Microphysique du manteau neigeux : évolution de la surface spécifique de la neige dans les Alpes et l'Antarctique

• Main Author: Cabanes, Axel
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), 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 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)-Centre National de la Recherche Scientifique (CNRS), Université Joseph-Fourier - Grenoble I, Florent Dominé
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2002
• Subjects: neige; gaz traces; atmosphère; sublimation/condensation; Alpes; Arctique; surface spécifique; métamorphisme; microphysique; manteua neigeux; méthane; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Arctic; Arctique*
• Online Access: https://theses.hal.science/tel-00705165; https://theses.hal.science/tel-00705165/document; https://theses.hal.science/tel-00705165/file/These-Cabanes-2002.pdf

Snow covers up to 50% of land masses in the northern hemisphere in winter and its potential for interaction with the atmosphere has been demonstrated by studies in Polar Regions. This can proceed by complex processes that include heterogeneous reactions on the snow surface, adsorption/ desorption of gases, sublimation of snow and its solutes and co-condensation of water vapor and other gases. Understanding and quantifying theses processes requires the knowledge of physical parameters among which the specifie surface area (SSA) of snow. It represents the surface area accessible to gases per mass unit. ln spite of the Importance of this parameter, few data have been obtalned earlier, which led us to perform this study on the SSA of snow and its evolution ln the snowpack. SSA was measured by methane adsorption at liquid nltrogen temperature (77K). In order to understand processes involved ln SSA evolution, photomacrographs and plctures obtained by scanning electronic microscopy were used. SSA values obtained were in the range 1540 to 400 cm2/g for fresh snow. Values decrease down to 100 cm2/g for aged snow. This decrease results from morphological changes associated to snow metamorphism. Temperature and wind are the main factors which drive the kinetics of SSA decrease. At AJert (Canadian Arctic), a detailed study of the microphysics of the snowpack allowed the measurement of the uptake capaclty of adsorbable trace gases by the snowpack. The total surface area of the snowpack ranged from 1160 to 3710 m2/m2. Therefore, we demonstrated that snowpack may sequester most of the species in the (snow + boundary layer) system. SSA values were also used to determinate incorporation pro cesses of formaldehyde in snow. La neige recouvre jusqu'à 50 % des surfaces émergées de l'hémisphère Nord en hiver. Une telle importance de la glace à la surface de la terre suggère un fort potentiel d'interaction avec l'atmosphère. De telles interactions ont été mises en évidence ces dernières années, et impliquent des processus complexes, ...