Sources of dissolved iron to oxygen minimum zone waters on the Senegalese continental margin in the tropical North Atlantic Ocean: Insights from iron isotopes.

Klar, J. K., Schlosser, Christian , Milton, J. A., Woodward, E. M. S., Lacan, F., Parkinson, I. J., Achterberg, Eric P. and James, R. H. (2018) Sources of dissolved iron to oxygen minimum zone waters on the Senegalese continental margin in the tropical North Atlantic Ocean: Insights from iron isotopes. Open Access Geochimica et Cosmochimica Acta, 236 . pp. 60-78. DOI 10.1016/j.gca.2018.02.031.

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Abstract

Oxygen minimum zones (OMZs) cover extensive areas of eastern boundary ocean regions and play an important role in the cycling of the essential micronutrient iron (Fe). The isotopic composition of dissolved Fe (dFe) in shelf and slope waters on the Senegalese margin was determined to investigate the processes leading to enhanced dFe concentrations (up to 2 nM) in this tropical North Atlantic OMZ. On the shelf, the delta Fe-56 value of dFe (relative to the reference material IRMM-014) was as low as -0.33 parts per thousand, which can be attributed to input of dFe from both reductive and nonreductive dissolution of sediments. Benthic inputs of dFe are subsequently upwelled to surface waters and recycled in the water column by biological uptake and remineralisation processes. Remineralised dFe is characterised by relatively high delta Fe-56 values (up to + 0.41 parts per thousand), and the contribution of remineralised Fe to the total dFe pool increases with distance from the shelf. Remineralisation plays an important role in the redistribution of dFe that is mainly supplied by benthic and atmospheric inputs, although dust inputs, estimated from dissolved aluminium concentrations, were low at the time of our study (2-9 nmol dFe m(-2) d(-1)). As OMZs are expected to expand as climate warms, our data provide important insights into Fe sources and Fe cycling in the tropical North Atlantic Ocean.

Document Type: Article
Keywords: Tropical Atlantic Ocean, Iron isotopes, Oxygen minimum zone, Benthic iron, Remineralisation, Dissolved aluminium, Dust, GEOTRACES
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
NOC
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.gca.2018.02.031
ISSN: 0016-7037
Projects: GEOTRACES
Date Deposited: 06 Sep 2018 08:23
Last Modified: 01 Feb 2019 15:16
URI: http://oceanrep.geomar.de/id/eprint/44153

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