Circulation InTeRmédiaire dans l’Océan iNdien depuis le dernier maximum GLACiairE
INSU-LEFE-IMAGO 2017 (2017-2019)
S. Sepulcre (GEOPS
The objectives of this research project fall within a study on the role of ocean circulation in the modalities of heat and salt transfer between low and high latitudes during the glacial-interglacial terminations. In particular, we are interested in changes that occurred between the Last Glacial Maximum and the Holocene at intermediate depths within the Bay of Bengal. In fact, while the role of intermediate water masses in the processes of teleconnection involved in the terminations is increasingly being studied for the Atlantic, Pacific and Southern Oceans, it remains little studied in the case of the Indian Ocean despite the presence of globally significant water masses. In order to meet our objectives, we propose a combined study of benthic foraminifera assemblages, which are sensitive to geochemical variations in water masses and sediment (trophic level, oxygen concentration), and geochemical tracers for a key period of the Earth’s climate history, Termination I: 1) Oxygen (δ18O) and Carbon (δ13C) isotopic composition; 2) element ratios measured in tests of benthic foraminifera (Cd/Ca, Mg/Ca, B/Ca, Sr/Ca et U/Ca); 3) Δ14C (the difference between the C14 of planktonic and benthic foraminifera); 4) εNd. These different complementary records, which are unprecedented for the study zone, allow us to accurately characterize variations in circulation at intermediate depths in the Bay of Bengal. These measurements will be compared to changes occurring at the surface and at depth both at the study site and at the scale of the Indian Ocean; ultimately, this will allow us to integrate these variations at a global scale. We will thus improve our understanding of the role of intermediate water masses during Termination I and the teleconnections between high latitudes and low latitudes.
Reconstruction of the extension of Antarctic Intermediate Waters a) at present and b) during the Last Deglaciation and its relationships to ventilation in the Southern Ocean and to CO2 degassing (Yu et al., EPSL, 2018.)