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Accueil > Recherche > Thèses / HDR > Thèses en cours

ZHOU Xinquan

Projet de thèse en Météorologie, océanographie, physique de l’environnement
Ecole doctorale : Sciences Mécaniques et Energétiques, Matériaux, Géosciences (SMEMaG)
Financement : China Scholarship Council (CSC)
Sujet : Variabilité de la mousson Indo-Asiatique et son impact sur la productivité primaire depuis le Dernier Maximum Glaciaire : des processus locaux aux processus globaux
Directeur de thèse : Christophe Colin (GEOPS)
Co-directrice de thèse : Stéphanie Duchamp-Alphonse (GEOPS)
Unités de recherche : GEOPS - Géosciences de Paris Sud UMR 8148, Orsay
Intitulé de l’équipe : Paléoclimats et Dynamique Sédimentaire, GEOPS
Mots clés : Paleoclimats, mousson Indo-Asiatique, Productivité, Micropaleontologie, Géochimie isotoque et élémentaire
Résumé (En Anglais) :

The aims of this PhD work are to reconstruct high-resolution Indian and Asian Monsoon dynamics over the last 25 kyrs, i.e. when tectonic uplift can be considered as negligible, and understand the natural (pre-anthropoid) forcing factors behind their variability. Mechanisms will be study at decadal to millennial scales, under several boundary conditions (isolation forcing, ice extension, atmospheric CO2 level), with a special emphasis on winter seasons and wind stress dynamic based on paleoproductivity proxies. This multiproxy study will be based on three long marine sediment cores, MD77-176, BAR94-24 and MD77-191 retrieved in the Bay of Bengal and the Arabian Sea respectively, and characterized by robust chronological frameworks, and high sedimentation rates, which is crucial to study short-term changes of monsoon climate system in the past. This work will concentrate on calcareous nannofossil assemblages from the selected cores. The candidate will quantify abundances, sizes, weights and assemblages of the dominant coccolith using the automatic optical microscope LEICA DM6000 combined with SYRACO automatic coccolith grabbing software) in order to assess paleoproductivity changes linked to wind stress variability and winter monsoon dynamics. The candidate will also run total organic carbon (TOC) and X-ray fluorescence (XRF) measurements in order to document high-resolution changes in Biological Pump efficiency associated to the Indo-Asian monsoonal dynamic. Several indices might be used to evaluate the Biological Pump (Ba/Ti, Ca/Ti, Ca/Ba, Br/Ca. Empirical results will be compared to results from ocean biogeochemical modeling experiments (PISCES) to improve local vs regional vs global mechanisms behind changes in paleoproductivity and their relationships to the monsoon variability.