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Effects of the Pearl River plume on the vertical structure of coastal currents in the Northern South China Sea during summer 2008

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Abstract

Analyses of moored current meter data from the South China Sea (SCS) Coastal Oceanographic Process Experiment Pilot Project (SCOPE-PP) reveal that strong spatial variation in the vertical structure of coastal currents in the northern SCS (NSCS) was caused by the interaction between the Pearl River plume (PRP) and the alongshore coastal jet. Observations indicate that the NSCS coastal current was generally eastward, spreading the PRP water eastward. The lighter brackish plume residing on the top of the saline, coastal water strengthened the stratification near the surface and blocked the downward momentum transport, resulting in a strong vertical shear of the velocity at the mooring site S205. Meanwhile, the plume water raised the sea level. Because of the geostrophic balance in the across-shore direction, the eastward coastal current in the upper layer strengthened on the onshore side (near S205) and weakened on the offshore side (near S206 and S305) due to the plume water intrusion. Therefore, the vertical shear of the velocity was enhanced at S205 and reduced at S206 and S305. Moreover, because the plume varied substantially with the wind, the vertical shear of the velocity responding to the wind was different between S205 and S206. The numerical simulation during summer 2008 confirms that the PRP enhances (weakens) the vertical shear of the velocity on the onshore (offshore) side by increasing (decreasing) the upper-layer current by about 0.2 m s-1 and decreasing (increasing) the middle-layer current slightly.

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Acknowledgments

This work is supported by the Ministry of Science and Technology (2011CB403504), the CAS (XDA10010405), the NSFC (No. 41476012), the General Research Fund of Hong Kong Research Grants Council under grants CUHK 402912 and 403113, and the SCSIO (No. SQ201001). The authors thank the SCOPE-PP cruise in July 2008, co-organized by Profs. J. Zhu, J.Y. Hu, X.G. Guo, M.H. Dai, and J.P. Gan. We also thank two anonymous reviewers for their helpful comments.

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Authors and Affiliations

  1. State Key laboratory of tropical oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, People’s Republic of China

    Yeqiang Shu, Ju Chen, Jinglong Yao, Weiwen Wang, Huabin Mao & Dongxiao Wang

  2. Institute of Space and Earth Information Science, The Chinese University of Hong Kong, Hong Kong, People’s Republic of China

    Jiayi Pan

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  1. Yeqiang Shu
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  2. Ju Chen
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  3. Jinglong Yao
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  5. Weiwen Wang
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  7. Dongxiao Wang
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Correspondence to Dongxiao Wang.

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Shu, Y., Chen, J., Yao, J. et al. Effects of the Pearl River plume on the vertical structure of coastal currents in the Northern South China Sea during summer 2008. Ocean Dynamics 64, 1743–1752 (2014). https://doi.org/10.1007/s10236-014-0779-5

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  • DOI: https://doi.org/10.1007/s10236-014-0779-5

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