Long-range propagation and associated variability of internal tides in the South China Sea

The disintegration of the equatorward-propagating K1 internal tide in the South China Sea (SCS) by parametric subharmonic instability (PSI) at its critical latitude of 14.52&#186;N is investigated numerically. The multiple-source generation and long-range propagation of K1 internal tides are successfully reproduced. Using equilibrium analysis, the internal wave field near the critical latitude is found to experience two quasi-steady states, between which the subharmonic waves develop constantly. The simulated subharmonic waves agree well with classic PSI theoretical prediction. The PSI-induced near-inertial waves are of half the K1 frequency and dominantly high modes, the vertical scales ranging from 50 to 180 m in the upper ocean. From an energy perspective, PSI mainly occurs in the critical latitudinal zone from 13&#8211;15&#186;N. In this zone, the incident internal tide loses ~14% energy in the mature state of PSI. PSI triggers a mixing elevation of O(10-5&#8211;10-4 m2/s) in the upper ocean at the critical latitude, which is several times larger than the background value. The contribution of PSI to the internal tide energy loss and associated enhanced mixing may differ regionally and is closely dependent on the intensity and duration of background internal tide. The results elucidate the far-field dissipation mechanism by PSI in connecting interior mixing with remotely generated K1 internal tides in the Luzon Strait.

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Determination of Harmonic Parameters with Temporal Variations: An Enhanced Harmonic Analysis Algorithm and Application to Internal Tidal Currents in the South China Sea

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-16-0239.1 ◽

2018 ◽

Vol 35 (7) ◽

pp. 1375-1398 ◽

Cited By ~ 9

Author(s):

Guangzhen Jin ◽

Haidong Pan ◽

Qilin Zhang ◽

Xianqing Lv ◽

Wei Zhao ◽

...

Keyword(s):

South China Sea ◽

Harmonic Analysis ◽

South China ◽

Spline Interpolation ◽

Temporal Variations ◽

Tidal Currents ◽

The South China Sea ◽

Internal Tides ◽

The South ◽

China Sea

AbstractAs an effective tool to distinguish different tidal components, classical tidal current harmonic analysis has been widely used to obtain harmonic parameters of internal tidal currents. However, harmonic parameters cannot exactly reveal the motion of internal tides, as the irregular temporal variations for internal tides are significant in many regions of the world’s oceans. An enhanced harmonic analysis (EHA) algorithm based on the independent point scheme and cubic spline interpolation is presented in this paper to obtain harmonic parameters with temporal variations for different tidal constituents of internal tides. Moreover, this algorithm is applied to analyze 14 months of current data obtained from a mooring located on the continental shelf in the northeastern region of the South China Sea. The obvious irregular temporal variations for the four principal constituents—M2, K1, S2, and O1—of internal tides in this region are indicated. It is hoped that this algorithm might present a brand-new view for researchers to investigate the irregular temporal motions of internal tides.

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Long-range correlations in remotely sensed chlorophyll in the South China Sea

Chinese Science Bulletin ◽

10.1007/s11434-006-9045-7 ◽

2006 ◽

Vol 51 (S2) ◽

pp. 45-49

Author(s):

Haigang Zhan ◽

Ping Shi ◽

Qinwen Mao ◽

Tonghui Zhang

Keyword(s):

South China Sea ◽

Long Range ◽

South China ◽

Remotely Sensed ◽

The South China Sea ◽

The South ◽

Long Range Correlations ◽

China Sea

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Influence of Remote Internal Tides on the Locally Generated Internal Tides upon the Continental Slope in the South China Sea

Journal of Marine Science and Engineering ◽

10.3390/jmse9111268 ◽

2021 ◽

Vol 9 (11) ◽

pp. 1268

Author(s):

Zheng Guo ◽

Anzhou Cao ◽

Shuya Wang

Keyword(s):

South China Sea ◽

Continental Slope ◽

South China ◽

Maximum Energy ◽

The South China Sea ◽

Internal Tides ◽

The South ◽

China Sea ◽

The Taiwan Strait ◽

Local Generation

In this paper, the M2 internal tides (ITs) originating from the continental slope in the South China Sea are studied using the CROCO model. The simulation results show that there are two origins of ITs on the continental slope: at 118°–119.5° E along 22° N near the southern entrance of the Taiwan Strait and at 117°–118° E along 20° N near Dongsha Island. The local generation of ITs is greatly influenced by the ITs that radiate from the Luzon Strait (LS). The integrated conversion at the first generation site is increased by 31% to 0.42 GW compared to the case where the LS is excluded from the simulation region. Its maximum energy flux almost doubles to 2.5 kW/m, which is 10% of the westward component. The existence of the other IT beams from Dongsha Island is attributed to the ITs from the LS. The local generation on the continental slope changes when remotely generated ITs alter the amplitudes and phases of the bottom pressure perturbation. These results indicate that the ITs originating from the LS contribute to the spatial variation of ITs in the SCS by modulating the IT generation on the continental slope.

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Disintegration of the K1 Internal Tide in the South China Sea due to Parametric Subharmonic Instability

Journal of Physical Oceanography ◽

10.1175/jpo-d-19-0320.1 ◽

2020 ◽

Vol 50 (12) ◽

pp. 3605-3622

Author(s):

Kun Liu ◽

Zhongxiang Zhao

Keyword(s):

South China Sea ◽

South China ◽

Internal Tide ◽

The South China Sea ◽

Internal Tides ◽

Upper Ocean ◽

The South ◽

China Sea ◽

Parametric Subharmonic Instability ◽

Critical Latitude

AbstractThe disintegration of the equatorward-propagating K1 internal tide in the South China Sea (SCS) by parametric subharmonic instability (PSI) at its critical latitude of 14.52°N is investigated numerically. The multiple-source generation and long-range propagation of K1 internal tides are successfully reproduced. Using equilibrium analysis, the internal wave field near the critical latitude is found to experience two quasi-steady states, between which the subharmonic waves develop constantly. The simulated subharmonic waves agree well with classic PSI theoretical prediction. The PSI-induced near-inertial waves are of half the K1 frequency and dominantly high modes, the vertical scales ranging from 50 to 180 m in the upper ocean. From an energy perspective, PSI mainly occurs in the critical latitudinal zone from 13° to 15°N. In this zone, the incident internal tide loses ~14% energy in the mature state of PSI. PSI triggers a mixing elevation of O(10−5–10−4) m2 s−1 in the upper ocean at the critical latitude, which is several times larger than the background value. The contribution of PSI to the internal tide energy loss and associated enhanced mixing may differ regionally and is closely dependent on the intensity and duration of background internal tide. The results elucidate the far-field dissipation mechanism by PSI in connecting interior mixing with remotely generated K1 internal tides in the Luzon Strait.

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Tidal Mixing in the South China Sea: An Estimate Based on the Internal Tide Energetics

Journal of Physical Oceanography ◽

10.1175/jpo-d-15-0082.1 ◽

2016 ◽

Vol 46 (1) ◽

pp. 107-124 ◽

Cited By ~ 28

Author(s):

Xiaowei Wang ◽

Shiqiu Peng ◽

Zhiyu Liu ◽

Rui Xin Huang ◽

Yu-Kun Qian ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Dissipation Rate ◽

Internal Tide ◽

The South China Sea ◽

Internal Tides ◽

Tidal Mixing ◽

The South ◽

China Sea ◽

Diapycnal Diffusivity

AbstractBy taking into account the contributions of both locally and remotely generated internal tides, the tidal mixing in the Luzon Strait (LS) and the South China Sea (SCS) is investigated through internal-tide simulation and energetics analysis. A three-dimensional nonhydrostatic high-resolution model driven by four primary tidal constituents (M2, S2, K1, and O1) is used for the internal-tide simulation. The baroclinic energy budget analysis reveals that the internal tides radiated from the LS are the dominant energy source for the tidal dissipation in the SCS. In the LS, the estimated depth-integrated turbulent kinetic energy dissipation exceeds O(1) W m−2 atop the two subsurface ridges, with a dissipation rate of >O(10−7) W kg−1 and diapycnal diffusivity of ~O(10−2) m2 s−1. In the SCS, the most intense turbulence occurs in the deep-water basin with a dissipation rate of O(10−8–10−6) W kg−1 and diapycnal diffusivity of O(10−3–10−1) m2 s−1 within the ~2000-m water column above the seafloor as well as in the shelfbreak region with a dissipation rate of O(10−7–10−6) W kg−1 and diapycnal diffusivity of O(10−4–10−3) m2 s−1. These estimated values are consistent with observations reported in previous studies and are at least one order of magnitude larger than those based solely on locally generated internal tides.

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