State and evolution of the Bérard rock glacier (Southern French Alps) after its collapse in 2006: insights from geophysical, geodetic and thermal datasets

• Main Authors: Krysiecki, Jean-Michel, Le Roux, Olivier, Bodin, Xavier, Schoeneich, Philippe
• Other Authors: Université Joseph Fourier - Grenoble 1 - Institut de géographie alpine (UJF IGA), Université Joseph Fourier - Grenoble 1 (UJF), Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS), Instituto de Geografia, Pontifica Universidad Catolica de Chile
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2010
• Subjects: [SDE.MCG]Environmental Sciences/Global Changes; Ice; permafrost
• Online Access: https://hal.archives-ouvertes.fr/halsde-00594342

Poster International audience In the French Alps, the summer 2006 has been marked by the sudden collapse of the Bérard rockglacier, a rare event, exceptional by the quasi complete destabilization of the landform. This case raises questions on the evolution of mountain permafrost under warming conditions, especially those ice-rich debris accumulations located close to the altitudinal and/or latitudinal limits of permafrost and that may be experiencing morphogenetic crisis. The Bérard site (2500-2900 m asl; 44°26' N. - 6°40' E.) is located in the Parpaillon range, near the Southern limits of the Alpine permafrost and under Mediterranean climatic conditions. The objectives of our study are to analyse the present state of the Bérard rock glacier (collapsed and non-collapsed mass) and its evolution after the major movements of summer 2006 that mobilized 1.5 millions m3 of material. In this purpose, electrical resistivity and seismic refraction tomographies were repeated along two profiles in summers 2007 and 2009, GPS survey of 40 points was initiated in summer 2007 and a thermal monitoring, composed of 6 miniature temperature dataloggers and an automatic weather station was installed on the site on summer 2007. First, the combination of the thermal and geodetic data allows us to distinguish three areas: 1) the unstable but non-collapsed upper part of the rock glacier, characterized by creeping signs and which displays surface velocity between 0.1 and 0.6 m/yr and WEqT (Winter Equilibrium Temperature) values > - 2°C in 2008 and 2009; 2) the highly unstable but non-collapsed median part, characterized by destabilization signs like wide fractures and which displays surface velocity up to 8 m/yr (no ground temperature available); 3) the collapsed mass, characterized by strong morphological changes (rapid downwasting of ice/debris packets) just after the deposition but no visible signs of evolution since 2007 and which displays surface velocity below 0.1 m/yr and WEqT around 0°C. The electrical resistivity ...