Relations entre surface océanique et composition isotopique des précipitations antarctiques : simulation pour différents climats

• Main Author: Delaygue, Gilles
• Other Authors: Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de droit, d'économie et des sciences - Aix-Marseille III, Bard Edouard
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2000
• Subjects: modélisation; géochimie isotopique; relation isotope-salinité; thermomètre isotopique; Antarctique; paléoclimat; [SDU.OTHER]Sciences of the Universe [physics]/Other; Antarctic; The Antarctic; Vidal; Antarc*; Antarctique*
• Online Access: https://theses.hal.science/tel-00002821; https://theses.hal.science/tel-00002821/document; https://theses.hal.science/tel-00002821/file/tel-00002821.pdf

Dr Gavin SCHMIDT Pr Laurent LABEYRIE Dr Laurence VIDAL Dr Christophe GENTHON Dr Jean JOUZEL Pr Edouard BARD Interactions between ocean temperature and isotopic content of Antarctic precipitation are studied with the help of a General Circulation Model (GCM), by distinguishing different geographic sources for the precipitation. The contribution of these sources is estimated for modern as well as glacial (21,000 years ago) climatic conditions. Climatic variations arose from the ocean cooling and the intensification of the meridional gradient of temperature. We have tried different reconstructions of tropical ocean temperatures, which are not well constrained for glacial time, and the source contributions are found quite sensitive to this parameter. For the high latitudes, the isotopic content of precipitation, originating from different sources, are related to the source temperature and its distance to the precipitation site. Contrary to the idea developped by Boyle (1997), a global cooling is not susceptible to bias the classical interpretation of isotopes as paleothermometer, because this cooling is compensated for, in our simulations, by a stronger contribution from the warmer sources. The oceanic field of oxygen-18 is simulated with an ocean GCM, by prescribing at the surface isotopic fluxes derived from the atmospheric GCM. The same fluxes are used to simulate a 'passive' salinity field, consistent with the oxygen-18. The observed features of both fields, as well as their relationships, are well simulated. This modelling allows us to study the sensitivity of their relationships to the surface fluxes, esp. to the continental runoff. The importance of horizontal mixing is estimated by comparing the GCM fields with a box model of the ocean. We also estimate the sensitivity of the deuterium-excess in the Antarctic precipitation to the oceanic temperature, humidity, and isotopic content. L'interaction entre la température des océans et la teneur isotopique des précipitations antarctiques est étudiée à l'aide ...