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| Titel |
Changes in dissolved iron deposition to the oceans driven by human activity: a 3-D global modelling study |
| VerfasserIn |
S. Myriokefalitakis, N. Daskalakis, N. Mihalopoulos, A. R. Baker, A. Nenes, M. Kanakidou |
| 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 ; 12, no. 13 ; Nr. 12, no. 13 (2015-07-02), S.3973-3992 |
| Datensatznummer |
250118007
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| Publikation (Nr.) |
 copernicus.org/bg-12-3973-2015.pdf |
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| Zusammenfassung |
| The global atmospheric iron (Fe) cycle is parameterized in the global 3-D
chemical transport model TM4-ECPL to simulate the proton- and the organic
ligand-promoted mineral-Fe dissolution as well as the aqueous-phase
photochemical reactions between the oxidative states of Fe (III/II). Primary
emissions of total (TFe) and dissolved (DFe) Fe associated with dust and
combustion processes are also taken into account, with TFe mineral emissions
calculated to amount to ~ 35 Tg-Fe yr−1 and TFe emissions from
combustion sources of ~ 2 Tg-Fe yr−1. The model reasonably
simulates the available Fe observations, supporting the reliability of the
results of this study. Proton- and organic ligand-promoted Fe dissolution in
present-day TM4-ECPL simulations is calculated to be
~ 0.175 Tg-Fe yr−1, approximately half of the calculated total
primary DFe emissions from mineral and combustion sources in the model
(~ 0.322 Tg-Fe yr−1). The atmospheric burden of DFe is
calculated to be ~ 0.024 Tg-Fe. DFe deposition presents strong spatial
and temporal variability with an annual flux of
~ 0.496 Tg-Fe yr−1, from which about 40 %
(~ 0.191 Tg-Fe yr−1) is deposited over the ocean. The impact of
air quality on Fe deposition is studied by performing sensitivity simulations
using preindustrial (year 1850), present (year 2008) and future (year 2100)
emission scenarios. These simulations indicate that about a 3 times increase
in Fe dissolution may have occurred in the past 150 years due to increasing
anthropogenic emissions and thus atmospheric acidity. Air-quality regulations
of anthropogenic emissions are projected to decrease atmospheric acidity in
the near future, reducing to about half the dust-Fe dissolution relative to
the present day. The organic ligand contribution to Fe dissolution shows an
inverse relationship to the atmospheric acidity, thus its importance has
decreased since the preindustrial period but is projected to increase in the
future. The calculated changes also show that the atmospheric DFe supply to
the globe has more than doubled since the preindustrial period due to 8-fold
increases in the primary non-dust emissions and about a 3-fold increase in the
dust-Fe dissolution flux. However, in the future the DFe deposition flux is
expected to decrease (by about 25 %) due to reductions in the primary
non-dust emissions (about 15 %) and in the dust-Fe dissolution flux
(about 55 %). The present level of atmospheric deposition of
DFe over the global ocean is calculated to be about 3 times higher than for 1850 emissions, and
about a 30 % decrease is projected for 2100 emissions. These changes are
expected to impact most on the high-nutrient–low-chlorophyll oceanic regions. |
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