Anticyclonic Eddy Edge Effects on Phytoplankton Communities and Particle Export in the Northern South China Sea

AbstractA process-oriented numerical modeling study was conducted to investigate the formation and underlying forcing of an anticyclonic eddy train observed in the northern South China Sea. Observations showed that long-lived anticyclonic eddies formed an eddy train along an eastward separated jet across the northern South China Sea in summer. The eddy train plays a critical role in regulating ocean circulation in the region. Forced by the southwesterly monsoon and prevailing dipole wind stress curl in the summer, the northward coastal jet separates from the west boundary of the South China Sea basin and overshoots northeastward into the basin. The anticyclonic recirculation of the separated jet forms the first anticyclonic eddy in the eddy train. The jet meanders downstream with a strong negative shear vorticity that forms a second and a third anticyclonic eddy along the jet’s path. These three eddies form the eddy train. These eddies weaken gradually with depth from surface, but they can extend to approximately 500 m deep. The inherent stratification in the region regulates the three-dimensional scale of the anticyclonic eddies and constrains their intensity vertical extension by weakening the geostrophic balance within these eddies. Analyses of the vorticity balance indicate that the eddy train’s negative vorticity originates from the beta effect of northward western boundary current and from the subsequent downstream vorticity advection in the jet. The jet separation is a necessary condition for the formation of the eddy train, and the enhanced stratification, increased summer wind stress, and associated negative wind stress curl are favorable conditions for the formation of the anticyclonic eddies.

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Glider-observed anticyclonic eddy in northern South China Sea

Aquatic Ecosystem Health & Management ◽

10.1080/14634988.2016.1208028 ◽

2016 ◽

Vol 19 (3) ◽

pp. 233-241 ◽

Cited By ~ 23

Author(s):

Yeqiang Shu ◽

Peng Xiu ◽

Huijie Xue ◽

Jinglong Yao ◽

Jiancheng Yu

Keyword(s):

South China Sea ◽

South China ◽

Northern South China Sea ◽

Anticyclonic Eddy ◽

China Sea

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Evaluation on phytoplankton communities fluctuations in a natural gas hydrate deposit of Northern South China Sea

Estuarine Coastal and Shelf Science ◽

10.1016/j.ecss.2020.106891 ◽

2020 ◽

Vol 243 ◽

pp. 106891

Author(s):

Yu Wang ◽

Jianhua Kang ◽

Qianyong Liang ◽

Xuebao He ◽

Binbin Guo ◽

...

Keyword(s):

Natural Gas ◽

South China Sea ◽

South China ◽

Gas Hydrate ◽

Northern South China Sea ◽

Natural Gas Hydrate ◽

China Sea ◽

Phytoplankton Communities ◽

Hydrate Deposit

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Formation of an anticyclonic eddy and the mechanism involved: a case study using cruise data from the northern South China Sea

Journal of Oceanology and Limnology ◽

10.1007/s00343-019-8275-x ◽

2019 ◽

Vol 37 (5) ◽

pp. 1481-1494

Author(s):

Huaqian Hou ◽

Qiang Xie ◽

Huijie Xue ◽

Yeqiang Shu ◽

Feng Nan ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Northern South China Sea ◽

Anticyclonic Eddy ◽

China Sea

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Nutrient limitation of phytoplankton in anticyclonic eddies of the northern South China Sea

Biogeosciences Discussions ◽

10.5194/bgd-5-4591-2008 ◽

2008 ◽

Vol 5 (6) ◽

pp. 4591-4619 ◽

Cited By ~ 9

Author(s):

X. Ning ◽

X. Peng ◽

F. Le ◽

Q. Hao ◽

J. Sun ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Northern South China Sea ◽

Anticyclonic Eddy ◽

Nitrogen And Phosphorus ◽

Phytoplankton Assemblages ◽

Chl A ◽

China Sea ◽

Anticyclonic Eddies

Abstract. Baroclinic instability modulated by topography leads to the formation of two anticyclonic eddies in the northern South China Sea: the Hong Kong Southeast Anticyclonic Eddy (HKSEACE) and the Hainan Island East Anticyclonic Eddy (HIEACE). In these eddies, downwelling caused by a depressed pycnocline leads to high temperature, low salinity, impoverished nutrients, reduced Chl-a concentrations, and picoplankton dominance of phytoplankton assemblages in the euphotic zone. We tested the hypothesis that experimental nutrient enrichment would relieve biomass limitation of phytoplankton by opportunistic response of taxa with low nutrient affinity. Our results confirm that phytoplankton samples incubated in vitro under nutrient enriched conditions attained higher biomass, change in taxonomic dominance from dinoflagellates to diatoms, and shift in size class dominance from picoplankton to nanoplankton and netplankton. These responses were evident only when limitation to more than one nutrient was relieved. Phytoplankton in HKSEACE appeared to be co-limited by nitrogen and phosphorus, whereas at HIEACE it was co-limited by nitrogen, phosphorus and also silicon.

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