Indian-Atlantic subsurface- and deep-water mass exchange over the past 600 kyrs

• Published in: Goldschmidt2021 abstracts
• Main Authors: Perez-Asensio, Jose, Kazuyo, Tachikawa, Vidal, Laurence, de Garidel-Thoron, Thibault, Sonzogni, Corinne, Guihou, Abel, Deschamps, Pierre, Jorry, Stephan, Chen, Min-Te
• Other Authors: Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2021
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Indian; North Atlantic Deep Water; North Atlantic
• Online Access: https://hal.science/hal-03541193; https://doi.org/10.7185/gold2021.7050

International audience The water-mass exchange between Indian and Atlantic oceans, occurring through Agulhas current and its leakage, is one of the return flows of global thermohaline circulation. To investigate the Indian-Atlantic subsurface- and deep-water mass exchangeover the last 600 kyrs, we analyzed Nd isotopic composition (εNd) on planktic foraminiferal authigenic fraction, epibenthic foraminiferal stable carbon isotopes ( δ13C), and planktic foraminiferal warm species in the sediment core MD96-2077 (SW Indian Ocean, 3,781 m). At present, this sedimentary sequence is bathed by modified Circumpolar Deep Water and it is below the flow path of the Agulhas current. The obtained εNd and δ13C records show glacial/interglacial variability ranging between -8.0 and -10.3, and between -1.1 and 0.7 ‰, respectively, with higher εNd values coinciding with more depleted δ13C values and vice versa. Planktic warm species relative abundances vary from 1.2 to 37.6 % with a marked increase during terminations. The most striking feature of our record is systematic very low glacial δ13C values similar torecords from the deep SE Atlantic (ODP Site 1090). Relationship between εNd and δ13C of the studied core compared with existing records indicates similar trends with deep SE Atlantic water masses, suggesting that deep glacial carbon-rich water extendedfrom the SE Atlantic into the SW Indian Ocean. Contribution of Indian deep water cannot account for the low benthic δ13C values observed at the study site. The increases in warm planktic species relative abundances during the terminations are coincident withreconstructed Agulhas leakage peaks, suggesting a possible link between Agulhas current and Agulhas leakage during terminations. To better constrain the deep-water variability of the northern and southern source water masses arriving at the SWIndian Ocean, we are analyzing the foraminiferal εNd in core MD96-2052 (2,627 m water depth) from the Mozambique Channel. This core is currently occupied by North Atlantic Deep Water ...