Millennial-scale variations of the intermediate water circulation in the Indian Ocean since the last glacial period inferred from assemblages and geochemistry of benthic foraminifera.

• Main Author: Ma, Ruifang
• Other Authors: Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Université Paris Saclay (COmUE), Christophe Colin
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2019
• Subjects: Intermediate water circulation; Benthic foraminifera; Geochemistry; Assemblages; Bay of Bengal; Eastern Equatorial Indian Ocean; Circulation d'eau intermédiaire; Foraminifères benthiques; Géochimie; Dernier maximum glaciaire; Océan Indien septentrional; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; Antarctic; Indian; Southern Ocean; Antarc*; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://theses.hal.science/tel-03767514; https://theses.hal.science/tel-03767514/document; https://theses.hal.science/tel-03767514/file/74416_MA_2019_archivage.pdf

The main objective of this study was to reconstruct the evolution of the intermediate water circulation since the last glacial period by the investigation of marine cores collected from the Bay of Bengal (BoB), Arabian Sea (AS) and Eastern Equatorial Indian Ocean (EEIO). The scientific strategy involves benthic foraminiferal assemblages and geochemical proxies to better constrain past changes in the source and ventilation of water masses. Records from the BoB allowed reconstructing hydrological changes at intermediate depth over the last 40 cal kyr. The records highlight changes in the source of water masses, with a balance between the contribution of southern Antarctic Intermediate Water (AAIW) versus North Atlantic Deep Water (NADW) at glacial-interglacial timescale as well as during millennial events. This work also provided the first high-resolution benthic foraminifera elemental ratio records (Mg/Ca, Sr/Ca, U/Ca and Li/Ca) from the BoB and the AS. These records especially help to better constrain the northward penetration of AAIW over the last glacial period. The reconstruction of the carbonate ion concentration allowed to discuss the relationships between the intermediate water circulation and deep changes in the global Carbon cycle, with a special interest for the Southern Ocean. This work also provides the first continuous and high-resolution benthic Cd/Ca and Ba/Ca records in the northern Indian Ocean, could reconstruct past changes in the nutrient content. Geochemical records from the EEIO exhibit strong changes in the chemical properties of the intermediate water masses, related to global circulation changes in the area. L'objectif principal de cette thèse était de reconstituer l'évolution de la circulation intermédiaire depuis la dernière période glaciaire à partir de carottes de sédiments marins prélevées dans le golfe du Bengale GB, la Mer d’Arabie MA et l’océan Indien équatorial oriental OIEO. La stratégie scientifique mise en œuvre inclut l’étude des assemblages et de la géochimie des ...