Utilisation combinée de l’interférométrie SAR spatiale et des mesures in-situ pour la surveillance des glaciers dans les zones de montagne

Dans les zones de montagne, la surveillance des glaciers alpins est cruciale pour évaluer l’impact local du réchauffement climatique. Les satellites d’observation de la Terre fournissent des informations importantes pour l’observation régulière de la surface du glacier sur de vastes zones.

Dans cet article, nous combinons des mesures InSAR spatialement étendues et ponctuelles comme des mesures in situ afin de mesurer le déplacement de surface sur les glaciers et les moraines environnantes (…)

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Combined use of spaceborne SAR interferometry and in-situ measurements for glacier monitoring in mountain areas

In mountain areas, the monitoring of Alpine glaciers is crucial to assess the local impact of global warming. The motion of glaciers and the instabilities in their surrounding moraines, due to glacial conditions and local geomorphological factors, represent a major issue of risk and require the development of sophisticated monitoring techniques. Earth observation satellites provide important information for regular observation of the glacier surface over large areas. Synthetic Aperture Radar (SAR) imagery can be used to derive surface displacement fields by two main techniques: offset tracking based on the amplitude information and SAR Interferometry (InSAR) based on the phase information with an accuracy on the order of centimeters. In this paper, we combine both spatially extended InSAR measurements and point like in situ measurements (including GPS data and information on Corner Reflectors installed over the moraines) in order to measure the surface displacement over the glaciers and the surrounding moraines. The uncertainties associated with each type of measurements are quantified. The spatial and temporal characteristics between both types of measurements are analysed, from which the combination strategy is determined. In situ measurements are used to improve the InSAR processing and to reduce the InSAR measurements uncertainty. The techniques to obtain different measurements and the combined use of the latter are illustrated over the Argentière glacier with SAR images acquired by Sentinel-1 satellites since 2015.