Mountain permafrost and associated geomorphological processes: recent changes in the French Alps

Bodin, Xavier; Schoeneich, Philippe; Deline, Philip; Ravanel, Ludovic; Magnin, Florence; Krysiecki, Jean-Michel; Echelard, Thomas

doi:10.4000/rga.2885

Cited by 28 publications

(40 citation statements)

References 22 publications

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“…Initially, blocks were positioned using a tacheometer [21], then a total station was used from 1992-2013, and since 2012, a differential dual-frequency GPS has been used in real-time kinematic (RTK) mode. This still ongoing long-term survey has allowed quantifying the annual surface velocity of the Laurichard rock glacier along its main flow line for more than three decades [25,26] with an overall centimetric accuracy.…”

Section: Previous Studies and Monitoring Activitymentioning

confidence: 99%

Multi-Annual Kinematics of an Active Rock Glacier Quantified from Very High-Resolution DEMs: An Application-Case in the French Alps

et al. 2018

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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.

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Section: Previous Studies and Monitoring Activitymentioning

confidence: 99%

Multi-Annual Kinematics of an Active Rock Glacier Quantified from Very High-Resolution DEMs: An Application-Case in the French Alps

et al. 2018

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“…The location of the miniature temperature dataloggers and DGPS points is shown in the sketch map on the right. LAU = Laurichard rock glacier, 65 km further north (Bodin et al, 2015). Zone A and B (eastern tongue and upper part of the rock glacier) display a common increase in both surface displacement and mean GST during summer 2009, probably responding to unusually warm atmospheric conditions as observed elsewhere in the Alps (e.g.…”

Section: Synthesis On the Rock Glacier Evolution Since Its Collapsementioning

confidence: 94%

“…This raises questions about the evolution of mountain permafrost under warming conditions, especially concerning ice-rich debris accumulations near the altitudinal and/or latitudinal limits of permafrost (e.g. Harris et al, 2009;Springman et al, 2013;Bodin et al, 2015). The local geological and topographical contexts, as well as the geomorphological dynamics and their possible change, might nevertheless also favour the triggering of high-amplitude movements, as suggested by several cases of destabilised rock glaciers in the Mattertal, Switzerland (Delaloye et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

The 2006 Collapse of the Bérard Rock Glacier (Southern French Alps)

Bodin

Krysiecki²,

Schoeneich

et al. 2016

Permafrost and Periglac. Process.

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In the Mediterranean French Alps, the Bérard rock glacier suddenly collapsed during the summer of 2006; this was a rarely documented event in the world, exceptional for the amount of disturbed material (estimated at 250 000–500 000 m3). Located near the lower limit of permafrost, the Bérard rock glacier collapse might exemplify the possible consequences of the degradation of ice‐rich mountain permafrost. The causes of the collapse may include long‐term atmospheric warming, recent air temperature anomalies, niveo‐meteorological conditions prior to the collapse, geological settings and topographical context. Geomorphological interpretations and analysis of climatic data‐sets allow us to specify the different stages of the collapse and discuss the respective roles of the geological and hydro‐climatic factors and unfrozen water in the ground which could have led to the collapse. Geophysical measurements and ice observations in the scarp reveal that the internal structure of the intact part of the rock glacier is composed of both ice‐cemented and massive‐ice layers. The rock glacier also contains a high proportion of fine material (essentially silt and clay), which could have played an important role in the collapse. Geodetic measurements repeated since 2007 show that, with the exception of the upper part, the whole rock glacier was still experiencing destabilisation in 2010, with very high deformation rates exceeding 30 m in 3 years. The continuous monitoring of surface displacement carried out during the summer of 2007 has not shown any clear meteorological control on the post‐collapse rock glacier dynamics. Copyright © 2016 John Wiley & Sons, Ltd.

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“…This destabilization phase, also referred as a "surge" (Schoeneich et al, 2015) or a "crisis" (Delaloye et al, 2013), may last decades and it usually results in a deceleration or inactivation of the landform. In very rare circumstances, destabilized rock glaciers may reach complete failure and collapse in a landslide (Bodin et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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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.

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Mountain permafrost and associated geomorphological processes: recent changes in the French Alps

Cited by 28 publications

References 22 publications

Multi-Annual Kinematics of an Active Rock Glacier Quantified from Very High-Resolution DEMs: An Application-Case in the French Alps

Multi-Annual Kinematics of an Active Rock Glacier Quantified from Very High-Resolution DEMs: An Application-Case in the French Alps

The 2006 Collapse of the Bérard Rock Glacier (Southern French Alps)

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

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