Microstructure, recristallisation et déformation des glaces polaires de la carotte EPICA, Dôme Concordia, Antarctique

• Main Author: Durand, Gaël
• 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, Jérome Weiss
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2004
• Subjects: carottes de glace; European Project for Ice Coring in Antarctica; Dôme Concordia; microstructure grain; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Antarc*; Antarctica; Antarctique*; EPICA; ice core
• Online Access: https://theses.hal.science/tel-00701364; https://theses.hal.science/tel-00701364/document; https://theses.hal.science/tel-00701364/file/These-Durand-2004-1.pdf

Ice cores are a fantastic tool to study the past climate of our planet. Recently, the European Project for Ice Coring in Antarctica (EPICA) allowed to extract the Dome Concordia ice core (75◦06′ S; 123◦21′ E). The first studies show that the last 740000 years of our climatic history are recorded. In this manuscript, a study on the microstructure (grain boundaries network) evolution along the Dome concordia ice core is presented. In a first part, we study the mean grain size evolution along the core which is showing sharp variations during climatic transitions. The analysis of the grain size distribution parameters as well as correlations between mean grain size and impurities content show that the dust particles decrease the normal grain growth rate during Glacial period. This can explain the observed grain size variations. The development of a mean field approximation model, which is able to calculate the mean grain size evolution, confirms quantitatively this result. It allows also to study the role of bubbles, clathrates and rotation recrystallization on the mean grain size. The geometry of the microstructure can also reveal the deformation of the ice layers. From a procedure developed initially to measure the deformation field of foams and which has been adapted to ice, we show that our measurements contradict two classical assumptions used to describe the ice deformation at a dome: (i) shearing is present and its value increases with depth, (ii) the vertical deformation is not homogeneous (some layers are more deformed than their neighbours). Classical glaciological dating models use these assumptions, therefore opening some questions on their validity. Then, we examine the impact of the vertical deformation heterogeneities on the dating. Particularely, we focus on the determination of the duration of brief events. Les carottes de glace sont un fantastique outil d'étude du climat de notre planète. Récemment, le projet européen EPICA (European Project for Ice Coring in Antarctica) a permis d'extraire une ...