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| Titel |
Riverine influence on the tropical Atlantic Ocean biogeochemistry |
| VerfasserIn |
L. C. Cunha, E. T. Buitenhuis |
| 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 ; 10, no. 10 ; Nr. 10, no. 10 (2013-10-09), S.6357-6373 |
| Datensatznummer |
250085354
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| Publikation (Nr.) |
 copernicus.org/bg-10-6357-2013.pdf |
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| Zusammenfassung |
| We assess the role of riverine inputs of N, Si, Fe, organic and inorganic C
in the tropical Atlantic Ocean using a global ocean biogeochemistry model. We
use a standard model scenario and three sensitivity tests to investigate the
role of total river nutrient and carbon inputs, as well as the western (South
American) and eastern (African) river inputs on the tropical
Atlantic Ocean biogeochemistry, between 20° S–20° N and
70° W–20° E. Increased nutrient availability from river
inputs in this area (compared to a sensitivity scenario without river
nutrient inputs, NO_RIVER) leads to an increase in primary production (PP) and export
production (EP), mainly in the coastal ocean area (modeled ocean area with
bathymetry <200 m). Model results suggest an enhanced N-fixation by
diazotrophs on the tropical Atlantic mainly in open ocean areas. The
increased rate of N-fixation in the TODAY scenario is proportional to the
increase in PP and EP relative to the NO_RIVER scenario, and may support up to
14% of the coastal ocean export production. Inputs from South American
rivers have an impact in coastal PP and EP two times higher than those from
African rivers. On the other hand, results suggest that the contribution of
African and South American rivers to the total increase in open ocean PP and
EP is similar. Considering the amount of delivered nutrients (2–3 times less
nutrients and carbon inputs by African rivers) one concludes that African
riverine inputs may have a larger impact on the whole tropical Atlantic Ocean
biogeochemistry. This is probably due to a combination of nutrient trapping
in upwelling areas off the large rivers' outflows and shallow mixed layers in
the eastern tropical Atlantic, concomitantly to the differences in delivered
nutrient ratios leading to alleviation in limitation conditions, mainly for
diatoms. When river inputs are added to the model, we estimate a modest decrease in open ocean sea-air CO2 fluxes
(−5.2 Tg C a−1) and an increase in coastal ocean CO2 fluxes, mainly provoked by the
remineralization of riverine organic matter delivered by the South American
rivers. |
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