Local and regional permafrost monitoring in the actual climate change context: application to the Clarée and Ubaye valleys (French Southern Alps)

• Main Author: PERRIER, Romain
• Other Authors: Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris-Sorbonne (UP4)-AgroParisTech-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris Diderot, Monique Fort, Etienne Cossart
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2014
• Subjects: rockglacier; French Southern Alps; Ubaye valley; Clarée valley; climate change; Permafrost; Pergélisol; glacier rocheux; changement climatique; Clarée; Ubaye; Alpes du sud; [SHS.GEO]Humanities and Social Sciences/Geography; Ice; permafrost; pergélisol
• Online Access: https://tel.archives-ouvertes.fr/tel-01113468; https://tel.archives-ouvertes.fr/tel-01113468/document; https://tel.archives-ouvertes.fr/tel-01113468/file/Th%C3%A8se_PERRIER_7.pdf

This work intends to characterize the distribution, the state and the functioning of permafrost at various spatial scales and in various topoclimatic contexts. It also intends determine permafrost response(s) to actual climate change. In order to realize these objectives, our investigations have been carried out in two valleys (Clarée and Ubaye) of the French Southern Alps. Firstly, permafrost spatial distribution has been studied at regional scale by means of a statistico-empirical model. Results show that permafrost may be found between 2600 and 3000 m and its distribution is influenced by altitude and solar radiation. Secondly and at the local scale, the implementation of a geophysical, thermal and geodetic monitoring has helped to qualify the regional spatial model as well as to characterize actual permafrost functioning. At rockglacier scale, geophysical investigations reveal a patchy permafrost distribution and a high heterogeneity of ground ice that both may be explained by local geodynamics and recent glacial (LIA) history. Thermal monitoring has revealed the existence of 4 main thermal regimes that mainly depend on snow cover specificities and permafrost occurrence. During the two years (2010-2012) period of monitoring some sites have shown some permafrost thermal disequilibrium with current climate conditions. Geodetic monitoring of rockglaciers shows an annual velocity as well as vertical displacements that range from few centimeters up to a meter. More generally surface displacements are mainly conditioned by local topography and ground ice type. Thirdly, permafrost degradation assessment through rockglacier morphological changes is difficult to determine. Significant morphological changes have only been observed on rockglacier areas that contain ground massive ice inherited from LIA advance. However, the use of permafrost thermal disequilibrium proxies has enabled to build up a regional topo-climatic model together with a map of areas susceptible to thermal disequilibrium. Le présent travail vise ...