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| Titel |
Impact of the Kuroshio intrusion on the nutrient inventory in the upper northern South China Sea: insights from an isopycnal mixing model |
| VerfasserIn |
C. Du, Z. Liu, M. Dai, S.-J. Kao, Z. Cao, Y. Zhang, T. Huang, L. Wang, Y. Li |
| 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 (2013-10-10), S.6419-6432 |
| Datensatznummer |
250085359
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| Publikation (Nr.) |
 copernicus.org/bg-10-6419-2013.pdf |
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| Zusammenfassung |
| Based on four cruises covering a seasonal cycle in 2009–2011, we examined
the impact of the Kuroshio intrusion, featured by extremely oligotrophic
waters, on the nutrient inventory in the central northern South China Sea
(NSCS). The nutrient inventory in the upper 100 m of the water column in the
study area ranged from ∼200 to ∼290 mmol m−2 for
N + N (nitrate plus nitrite), from ∼13 to
∼24 mmol m−2 for soluble reactive phosphate and from
∼210 to ∼430 mmol m−2 for silicic acid. The nutrient
inventory showed a clear seasonal pattern with the highest value appearing in
summer, while the N + N inventory in spring and winter had a reduction of
∼13 and ∼30%, respectively, relative to that in
summer. To quantify the extent of the Kuroshio intrusion, an isopycnal mixing
model was adopted to derive the proportional contribution of water masses
from the SCS proper and the Kuroshio along individual isopycnal surfaces. The
derived mixing ratio along the isopycnal plane was then employed to predict
the genuine gradients of nutrients under the assumption of no biogeochemical
alteration. These predicted nutrient concentrations, denoted as
Nm, are solely determined by water mass mixing. Results showed
that the nutrient inventory in the upper 100 m of the NSCS was overall
negatively correlated to the Kuroshio water fraction, suggesting that the
Kuroshio intrusion significantly influenced the nutrient distribution in the
SCS and its seasonal variation. The difference between the observed nutrient
concentrations and their corresponding Nm allowed us to further
quantify the nutrient removal/addition associated with the biogeochemical
processes on top of the water mass mixing. We revealed that the nutrients in
the upper 100 m of the water column had a net consumption in both winter and
spring but a net addition in fall. |
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