Volume and frequency of ice avalanches from Taconnaz hanging glacier, French Alps

• Published in: Annals of Glaciology
• Main Authors: Vincent, C., Thibert, Emmanuel, Härter, M., Soruco, A., Gilbert, A.
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Erosion torrentielle neige et avalanches (UR ETGR (ETNA)), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), UNIVERSITY OF MAYOR SAN ANDRES LA PAZ BOL, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), GlaRiskAlp Alcotra Programme, AQWA European Programme : 212250
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: GLACIER HAZARDS; GLACIOLOGICAL INSTRUMENTS AND METHODS; MOUNTAIN GLACIERS; GLACIOLOGICAL NATURAL HAZARDS; TACONNAZ; [SDE]Environmental Sciences; Annals of Glaciology
• Online Access: https://hal.inrae.fr/hal-02602992; https://hal.inrae.fr/hal-02602992/document; https://hal.inrae.fr/hal-02602992/file/volume-and-frequency-of-ice-avalanches-from-taconnaz-hanging-glacier-french-alps.pdf; https://doi.org/10.3189/2015AoG70A017

International audience Very large volumes of ice break off regularly from Taconnaz hanging glacier, French Alps. During winter, when the snow mantle is unstable, these collapses can trigger very large avalanches that represent a serious threat to inhabited areas below. Photogrammetric measurements have been performed over 1 year to assess the volume and frequency of the largest collapses. Major collapses occur when the glacier reaches a critical geometry. After a major ice collapse, the glacier is in a minimal position and subsequently recharges over 6 months to reach the maximum position again. This critical geometry is a necessary but not sufficient condition for further large collapses. Large collapses do not systematically occur in the maximum position, as ice is often removed by disintegration into small ice blocks. For two major collapses, the volume of ice breaking off has been assessed at,similar to 275 000 m(3). Photogrammetric measurements were used to determine an ice flux of 820 000 m(3) a(-1) through the studied ice stream, in agreement with an assessment based on ice-flow modeling. This ice flux estimation was used to determine the average ice volumes breaking off over surveyed periods.