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Analyse de la dynamique des glaciers himalayens et alpins à partir de 40 ans de données d’observation de la Terre

Abstract : Mountain glaciers have a high societal impact, first at a local scale since they influence the water ressources and the touristic attractivity of a region, but also at a global scale, being major contributors to the present sea-level rise. Moreover, mountain glaciers are sensitive to climate forcing and are thus relevant indicators of past and present climate change and particularly present global warming. It is thus important to analyse the dynamic of these glaciers and quantify the changes that are affecting them so that their contribution to the Earth system and their future evolution can be better estimated. Satellite Earth Observation imagery, with its global coverage and repeated acquisition, represents a unique tool to quantify temporal changes affecting glaciers. The available archive is huge and the flux of new data will increase it even more.It is thus necessary to develop new methods to process this large archive.The objective of this thesis is to quantify the dynamic response of mountain glaciers in the Pamir-Karakoram-Himalaya (PKH) and in the Alps to a changing climate, with the use of the 40-year long satellite archive. We first developped a semi-automated processing chain to derive annual ice flow velocities from feature-tracking of satellite images. The chain takes advantage of the redundancy in the archive to obtain more spatially complete and robust velocity fields and to statistically estimate the uncertainty. Application to the Landsat archive leads to the determination of an unprecedented velocity field for the entire PKH region (~92 000 km2) for the period 1998-2014 and over the Alps (2 000 km2, period 1999-2014) with a coverage of 60-80 % and a mean uncertainty of 4 m/yr.. Flow velocities have been derived less systematically for the period 1972-1998 over the PKH. Secondly, the analysis of velocity changes show a slow-down of the glaciers for most of the 2 regions. The velocity changes are spatially contrasted and coherent with the patterns of elevation changes. In particular, glaciers in the Karakoram and West Kunlun that are stable or advancing show also a clear speed-up, whereas regions where thinning is the most important (Western Himalaya, Nyenchen Tangla, Alps) show the most important slow-down. The observed velocity changes is thus primarily determined by a climatic signal.
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Submitted on : Monday, December 7, 2015 - 4:48:07 PM
Last modification on : Friday, November 6, 2020 - 3:26:27 AM
Long-term archiving on: : Tuesday, March 8, 2016 - 4:16:30 PM


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  • HAL Id : tel-01239364, version 1



Amaury Dehecq. Analyse de la dynamique des glaciers himalayens et alpins à partir de 40 ans de données d’observation de la Terre. Glaciologie. Université Grenoble Alpes, 2015. Français. ⟨NNT : 2015GREAA027⟩. ⟨tel-01239364⟩



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