Permafrost investigation in the Mont Blanc massif steep rock walls: a combined measurement, modelling and geophysical approach
Poster The steep rockwalls of the Mont Blanc massif have been affected by an increase in rockfall activity in the last decades. Permafrost degradation is suggested as the most likely triggering factor. To better understand geomorphic processes we investigate permafrost distribution and address quest...
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ftccsdartic:oai:HAL:halsde-01023167v1 2023-05-15T17:56:12+02:00 Permafrost investigation in the Mont Blanc massif steep rock walls: a combined measurement, modelling and geophysical approach Magnin, Florence Deline, Philip Ravanel, Ludovic Gruber, Stephan Krautblatter, Michael Environnements, Dynamiques et Territoires de la Montagne (EDYTEM) Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS) Glaciology, Geomorphodynamics and Geochronology Department of Geography Zürich Universität Zürich Zürich (UZH)-Universität Zürich Zürich (UZH) Geographisches Institut Rheinische Friedrich-Wilhelms-Universität Bonn Vienne, Austria 2014 https://hal.archives-ouvertes.fr/halsde-01023167 en eng HAL CCSD halsde-01023167 https://hal.archives-ouvertes.fr/halsde-01023167 EGU 2014 https://hal.archives-ouvertes.fr/halsde-01023167 EGU 2014, 2014, Vienne, Austria [SDE]Environmental Sciences info:eu-repo/semantics/conferenceObject Conference papers 2014 ftccsdartic 2021-12-26T00:16:02Z Poster The steep rockwalls of the Mont Blanc massif have been affected by an increase in rockfall activity in the last decades. Permafrost degradation is suggested as the most likely triggering factor. To better understand geomorphic processes we investigate permafrost distribution and address questions on its pattern in steep alpine bedrock. We use GIS-modeling to simulate Mean Annual Rock Surface Temperature (MARST) distribution. Rock temperature measurements including three 10-m-deep borehole monitoring at the Aiguille du Midi (AdM, 3842 m a.s.l) serve to estimate the temperature offset (i.e. temperature difference between rock surface and depth of negligible inter-annual temperature varibility). The estimation of the lower extent of permafrost distribution is derived from a combination of both approaches and hypotheses on permafrost occurrence are evaluated with Electrical Resistivity Tomography (ERT) measurements. The MARST model indicates that the 0 °C isotherm extends down to 2600 m a.s.l in the most shaded faces and rises up to 3800 m in the most sun-exposed areas. According to recent literature and the AdM borehole thermal profiles, we postulate that permafrost could extends down below MARST reaching up to 3°C due to temperature offset processes. ERT measurements performed along 160-m-long profiles at six different sites which the top are located from 3360 m a.s.l to 2760 m a.s.l and the MARST range from <-1°C to > 3°C are the first of this kind. Five of sites are located in the granite area making them directly comparable. They all show high resistivity values at depth (>200 k) interpreted as permafrost bodies. Lower resistivity values (< 90 k ) are found either above the high resistivity bodies and interpreted as thawed active layer, or below MARST warmer than 2-3°C and interpreted as non-perenially frozen rock. Two sites were measured in autumn 2012 and autumn 2013 allowing for time-lapse investigation which demonstrates the change in resistivity in repeated measurements. These ... Conference Object permafrost Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Mont Blanc ENVELOPE(69.468,69.468,-49.461,-49.461) |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
[SDE]Environmental Sciences |
spellingShingle |
[SDE]Environmental Sciences Magnin, Florence Deline, Philip Ravanel, Ludovic Gruber, Stephan Krautblatter, Michael Permafrost investigation in the Mont Blanc massif steep rock walls: a combined measurement, modelling and geophysical approach |
topic_facet |
[SDE]Environmental Sciences |
description |
Poster The steep rockwalls of the Mont Blanc massif have been affected by an increase in rockfall activity in the last decades. Permafrost degradation is suggested as the most likely triggering factor. To better understand geomorphic processes we investigate permafrost distribution and address questions on its pattern in steep alpine bedrock. We use GIS-modeling to simulate Mean Annual Rock Surface Temperature (MARST) distribution. Rock temperature measurements including three 10-m-deep borehole monitoring at the Aiguille du Midi (AdM, 3842 m a.s.l) serve to estimate the temperature offset (i.e. temperature difference between rock surface and depth of negligible inter-annual temperature varibility). The estimation of the lower extent of permafrost distribution is derived from a combination of both approaches and hypotheses on permafrost occurrence are evaluated with Electrical Resistivity Tomography (ERT) measurements. The MARST model indicates that the 0 °C isotherm extends down to 2600 m a.s.l in the most shaded faces and rises up to 3800 m in the most sun-exposed areas. According to recent literature and the AdM borehole thermal profiles, we postulate that permafrost could extends down below MARST reaching up to 3°C due to temperature offset processes. ERT measurements performed along 160-m-long profiles at six different sites which the top are located from 3360 m a.s.l to 2760 m a.s.l and the MARST range from <-1°C to > 3°C are the first of this kind. Five of sites are located in the granite area making them directly comparable. They all show high resistivity values at depth (>200 k) interpreted as permafrost bodies. Lower resistivity values (< 90 k ) are found either above the high resistivity bodies and interpreted as thawed active layer, or below MARST warmer than 2-3°C and interpreted as non-perenially frozen rock. Two sites were measured in autumn 2012 and autumn 2013 allowing for time-lapse investigation which demonstrates the change in resistivity in repeated measurements. These ... |
author2 |
Environnements, Dynamiques et Territoires de la Montagne (EDYTEM) Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS) Glaciology, Geomorphodynamics and Geochronology Department of Geography Zürich Universität Zürich Zürich (UZH)-Universität Zürich Zürich (UZH) Geographisches Institut Rheinische Friedrich-Wilhelms-Universität Bonn |
format |
Conference Object |
author |
Magnin, Florence Deline, Philip Ravanel, Ludovic Gruber, Stephan Krautblatter, Michael |
author_facet |
Magnin, Florence Deline, Philip Ravanel, Ludovic Gruber, Stephan Krautblatter, Michael |
author_sort |
Magnin, Florence |
title |
Permafrost investigation in the Mont Blanc massif steep rock walls: a combined measurement, modelling and geophysical approach |
title_short |
Permafrost investigation in the Mont Blanc massif steep rock walls: a combined measurement, modelling and geophysical approach |
title_full |
Permafrost investigation in the Mont Blanc massif steep rock walls: a combined measurement, modelling and geophysical approach |
title_fullStr |
Permafrost investigation in the Mont Blanc massif steep rock walls: a combined measurement, modelling and geophysical approach |
title_full_unstemmed |
Permafrost investigation in the Mont Blanc massif steep rock walls: a combined measurement, modelling and geophysical approach |
title_sort |
permafrost investigation in the mont blanc massif steep rock walls: a combined measurement, modelling and geophysical approach |
publisher |
HAL CCSD |
publishDate |
2014 |
url |
https://hal.archives-ouvertes.fr/halsde-01023167 |
op_coverage |
Vienne, Austria |
long_lat |
ENVELOPE(69.468,69.468,-49.461,-49.461) |
geographic |
Mont Blanc |
geographic_facet |
Mont Blanc |
genre |
permafrost |
genre_facet |
permafrost |
op_source |
EGU 2014 https://hal.archives-ouvertes.fr/halsde-01023167 EGU 2014, 2014, Vienne, Austria |
op_relation |
halsde-01023167 https://hal.archives-ouvertes.fr/halsde-01023167 |
_version_ |
1766164302174093312 |