Le permafrost de montagne et les processus géomorphologiques associés : évolutions récentes dans les Alpes françaises

• Published in: Revue de géographie alpine
• Main Authors: Bodin, Xavier, Schoeneich, Philippe, Deline, Philip, Ravanel, Ludovic, Magnin, Florence, Krysiecki, Jean-Michel, Echelard, Thomas
• Other Authors: Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Pacte, Laboratoire de sciences sociales (PACTE), Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Sciences Po Grenoble - Institut d'études politiques de Grenoble (IEPG)-Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier - Grenoble 1 - Institut de géographie alpine (UJF IGA), Université Joseph Fourier - Grenoble 1 (UJF), GIPSA - Signal Images Physique (GIPSA-SIGMAPHY), Département Images et Signal (GIPSA-DIS), Grenoble Images Parole Signal Automatique (GIPSA-lab), Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Stendhal - Grenoble 3-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Stendhal - Grenoble 3-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Grenoble Images Parole Signal Automatique (GIPSA-lab), Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Stendhal - Grenoble 3-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Stendhal - Grenoble 3-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: French
• Published: HAL CCSD 2015
• Subjects: Alpes françaises; permafrost; changement climatique; French Alps; geomorphological dynamics; climate change; dynamiques géomorphologiques; [SDE.MCG]Environmental Sciences/Global Changes; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDE.ES]Environmental Sciences/Environmental and Society; [SHS.GEO]Humanities and Social Sciences/Geography
• Online Access: https://hal.science/hal-01349499; https://doi.org/10.4000/rga.2806

International audience Alpine mountains are affected by significant geomorphological processes whose evolution is partly conditioned by permafrost warming: rockfalls of various volumes, destabilisation of rock glaciers, and cryokarst. These phenomena, because of their intensity, may generate risks for territories. This paper provides a synthesis of the knowledge about the current status of the mountain permafrost in the French Alps and its recent evolution. This state-of-the-art overview is based on research conducted over the past 10 years and the measurements collected within PermaFRANCE, the French network for long-term observation of the mountain permafrost. The analysis of the available data shows that for a rock wall located at 3800 m asl., the temperature is between -4.5 and -1.5°C at a depth of 10 m, according to the aspect, whereas it is close to the melting point in surficial deposits at 2800 m asl. on a northern slope. Since the beginning of these measurements at depth in 2010, a trend of increasing temperature has been discernible, as found in other alpine boreholes. As clearly shown by the surface measurements conducted since 2003, the thermal regime is influenced by snow, particularly in surficial deposits and to a much lesser extent in rock walls. This inter-annual variability is combined with longer-term trends, which probably induce the observed changes in geomorphological dynamics associated with alpine permafrost: an increased frequency of gravitational processes such as rockfalls and fluctuation in rock glacier velocities. The possible increase in extreme events, such as rock avalanches or the destabilisation of rock glaciers, in the coming decades could create new or increased risks, to which territories must thus adapt. La montagne alpine est affectée par des processus géomorphologiques dont l’évolution est en partie conditionnée par la dégradation du permafrost : écroulements d’ampleur variable, déstabilisation de glaciers rocheux ou apparition de dépressions cryokarstiques. Ces ...