scholarly journals The Lifecycle of Nonlinear Internal Waves in the Northwestern South China Sea

2019 ◽  
Vol 49 (8) ◽  
pp. 2133-2145 ◽  
Author(s):  
Jianjun Liang ◽  
Xiao-Ming Li ◽  
Jin Sha ◽  
Tong Jia ◽  
Yongzheng Ren
Keyword(s):  
South China Sea ◽  
Internal Waves ◽  
South China ◽  
Internal Tide ◽  
In Situ Measurements ◽  
Shelf Break ◽  
Undular Bore ◽  
Nonlinear Internal Waves ◽  
Seasonal Thermocline

AbstractThe life cycle of nonlinear internal waves (NIWs) to the southeast of Hainan Island in the northwestern South China Sea is investigated using synergistic satellite observations, in situ measurements, and numerical simulations. A three-dimensional, fully nonlinear and nonhydrostatic model with ultrafine resolution shows that a diurnal internal tide emanates from a sill in the Xisha Islands at approximately 215 km away from the local shelf break. The internal tide transits the deep basin toward the shelf break and reflects at the sea bottom and seasonal thermocline in the form of a wave beam. Arriving at the shelf break, the internal tide undergoes nonlinear transformation and produces an undular bore. Analyses of in situ measurements reveal that the undular bore appears as sharp depressions of the strong near-surface seasonal thermocline. The undular bore gradually evolves into an internal solitary wave train on the midshelf, which was detected by the spaceborne synthetic aperture radar. This finding has great implications for investigating NIWs in other coastal oceans where waves are controlled by remotely generated internal tides.

scholarly journals The Generation and Evolution of Nonlinear Internal Waves in the Deep Basin of the South China Sea

2011 ◽  
Vol 41 (7) ◽  
pp. 1345-1363 ◽  
Author(s):  
Qiang Li ◽  
David M. Farmer
Keyword(s):  
South China Sea ◽  
Internal Waves ◽  
South China ◽  
Internal Tide ◽  
Luzon Strait ◽  
The South China Sea ◽  
The South ◽  
Deep Basin ◽  
Nonlinear Internal Waves ◽  
China Sea

Abstract Time series observations of nonlinear internal waves in the deep basin of the South China Sea are used to evaluate mechanisms for their generation and evolution. Internal tides are generated by tidal currents over ridges in Luzon Strait and steepen as they travel west, subsequently generating high-frequency nonlinear waves. Although nonlinear internal waves appear repeatedly on the western slopes of the South China Sea, their appearance in the deep basin is intermittent and more closely related to the amplitude of the semidiurnal than the predominant diurnal tidal current in Luzon Strait. As the internal tide propagates westward, it evolves under the influence of nonlinearity, rotation, and nonhydrostatic dispersion. The interaction between nonlinearity and rotation transforms the internal tide into a parabolic or corner shape. A fully nonlinear two-layer internal wave model explains the observed characteristics of internal tide evolution in the deep basin for different representative forcing conditions and allows assessment of differences between the fully and weakly nonlinear descriptions. Matching this model to a wave generation solution for representative topography in Luzon Strait leads to predictions in the deep basin consistent with observations. Separation of the eastern and western ridges is close to the internal semidiurnal tidal wavelength, contributing to intensification of the westward propagating semidiurnal component. Doppler effects of internal tide generation, when combined with a steady background flow, suggest an explanation for the apparent suppression of nonlinear wave generation during periods of westward intrusion of the Kuroshio.

Study of Nonlinear Internal Waves and Impact on Offshore Drilling Units

2011 ◽  
Author(s):  
Nishu V. Kurup ◽  
Shan Shi ◽  
Zhongmin Shi ◽  
Wenju Miao ◽  
Lei Jiang
Keyword(s):  
Numerical Model ◽  
South China Sea ◽  
Internal Wave ◽  
Internal Waves ◽  
South China ◽  
Andaman Sea ◽  
Offshore Drilling ◽  
Nonlinear Internal Waves ◽  
Drilling Operations ◽  
Drilling System

Internal waves near the ocean surface have been observed in many parts of the world including the Andaman Sea, Sulu Sea and South China Sea among others. The factors that cause and propagate these large amplitude waves include bathymetry, density stratification and ocean currents. Although their effects on floating drilling platforms and its riser systems have not been extensively studied, these waves have in the past seriously disrupted offshore exploration and drilling operations. In particular a drill pipe was ripped from the BOP and lost during drilling operations in the Andaman sea. Drilling riser damages were also reported from the south China Sea among other places. The purpose of this paper is to present a valid numerical model conforming to the physics of weakly nonlinear internal waves and to study the effects on offshore drilling semisubmersibles and riser systems. The pertinent differential equation that captures the physics is the Korteweg-de Vries (KdV) equation which has a general solution involving Jacobian elliptical functions. The solution of the Taylor Goldstein equation captures the effects of the pycnocline. Internal wave packets with decayed oscillations as observed from satellite pictures are specifically modeled. The nonlinear internal waves are characterized by wave amplitudes that can exceed 50 ms and the present of shearing currents near the layer of pycnocline. The offshore drilling system is exposed to these current shears and the associated movements of large volumes of water. The effect of internal waves on drilling systems is studied through nonlinear fully coupled time domain analysis. The numerical model is implemented in a coupled analysis program where the hull, moorings and riser are considered as an integrated system. The program is then utilized to study the effects of the internal wave on the platform global motions and drilling system integrity. The study could be useful for future guidance on offshore exploration and drilling operations in areas where the internal wave phenomenon is prominent.

Observed acoustic arrival structure and intensity variability induced by transbasin nonlinear internal waves in the South China Sea basin

2008 ◽  
Vol 123 (5) ◽  
pp. 3588-3588 ◽  
Author(s):  
Chingsang Chiu ◽  
D. Benjamin Reeder ◽  
Christopher Miller ◽  
Justin Reeves ◽  
Steve Ramp ◽  
...  
Keyword(s):  
South China Sea ◽  
Internal Waves ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
Nonlinear Internal Waves ◽  
China Sea

The Generation of Nonlinear Internal Waves in the South China Sea: A Three‐Dimensional, Nonhydrostatic Numerical Study

2019 ◽  
Vol 124 (12) ◽  
pp. 8949-8968 ◽  
Author(s):  
Zhigang Lai ◽  
Guangzhen Jin ◽  
Yongmao Huang ◽  
Haiyun Chen ◽  
Xiaodong Shang ◽  
...  
Keyword(s):  
South China Sea ◽  
Internal Waves ◽  
South China ◽  
Numerical Study ◽  
Three Dimensional ◽  
The South China Sea ◽  
The South ◽  
Nonlinear Internal Waves ◽  
China Sea

scholarly journals Energy flux of nonlinear internal waves in northern South China Sea

2006 ◽  
Vol 33 (3) ◽  
Author(s):  
Ming-Huei Chang ◽  
Ren-Chieh Lien ◽  
Tswen Yung Tang ◽  
Eric A. D'Asaro ◽  
Yiing Jang Yang
Keyword(s):  
South China Sea ◽  
Internal Waves ◽  
Energy Flux ◽  
South China ◽  
Northern South China Sea ◽  
Nonlinear Internal Waves ◽  
China Sea

scholarly journals Speed and Evolution of Nonlinear Internal Waves Transiting the South China Sea

2010 ◽  
Vol 40 (6) ◽  
pp. 1338-1355 ◽  
Author(s):  
Matthew H. Alford ◽  
Ren-Chieh Lien ◽  
Harper Simmons ◽  
Jody Klymak ◽  
Steve Ramp ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Slope ◽  
Internal Waves ◽  
South China ◽  
The South China Sea ◽  
Internal Tides ◽  
Deep Basin ◽  
Nonlinear Internal Waves ◽  
The Waves ◽  
Upper Slope

Abstract In the South China Sea (SCS), 14 nonlinear internal waves are detected as they transit a synchronous array of 10 moorings spanning the waves’ generation site at Luzon Strait, through the deep basin, and onto the upper continental slope 560 km to the west. Their arrival time, speed, width, energy, amplitude, and number of trailing waves are monitored. Waves occur twice daily in a particular pattern where larger, narrower “A” waves alternate with wider, smaller “B” waves. Waves begin as broad internal tides close to Luzon Strait’s two ridges, steepening to O(3–10 km) wide in the deep basin and O(200–300 m) on the upper slope. Nearly all waves eventually develop wave trains, with larger–steeper waves developing them earlier and in greater numbers. The B waves in the deep basin begin at a mean speed of ≈5% greater than the linear mode-1 phase speed for semidiurnal internal waves (computed using climatological and in situ stratification). The A waves travel ≈5%–10% faster than B waves until they reach the continental slope, presumably because of their greater amplitude. On the upper continental slope, all waves speed up relative to linear values, but B waves now travel 8%–12% faster than A waves, in spite of being smaller. Solutions of the Taylor–Goldstein equation with observed currents demonstrate that the B waves’ faster speed is a result of modulation of the background currents by an energetic diurnal internal tide on the upper slope. Attempts to ascertain the phase of the barotropic tide at which the waves were generated yielded inconsistent results, possibly partly because of contamination at the easternmost mooring by eastward signals generated at Luzon Strait’s western ridge. These results present a coherent picture of the transbasin evolution of the waves but underscore the need to better understand their generation, the nature of their nonlinearity, and propagation through a time-variable background flow, which includes the internal tides.

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