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Dynamique climatique de l'océan Pacifique ouest équatorial au cours du Pléistocène récent

Abstract : The western equatorial Pacific warm pool (WPWP), warmest ocean area of the globe, fuels the meridian monsoon and zonal Walker atmospheric circulation cells. Using planktonic foraminifera assemblages, stable isotope geochemistry and morphometry, and coccolithophorids assemblages, we investigated past climate dynamics of this area during the Late Pleistocene. We developped a new planktonic foraminifera transfer function which is not biased by the ecosystem structure like was the CLIMAP study. Using this method, the last 185 kyrs SSTs in the WPWP oscillated between 27 and 29.5°C, in agreement with alkenones estimates. The “deep” atmospheric convection over the WPWP was thus a stable feature of the Late Pleistocene climate. These temperatures appear to be modulated by the precession cycles which also force a rocking of the Indo-Pacific thermocline, following an “El Niño-Southern Oscillation-like” mechanism. At millenial time-scale, the high-latitudes Dansgaard-Oeschger cycles were find in past changes in East Asian winter monsoon strength from the northern edge of the WPWP. A 1500 yrs cycle imprints this monsoon record, which is not ice volume modulated, and thus not driven by some high-latitude process. A potential climatic feedback is attributed to thermal dissociation of methane gas-hydrates from low-latitude sedimentary margins. Indeed, a high-resolution of carbon isotopic changes in the WPWP, exhibits the occurrence of large methane gas-hydrates releases during the last glacial stage.
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Contributor : Thibault de Garidel-Thoron <>
Submitted on : Saturday, April 2, 2005 - 3:17:30 AM
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Thibault de Garidel-Thoron. Dynamique climatique de l'océan Pacifique ouest équatorial au cours du Pléistocène récent. Géologie appliquée. Université de droit, d'économie et des sciences - Aix-Marseille III, 2002. Français. ⟨tel-00008934⟩



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