Local and regional permafrost monitoring in the actual climate change context: application to the Clarée and Ubaye valleys (French Southern Alps)
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 bee...
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Other Authors: | , , , , , |
Format: | Doctoral or Postdoctoral Thesis |
Language: | French |
Published: |
HAL CCSD
2014
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Subjects: | |
Online Access: | https://theses.hal.science/tel-01113468 https://theses.hal.science/tel-01113468/document https://theses.hal.science/tel-01113468/file/Th%C3%A8se_PERRIER_7.pdf |
Summary: | 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 ... |
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