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 empiricalstatistical 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. 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 empiricalstatistical models, and physically based ...

Direct shear box tests have revealed that the stiffness and strength of an ice‐filled joint are a function of both normal stress and temperature. Comparison of these data with the results of similar experiments conducted on unfrozen joints indicates that at low temperatures and normal stresses the strength of an ice‐filled joint can be significantly higher than that of an unfrozen joint. However, in the absence of sufficient closure pressure, the strength of an ice‐filled joint can be significantly less than that of an unfrozen joint. This implies that if the stability of a slope is maintained by ice‐filled joints, its factor of safety will reduce with temperature rise. This hypothesis suggests that a jointed rock slope that is stable when there is no ice in the joints and is also stable when ice in the joints is at low temperatures will become unstable as the ice warms. Results from the model tests have confirmed this hypothesis. Copyright © 2001 John Wiley & Sons, Ltd.RÉSUMÉDes tests de cisaillement directs ont révélés que la rigidité et la résistance d'un joint rempli de glace est fonction à la fois de la contrainte normale et de la température (Davies et al., 2000). La comparaison de ces données avec les résultats d'expériences semblables conduites sur des joints non gelés indique qu'à basse température et pour des contraintes normales identiques, la résistance d'un joint rempli de glace peut être plus élevée d'une manière significative que celle d'un joint non gelé. Toutefois, en l'absence d'une pression de fermeture suffisante, la résistance d'un tel joint rempli de glace peut être significativement moindre que celle d'une fissure non gelée. Ceci implique que si la stabilité de la pente est maintenue par des joints remplis de glace, son facteur de sécurité sera réduit avec l'augmentation de la température. Cette hypothèse suggère qu'une pente de roches fissurées qui est stable quand il n'y a pas de glace dans les joints et est aussi stable quand la glace dans les joints est à basse température, deviendra instable quand la glace s'échauffe. Des résultats obtenus par des tests ont confirmé ce résultat. Copyright © 2001 John Wiley & Sons, Ltd.

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[1] Three deep boreholes (!100 m) in mountain permafrost were recently drilled in Svalbard (Janssonhaugen) and in Scandinavia (Tarfalaryggen and Juvvasshøe) for longterm permafrost monitoring. These holes form part of a latitudinal transect of boreholes in permafrost through Europe, established by the Permafrost and Climate in Europe (PACE) project. Six-year thermal time series data collected from the three boreholes are presented. These data provide the first opportunity for temporal trends in permafrost temperatures in Svalbard and Scandinavia to be analyzed. Results show that the permafrost has warmed considerably at all three sites. Significant warming is detectable down to at least 60 m depth, and present decadal warming rates at the permafrost surface are on the order of 0.04°-0.07°C yr À1 , with greatest warming in Svalbard and in northern Scandinavia. The present regional trend shows accelerated warming during the last decade.

The presence and thermal character of permafrost reflect past and present surface energy balances plus the heat flux from the Earth's interior. Analysis of permafrost ground temperatures constitutes a key research tool for detecting thermal anomalies caused by twentieth‐century warming. Three deep boreholes in alpine permafrost were drilled in Svalbard and Scandinavia and form part of the latitudinal transect of mountain permafrost boreholes through the mountains of Europe established under the EU PACE (Permafrost and Climate in Europe) project. The northernmost borehole in the transect, at Janssonhaugen (depth 102 m), western Svalbard (78°10′46′′N, 16°28′01′′E, 270 m ASL) was drilled in May 1998. In Scandinavia, boreholes were drilled at Tarfalaryggen (depth 100 m), northern Sweden (67°55′09′′N, 18°38′29′′E, 1550 m ASL) in March 2000 and at Juvvasshøe (depth 129 m), southern Norway (61°40′32′′N, 08°22′04′′E, 1894 m ASL) in August 1999. Permafrost thickness at Janssonhaugen is estimated as approximately 220 m. The temperature profiles on Tarfalaryggen and Juvvasshøe show anomalously low geothermal gradients, indicating low heat flow through thick permafrost (∼350 m and ∼380 m respectively). Palaeoclimatic analysis based on inversion modelling of the ground temperature measurements at Janssonhaugen shows near surface warming of 1.5 ± 0.5 °C during the twentieth century. Both the Tarfalaryggen and Juvvasshøe boreholes also reveal thermal anomalies, which reflect a surface warming over the past decades, with a magnitude of approximately 0.5–1.0 °C. Copyright © 2001 John Wiley & Sons, Ltd.RÉSUMÉL'existence d'un pergélisol ainsi que ses caractères thermiques reflètent la balance entre l'énergie de surface (passée et actuelle) et le flux de chaleur interne de la terre. L'étude des températures du pergélisol constitue ainsi une recherche fondamentale pour détecter les anomalies thermiques dues au réchauffement du vingtième siècle. Trois sondages profonds dans le pergélisol alpin ont été réalisés au Svalbard et en Scandinavie. Ils constituent une partie du transect en latitude de sondages du pergélisol de montagne réalisé dans le cadre du projet de l'Union Européenne Pace (Pergélisol et Climat en Europe). Le sondage le plus septentrional du transect a été foré en mai 1998 à Janssonhaugen (profondeur 102 m), à l'ouest de Svalbard (78°10′46′′N, 16°28′01′′E, à 270 m d'altitude). En Scandinavie, des sondages ont été réalisés en mars 2000 à Tarfallaryggen (profondeur 100 m) au nord de la Suède (67°55′09′′N, 18°38′29′′E, à 1550 m d'altitude) et en août 1999 à Juvvasshoe (profondeur 129 m), au sud de la Norvège (61°40′32′′N, 08°22′04′′E, à 1894 m d'altitude). L'épaisseur du pergélisol à Janssonhaugen est approximativement de 220 m. Les profils de température à Tarfalaryggen et à Juvvasshoe montrent des gradients géothermiques anormalement faibles, indiquant un faible écoulement de chaleur au travers d'un pergélisol épais (respectivement d'environ 350 m et 380 m). Des analyses paléoclimatiques basées sur un modèle d'inversion des mesures de la température du sol à Janssonhaugen indiquent un réchauffement près de la surface de 1.5 0.5 °C pendant le 20e siècle. A la fois à Tarfalarygen et à Juvvasshoe, les anomalies thermiques existantes révèlent un réchauffement de la surface d'une ampleur de approximative de 0.5 à 1.0 °C au cours des dernières décades