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| Titel |
Sedimentary and atmospheric sources of iron around South Georgia, Southern Ocean: a modelling perspective |
| VerfasserIn |
I. Borrione, O. Aumont, M. C. Nielsdóttir, R. Schlitzer |
| 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. 7 ; Nr. 11, no. 7 (2014-04-09), S.1981-2001 |
| Datensatznummer |
250117353
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| Publikation (Nr.) |
 copernicus.org/bg-11-1981-2014.pdf |
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| Zusammenfassung |
| In high-nutrient low-chlorophyll waters of the western Atlantic sector of the
Southern Ocean, an intense phytoplankton bloom is observed annually north of
South Georgia. Multiple sources, including shallow sediments and atmospheric
dust deposition, are thought to introduce iron to the region. However, the
relative importance of each source is still unclear, owing in part to the
scarcity of dissolved iron (dFe) measurements in the South Georgia region. In
this study, we combine results from a recently published dFe data set around
South Georgia with a coupled regional hydrodynamic and biogeochemical model
to further investigate iron supply around the island. The biogeochemical
component of the model includes an iron cycle, where sediments and dust
deposition are the sources of iron to the ocean. The model captures the
characteristic flow patterns around South Georgia, hence simulating a large
phytoplankton bloom to the north (i.e. downstream) of the island. Modelled
dFe concentrations agree well with observations (mean difference and root
mean square errors of ~0.02 nM and ~0.81 nM) and form a large
plume to the north of the island that extends eastwards for more than
800 km. In agreement with observations, highest dFe concentrations are
located along the coast and decrease with distance from the island.
Sensitivity tests indicate that most of the iron measured in the main bloom
area originates from the coast and very shallow shelf-sediments (depths
< 20 m). Dust deposition exerts almost no effect on surface
chlorophyll a concentrations. Other sources of iron such as run-off and
glacial melt are not represented explicitly in the model, however we discuss
their role in the local iron budget. |
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