University of Cambridge > Talks.cam > Department of Earth Sciences Seminars (downtown) > Impact of the Boundary Exchange on the Element Cycle

Impact of the Boundary Exchange on the Element Cycle

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Since the end of the eighties, it is recognized that the Nd isotopic composition (expressed as εNd ) varies from ca -13 in the North Atlantic to ca -5 in the Pacific. It has been clearly established that far from any source of lithogenic material, εNd is a conservative tracer of water mass mixing. Since the range of εNd values of the deep waters are imprinted in the metalliferous sediments, they are used by paleoceanographers to trace the past variations of the thermohaline circulation. However, many studies conducted in the present day ocean highlight that the Nd budgets based only on dust/riverine inputs were not able to reconcile the Nd content and εNd variations between the 3 oceanic basins (the “Nd paradox”). The “missing source” was often suspected to be input from sediments deposited on oceanic margins although this has never been quantified. The results presented here partly solve this question by establishing that the boundary exchanges at the oceanic margins appear as a key process for the Nd cycle. Such process could affect the distributions of other reactive elements, until remote areas as the middle of the oceanic basins. Enlarging such studies to other trace elements and isotopic tracers is among the goals of the forthcoming GEOTRACES program.

This talk is part of the Department of Earth Sciences Seminars (downtown) series.

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