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Assessment of 231pa/230th as a tracer of past and present ocean circulation rates

Objective

This project is focused on climate variability within the Quaternary. The objective is to improve the understanding of ^ 231Pa and ^230Th behaviors in ocean fast flowing currents, both in the water column and in the underlying sediments. For this purpose, we propose to measure the concentrations of both nuclides by MC-ICP-MSin water column samples, particulate material, and sediments top-cores collected along the fast flowing western boundary current that fills the Indian Ocean. The results will allow us to check the influences of the particle flux, the chemical composition of the particles, and the age of the water. Cores for which the (^231Pa/^230Th) budget is at equilibrium between sediment top-cores and water column profiles will be analyzed to reconstruct the past flowing rate of the western boundary current. We will also explore the potential of (^231Pa/^230Th) ratio in the surface waters as a proxy of interannual surface current variability by analyzing water samples collected every 6 months at the same stations along the Atlantic Meridional Transect. The results should provide a better understanding of surface-waters ventilation, shallow/seasonal upwelling rate and removal rate of^231Pa and ^230Th by biological productivity. This latter aspect will be complemented by coccoliths and diatoms culture experiments. The data regarding the behavior of 231Pa and 230Th in the water column will then be integrated in simple box models to assess the oceanic budget of both isotopes. This project has direct implications for a better understanding of the past climate. Reconstructing water flowing rate is essential to determine the transport of heat and the cycling elements in the oceans. Oxford Earth Sciences is a world-class institute in mass spectrometry with 10 instruments and a large number of expert users. Working there will offer me the opportunity to be trained in the use of 2^nd generation MC-ICP-MS and improve my experience in water samples analysis. The research project will enable me to discover 2 aspects of climate research I have not explored so far. I will benefit from Dr. Henderson's experience in modeling and I will be trained to culture experiments that are useful in various oceanographic research areas like trace metals studies, a subject I am very interested in. I will also have the chance of interacting with over 25 geochemists from various fields: paleoceanography, ocean chemistry, biogeochemistry, U-series geochemistry, and mineral-surface chemistry. I will bring my geochemical experience, especially in Pa, Th, U, Pb and Zn analysis, which well complements that at Oxford. My experience in 1^st generation MC-ICP-MS will inform the use of the 2^nd generation MC-ICP-MS housed at Oxford. My knowledge of U-series behavior in natural waters and sediments should allow me to have active discussion and collaboration with Oxford scientists.

Funding Scheme

RGI - Research grants (individual fellowships)

Coordinator

THE CHANCELLOR, MASTERS AND SCHOLARS OF THE UNIVERSITY OF OXFORD
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