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| Titel |
Spatial variations in the Kuroshio nutrient transport from the East China Sea to south of Japan |
| VerfasserIn |
X. Y. Guo, X.-H. Zhu, Y. Long, D. J. Huang |
| 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.6403-6417 |
| Datensatznummer |
250085358
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| Publikation (Nr.) |
 copernicus.org/bg-10-6403-2013.pdf |
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| Zusammenfassung |
| Based on absolute geostrophic velocity, which was calculated using repeated
hydrographic data of 39 cruises from 2000 to 2009 and nitrate concentrations
measured in the same areas from 1964 to 2009, we obtained the temporally
averaged nitrate flux (the product of velocity and nitrate concentration) and
nitrate transport (integration of flux over one section) of four sections
across the Kuroshio from the East China Sea (sections PN and TK) to an area
south of Japan (sections ASUKA and 137E). In addition, we examined section OK
east of the Ryukyu Islands in order to understand how the Ryukyu Current
contributes to the transport of nutrients by the Kuroshio south of Japan. The
mean nitrate flux shows a subsurface maximum core with values of 9.6, 10.6,
11.2, 10.5, and 5.7 mol m−2 s−1 at sections PN, TK, ASUKA, 137E,
and OK, respectively. The depth of the subsurface maximum core changes among
these five sections and is approximately 400, 500, 500, 400, and 800 m at
sections PN, TK, ASUKA, 137E, and OK, respectively. The mean downstream
nitrate transport is 204.8, 165.8, 879.3, 1230.4, and 338.6 kmol s−1
at sections PN, TK, ASUKA, 137E, and OK, respectively. The transport of
nutrients in these sections suggests the presence of the Kuroshio nutrient
stream from its upstream to downstream regions. The deep current structure of
the Ryukyu Current (section OK) contributes to the same order of nitrate
transport as does the Kuroshio from the East China Sea (section TK) to the
area south of Japan; however, the former only has one-fifth the volume
transport of the latter. A budget calculation suggests that the downstream
increase of transported nitrate along the Kuroshio is mainly caused by the
recirculation of nitrate into the Kuroshio. This conclusion, however, depends
on water depth. In the upper layers (< 26.5σθ), the
downstream change of nitrate concentration along the Kuroshio and that from
the recirculation of nitrate has a significant contribution to the downstream
increase of nitrate transport along the Kuroshio. In the deep layers
(> 26.5σθ), the change in nitrate concentration is small
and the Kuroshio recirculation dominates the downstream increase of nitrate
transport. |
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