Evaluating the destabilization susceptibility of active rock glaciers in the French Alps

Abstract

Abstract. In this study, we propose a methodology to estimate the spatial distribution of destabilizing rock glaciers, with a focus on the French Alps. We mapped geomorphological features that can be typically found in cases of rock glacier destabilization (e.g. crevasses and scarps) using orthoimages taken from 2000 to 2013. A destabilization rating was assigned by taking into account the evolution of these mapped destabilization geomorphological features and by observing the surface deformation patterns of the rock glacier, also using the available orthoimages. This destabilization rating then served as input to model the occurrence of rock glacier destabilization in relation to terrain attributes and to spatially predict the susceptibility to destabilization at a regional scale. Significant evidence of destabilization could be observed in 46 rock glaciers, i.e. 10 % of the total active rock glaciers in the region. Based on our susceptibility model of destabilization occurrence, it was found that this phenomenon is more likely to occur in elevations around the 0 ∘C isotherm (2700–2900 m a.s.l.), on north-facing slopes, steep terrain (25 to 30∘) and flat to slightly convex topographies. Model performance was good (AUROC = 0.76), and the susceptibility map also performed well at reproducing observable patterns of destabilization. About 3 km2 of creeping permafrost, or 10 % of the surface occupied by active rock glaciers, had a high susceptibility to destabilization. Considering we observed that only half of these areas of creep are currently showing destabilization evidence, we suspect there is a high potential for future rock glacier destabilization within the French Alps.

Monitoring Rock Glacier Kinematics with Satellite Synthetic Aperture Radar

“…Similar to what is observed in the Alps [3,41], some cases of rock glacier destabilization observed in this region suggest that the geomorphological processes related to rock glacier dynamics is changing because of warming conditions in the ground [60,61]. The assessment of the activity status of the rock glacier, which is of crucial importance for further studying their sensitivity to climate-and human-induced impacts, is, generally, only done based on expert knowledge.…”

“…Among them, at least eleven rock glaciers have experienced, in the decades prior to 2010, strong changes in their kinematics and geometry [40]. These features, displaying exceptionally high velocities up to 10 m/a and more, and often showing distinct cracks as well as significant changes at their front, have been termed destabilized [41]. When located on steep slopes, they are the source for gravitative movements such as rock falls or debris flows [42].…”

Analyse multi-méthodes de la déstabilisation d’un pylône de remontée mécanique implanté sur un glacier rocheux des Alpes françaises

“…Un lac temporaire -contraint par le glacier rocheux et cette arête rocheuse -est présent immédiatement à l'Est du glacier rocheux. La carte d'indice de dégradation du permafrost (Potentially hawing Permafrost -PTP) (Marcer et al, 2019. ), qui propose une distribution spatiale du permafrost en cours de dégradation dans les Alpes françaises, indique un PTP de 0,95. le glacier rocheux est situé dans une zone à « permafrost subissant une dégradation importante » provoquée par l'augmentation de la température moyenne annuelle de l'air.…”

“…), qui propose une distribution spatiale du permafrost en cours de dégradation dans les Alpes françaises, indique un PTP de 0,95. le glacier rocheux est situé dans une zone à « permafrost subissant une dégradation importante » provoquée par l'augmentation de la température moyenne annuelle de l'air. Extension des glaciers d'après Gardent et al (2014) ; modélisation du permafrost en cours de dégradation d'après Marcer et al (2019). 1.…”

“…Extension of glaciers according to Gardent et al (2014); map of the permafrost undergoing degradation according to Marcer et al (2019). 1.…”