Hydrological processes and thermal dynamics in high mountain permafrost-affected rock walls

• Main Authors: Ben-Asher, Matan, Magnin, Florence, Bock, Josué, Josnin, Jean-Yves, Westermann, Sebastian, Ravanel, Ludovic, Deline, Philip
• Other Authors: 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), University of Oslo (UiO), ANR-19-CE01-0018,WISPER,Processus thermo-mécaniques liés à l'eau et à la glace dans les fractures des parois alpines à permafrost(2019)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDE.ES]Environmental Sciences/Environment and Society; [SDE]Environmental Sciences; [SDE.MCG]Environmental Sciences/Global Changes; Flatrock; Mont Blanc; Ice; permafrost
• Online Access: https://hal.science/hal-03886203; https://hal.science/hal-03886203/document; https://hal.science/hal-03886203/file/PRF2022_poster_BenAsher.pdf

International audience The increased rockfall activity in high Alpine ranges observed during the last two decades is commonly attributed to permafrost degradation associated with atmospheric warming. Although the connection between mountain permafrost warming and rockfall initiation is intuitive and supported by field and lab observations, the physical processes behind it are still poorly understood. In this study, we focus on the role of hydrologic and thermo-mechanical processes acting in fractures of steep alpine bedrock permafrost. Key challenges of the model scheme are related to the quantification of snow meltwater available for infiltration at different time scales. We combine field observations from a high elevation Alpine site in the Mont-Blanc massif (the Aiguille du Midi, 3842 m a.s.l) with numerical models of surface heat balance and mass transport. We were able to simulate snowmelt between 1959-2020 using the SAFRAN S2M dataset and show that annual snowmelt vary between 0.1-0.4 m/year and that its infiltration potential is limited by the accumulation of an ice crust in the rock-snow interface. Progress on these issues will help us decipher the governing processes in the degradation of high mountain permafrost and its link with rockfall occurrence.