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| Titel |
Dissolved Fe across the Weddell Sea and Drake Passage: impact of DFe on nutrient uptake |
| VerfasserIn |
M. B. Klunder, P. Laan, H. J. W. de Baar, R. Middag, I. Neven, J. Van Ooijen |
| 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. 3 ; Nr. 11, no. 3 (2014-02-06), S.651-669 |
| Datensatznummer |
250117189
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| Publikation (Nr.) |
 copernicus.org/bg-11-651-2014.pdf |
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| Zusammenfassung |
This manuscript reports the first full depth distributions of dissolved iron
(DFe) over a high-resolution Weddell Sea and Drake Passage transect. Very low
dissolved DFe concentrations (0.01–0.1 nM range) were observed in the
surface waters of the Weddell Sea, and within the Drake Passage polar regime.
Locally, enrichment in surface DFe was observed, likely due to recent ice
melt (Weddell Sea) or dust deposition (Drake Passage). As expected, in low
DFe regions, usually a small silicate drawdown compared to the nitrate
drawdown was observed. However, the difference in drawdown between these
nutrients appeared not related to DFe availability in the western Weddell
Sea. In this region with relatively small diatoms, no relationship between
N : P and N : Si removal ratios and DFe was observed. In comparison,
along the Greenwich Meridian (Klunder et al., 2011a), where diatoms are
significantly larger, the N : P and N : Si removal ratios did increase
with increasing DFe. These findings confirm the important role of DFe in
biologically mediated nutrient cycles in the Southern Ocean and imply DFe
availability might play a role in shaping phytoplankton communities and
constraining cell sizes.
Over the shelf around the Antarctic Peninsula, higher DFe concentrations
(>1.5 nM) were observed. These elevated concentrations of Fe were
transported into Drake Passage along isopycnal surfaces. Near the South
American continent, high (>2 nM) DFe concentrations were caused by
fluvial/glacial input of DFe.
On the Weddell Sea side of the Peninsula region, formation of deep water (by
downslope convection) caused relatively high Fe (0.6–0.8 nM) concentrations
in the bottom waters relative to the water masses at mid-depth
(0.2–0.4 nM). During transit of Weddell Sea Bottom Water to the Drake
Passage, through the Scotia Sea, additional DFe is taken up from seafloor
sources, resulting in highest bottom water concentrations in the southernmost
part of the Drake Passage in excess of 1 nM. The Weddell Sea Deep Water
concentrations (∼0.32 nM) were consistent with the lowest DFe
concentrations observed in Antarctic bottom water in the Atlantic Ocean. |
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