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| Titel |
Atmospheric dissolved iron deposition to the global oceans: effects of oxalate-promoted Fe dissolution, photochemical redox cycling, and dust mineralogy |
| VerfasserIn |
M. S. Johnson, N. Meskhidze |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 6, no. 4 ; Nr. 6, no. 4 (2013-08-07), S.1137-1155 |
| Datensatznummer |
250084969
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| Publikation (Nr.) |
 copernicus.org/gmd-6-1137-2013.pdf |
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| Zusammenfassung |
| Mineral dust deposition is suggested to be a significant atmospheric supply
pathway of bioavailable iron (Fe) to Fe-depleted surface oceans. In this
study, mineral dust and dissolved Fe (Fed) deposition rates are
predicted for March 2009 to February 2010 using the 3-D chemical transport
model GEOS-Chem implemented with a comprehensive dust-Fe dissolution scheme.
The model simulates Fed production during the atmospheric
transport of mineral dust, taking into account inorganic and organic
(oxalate)-promoted Fe dissolution processes, photochemical redox cycling
between ferric (Fe(III)) and ferrous (Fe(II)) forms of Fe, dissolution of
three different Fe-containing minerals (hematite, goethite, and
aluminosilicates), and detailed mineralogy of wind-blown dust from the major
desert regions. Our calculations suggest that during the year-long simulation
~0.26 Tg (1 Tg = 1012 g) of Fed was deposited
to global oceanic regions. Compared to simulations only taking into account
proton-promoted Fe dissolution, the addition of oxalate and Fe(II)/Fe(III)
redox cycling to the dust-Fe mobilization scheme increased total annual
model-predicted Fed deposition to global oceanic regions by
~75%. The implementation of Fe(II)/Fe(III) photochemical redox
cycling in the model also allows for the distinction between different
oxidation states of deposited Fed. Our calculations suggest that
during the daytime, large fractions of Fed deposited to the
global oceans is likely to be in Fe(II) form, while nocturnal fluxes of
Fed are largely in Fe(III) form. Model sensitivity simulations
suggest Fed fluxes to the oceans can range from ~50%
reduction to ~150% increase associated with the uncertainty in
Fe-containing minerals commonly found in dust particles. This study indicates
that Fed deposition to the oceans is controlled by total dust-Fe
mass concentrations, mineralogy, the surface area of dust particles,
atmospheric chemical composition, cloud processing, and meteorological
parameters and exhibits complex and spatiotemporally variable patterns. Our
study suggests that the explicit model representation of individual processes
leading to Fed production within mineral dust are needed to
improve the understanding of the atmospheric Fe cycle, and quantify the
effect of dust-Fe on ocean biological productivity, carbon cycle, and
climate. |
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