Snow of the Antarctica's plateau. Specific surface area and applications.

Snow is the most reflective surface on Earth and its presence on vast expanses such as Antarctica considerably impacts the climate of the Earth. Snow albedo depends on its physical properties, and particularly on its specific surface area i.e. the surface area of this porous medium that is accessibl...

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Bibliographic Details
Main Author: Gallet, Jean-Charles
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 Domine(florent@lgge.obs.ujf-grenoble.fr)
Format: Doctoral or Postdoctoral Thesis
Language:French
Published: HAL CCSD 2010
Subjects:
Online Access:https://theses.hal.science/tel-00536162
https://theses.hal.science/tel-00536162/document
https://theses.hal.science/tel-00536162/file/Thesis_Gallet-2010.pdf
Description
Summary:Snow is the most reflective surface on Earth and its presence on vast expanses such as Antarctica considerably impacts the climate of the Earth. Snow albedo depends on its physical properties, and particularly on its specific surface area i.e. the surface area of this porous medium that is accessible to gases, per unit mass. The specific surface area (SSA) is also an important variable for the chemistry of atmosphere-snow interactions, because it allows the quantification of adsorbed gases. However, for lack of simple methods to measure it, the SSA of Antarctic snow has been little studied. One of the objectives of this study was to design and build a novel experimental apparatus to measure snow SSA from its infrared reflectance. This apparatus allows the rapid measurement of snow SSA, with an accuracy of 10 % and it is simple to operate in hostile polar conditions. We have performed the first SSA measurements of the surface snow on the Antarctic plateau, at Dome C (DC) and on the traverse between DC and the coastal base Dumont D'Urville (DDU). These measurements took place in pits about 1 m deep. Daily variations of snow SSA were also studied. Our data indicate that snow physical properties are heterogeneous at a scale of several meters on the Antarctic plateau, because accumulation is very low and wind remobilizes surface snow, and redistributes it in discontinuous layers. Heterogeneities were also observed between DC and DDU, in particular because of the increase in wind speed closer to the coast. At the diurnal time scale, SSA variations observed for the top two centimetres of the snow are explained by the formation of surface hoar at night and of sublimation crystals during the day. These measurements allowed the calculation of snow albedo on the Antarctic plateau and its diurnal variations. A preliminary comparison of the calculated albedos with satellite measurements show an encouraging agreement, and lead to the conclusion that the determination of snow SSA from space can be envisaged with optimism. La ...