InSAR monitoring and modeling of solifluction processes in Tibet
Etablissement – Université de Lorraine
École doctorale SIReNa – SCIENCE ET INGENIERIE DES RESSOURCES NATURELLES
Spécialité Géosciences
Unité de recherche CRPG – Centre de Recherches Pétrographiques et Géochimiques
Encadrement de la thèse Jérôme LAVÉ (detailResp.pl?resp=6530)
Financement du 01-10-2023 au 30-09-2026 origine bourse ministère Employeur CRPG
Début de la thèse le 1 octobre 2023
Date limite de candidature (à 23h59) 1 juin 2023
PhD supervisors: Simon Daout (CRPG, University of Lorraine, simon.daout@univ-lorraine.fr), Jérôme Lavé (CRPG, DR CNRS, jerome.lave@univ-lorraine.fr)
Keywords :
InSAR, permafrost, solifluxion, Tibet, modeling
Project description
The Tibetan plateau is characterized by a high periglacial landscape. Above ~3500 m, the average surface temperature is below 0°C, so permafrost (permanently frozen ground) is present in the ground. Excess ice in the frost-sensitive materials of the active layer, above the permafrost, thaws during the summer and autumn months and freezes during the winter and spring months. These freezing and thawing phenomena lead to cyclical movements of the surface that can be measured by spatial geodesy techniques such as Synthetic Aperture Radar Interferometry (InSAR, e.g. Daout et al., GRL, 2017: https://doi.org/10.1002/2016GL070781). On the slopes, solifluction phenomena take place, associated with soil expansion normal to the slope during freezing and with more or less vertical collapse and water saturation of the sedimentary layers during thawing. Long-term erosion rates measured in Tibet using cosmogenic nuclides are of the order of 0.01mm/year, 2-3 orders of magnitude lower than the surface displacements due to solifluction processes observed by recent InSAR measurements (Daout et al., EPSL, 2020: https://doi.org/10.1016/j.epsl.2020.116404). The objective of the project is to find out if those solifluction phenomena are recent and are related to global temperature increase and ice loss within Tibet, having a direct impact on the stability of the slopes; or if, on the contrary, they are more perennial processes with stationary or transient material fluxes and erosion rates, undocumented so far on the Tibetan plateau, that could have played a major role in the low relief morphology of the Tibetan plateau. In this project, the student will carry out an analysis of InSAR data recently processed on a very large scale on the Tibetan plateau, by the CNES-ForM@Ter FLATSIM (https://flatsim.cnes.fr/doi/) massive and automatic processing service, in order to document transient (annual cycle) and cumulative permafrost deformations. The work will include validation, analysis of the products, and the development of tools to (1) automatically extract slope instabilities and (2) better characterize the kinematics of cyclic and secular motions in the slope and in the normal to the surface. The measurements (seasonal and cumulative cycles in the slope and normal) will be correlated to the lithology, the nature of the surface formations and morphometric parameters in order to characterize the distribution of these processes. In parallel, the project will consist of finite difference modeling of cyclic and secular measurements in the slope and surface normal by associating sediment diffusion on the slopes and thermal diffusion at depth in order to explore the deformation mechanisms of solifluction processes. The expected results of this analysis and modeling work are a quantification of the permafrost thaw and the stakes of this degradation on the slope instabilities, work that could be extrapolated in other regions of the globe, such as the European Alps. These large-scale measurements on the Tibetan plateau will also allow quantifying the role of these phenomena on the long-term geomorphologic evolution of the Tibetan plateau relief, and on the effacement of the traces of tectonic deformations on the surface.
Références bibliographiques
Daout, S., Doin, M. P., Peltzer, G., Socquet, A., & Lasserre, C. (2017). Large-scale InSAR monitoring of permafrost freeze-thaw cycles on the Tibetan Plateau. Geophysical Research Letters, 44(2), 901-909.
Daout, S., Dini, B., Haeberli, W., Doin, M. P., & Parsons, B. (2020). Ice loss in the Northeastern Tibetan Plateau permafrost as seen by 16 yr of ESA SAR missions. Earth and Planetary Science Letters, 545, 116404.
Details on the thesis supervision
Simon Daout (Maître de conférences CRPG-ENSG _ SIRENA n°104336)
Profile and skills required
Candidate should hold a Master degree in Earth Sciences or equivalent. A significant part of the thesis work involve numerical computing using programming, signal processing (image processing, time series analysis) modelling and inversion. Consequently the candidate should demonstrate some skills and/or interest related to those fields. Any of the following points are welcome (but not mandatory): programming skills in Python or Fortran; experience in GPS or InSAR processing; experience on GIS; background in space geodesy, remote-sensing, or geomorphology. Good knowledge of the written and spoken English language is also expected.