The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data

Tachikawa, Kazuyo and Arsouze, Thomas and Bayon, Germain and Bory, Aloys and Colin, Christophe and Dutay, Jean-Claude and Frank, Norbert and Giraud, Xavier and Gourlan, Alexandra T. and Jeandel, Catherine and Lacan, François and Meynadier, Laure and Montagna, Paolo and Piotrowski, Alexander M. and Plancherel, Yves and Pucéat, Emmanuelle and Roy-Barman, Matthieu and Waelbroeck, Claire (2017) The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data. Chemical Geology. ISSN 0009-2541 DOI 10.1016/j.chemgeo.2017.03.018

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Official URL: http://doi.org/10.1016/j.chemgeo.2017.03.018

Abstract

Neodymium isotopic compositions (143Nd/144Nd or εNd) have been used as a tracer of water masses and lithogenic inputs to the ocean. To further evaluate the faithfulness of this tracer, we have updated a global seawater εNd database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive εNd data are also compiled for leachates, foraminiferal tests, deep-sea corals and fish teeth/debris from the Holocene period (< 10,000 years). At water depths ≥ 1500 m, property-property plots show clear correlations between seawater εNd and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater εNd distribution. At ≥ 200 m, basin-scale seawater T-S-εNd diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive εNd values are compared using property-property plots and T-S-εNd diagrams. Archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the Pacific. Both positive and negative offsets exist in the northern North Atlantic. Applying multiple regression analysis to deep (≥ 1500 m) seawater data, we established empirical equations that predict the main, large-scale, deepwater εNd trends from hydrography parameters. Large offsets from the predicted values are interpreted as a sign of significant local/regional influence. Dominant continental influence on seawater and archive εNd is observed mainly within 1000 km from the continents. Generally, seawater and archive εNd values form gradual latitudinal trend in the Atlantic and Pacific at depths ≥ 600 m, consistent with the idea that Nd isotopes help distinguish between northern/southern sourced water contributions at intermediate and deep water depths.

Item Type: Article
Uncontrolled Keywords: 2016AREP; IA72;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
08 - Green Open Access
Journal or Publication Title: Chemical Geology
Identification Number: 10.1016/j.chemgeo.2017.03.018
Depositing User: Sarah Humbert
Date Deposited: 12 Apr 2017 21:38
Last Modified: 28 Apr 2017 16:39
URI: http://eprints.esc.cam.ac.uk/id/eprint/3926

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