Oceanography The Official Magazine of
The Oceanography Society
Volume 24 Issue 04

View Issue TOC
Volume 24, No. 4
Pages 64 - 77

OpenAccess

From Luzon Strait to Dongsha Plateau: Stages in the Life of an Internal Wave

By David M. Farmer , Matthew H. Alford , Ren-Chieh Lien, Yiing Jiang Yang , Ming-Huei Chang, and Qiang Li  
Jump to
Article Abstract Citation References Copyright & Usage
Article Abstract

Tidal currents in Luzon Strait south of Taiwan generate some of the largest internal waves anywhere in the ocean. Recent collaborative efforts between oceanographers from the United States and Taiwan explored the generation, evolution, and characteristics of these waves from their formation in the strait to their scattering and dissipation on Dongsha Plateau and the continental slope of mainland China. Nonlinear internal waves affect offshore engineering, navigation, biological productivity, and sediment resuspension. Observations within Luzon Strait identified exceptionally large vertical excursions of density (as expressed primarily in temperature profiles) and intense turbulence as tidal currents interact with submarine ridges. In the northern part of the strait, the ridge spacing is close to the internal semidiurnal tidal wavelength, allowing wave generation at both ridges to contribute to amplification of the internal tide. Westward radiation of semidiurnal internal tidal energy is predominant in the north, diurnal energy in the south. The competing effects of nonlinearity, which tends to steepen the stratification, and rotational dispersion, which tends to disperse energy into inertial waves, transform waves traveling across the deep basin of the South China Sea. Rotation inhibits steepening, especially for the internal diurnal tide, but despite the rotational effect, the semidiurnal tide steepens sufficiently so that nonhydrostatic effects become important, leading to the formation of a nonlinear internal wave train. As the waves encounter the continental slope and Dongsha Plateau, they slow down, steepen further, and are modified and scattered into extended wave trains. At this stage, the waves can “break,” forming trapped cores. They have the potential to trap prey, which may account for their attraction to pilot whales, which are often seen following the waves as they advance toward the coast. Interesting problems remain to be explored and are the subjects of continuing investigations.

Citation

Farmer, D.M., M.H. Alford, R.-C. Lien, Y.J. Yang, M.-H. Chang, and Q. Li. 2011. From Luzon Strait to Dongsha Plateau: Stages in the life of an internal wave. Oceanography 24(4):64–77, https://doi.org/10.5670/oceanog.2011.95.

References
    Alford, A., and Z. Zhao. 2007. Global patterns of low-mode internal-wave propagation. Part II. Group velocity. Journal of Physical Oceanography 33:1,510–1,527, https://doi.org/10.1175/JPO3086.1.
  1. Alford, M.H., M.C. Gregg, and M.A. Merrifield. 2006. Structure, propagation and mixing of energetic baroclinic tides in Mamala Bay, Oahu, Hawaii. Journal of Physical Oceanography 36:997–1,018, https://doi.org/10.1175/JPO2877.1.
  2. Alford, M.H., R.-C. Lien, H. Simmons, J. Klymak, S. Ramp, Y.J. Yang, D. Tang, and M.-H. Chang. 2010. Speed and evolution of nonlinear internal waves transiting the South China Sea. Journal of Physical Oceanography 40:1,338–1,355, https://doi.org/10.1175/2010JPO4388.1
  3. Alford, M.H., J.A. MacKinnon, J.D. Nash, H. Simmons, A. Pickering, J.M. Klymak, R. Pinkel, O. Sun, L. Rainville, R. Musgrave, and others. In press. Energy flux and dissipation in Luzon Strait: Two tales of two ridges. Journal of Physical Oceanography, https://doi.org/10.1175/JPO-D-11-073.1.
  4. Buijsman, M.C., Y. Kanarska, and J.C. McWilliams. 2010a. On the generation and evolution of nonlinear internal waves in the South China Sea. Journal of Geophysical Research 115, C02012, https://doi.org/10.1029/2009JC005275.
  5. Buijsman, M.C., J.C. McWilliams, and C.R. Jackson. 2010b. East-west asymmetry in nonlinear internal waves from Luzon Strait. Journal of Geophysical Research 115, C10057, https://doi.org/10.1029/2009JC006004.
  6. Chang, M.-H., R.-C. Lien, T.Y. Tang, E.A. D’Asaro, and Y.J. Yang. 2006. Energy flux of nonlinear internal waves in northern South China Sea. Geophysical Research Letters 33, L03607, https://doi.org/10.1029/2005GL025196.
  7. Chang, M.-H., R.-C. Lien, T.Y. Tang, Y.J. Yang, and J. Wang. 2008. A composite view of surface signatures and interior properties of nonlinear internal waves: Observations and applications. Journal of Atmospheric and Oceanic Technology 25:1,218–1,227, https://doi.org/10.1175/2007JTECHO574.1.
  8. Dillon, T.M. 1982. Vertical overturns: A comparison of Thiorpe and Ozmidov length scales. Journal of Geophysical Research 87:9,601–9,613, https://doi.org/10.1029/JC087iC12p09601.
  9. Echeverri, P., and T. Peacock. 2010. Internal tide generation by arbitrary two-dimensional topography. Journal of Fluid Mechanics 659:247–266.
  10. Farmer, D.M., Q. Li, and J.-H. Park. 2009. Internal wave observations in the South China Sea: The role of rotation and nonlinearity. Atmosphere-Ocean 47:267–280, https://doi.org/10.3137/OC313.2009.
  11. Gregg, M. 1989. Scaling turbulent dissipation in the thermocline. Journal of Geophysical Research 94:9,686–9,698, https://doi.org/10.1029/JC094iC07p09686.
  12. Helfrich, K.R. 2007. Decay and return of internal solitary waves with rotation. Physics of Fluids 19, 026601, https://doi.org/10.1063/1.2472509.
  13. Hibiya, T. 1986. Generation mechanism of internal waves by tidal flow over a sill. Journal of Geophysical Research 91:7,697–7,708.
  14. Jackson, C.R. 2009. An empirical model for estimating the geographic location of nonlinear internal solitary waves. Journal of Atmospheric and Oceanic Technology 26:2,243–2,255, https://doi.org/10.1175/2009JTECHO638.1.
  15. Klymak, J.M., M.H. Alford, R. Pinkel, R.-C. Lien, Y.J. Yang, and T.-Y. Tang. 2011. The breaking and scattering of the internal tide on a continental slope. Journal of Physical Oceanography 41:926–945, https://doi.org/10.1175/2010JPO4500.1.
  16. Klymak, J.M., R. Pinkel, C.-T. Liu, A.K. Liu, and L. David. 2006. Prototypical solitons in the South China Sea. Journal of Geophysical Research 33, L11607, https://doi.org/10.1029/2006GL025932.
  17. Lamb, K.G. 2002. A numerical investigation of solitary internal waves with trapped cores formed via shoaling. Journal of Fluid Mechanics 451:109–144, https://doi.org/10.1017/S002211200100636X.
  18. Li, Q., and D.M. Farmer. 2011. The generation and evolution of nonlinear internal waves in the deep basin of the South China Sea. Journal of Physical Oceanography 41:1,345–1,363, https://doi.org/10.1175/2011JPO4587.1.
  19. Li, Q., D.M. Farmer, T.F. Duda, and S. Ramp. 2009. Acoustical measurement of nonlinear internal waves using the inverted echo sounder. Journal of Atmospheric and Oceanic Technology 26:2,228–2,242, https://doi.org/10.1175/2009JTECHO652.1.
  20. Lien, R.-C., T.Y. Tang, M.H. Chang, and E.A. D’Asaro. 2005. Energy of nonlinear internal waves in the South China Sea. Geophysical Research Letters 32, L05615, https://doi.org/10.1029/2004GL022012.
  21. Lighthill, J. 1978. Waves in Fluids. Cambridge University Press, New York, 524 pp.
  22. Martini, K.I., M.H. Alford, E. Kunze, S.M. Kelly, and J.D. Nash. 2011. Observations of internal tides on the Oregon continental slope. Journal of Physical Oceanography 41:1,772–1,794, https://doi.org/10.1175/2011JPO4581.1.
  23. Moore, S.E., and R.-C. Lien. 2007. Pilot whales follow internal solitary waves in the South China Sea. Marine Mammal Science 23:193–196, https://doi.org/10.1111/j.1748-7692.2006.00086.x.
  24. Munk, W. 1966. Abyssal recipes. Deep Sea Research and Oceanographic Abstracts 13:707–730.
  25. Nash, J.D., E. Kunze, J.M. Toole, and R.W. Schmitt. 2004. Internal tide reflection and turbulent mixing on the continental slope. Journal of Physical Oceanography 34:1,117–1,134, https://doi.org/10.1175/1520-0485(2004)034<1117:ITRATM>2.0.CO;2.
  26. Ostrovsky, V.A. 1978. Nonlinear internal waves in a rotating ocean. Oceanology 18:119–125.
  27. Rudnick, D., S. Jan, L. Centurioni, C.M. Lee, R.-C. Lien, J. Wang, D.-K. Lee, R.-S. Tseng, Y.Y. Kim, and C.-S. Chern. 2011. Seasonal and mesoscale variability of the Kuroshio near its origin. Oceanography 24(4):52–63, https://doi.org/10.5670/oceanog.2011.95.
  28. Thorpe, S.A. 1977. Turbulence and mixing in a Scottish Loch. Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 286(1334):125–181.
  29. Vlasenko, V., N. Stashchuk, and K. Hutter. 2005. Baroclinic Tides: Theoretical Modeling and Observational Evidence. Cambridge University Press, 351 pp.
  30. Warn-Varnas, A., J. Hawkins, K.G. Lamb, S. Piacsek, S. Chin-Bing, D. King, and G. Burgos. 2010. Solitary wave generation dynamics in Luzon Strait. Ocean Modelling 31:9–27, https://doi.org/10.1016/j.ocemod.2009.08.002.
  31. Zhang, Z., O.B. Fringer, and S.R. Ramp. 2011. Three-dimensional, nonhydrostatic numerical simulation of nonlinear internal wave generation and propagation in the South China Sea. Journal of Geophysical Research 116, C05022, https://doi.org/10.1029/2010JC006424.
Copyright & Usage

This is an open access article made available under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and reproduction in any medium or format as long as users cite the materials appropriately, provide a link to the Creative Commons license, and indicate the changes that were made to the original content. Images, animations, videos, or other third-party material used in articles are included in the Creative Commons license unless indicated otherwise in a credit line to the material. If the material is not included in the article’s Creative Commons license, users will need to obtain permission directly from the license holder to reproduce the material.