the potential effects of changing snow cover in addition to atmospheric temperatures.

Alpine permafrost is particularly sensitive to climate change, since it’s temperature is often close to the melting point of ice. In summer 1987, several hundred debris flows caused considerable damage and several victims in the Swiss Alps. Analysis showed that one out of three debris flows started at the lower boundary of mountain permafrost. A 58m deep borehole through creeping permafrost was drilled in 1987 near Piz Corvatsch (Upper Engadine, Swiss Alps). Temperatures have been measured regularly since then. Comparisons of two permafrost boreholes some 20km apart, where temperatures were measured once a year, indicated at least the regional character of the signal. Between 1987 and 1994, the uppermost 25m warmed rapidly. Surface temperature is estimated to have increased from -3.3°C (1988) to -2.3°C (1994), thereby probably exceeding previous peak temperatures during the 20th century. In the two-year period from 1994 to 1996, when winter snowfall was low, intensive cooling of the ground occurred, the temperatures reaching values similar to those in 1987. Since 1996, permafrost temperatures have once again been raising, followed by a cooling last winter. The variability of the observed permafrost temperatures is caused by several processes, including: (1) a reduced period of negative temperatures within the active layer due to long-lasting zero-curtains in autumn; (2) global radiation and air temperature changes influencing ground temperatures mainly in summer; and (3) variations in the duration of winter snow-cover. If the observed warming trend in alpine mountain permafrost temperatures continues into the foreseeable future, widespread permafrost degradation is likely, with potentially serious consequences with regard to mountain slope instability.

Mountain permafrost is highly vulnerable to present and future climate warming, since ground temperatures are generally only a few degrees below zero. The European Union PACE Project (Permafrost and Climate in Europe), which includes partners from Norway, Sweden, U.K., Germany, Switzerland, Italy and Spain, was established to develop new methods of assessing the potential impact of warming climate on mountain permafrost slopes in Europe. The research programme is first described and then progress in selected topics is summarized.

Flood and debris-flow hazards at Grubengletscher near Saas Balen in the Saas Valley, Valais, Swiss Alps, result from the formation and growth of several lakes at the glacier margin and within the surrounding permafrost. In order to prevent damage related to such hazards, systematic investigations were carried out and practical measures taken. The evolution of the polythermal glacier, the creeping permafrost within the large adjacent rock glacier and the development of the various periglacial lakes were monitored and documented for the last 25 years by photogrammetric analysis of annually flown high-resolution aerial photographs. Seismic refraction, d.c. resistivity and gravimetry soundings were performed together with hydrological tracer experiments to determine the structure and stability of a moraine dam at a proglacial lake. The results indicate a maximum moraine thickness of > 100 m; extremely high porosity and even ground caverns near the surface may have resulted from degradation of sub- and periglacial permafrost following 19th/20th-century retreat of the partially cold glacier tongue. The safety and retention capacity of the proglacial lake were enhanced by deepening and reinforcing the outlet structure on top of the moraine complex. The water level of an ice-dammed lake was lowered and a thermokarst lake artficially drained.

In the European Alps, thawing permafrost caused by warmer temperatures has been recognised as a possible danger for slope instabilities in the past few years. The permanently frozen layer (permafrost) is often only a few metres thick. Consequently it is very vulnerable to small changes in local climate. Furthermore, the detection and localisation of such shallow permafrost sites is difficult. The heterogeneity of the material and the difficult access of the steep slopes make commonly used techniques such as reflection seismics or Ground Penetrating Radar (GPR) less adequate for alpine permafrost studies.

The principal goal of georadar investigations is to determine the geometries of fine structures in the shallow subsurface. If strongly dipping reflections or diffraction hyperbolas are present in the georadar data, migration is a necessary processing step. Classical migration routines normally employed in seismic data processing may not be suitable for georadar data collected across regions of moderate to high topographic relief. To address this problem, we have written a modified Kirchhoff migration program that accounts automatically for antenna separation and topographic variations. INTRODUCTION In standard migration routines, georadar data sets are usually treated as zero-offset sections, and topographic relief is presumed to be negligible or accountable via appropriate elevation static corrections (Fisher et al., 1992; Fisher et al., 1994; Grasmiick, 1996; Grasmtick and Green, 1996). These two assumptions may cause significant errors in the migration. Here, we describe a migration algorithm that accounts for the finite offset of georadar data and at the same time includes the effects of topographic variations that may be of the same order as the penetration depths of the georadar signal. THEORY 1. Constant Offset Corrections Georadar data are typically displayed with “zero time” equated to the onset of the direct airwave arrival. To adjust zero time to be equal to the start of georadar signal transmission (i.e. apply a form of static correction) and to remove the travel-time effects of finite antenna separations (i.e. apply normal moveout corrections), we need to correct the time of each recording point of each trace as follows