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

Abstract : 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.
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https://tel.archives-ouvertes.fr/tel-00002821
Contributor : Gilles Delaygue <>
Submitted on : Wednesday, May 14, 2003 - 9:25:04 PM
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Gilles Delaygue. Relations entre surface océanique et composition isotopique des précipitations antarctiques : simulation pour différents climats. Autre. Université de droit, d'économie et des sciences - Aix-Marseille III, 2000. Français. ⟨tel-00002821⟩

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