Distribution of neodymium isotopes and trace elements in the West Pacific: sources, sinks, and water mass signatures

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Neodymium isotopes and rare earth elements (REE) are versatile tracers for processes and changes in the modern and past ocean. They are supplied to the ocean by continental weathering and hence provide information on the source and transport pathways of water masses and terrigenous particles, and afford estimates of element fluxes between reservoirs (e.g., sediment/particle - seawater exchange). This makes them particularly useful for tracing the origin and fate of other trace elements that play important roles as micronutrients, tracers, or contaminants in the ocean. Yet, due to the scarcity of data, particularly from the Pacific Ocean, our understanding of the different sources, sinks, and cycling of Nd isotopes and REEs under different oceanic settings is so far limited, preventing a full exploitation of their potential as tracers in the ocean. The proposed study is designed to conduct a rigorous survey of the distribution of dissolved Nd isotopes and REE concentrations along a transect from South Korea to Fiji in the West Pacific that will afford insights into the biogeochemical and physical processes that control these distributions. The focus will be on the following key objectives: 1) direct comparison of hydrographic and trace element and isotope data for the characterization of chemical water mass signatures, their evolution along circulation pathways, and deviations of these signatures from those expected from water mass mixing alone, providing insight into trace element additions and exchange processes, 2) documentation and identification of sources, sinks, and the behavior of REEs and other non-contamination-prone trace elements (Ba, Tl, V, U, Mo, Re) in the West Pacific, and 3) verification of the seawater integrity of Nd isotope ratios in paleo-archives in marine sediments that are commonly used for the reconstruction of past ocean circulation. The results will contribute to the efforts of the international GEOTRACES program.