How does rock glaciers deactivate? Geomorphic and activity states of French Alpine rock glaciers in transition

• Main Authors: Agziou, Julia, Cusicanqui, Diego, Lehmann, Benjamin, Bodin, Xavier, Duvanel, Thibaut, Schoeneich, Philippe
• Other Authors: Pacte, Laboratoire de sciences sociales (PACTE), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Sciences Po Grenoble - Institut d'études politiques de Grenoble (IEPG), Université Grenoble Alpes (UGA), Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Institute of Arctic Alpine Research University of Colorado Boulder (INSTAAR), University of Colorado Boulder, EGU
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2024
• Subjects: [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology; Ice; permafrost
• Online Access: https://hal.science/hal-04614752; https://doi.org/10.5194/egusphere-egu24-18492

International audience Rock glaciers are the visible expression of mountain permafrost. The deformation of internal ice and basal horizon make them creeping downward, which allows their detection. Their geomorphological characteristics tend to evolve as a response to degrading permafrost conditions. If the internal ice is melting, the surface creeping gradually decreases until the landform stabilizes. This gradual deactivation has led to the definition of “rock glaciers in transition”. Recent studies highlighted a general trend of active rock glaciers’ increasing surface velocity in the last decades. In this context, we are asking if remaining ice in rock glaciers in transition could allow an increase of surface velocity trend similar to active rock glaciers? This study aims to describe rock glaciers in transition geomorphic settings and their present-day kinematics, and explore how their intrinsic and extrinsic characteristics can explain their activity. To answer this question, we applied remote sensing techniques from a French inventory of rock glaciers such as i) High resolution differential radar interferometry images to describe present days surface velocities for all “inactive” inventoried rock glaciers and reveal global trends at a large scale. ii) Geomorphic mapping of the rock glaciers characteristics such as their geometry, geomorphological and geological settings (rock glacier system, slope, latitude/longitude, altitude, concavities, vegetation cover, exposition, aspect and lithology of the blocks…). iii) By combining a dataset with i) and ii), we analyze correlations and dominant parameters using an MCA factorial analysis and a multimodal linear regression. Over 521 rock glaciers, 305 present displacements detectable from 30 InSAR images during summer period between 2016 and 2018. Most of them have velocities rates lower than 10 cm. yrˉ¹ (N=184), and for 1/3 (N=120) it ranges from 10 to 50 cm. yrˉ¹. Higher rates only concern 11 rock glaciers. For 80% of them (N=247), the mean surface area of ...