A dissolved cobalt plume in the oxygen minimum zone of the eastern tropical South Pacific
Name
Hawco-2016-A dissolved cobalt plume in the oxy.pdf
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4.39 MB
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Author(s)
Ohnemus, Daniel C.
Resing, Joseph A.
Twining, Benjamin S.
Saito, Mak A.
Hawco, Nicholas James
Date Issued
October 2016
Journal
Biogeosciences
Publisher
Copernicus GmbH/European Geosciences Union
Citation
Hawco, Nicholas J. et al. “A Dissolved Cobalt Plume in the Oxygen Minimum Zone of the Eastern Tropical South Pacific.” Biogeosciences 13.20 (2016): 5697–5717.
Version
Final published version
Abstract
Cobalt is a nutrient to phytoplankton, but knowledge about its biogeochemical cycling is limited, especially in the Pacific Ocean. Here, we report sections of dissolved cobalt and labile dissolved cobalt from the US GEOTRACES GP16 transect in the South Pacific. The cobalt distribution is closely tied to the extent and intensity of the oxygen minimum zone in the eastern South Pacific with highest concentrations measured at the oxycline near the Peru margin. Below 200 m, remineralization and circulation produce an inverse relationship between cobalt and dissolved oxygen that extends throughout the basin. Within the oxygen minimum zone, elevated concentrations of labile cobalt are generated by input from coastal sources and reduced scavenging at low O2. As these high cobalt waters are upwelled and advected offshore, phytoplankton export returns cobalt to low-oxygen water masses underneath. West of the Peru upwelling region, dissolved cobalt is less than 10 pM in the euphotic zone and strongly bound by organic ligands. Because the cobalt nutricline within the South Pacific gyre is deeper than in oligotrophic regions in the North and South Atlantic, cobalt involved in sustaining phytoplankton productivity in the gyre is heavily recycled and ultimately arrives from lateral transport of upwelled waters from the eastern margin. In contrast to large coastal inputs, atmospheric deposition and hydrothermal vents along the East Pacific Rise appear to be minor sources of cobalt. Overall, these results demonstrate that oxygen biogeochemistry exerts a strong influence on cobalt cycling.
MIT Department
Joint Program in Oceanography/Applied Ocean Science and Engineering
Woods Hole Oceanographic Institution
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Creative Commons Attribution 3.0 License
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DOI of Published Version
https://doi.org/10.5194/bg-13-5697-2016
