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| Titel |
Physical and remineralization processes govern the cobalt distribution in the deep western Atlantic Ocean |
| VerfasserIn |
G. Dulaquais, M. Boye, M. J. A. Rijkenberg, X. Carton |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 6 ; Nr. 11, no. 6 (2014-03-24), S.1561-1580 |
| Datensatznummer |
250117305
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| Publikation (Nr.) |
 copernicus.org/bg-11-1561-2014.pdf |
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| Zusammenfassung |
| The distributions of the bio-essential trace element dissolved cobalt (DCo) and
the apparent particulate Co (PCo) are presented along the GEOTRACES-A02 deep
section from 64° N to 50° S in the western Atlantic Ocean (longest section of international GEOTRACES marine environment program).
PCo was determined as the difference between total cobalt (TCo, unfiltered
samples) and DCo. DCo concentrations ranged from 14.7 pM to 94.3 pM, and PCo
concentrations from undetectable values to 18.8 pM. The lowest DCo
concentrations were observed in the subtropical domains, and the highest in
the low-oxygenated Atlantic Central Waters (ACW), which appears to be the
major reservoir of DCo in the western Atlantic. In the Antarctic Bottom Waters,
the enrichment in DCo with aging of the water mass can be related to
suspension and redissolution of bottom sediments a well as diffusion of DCo
from abyssal sediments. Mixing and dilution of deep water masses, rather
than scavenging of DCo onto settling particles, generated the meridional
decrease of DCo along the southward large-scale circulation in the deep
western Atlantic. Furthermore, the apparent scavenged profile of DCo observed in the
deep waters likely resulted from the persistence of relatively high
concentrations in intermediate waters and low DCo concentrations in
underlaying bottom waters. We suggest that the 2010 Icelandic volcanic
eruption could have been a source of DCo that could have been transported into the core
of the Northeast Atlantic Deep Waters. At intermediate depths, the high
concentrations of DCo recorded in the ACW linearly correlated with the
apparent utilization of oxygen (AOU), indicating that remineralization of
DCo could be significant (representing up to 37% of the DCo present).
Furthermore, the preferential remineralization of phosphate (P) compared to
Co in these low-oxygenated waters suggests a decoupling between the deep
cycles of P and Co. The vertical diffusion of DCo from the ACW appears to
be a significant source of DCo into the surface waters of the equatorial
domain. Summarizing, the dilution due to mixing processes rather than
scavenging of DCo and the above-mentioned remineralization could be the two major pathways
controlling the cycling of DCo into the intermediate and deep western Atlantic. |
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