Atmospheric iron deposition and sea-surface dissolved iron concentrations in the eastern Atlantic Ocean

Géraldine Sarthou 1, * Alex Baker 2 Stéphane Blain 3 E. P. Achterberg 4 Marie Boye 5 Andrew Bowie 6 Peter Croot 5 Patrick Laan 5 H. J. W. De Baar 5 T. Jickells 2 Paul Worsfold 6
* Auteur correspondant
1 LEMAR - Laboratoire des Sciences de l'Environnement Marin (LEMAR)
2 School of Environmental Sciences [Norwich]
3 LOB - Laboratoire d'océanographie et de biogéochimie
4 National Oceanography Centre Southampton
5 NIOZ - Royal Netherlands Institute for Sea Research
6 Department of Environmental Sciences
Abstract : Atmospheric iron and underway sea-surface dissolved (<0.2 μm) iron (DFe) concentrations were investigated along a north–south transect in the eastern Atlantic Ocean (27°N/16°W–19°S/5°E). Fe concentrations in aerosols and dry deposition fluxes of soluble Fe were at least two orders of magnitude higher in the Saharan dust plume than at the equator or at the extreme south of the transect. A weaker source of atmospheric Fe was also observed in the South Atlantic, possibly originating in southern Africa via the north-easterly outflow of the Angolan plume. Estimations of total atmospheric deposition fluxes (dry plus wet) of soluble Fe suggested that wet deposition dominated in the intertropical convergence zone, due to the very high amount of precipitation and to the fact that a substantial part of Fe was delivered in dissolved form. On the other hand, dry deposition dominated in the other regions of the transect (73–97%), where rainfall rates were much lower. Underway sea-surface DFe concentrations ranged 0.02–1.1 nM. Such low values (0.02 nM) are reported for the first time in the Atlantic Ocean and may be (co)-limiting for primary production. A significant correlation (Spearman's RHO=0.862, p<0.01) was observed between mean DFe concentrations and total atmospheric deposition fluxes, confirming the importance of atmospheric deposition on the iron cycle in the Atlantic. Residence time of DFe in the surface waters relative to atmospheric inputs were estimated in the northern part of our study area (17±8 to 28±16 d). These values confirmed the rapid removal of Fe from the surface waters, possibly by colloidal aggregation.
Keywords : Dissolved iron Aerosol iron Sea surface Iron supply Atmospheric (wet and dry) deposition Residence time
Type de document :
Article dans une revue
Deep Sea Research Part I: Oceanographic Research Papers, Elsevier, 2003, 50 (10-11), pp.1339-1352. 〈10.1016/S0967-0637(03)00126-2〉
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Contributeur : Ivo Grigorov <>
Soumis le : lundi 15 février 2010 - 11:08:44
Dernière modification le : mardi 29 mai 2018 - 12:50:38

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Géraldine Sarthou, Alex Baker, Stéphane Blain, E. P. Achterberg, Marie Boye, et al.. Atmospheric iron deposition and sea-surface dissolved iron concentrations in the eastern Atlantic Ocean. Deep Sea Research Part I: Oceanographic Research Papers, Elsevier, 2003, 50 (10-11), pp.1339-1352. 〈10.1016/S0967-0637(03)00126-2〉. 〈hal-00456460〉

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