Pervasive sources of isotopically light zinc in the North Atlantic Ocean

Type Article
Date 2020-06
Language English
Author(s) Lemaitre Nolwenn1, de Souza Gregory F.1, Archer Corey1, Wang Ruo-Mei1, 2, Planquette Helene3, Sarthou Geraldine3, Vance Derek1
Affiliation(s) 1 : Department of Earth Sciences, Institute of Geochemistry and Petrology, ETH-Zürich, Zürich, Switzerland
2 : Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
3 : CNRS, Univ Brest, IRD, Ifremer, LEMAR, F-29280 Plouzane, France
Source Earth And Planetary Science Letters (0012-821X) (Elsevier BV), 2020-06 , Vol. 539 , P. 116216 (12p.)
DOI 10.1016/j.epsl.2020.116216
WOS© Times Cited 30
Keyword(s) zinc isotopes, North Atlantic, zinc sources, GEOTRACES, GEOVIDE

In this study, we report seawater dissolved zinc (Zn) concentration and isotope composition (Zn) from the GEOTRACES GA01 (GEOVIDE) section in the North Atlantic. Across the transect, three subsets of samples stand out due to their isotopically light signature: those close to the Reykjanes Ridge, those close to the sediments, and those, pervasively, in the upper ocean. Similar to observations at other locations, the hydrothermal vent of the Reykjanes Ridge is responsible for the isotopically light Zn composition of the surrounding waters, with an estimated source

Zn of -0.42 ‰. This isotopically light Zn is then transported over a distance greater than 1000 km from the vent. Sedimentary inputs are also evident all across the trans-Atlantic section, highlighting a much more pervasive process than previously thought. These inputs of isotopically light Zn, ranging from -0.51 to +0.01 ‰, may be caused by diffusion out of Zn-rich pore waters, or by dissolution of sedimentary particles.

The upper North Atlantic is dominated by low

Zn, a feature that has been observed in all Zn isotope datasets north of the Southern Ocean. Using macronutrient to Zn ratios to better understand modifications of preformed signatures exported from the Southern Ocean, we suggest that low upper-ocean Zn results from addition of isotopically light Zn to the upper ocean, and not necessarily from removal of heavy Zn through scavenging. Though the precise source of this isotopically light upper-ocean Zn is not fully resolved, it seems possible that it is anthropogenic in origin. This view of the controls on upper-ocean Zn is fundamentally different from those put forward previously.

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