Vertical velocity and transport in the South China Sea

Yaohua Zhu Dingqi Wang Yonggang Wang Shujiang Li Tengfei Xu Zexun Wei

Yaohua Zhu, Dingqi Wang, Yonggang Wang, Shujiang Li, Tengfei Xu, Zexun Wei. Vertical velocity and transport in the South China Sea[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1954-4
Citation: Yaohua Zhu, Dingqi Wang, Yonggang Wang, Shujiang Li, Tengfei Xu, Zexun Wei. Vertical velocity and transport in the South China Sea[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1954-4

doi: 10.1007/s13131-021-1954-4

Vertical velocity and transport in the South China Sea

Funds: The National Key Research and Development Program of China under contract No. 2019YFC1408400; the National Natural Science Foundation of China under contract Nos 41876029, 41821004 and 41776042.
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  • Figure  1.  Topography of the South China Sea. The abbreviations LS, TS, KS, MS, BS denote the Luzon Strait, Taiwan Strait, Karimata Strait, Mindoro Strait, Balabac Strait, respectively; and ZSI and NSI denote the Zhongsha Islands and Nansha Islands, respectively. Yellow line indicates the mooring section deployed off the Zhongsha Islands in Zhou et al. (2017). White stars represent the northern and southern ends of the abyssal basin below 3 000 m, where the abyssal water upwells. Red dots stand for gaps in the Heng-Chun Ridge, through which the Luzon Strait overflow sinks into the Manila Trench.

    Figure  2.  Time-mean alongshore velocity in the DWBC east of Zhongsha Islands from mooring observations (a), after Zhou et al. (2017), and HYCOM GOFS3.1 reanalysis (b). In a and b, color shading indicates the time-mean velocity, positive southwestward. Gray shading represents the topography. Black lines stand for the standard deviation of the alongshore velocity. Monthly mean alongshore velocity in the DWBC core east of Zhongsha Islands during 2012.08–2013.09 from mooring observations (c), after Zhou et al. (2017), and HYCOM GOFS3.1 reanalysis (d). In c and d, standard deviations are indicated by red bars.

    Figure  3.  Comparison of monthly mean transport from the HYCOM GOFS3.1 reanalysis (black) with that from observations (red) in the Karimata Strait (a). Positive transport is flow into the SCS and negative transport is flow into the Java Sea through the Karimata Strait. Comparison of monthly mean transport from the HYCOM GOFS3.1 reanalysis (black) with along channel velocity (red) observed in the Luzon Trough (b). Negative velocity/transport indicates westward flow. Bars indicate the standard deviations.

    Figure  4.  Domain-integrated vertical transport (a) and domain-averaged vertical velocity (b) from the HYCOM GOFS3.1 reanalysis. Domain-integrated vertical transport from the HYCOM GOFS3.0 reanalysis (c). Separately integrated upward transport and downward transports from the HYCOM GOFS3.1 reanalysis (d).

    Figure  5.  Time-mean vertical velocity at 50 m (a), and 250 m (b), and time-mean horizontal velocity field at 50 m (c), and 250 m (d).

    Figure  6.  Alternating bands of the upward-downward velocity seen from vertical sections in the thermocline cell.

    Figure  7.  Vertical velocity at 50 m (a), and 250 m (b) in winter, and at 50 m (c), and 250 m (d) in summer.

    Figure  8.  Time-mean vertical velocity at 1 500 m (a), and 2 500 m (b), and associated horizontal velocity field in (c) and (d).

    Figure  9.  Upward vertical velocity generates on the seaward side of the 3 000 m isobath along transect to the southeast of Vietnam (a), on the southern slope (b), west of the Heng-Chun Ridge (c).

    Figure  10.  Distribution of $ \dfrac{\beta }{f}\left|\nabla H\right|/{H}^{2} $ derived from the HYCOM model topography (a), and etopo5 (b).

    Figure  11.  The role of vertical transport in the three-dimensional SCS circulation. Dark blue and red arrows indicate the Luzon Strait overflow and Kuroshio intrusion, respectively. The hollow arrows in vertical present the strength of domain-averaged vertical velocity, inferring a positive vertical gradient of vertical velocity in the upper and deep layer, and a negative one in the intermediate layer. The thin blue arrows encompassing the yellow planes denote the direction of layer-averaged horizontal circulation in the basin scale.

    Table  1.   Outflows in the upper 50 m (positive outward from the SCS, unit: 106 m3/s). The numbers in brackets indicate contribution from the Ekman drift

    Luzon St.Taiwan St.Mindoro St.Balabac St.Karimata St.Net outflow
    Mean−0.39 (−0.09)1.25 (0.11)0.09 (0.24)−0.27 (0.04)0.591.27 (0.3)
    Winter−1.81 (−0.54)0.17 (0.47)0.51 (0.96)−0.42 (−0.16)2.340.79 (0.73)
    Summer1.17 (0.20)2.60 (−0.04)−0.23 (−0.15)−0.24 (0.23)−1.172.13 (0.24)
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    Table  2.   Comparison of vertical transport on the seaward side of the 3 000 m isobath with the domain-integrated transport at different vertical levels (unit: 106 m3/s)

    100 m500 m1 500 m2 500 m
    Seaward side of 3 000 m0.19−0.421.131.97
    Domain-integrated1.25 0.941.490.69
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出版历程
  • 收稿日期:  2021-08-04
  • 录用日期:  2021-10-12
  • 网络出版日期:  2021-11-09

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