The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Xavier Bodin - One of the best experts on this subject based on the ideXlab platform.
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analysis of the mechanical behavior of the laurichard Rock Glacier french alps in the recent climatic changes
International Conference of the International Association for Computer Methods and Advances in Geomechanics, 2021Co-Authors: Samia Melki, Xavier Bodin, Dominique Daudon, Emmanuel ThibertAbstract:In mountain areas, Rock Glaciers are markers of climate change. Besides temperature effect, their surface flow velocity can be influenced by ice proportion and other mechanical and physical properties. To improve the understanding of the processes influencing thermal control and the seasonal and inter-annual variations, this study on the Laurichard Rock Glacier in France proposes the analysis of correlations between surface velocity variations and air temperature anomalies based on Staub et al. (2015), and evaluates the viscosity using surface velocities with steady shear flow hypothesis (Monnier et al. 2016) over 30 years of measurements.
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A general theory of Rock Glacier creep based on in‐situ and remote sensing observations
Permafrost and Periglacial Processes, 2020Co-Authors: Alessandro Cicoira, Xavier Bodin, Marco Marcer, Isabelle Gärtner-roer, Lukas U. Arenson, Andreas VieliAbstract:The ongoing acceleration in Rock Glacier velocities concurrent with increasing air temperatures, and the widespread onset of Rock Glacier destabilization have reinforced the interest in Rock Glacier dynamics and in its coupling to the climate system. Despite the increasing number of studies investigating this phenomenon, our knowledge of both the fundamental mechanisms controlling Rock Glacier dynamics, and their long‐term behaviour at the regional scale remain limited. We present a general theory to investigate Rock Glacier dynamics, its spatial patterns and temporal trends at both regional and local scale. To this end, we combine a model to calculate Rock Glacier thickness with an empirical creep model for ice‐rich debris, in order to derive the Bulk Creep Factor (BCF), which allows to disentangle the two contributions to the surface velocities from (i) material properties and (ii) geometry. Thereafter, we provide two examples of possible applications of this approach at a regional and local scale.
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multi annual kinematics of an active Rock Glacier quantified from very high resolution dems an application case in the french alps
Remote Sensing, 2018Co-Authors: Xavier Bodin, Emmanuel Thibert, Antoine Rabatel, Olivier Sanchez, Stephane JailletAbstract: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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multi annual kinematics of an active Rock Glacier quantified from very high resolution dems an application case in the french alps
Remote Sensing, 2018Co-Authors: Xavier Bodin, Emmanuel Thibert, Antoine Rabatel, Olivier Sanchez, Stephane JailletAbstract: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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permafrost favorability index spatial modeling in the french alps using a Rock Glacier inventory
Frontiers in Earth Science, 2017Co-Authors: Marco Marcer, Xavier Bodin, Alexander Brenning, Philippe Schoeneich, Raphaele Charvet, Frederic GottardiAbstract:In the present study we used the first Rock Glacier inventory for the entire French Alps to model spatial permafrost distribution in the region. The inventory, which does not originally belong to this study, was revised by the authors in order to obtain a database suitable for statistical modelling. Climatic and topographic data evaluated at the Rock Glacier locations were used as predictor variables in a Generalized Linear Model. Model performances are strong, suggesting that, in agreement with several previous studies, this methodology is able to model accurately Rock Glacier distribution. A methodology to estimate model uncertainties is proposed, revealing that the subjectivity in the interpretation of Rock Glacier activity and contours may substantially bias the model. The model highlights a North-South trend in the regional pattern of permafrost distribution which is attributed to the climatic influences of the Atlantic and Mediterranean climates. Further analysis suggest that lower amounts of precipitation in the early winter and a thinner snow cover, as typically found in the Mediterranean area, could contribute to the existence of permafrost at higher temperatures compared to the Northern Alps. A comparison with the Alpine Permafrost Index Map (APIM) shows no major differences with our model, highlighting the very good predictive power of the APIM despite its tendency to slightly overestimate permafrost extension with respect to our database. The use of Rock Glaciers as indicators of permafrost existence despite their time response to climate change is discussed and an interpretation key is proposed in order to ensure the proper use of the model for research as well as for operational purposes.
Andreas Kaab - One of the best experts on this subject based on the ideXlab platform.
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inventory and changes of Rock Glacier creep speeds in ile alatau and kungoy ala too northern tien shan since the 1950s
The Cryosphere, 2021Co-Authors: Andreas Kaab, Markus Stoffel, Tazio Strozzi, Tobias Bolch, Rafael Caduff, Hakon Trefall, Alexander KokarevAbstract:Abstract. Spatio-temporal patterns related to the viscous creep in perennially frozen sediments of Rock Glaciers in cold mountains have rarely been studied outside the densely populated European Alps. This study investigates the spatial and temporal variability of Rock Glacier movement in the Ile Alatau and Kungoy Ala-Too mountain ranges, northern Tien Shan, a region with particularly large and fast Rock Glaciers. Over the study region of more than 3000 km 2 , an inventory of slope movements was constructed using a large number of radar interferograms and high-resolution optical imagery. The inventory includes more than 900 landforms, of which around 550 were interpreted as Rock Glaciers. Out of the active Rock Glaciers inventoried, 45 are characterized by a rate of motion exceeding 100 cm/a. From these fast Rock Glaciers we selected six (Gorodetzky, Morenny, Archaly, Ordzhonikidze, Karakoram, and Kugalan Tash) and studied them in more detail using offset tracking between repeat aerial images and historical and modern high-resolution optical satellite data. Two of these Rock Glaciers showed a steady increase in decadal surface velocities from the 1950s onwards, with speeds being roughly 2 to 4 times higher in recent years compared to the 1950s and 1960s. Three Rock Glaciers showed similar accelerations over the last 1 to 2 decades but also phases of increased speeds in the 1960s. This development indicates a possible significant increase in current sediment and ice fluxes through Rock Glaciers and implies that their material transport in the region might gain geomorphodynamic importance relative to material transport by Glaciers, assuming the latter decreases together with the regional Glacier shrinkage. The study demonstrates how air and satellite image archives are exploited to construct one of the longest decennial times series of Rock Glacier speeds currently available. Our results are in line with findings from Europe about Rock Glacier speeds increasing with atmospheric warming and underline local variability of such an overall response.
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recent interannual variations of Rock Glacier creep in the european alps
Delaloye R; Perruchoud E; Avian M; Kaufmann V; Bodin X; Hausmann H; Ikeda A; Kääb A; Kellerer-Pirklbauer A; Krainer K; Lambiel C; Mihajlovic D; Staub , 2008Co-Authors: Reynald Delaloye, Xavier Bodin, Andreas Kaab, E Perruchoud, Michael Avian, H Hausmann, Atsushi Ikeda, Andreas Kellererpirklbauer, K Krainer, Christophe LambielAbstract:Recent interannual variations of Rock Glacier surface motion are compared for 16 landforms monitored for a few years in various parts of the European Alps. Large fluctuations have been observed particularly since 2002. Most investigated Rock Glaciers have shown a similar behavior whatever their location in the Alpine arc, their size, or their velocity. The observed interannual variations appear to be primarily related to external climatic factors rather than to internal characteristics. They are mostly well correlated with mean annual ground surface temperature shifts with a delay of a few months, reflecting the thermal wave propagation deeper into permafrost. Seasonal factors may also play a significant role: a lower intensity of winter ground freezing and/or a larger winter snow accumulation appear to facilitate a higher rate of Rock Glacier surface motion.
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fast deformation of perennially frozen debris in a warm Rock Glacier in the swiss alps an effect of liquid water
Journal of Geophysical Research, 2008Co-Authors: Atsushi Ikeda, Norikazu Matsuoka, Andreas KaabAbstract:[1] Surface movement, internal deformation, and temperature were monitored over 5 years on Buz North Rock Glacier, a small Rock Glacier located at the lower limit of the permafrost belt in the Swiss Alps. The permafrost in the Rock Glacier mainly consists of pebbles and cobbles filled with interstitial ice. Two inclinometers installed at 4 and 5 m depths showed fast deformation with large seasonal and interannual variations, while the permafrost temperatures remained almost at the melting point. The movement of the inclinometers coincided with changes in the surface velocities. The deformation rapidly accelerated during snowmelt periods, whereas it gradually decelerated below a dry snow cover in winter. The frozen debris was more deformable than typical Glacier ice at the melting point. These phenomena suggest that the frozen debris is permeable to snowmelt water. The fast deformation should result from significant annual relocation of debris particles, which probably creates a network of air voids in the frozen debris that eventually allows water infiltration. The meltwater infiltration accelerates the deformation by reducing effective stress, resulting in the reduced strength of the frozen debris. The refreezing of the pore water, which depends on the cooling intensity in winter, decelerates the deformation. The combination of these processes controls the temporal variations in the deformation.
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permafrost creep and Rock Glacier dynamics
Permafrost and Periglacial Processes, 2006Co-Authors: Wilfried Haeberli, Bernard Hallet, Lukas U. Arenson, Roger Elconin, Ole Humlum, Andreas Kaab, Viktor Kaufmann, B Ladanyi, Norikazu Matsuoka, Sarah M SpringmanAbstract:This review paper examines thermal conditions (active layer and permafrost), internal composition (Rock and ice components), kinematics and rheology of creeping perennially frozen slopes in cold mountain areas. The aim is to assemble current information about creep in permafrost and Rock Glaciers from diverse published sources into a single paper that will be useful in studies of the flow and deformation of subsurface ice and their surface manifestations not only on Earth, but also on Mars. Emphasis is placed on quantitative information from drilling, borehole measurements, geophysical soundings, photogrammetry, laboratory experiments, etc. It is evident that quantitative holistic treatment of permafrost creep and Rock Glaciers requires consideration of: (a) Rock weathering, snow avalanches and Rockfall, with grain-size sorting on scree slopes; (b) freezing processes and ice formation in scree at sub-zero temperatures containing abundant fine material as well as coarse-grained blocks; (c) coupled thermohydro-mechanical aspects of creep and failure processes in frozen Rock debris; (d) kinematics of non-isotropic, heterogeneous and layered, ice-rich permafrost on slopes with long transport paths for coarse surface material from the headwall to the front and, in some cases, subsequent re-incorporation into an advancing Rock Glacier causing corresponding age inversion at
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towards a palaeoclimatic model of Rock Glacier formation in the swiss alps
Annals of Glaciology, 2000Co-Authors: Regula Frauenfelder, Andreas KaabAbstract:Climate and its long-term variability govern ground thermal conditions, and for this reason represent one of the most important impacts on creeping mountain permafrost. The decoding and better understanding of the present-day morphology and distribution of Rock Glaciers opens up a variety of insights into past and present environmental, especially climatic, conditions on a local to regional scale. The present study was carried out in the Swiss Alps using two different approaches: (1) kinematic analysis of specific active Rock Glaciers, and (2) description of the altitudinal distribution of relict Rock Glaciers. Two theoretical shape concepts of active Rock-Glacier morphology were derived’ a"monomorphic" type, representing presumably undisturbed, continuous development over several millennia and a ˚polymorphic" type, reflecting a system of (possibly climatically affected) individual creep streams several centuries old. The topoclimatic-based inventory analysis indicated an average temperature increase at relict Rock-Glacier fronts of approximately +2°C since the time of their decay, which is a sign of Rock-Glacier ages reaching back to the Alpine Late Glacial. The temperature difference of some tenths of a degree Celsius found for active/inactive Rock Glaciers is typical for the bandwidth of Holocene climate variations. These results confirm the importance of Alpine Rock Glaciers as highly sensitive indicators of past temperature evolution.
Christophe Kinnard - One of the best experts on this subject based on the ideXlab platform.
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pluri decadal 1955 2014 evolution of Glacier Rock Glacier transitional landforms in the central andes of chile 30 33 s
Earth Surface Dynamics Discussions, 2016Co-Authors: Sebastien Monnier, Christophe KinnardAbstract:Abstract. Three Glacier–Rock Glacier transitional landforms in the central Andes of Chile are investigated over the last decades in order to highlight and question the significance of their landscape and flow dynamics. Historical (1955–2000) aerial photos and contemporary (> 2000) Geoeye satellite images were used together with common processing operations, including imagery orthorectification, digital elevation model generation, and image feature tracking. At each site, the Rock Glacier morphology area, thermokarst area, elevation changes, and horizontal surface displacements were mapped. The evolution of the landforms over the study period is remarkable, with rapid landscape changes, particularly an expansion of Rock Glacier morphology areas. Elevation changes were heterogeneous, especially in debris-covered Glacier areas with large heaving or lowering up to more than ±1 m yr−1. The use of image feature tracking highlighted spatially coherent flow vector patterns over Rock Glacier areas and, at two of the three sites, their expansion over the studied period; debris-covered Glacier areas are characterized by a lack of movement detection and/or chaotic displacement patterns reflecting thermokarst degradation; mean landform displacement speeds ranged between 0.50 and 1.10 m yr−1 and exhibited a decreasing trend over the studied period. One important highlight of this study is that, especially in persisting cold conditions, Rock Glaciers can develop upward at the expense of debris-covered Glaciers. Two of the studied landforms initially (prior to the study period) developed from an alternation between glacial advances and Rock Glacier development phases. The other landform is a small debris-covered Glacier having evolved into a Rock Glacier over the last half-century. Based on these results it is proposed that morphological and dynamical interactions between Glaciers and permafrost and their resulting hybrid landscapes may enhance the resilience of the mountain cryosphere against climate change.
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internal structure and composition of a Rock Glacier in the dry andes inferred from ground penetrating radar data and its artefacts
Permafrost and Periglacial Processes, 2015Co-Authors: Sebastien Monnier, Christophe KinnardAbstract:Using ground-penetrating radar (GPR), we studied an entire 2.2km long Rock Glacier (3780–4350m asl) in the dry Andes of Chile with the aim of inferring its composition. In the high-quality, unmigrated data, we identified the active layer base and the Rock Glacier floor. In between, hyperbolae generated by diffracting boulders were inventoried; the ones along the Rock Glacier floor (n=51) allowed determination of the average electromagnetic (EM) velocity in the Rock Glacier, the latter being further used for migration. Within the Rock Glacier (16–39m thick), the EM velocity varies between 0.076 and 0.167m.ns -1 ; the main stratigraphic features observed are upward-dipping reflectors. The low EM velocities (<0.10m.ns -1 ) found at some locations suggest the presence of significant unfrozen water fractions. A strong (R 2 =0.77), inverse linear relationship was also found between the diffracting point density and the EM velocity, and was used to indicate the ice content in the Rock Glacier. The fraction of ice in the Rock Glacier was estimated to vary between 0.22 and 0.83, with an average of 0.66; these results were tested by recalculation of the EM velocity. The relationships between Rock Glacier development and glacial processes are questioned. Copyright © 2015 John Wiley & Sons, Ltd.
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reconsidering the Glacier to Rock Glacier transformation problem new insights from the central andes of chile
Geomorphology, 2015Co-Authors: Sebastien Monnier, Christophe KinnardAbstract:Abstract The Glacier to Rock Glacier transformation problem is revisited from a previously unseen angle. A striking case in the Juncal Massif (located in the upper Aconcagua Valley, Chilean central Andes) is documented. There, the Presenteseracae debris-covered Glacier has advanced several tens of metres and has developed a Rock Glacier morphology in its lower part over the last 60 years. The conditions for a theoretically valid Glacier to Rock Glacier transformation are discussed and tested. Permafrost probability in the area of the studied feature is highlighted by regional-scale spatial modelling together with on-site shallow ground temperature records. Two different methods are used to estimate the mean surface temperature during the summer of 2014, and the sub-debris ice ablation rates are calculated as ranging between 0.05 and 0.19 cm d− 1, i.e., 0.04 and 0.17 m over the summer. These low ablation rates are consistent with the development of a coherent surface morphology over the last 60 years. Furthermore, the rates of Rock wall retreat required for covering the former Glacier at Presenteseracae lie within the common 0.1–2 mm y− 1 range, assuming an average debris thickness and a range of debris-covering time intervals. The integration of the geomorphological observations with the numerical results confirms that the studied debris-covered Glacier is evolving into a Rock Glacier.
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internal structure and composition of a Rock Glacier in the andes upper choapa valley chile using borehole information and ground penetrating radar
Annals of Glaciology, 2013Co-Authors: Sebastien Monnier, Christophe KinnardAbstract:This study uses boreholes, ground temperature monitoring and ground-penetrating radar (GPR) in order to understand the internal structure and composition of a Rock Glacier in the upper Choapa valley, northern Chile. The Rock Glacier is a small valley-side feature, 200 m long and ranging between 3710 and 3780 m a.s.l. Two boreholes were drilled down to depths of 20 and 25 m, respectively, using the diamond drillhole technique. An ice-Rock mixture was encountered in the boreholes, with heterogeneous ice content averaging 15-30%. Data from common-midpoint (CMP) and constant-offset (CO) GPR surveys acquired, respectively, near the boreholes and across the whole Rock Glacier were processed to highlight the internal stratigraphy and variations in the radar-wave velocity. The GPR profiles depict a Rock Glacier constituted of stacked and generally concordant layers, with a thickness ranging from 10 m in its upper part to � 30 m towards its terminus. The CMP analysis highlights radar- wave velocities of 0.13-0.16 m ns -1 in the first 20 m of the structure. Larger vertical and lateral velocity variations are highlighted from CO data, reflecting the heterogeneous composition of the Rock Glacier and the likely presence of unfrozen water in the structure. Given the average air temperature registered at the site (+0.58C), the near-melting-point temperature registered in the boreholes over more than a year and the presence of locally high water content inferred from GPR data, it is thought that the permafrost in the Rock Glacier is currently degrading.
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Structure and genesis of the Thabor Rock Glacier (Northern French Alps) determined from morphological and ground-penetrating radar surveys
Geomorphology, 2011Co-Authors: Sebastien Monnier, Christophe Kinnard, Christian Camerlynck, Fayçal Rejiba, Thierry Feuillet, Amine DhemaiedAbstract:Landform analysis and ground-penetrating radar (GPR) were used to investigate the Thabor Rock Glacier, in the Northern French Alps. The surface features of the Rock Glacier were classified and described, with emphasis on massive ice exposures. The retreat of the former Thabor Glacier since the Little Ice Age (LIA) was documented through an analysis of historical sources, and recent movements of the Rock Glacier were inferred from orthophoto-based measurements. Two-dimensional (2-D) models of the radar wave velocity were derived from the raw GPR data, using the numerous diffraction hyperbolae for local determinations of the velocity and kriging interpolation techniques. Subsequently, the profiles were migrated through a 2-D Kirchhoff migration method using the interpolated velocities. The 2-D velocity models exhibit pronounced spatial variations and, in several locations, high values (> 0.15 m ns−1) potentially corresponding to massive ice. On the other hand, while the migrated profiles show numerous layers, the internal stratigraphy of the Rock Glacier is dominated by a few prominent internal boundaries. The integration of morphology, radar wave velocity, and internal stratigraphy allowed us to identify the main structural units of the Rock Glacier as well as to explain its genesis: the Rock Glacier was formed by the imbrication of a massive ice core, originating from the retreat of the former Thabor Glacier since the LIA, into pre-existing glacial deposits.
Emmanuel Thibert - One of the best experts on this subject based on the ideXlab platform.
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analysis of the mechanical behavior of the laurichard Rock Glacier french alps in the recent climatic changes
International Conference of the International Association for Computer Methods and Advances in Geomechanics, 2021Co-Authors: Samia Melki, Xavier Bodin, Dominique Daudon, Emmanuel ThibertAbstract:In mountain areas, Rock Glaciers are markers of climate change. Besides temperature effect, their surface flow velocity can be influenced by ice proportion and other mechanical and physical properties. To improve the understanding of the processes influencing thermal control and the seasonal and inter-annual variations, this study on the Laurichard Rock Glacier in France proposes the analysis of correlations between surface velocity variations and air temperature anomalies based on Staub et al. (2015), and evaluates the viscosity using surface velocities with steady shear flow hypothesis (Monnier et al. 2016) over 30 years of measurements.
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multi annual kinematics of an active Rock Glacier quantified from very high resolution dems an application case in the french alps
Remote Sensing, 2018Co-Authors: Xavier Bodin, Emmanuel Thibert, Antoine Rabatel, Olivier Sanchez, Stephane JailletAbstract: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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multi annual kinematics of an active Rock Glacier quantified from very high resolution dems an application case in the french alps
Remote Sensing, 2018Co-Authors: Xavier Bodin, Emmanuel Thibert, Antoine Rabatel, Olivier Sanchez, Stephane JailletAbstract: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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multi temporal mapping of Rock Glacier displacements insights from sfm als and tls high resolution datasets on the laurichard Rock
11th International Conference on Permafrost., 2016Co-Authors: Xavier Bodin, Stephane Jaillet, Antoine Rabatel, Olivier Sanchez, Emmanuel ThibertAbstract:The deformation of Rock Glaciers is a climate-dependent process which affects many mountain debris slopes underlain with ice-rich permafrost (Haeberli et al., 2006). Under temperate conditions, like in the Alps, the typical magnitude of movement is in the order of a few dm/a to 1-2 m/a (Barsch, 1996). However, recent measurements of accelerating Rock Glaciers show that velocity can increase up to several m/a (Delaloye et al., 2012). This kinematics variability can locally lead to slope instabilities and trigger hazardous phenomena: in France, the collapse of the Berard Rock Glacier in 2006 (Bodin et al., 2016) and the debris-flow that started at the Lou Rock Glacier in 2015 (Paulhe et al., 2015) can be considered as two events that exemplify the possible impacts of permafrost degradation for human societies living in mountain territories. At the limit between the Northern and the Southern-more Mediterranean-influenced-French Alps, the Laurichard Rock Glacier benefits from a long-term monitoring since the early 80's (Francou & Reynaud, 1992). Using 30-year long annual geodetic surveys of blocks, we detected inter-annual fluctuations of velocity (Bodin et al., 2009), which synchronicity with many series on other surveyed Rock Glaciers in the Alps suggests that the atmospheric warming, modulated by the nivological conditions, is controlling the Rock Glacier deformation rates (Delaloye et al., 2012). Nevertheless the knowledge on the processes that govern such behavior is still lacking physical basis: a better understanding requires to model the geomechanics of Rock Glacier, and for that accurate multi-temporal maps of surface displacements are fundamental. For that purpose, we produced very high-resolution 3D models of the Laurichard Rock Glacier, acquired either by terrestrial laserscanning (TLS) in 2005, 2006, 2011 and 2013, airborne laserscanning (ALS) in 2012 and terrestrial photogrammetry (or structure-from-motion, SfM) in 2013 and 2015. The density of the generated point clouds we generated varies from 2 pt/m² to 20 pt/m² and the accuracy of the coordinates after co-registration between the different datasets (2012 ALS dataset chosen as the reference) is in the order of 12-15 cm (standard error computed on stable areas). The main challenges for correct topographic mapping arose from the multi-scale variability: microtopographic features like plurimetric ridges and furrows shield some areas from the laser, whereas surface roughness of the pluri-decimetric coarse blocky cover may be difficult to cope with when comparing point-clouds between each other's. We employed 3D point-cloud processing and image correlation tools to compare high resolution hillshaded digital elevation models together and to extract various spatially-distributed measurements of surface movements. Both amplitude and direction of the displacements computed by images correlation were validated from comparison to in situ high precision geodetic (milimetric accuracy) measurements: at the various considered time scales and for 8 measured points, the mean difference between TLS/ALS /SfM-derived measurements and geodetics measurements is lower than 5 cm/a, for velocity that range between 25 and 150 cm/a. The spatially-distributed information provides rich insights into the deformation mechanisms of Rock Glaciers and open new challenging opportunities to move further into rheological laws and physical models. The ongoing next step of this work will consist in extracting 3D point-clouds from two fixed cameras surveying the Laurichard Rock Glacier, which will soon give access to higher resolutions, in both space and time dimensions.
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two decades of responses 1986 2006 to climate by the laurichard Rock Glacier french alps
Permafrost and Periglacial Processes, 2009Co-Authors: Xavier Bodin, Emmanuel Thibert, Adriano Ribolini, Philippe Schoeneich, Denis Fabre, Bernard Francou, Louis Reynaud, Monique FortAbstract:The Laurichard active Rock Glacier is the permafrost-related landform with the longest record of monitoring in France, including an annual geodetic survey, repeated geoelectrical campaigns from 1979 onwards and continuous recording of ground temperature since 2003. These data were used to examine changes in creep rates and internal structure from 1986 to 2006. The control that climatic variables exert on Rock Glacier kinematics was investigated over three time scales. Between the 1980s and the early 2000s, the main observed changes were a general increase in surface velocity and a decrease in internal resistivity. At a multi-year scale, the high correlation between surface movement and snow thickness in the preceding December appears to confirm the importance of snow cover conditions in early winter through their influence on the ground thermal regime. A comparison of surface velocities, regional climatic datasets and ground sub-surface temperatures over six years suggests a strong relation between Rock Glacier deformation and ground temperature, as well as a role for liquid water due to melt of thick snow cover. Finally, unusual surface lowering that accompanied peak velocities in 2004 may be due to a general thaw of the top of the permafrost, probably caused both by two successive snowy winters and by high energy inputs during the warm summer of 2003. Copyright # 2009 John Wiley & Sons, Ltd.
Jan Beutel - One of the best experts on this subject based on the ideXlab platform.
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how Rock Glacier hydrology deformation velocities and ground temperatures interact examples from the swiss alps
Permafrost and Periglacial Processes, 2020Co-Authors: Robert Kenner, Jan Beutel, Luisa Pruessner, Philippe Limpach, Marcia PhillipsAbstract:An increasing number of studies highlight the controlling influence of water on Rock Glacier deformation velocities. The link between the concept of water‐driven shearing processes and numerous observations of correlating mean annual air or ground temperatures and Rock Glacier velocities is discussed here. We present a dataset measured at the Schafberg Rock Glacier in the Eastern Swiss Alps, complemented by temperature data from three other Rock Glaciers in the Swiss Alps, which allowed us to reconstruct the processes influencing both mean annual ground temperatures and Rock Glacier deformation velocity. Rock Glacier hydrology is the parameter linking Rock Glacier temperature and velocities and is a crucial influencing factor. The main external forcing parameter appart from mean annual air temperature is early winter snow coverage. The study shows that the concept of water being a controlling factor for Rock Glacier velocity is no contradiction to the observed correlations between air or ground temperature and Rock Glacier deformation.
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water controls the seasonal rhythm of Rock Glacier flow
Earth and Planetary Science Letters, 2019Co-Authors: Alessandro Cicoira, Jan Beutel, Jerome Faillettaz, Andreas VieliAbstract:Abstract Rock Glaciers are creeping periglacial landforms experiencing strong acceleration during recent atmospheric warming and raising concerns with regard to their future behaviour and stability. High resolution kinematic observations show strong seasonal and multi-annual variations in Rock Glacier creep, but the linking mechanisms to environmental forcing remain poorly understood and lack quantitative models. Here we investigate the interaction between Rock Glacier creep and climatic forcing - temperature and precipitation - by developing a novel conceptual and numerical modelling approach. The model is constrained and the results are compared with data from the Dirru Rock Glacier (Vallis - CH). We are able to reproduce the observed velocity variations both in magnitude and phase on seasonal and inter-annual time scales. We find that water from liquid precipitation and snow melt, rather than air temperature, is the main driver of variations in Rock Glacier creep. Our results imply that the influence of water on Rock Glacier creep is fundamental and must be considered when investigating the historic and future evolution of Rock Glaciers.
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towards early warning of gravitational slope failure with co detection of microseismic activity the case of an active Rock Glacier
Natural Hazards and Earth System Sciences, 2019Co-Authors: Jerome Faillettaz, Jan Beutel, Martin Funk, Andreas VieliAbstract:Abstract. We developed a new strategy for disaster risk reduction for gravitational slope failure: we propose validating on a case study a simple method for real-time early warning of gravity-driven failures that considers and exploits both the heterogeneity of natural media and characteristics of acoustic emissions attenuation. This method capitalizes on co-detection of elastic waves emanating from micro-cracks by a network of multiple and spatially distributed sensors. Event co-detection is considered to be surrogate for large event size with more frequent co-detected events marking imminence of catastrophic failure. In this study we apply this general method to a steep active Rock Glacier, a natural heterogeneous material sharing all relevant properties of gravitational slope failure, and demonstrate the potential of this simple strategy for real world cases, i.e., at slope scale. This new strategy being theoretically valid for all types of failures, it constitutes a first step towards the development of a new early warning system for gravitational slope failure.
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resolving the influence of temperature forcing through heat conduction on Rock Glacier dynamics a numerical modelling approach
The Cryosphere, 2019Co-Authors: Alessandro Cicoira, Jan Beutel, Jerome Faillettaz, Isabelle Gartnerroer, Andreas VieliAbstract:Abstract. In recent years, observations have highlighted seasonal and interannual variability in Rock Glacier flow. Temperature forcing, through heat conduction, has been proposed as one of the key processes to explain these variations in kinematics. However, this mechanism has not yet been quantitatively assessed against real-world data. We present a 1-D numerical modelling approach that couples heat conduction to an empirically derived creep model for ice-rich frozen soils. We use this model to investigate the effect of thermal heat conduction on seasonal and interannual variability in Rock Glacier flow velocity. We compare the model results with borehole temperature data and surface velocity measurements from the PERMOS and PermaSense monitoring network available for the Swiss Alps. We further conduct a model sensitivity analysis in order to resolve the importance of the different model parameters. Using the prescribed empirically derived rheology and observed near-surface temperatures, we are able to model the correct order of magnitude of creep. However, both interannual and seasonal variability are underestimated by an order of magnitude, implying that heat conduction alone cannot explain the observed variations. Therefore, we conclude that non-conductive processes, likely linked to water availability, must dominate the short-term velocity signal.
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monitoring mass movements using georeferenced time lapse photography ritigraben Rock Glacier western swiss alps
Cold Regions Science and Technology, 2018Co-Authors: Robert Kenner, Jan Beutel, Philippe Limpach, Marcia Phillips, Martin HillerAbstract:Abstract An automatic method was developed to monitor Rock Glacier kinematics. Displacements derived from monoscopic time-lapse images were scaled and projected into the Swiss Coordinate System CH1903. We tested this method at the front of the rapidly creeping Ritigraben Rock Glacier, where time-lapse pictures of the Rock Glacier front were taken by an automatic camera with a temporal resolution of 3 h. The images were automatically processed using a Matlab algorithm. The output data were spatially resolved creep velocities between successive images and mean relative velocities over time. The digital elevation model used for the projection of the time-lapse data was acquired using terrestrial laser scanning (TLS). The resulting horizontal displacement velocities and accelerations were validated against GPS data measured at one point on the Rock Glacier front. The high temporal resolution of the time-lapse image velocities provided new insights on the kinematics of the Rock Glacier front, which could not have been discerned with the GPS or TLS measurements applied. The Ritigraben study site is particularly suitable for our approach due to the temporally constant movement directions. Snow coverage and fog are disturbing factors which can lead to failure of the method.
