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Reconstitution de la variabilité climatique du littoral fluminense (Rio de janeiro, Brésil) au cours de l'holocène par l'étude de bio-indicateurs (diatomées, coccolithophoridés)

Abstract : Even though located in the humid tropical zone, the Fluminense coastline (23°S- 43°W, Rio de Janeiro, Brazil) exhibits an aridity gradient decreasing from east to west. This anomaly is due to a local upwelling in the east controlled by wind patterns. Physico-chemical characteristics of the lagoons of this coastline depend on the aridity gradient. They record the hydro-climatic variability generated by the upwelling. Lagoonal records collected in two lagoons (Brejo do Espinho and Padre) located respectively in- and out- of the upwelling influenced area and a marine record from the upwelling area are studied. Lagoonal hydroclimatological variability is deduced from the study of diatom assemblages coupled with salinity variations inferred by a diatom/salinity transfer function. This transfer function is based on a modern calibrated diatom model of lagoonal environments along the aridity gradient. Variability in the upwelling intensity is inferred by the primary productivity in the upwelling zone based on coccolith assemblages. A comparison of lagoonal and marine records, taking into account sea level fluctuations during the Holocene, evidences changes in the upwelling strength and in wind patterns on the Fluminense coastline. The influence of El Niño events, polar fronts position and ITCZ migration could explain these changes.
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Submitted on : Wednesday, December 10, 2008 - 11:03:24 AM
Last modification on : Wednesday, June 17, 2020 - 6:06:02 PM
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  • HAL Id : tel-00345840, version 1

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Bérengère Laslandes. Reconstitution de la variabilité climatique du littoral fluminense (Rio de janeiro, Brésil) au cours de l'holocène par l'étude de bio-indicateurs (diatomées, coccolithophoridés). Sciences de la Terre. Université d'Angers, 2007. Français. ⟨tel-00345840⟩

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