Abstract
Rock glaciers result from the long-term creeping of ice-rich permafrost along mountain slopes. Under warming conditions, deformation is expected to increase, and potential destabilization of those landforms may lead to hazardous phenomena. Monitoring the kinematics of rock glaciers at fine spatial resolution is required to better understand at which rate, where and how they deform. We present here the results of several years of in situ surveys carried out between 2005 and 2015 on the Laurichard rock glacier, an active rock glacier located in the French Alps. Repeated terrestrial laser-scanning (TLS) together with aerial laser-scanning (ALS) and structure-from-motion-multi-view-stereophotogrammetry (SFM-MVS) were used to accurately quantify surface displacement of the Laurichard rock glacier at interannual and pluri-annual scales. Six very high-resolution digital elevation models (DEMs, pixel size <50 cm) of the rock glacier surface were generated, and their respective quality was assessed. The relative horizontal position accuracy (XY) of the individual DEMs is in general less than 2 cm with a co-registration error on stable areas ranging from 20–50 cm. The vertical accuracy is around 20 cm. The direction and amplitude of surface displacements computed between DEMs are very consistent with independent geodetic field measurements (e.g., DGPS). Using these datasets, local patterns of the Laurichard rock glacier kinematics were quantified, pointing out specific internal (rheological) and external (bed topography) controls. The evolution of the surface velocity shows few changes on the rock glacier’s snout for the first years of the observed period, followed by a major acceleration between 2012 and 2015 affecting the upper part of the tongue and the snout.
Highlights
Because of their abundance in many poorly-glacierized mountain regions of the world [1], rock glaciers are key features to understand the response of the high altitude cryosphere to climate change [2]
In order to account for the possible effect of surface roughness and of the interannual variation of velocity, we compared mean annual surface velocity measured with GPS between 2003 and 2016 with slopes derived from a 10-m digital elevation models (DEM): no clear relationship appeared
We showed that interannual surface displacement fields of the Laurichard rock glacier can be derived in a rather straightforward way using high resolution DEMs
Summary
Because of their abundance in many poorly-glacierized mountain regions of the world [1], rock glaciers are key features to understand the response of the high altitude cryosphere to climate change [2]. Some cases of rock glaciers’ destabilization were observed in various mountain chains, such as in the Alps [5,6] or in the Andes [7], becoming a potential source of hazards [8] These temporal changes in rock glaciers’ deformation patterns pointed out various mechanical processes involved in their behavior [9]. In this context, developing a sound knowledge of the spatial and temporal variabilities of the surface velocity of rock glaciers, as a proxy of their deformation and an indicator of their climatic controls, is needed. It is a prerequisite for future efforts aiming at analyzing their physico-mechanical behavior and the driving factors, among which the climate probably plays a substantial role [3,10,11,12]
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