Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

The formation and fate of internal waves in the South China Sea

A Corrigendum to this article was published on 18 November 2015

Abstract

Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis1, sediment and pollutant transport2 and acoustic transmission3; they also pose hazards for man-made structures in the ocean4. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking5, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects6,7. For over a decade, studies8,9,10,11 have targeted the South China Sea, where the oceans’ most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. Here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.

Your institute does not have access to this article

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Overview of internal waves in the South China Sea.
Figure 2: Near-field processes in the Luzon Strait.
Figure 3: Internal wave energy fluxes in the South China Sea.
Figure 4: The Kuroshio and its impact on wave propagation.

References

  1. Wang, Y. H., Dai, C. F. & Chen, Y. Y. Physical and ecological processes of internal waves on an isolated reef ecosystem in the South China Sea. Geophys. Res. Lett. 34, 1–5 (2007)

    Google Scholar 

  2. Bogucki, D., Dickey, T. & Redekopp, L. Sediment resuspension and mixing by resonantly generated internal solitary waves. J. Phys. Oceanogr. 27, 1181–1196 (1997)

    Article  ADS  Google Scholar 

  3. Williams, K. L., Henyey, F. S., Rouseff, D., Reynolds, S. A. & Ewart, T. Internal wave effects on high-frequency acoustic propagation to horizontal arrays—experiment and implications to imaging. IEEE J. Oceanic Eng. 26, 102–112 (2001)

    Article  ADS  Google Scholar 

  4. Osborne, A. R., Burch, T. L. & Scarlet, R. I. The influence of internal waves on deep-water drilling. J. Petrol. Technol. 30, 1497–1504 (1978)

    Article  Google Scholar 

  5. Ray, R. D. & Mitchum, G. T. Surface manifestation of internal tides generated near Hawaii. Geophys. Res. Lett. 23, 2101–2104 (1996)

    Article  ADS  Google Scholar 

  6. Simmons, H., Jayne, S., Laurent, L. S. & Weaver, A. Tidally driven mixing in a num-erical model of the ocean general circulation. Ocean Model. 6, 245–263 (2004)

    Article  ADS  Google Scholar 

  7. Melet, A., Hallberg, R., Legg, S. & Polzin, K. L. Sensitivity of the ocean state to the vertical distribution of internal-tide-driven mixing. J. Phys. Oceanogr. 43, 602–615 (2013)

    Article  ADS  Google Scholar 

  8. Ramp, S. R. et al. Internal solitons in the northeastern South China Sea, part I: sources and deep-water propagation. IEEE J. Oceanic Eng. 29, 1157–1181 (2004)

    Article  ADS  Google Scholar 

  9. Jan, S., Lien, R. & Ting, C. Numerical study of baroclinic tides in Luzon Strait. J. Oceanogr. 64, 789–802 (2008)

    Article  Google Scholar 

  10. Cai, S., Xie, J. & He, J. An overview of internal solitary waves in the South China Sea. Surv. Geophys. 33, 927–943 (2012)

    Article  ADS  Google Scholar 

  11. Guo, C. & Chen, X. A review of internal solitary wave dynamics in the northern South China Sea. Prog. Oceanogr. 121, 7–23 (2014)

    Article  ADS  Google Scholar 

  12. Ferrari, R. & Wunsch, C. Ocean circulation kinetic energy: reservoirs, sources, and sinks. Annu. Rev. Fluid Mech. 41, 253–282 (2009)

    Article  ADS  MATH  Google Scholar 

  13. Moore, S. & Lien, R.-C. Pilot whales follow internal solitary waves in the South China Sea. Mar. Mamm. Sci. 23, 193–196 (2007)

    Article  Google Scholar 

  14. Rudnick, D. et al. From tides to mixing along the Hawaiian Ridge. Science 301, 355–357 (2003)

    CAS  Article  ADS  PubMed  Google Scholar 

  15. Alford, M. H. et al. Energy flux and dissipation in Luzon Strait: two tales of two ridges. J. Phys. Oceanogr. 41, 2211–2222 (2011)

    Article  ADS  Google Scholar 

  16. Alford, M. H. Energy available for ocean mixing redistributed through long-range propagation of internal waves. Nature 423, 159–162 (2003)

    CAS  Article  ADS  PubMed  Google Scholar 

  17. Buijsman, M. et al. Three-dimensional double-ridge internal tide resonance in Luzon Strait. J. Phys. Oceanogr. 44, 850–869 (2014)

    Article  ADS  Google Scholar 

  18. Pinkel, R., Buijsman, M. & Klymak, J. M. Breaking topographic lee waves in a tidal channel in Luzon Strait. Oceanography 25, 160–165 (2012)

    Article  Google Scholar 

  19. Qu, T., Du, Y. & Sasaki, H. South China Sea throughflow: a heat and freshwater conveyor. Geophys. Res. Lett. 33, L23617 (2006)

    Article  ADS  Google Scholar 

  20. Mercier, M. et al. Large-scale realistic modeling of M2 internal tide generation at the Luzon Strait. Geophys. Res. Lett. 40, 5704–5709 (2013)

    Article  ADS  Google Scholar 

  21. Helfrich, K. R. & Grimshaw, R. H. J. Nonlinear disintegration of the internal tide. J. Phys. Oceanogr. 38, 686–701 (2008)

    Article  ADS  Google Scholar 

  22. Farmer, D., Li, Q. & Park, J.-H. Internal wave observations in the South China Sea: the role of rotation and nonlinearity. Atmosphere-Ocean 47, 267–280 (2009)

    Article  Google Scholar 

  23. Li, Q. & Farmer, D. The generation and evolution of nonlinear internal waves in the deep basin of the South China Sea. J. Phys. Oceanogr. 41, 1345–1363 (2011).

  24. Park, J.-H. & Farmer, D. M. Effects of Kuroshio intrusions on nonlinear internal waves in the South China Sea during winter. J. Geophys. Res. 118, 7081–7094 (2013)

    Article  ADS  Google Scholar 

  25. Ramp, S. R., Yang, Y. & Bahr, F. L. Characterizing the nonlinear internal wave climate in the Northeastern South China Sea. Nonlinear Process. Geophys. 17, 481–498 (2010)

    Article  ADS  Google Scholar 

  26. Alford, M. H. et al. Speed and evolution of nonlinear internal waves transiting the South China Sea. J. Phys. Oceanogr. 40, 1338–1355 (2010)

    Article  ADS  Google Scholar 

  27. Lien, R.-C., Henyey, F., Ma, B. & Yang, Y.-J. Large-amplitude internal solitary waves observed in the northern South China Sea: properties and energetics. J. Phys. Oceanogr. 44, 1095–1115 (2014)

    Article  ADS  Google Scholar 

  28. Klymak, J. M. et al. An estimate of tidal energy lost to turbulence at the Hawaiian Ridge. J. Phys. Oceanogr. 36, 1148–1164 (2006)

    Article  ADS  Google Scholar 

  29. Klymak, J. M., Alford, M. H., Pinkel, R., Lien, R. C. & Yang, Y. J. The breaking and scattering of the internal tide on a continental slope. J. Phys. Oceanogr. 41, 926–945 (2011)

    Article  ADS  Google Scholar 

  30. Vitousek, S. & Fringer, O. B. Physical vs. numerical dispersion in nonhydrostatic ocean modeling. Ocean Model. 40, 72–86 (2011)

    Article  ADS  Google Scholar 

  31. Egbert, G. & Erofeeva, S. Efficient inverse modeling of barotropic ocean tides. J. Atmos. Ocean. Technol. 19, 183–204 (2002)

    Article  ADS  Google Scholar 

  32. Smith, W. H. F. & Sandwell, D. T. Global sea floor topography from satellite altimetry and ship depth soundings. Science 277, 1956–1962 (1997)

    CAS  Article  Google Scholar 

  33. Teague, W. J., Carron, M. J. & Hogan, P. J. A comparison between the generalized Digital Environmental Model and Levitus climatologies. J. Geophys. Res. 95, 7167–7183 (1990)

    Article  ADS  Google Scholar 

  34. Hallberg, R. & Rhines, P. Buoyancy-driven circulation in an ocean basin with isopycnals intersecting the sloping boundary. J. Phys. Oceanogr. 26, 913–940 (1996)

    Article  ADS  Google Scholar 

  35. Simmons, H. L. et al. Modeling and prediction of internal waves in the South China Sea. Oceanography 24, 88–99 (2011)

    Article  Google Scholar 

  36. Marshall, J., Adcroft, A., Hill, C., Perelman, L. & Heisey, C. A finite-volume, incompressible Navier Stokes model for studies of the ocean on parallel computers. J. Geophys. Res. 102 (C3). 5753–5766 (1997)

    Article  ADS  Google Scholar 

  37. Ko, D. S., Martin, P. J., Rowley, C. D. & Preller, R. H. A real-time coastal ocean prediction experiment for MREA04. J. Mar. Syst. 69, 17–28 (2008)

    Article  Google Scholar 

  38. Chen, Y.-J., Shan Ko, D. & Shaw, P.-T. The generation and propagation of internal solitary waves in the South China Sea. J. Geophys. Res. Oceans 118, 6578–6589 (2013)

    Article  ADS  Google Scholar 

  39. Ma, B. B., Lien, R.-C. & Ko, D. S. The variability of internal tides in the Northern South China Sea. J. Oceanogr. 69, 619–630 (2013)

    Article  Google Scholar 

  40. Ko, D. S., Martin, P. J., Rowley, C. D. & Preller, R. H. A real-time coastal ocean prediction experiment for MREA04. J. Mar. Syst. 69, 17–28 (2008)

    Article  Google Scholar 

  41. Chassignet, E. P. et al. The HYCOM (HYbrid Coordinate Ocean Model) data assimilative system. J. Mar. Syst. 65, 60–83 (2007)

    Article  Google Scholar 

  42. Sherman, J., Davis, R., Owens, W. & Valdes, J. The autonomous underwater glider “Spray”. IEEE J. Oceanic Eng. 26, 437–446 (2001)

    Article  ADS  Google Scholar 

  43. Doherty, K., Frye, D., Liberatore, S. & Toole, J. A moored profiling instrument. J. Atmos. Ocean. Technol. 16, 1816–1829 (1999)

    Article  ADS  Google Scholar 

  44. Li, Q., Farmer, D. M., Duda, T. F. & Ramp, S. Acoustical measurement of nonlinear internal waves using the inverted echo sounder. J. Atmos. Ocean. Technol. 26, 2228–2242 (2009)

    Article  ADS  Google Scholar 

  45. Gregg, M. C. in Physical Processes in Lakes and Oceans (ed. Imberger, J.) Vol. 54 305–338 (American Geophysical Union, 1998)

    Book  Google Scholar 

  46. Dillon, T. M. Vertical overturns: a comparison of Thorpe and Ozmidov length scales. J. Geophys. Res. 87, 9601–9613 (1982)

    Article  ADS  Google Scholar 

  47. Ferron, B. H., Mercier, H., Speer, K., Gargett, A. & Polzin, K. Mixing in the Romanche fracture zone. J. Phys. Oceanogr. 28, 1929–1945 (1998)

    Article  ADS  Google Scholar 

  48. Alford, M. H., Gregg, M. C. & Merrifield, M. A. Structure, propagation and mixing of energetic baroclinic tides in Mamala Bay, Oahu, Hawaii. J. Phys. Oceanogr. 36, 997–1018 (2006)

    Article  ADS  Google Scholar 

  49. Mater, B. D., Schaad, S. M. & Venayagamoorthy, S. K. Relevance of the Thorpe length scale in stably stratified turbulence. Phys. Fluids 25, 076604 (2013)

    Article  ADS  CAS  Google Scholar 

  50. Althaus, A., Kunze, E. & Sanford, T. Internal tide radiation from Mendocino Escarpment. J. Phys. Oceanogr. 33, 1510–1527 (2003)

    Article  ADS  Google Scholar 

  51. Pickering, A. I., Alford, M. H., Rainville, L., Nash, J. D. & Lim, B. Spatial and temporal variability of internal tides in Luzon Strait. J. Phys. Oceanogr. (in the press).

  52. Nash, J. D., Alford, M. H. & Kunze, E. Estimating internal-wave energy fluxes in the ocean. J. Atmos. Ocean. Technol. 22, 1551–1570 (2005)

    Article  ADS  Google Scholar 

  53. Johnston, T. M. S., Rudnick, D. L., Alford, M. H., Pickering, A. I. & Simmons, H. L. Internal tidal energy fluxes in the South China Sea from density and velocity measurements by gliders. J. Geophys. Res. 118, 1–11 (2013)

    Article  Google Scholar 

  54. Moum, J. N., Klymak, J. M., Nash, J. D., Perlin, A. & Smyth, W. D. Energy transport by nonlinear internal waves. J. Phys. Oceanogr. 37, 1968–1988 (2007)

    Article  ADS  MathSciNet  Google Scholar 

  55. Kelly, S. & Nash, J. D. Internal-tide generation and destruction by shoaling internal tides. Geophys. Res. Lett. 37, L23611 (2010)

    Article  ADS  Google Scholar 

  56. Klymak, J. M. & Legg, S. M. A simple mixing scheme for models that resolve breaking internal waves. Ocean Model. 33, 224–234 (2010)

    Article  ADS  Google Scholar 

  57. Alford, M. H., Klymak, J. M. & Carter, G. S. Breaking internal lee waves at Kaena Ridge, Hawaii. Geophys. Res. Lett. 41, 906–912 (2014)

    Article  ADS  Google Scholar 

  58. Chang, M.-H., Lien, R.-C., Tang, T.-Y., D’Asaro, E. & Yang, Y.-J. Energy flux of nonlinear internal waves in northern South China Sea. Geophys. Res. Lett. 33, 1–5 (2006)

    Google Scholar 

  59. St Laurent, L. C., Simmons, H. L., Tang, T. Y. & Wang, Y. H. Turbulent properties of internal waves in the South China Sea. Oceanography 24, 78–87 (2011)

    Article  Google Scholar 

Download references

Acknowledgements

This article is dedicated to the memory of author T.-Y. Tang. Our work was supported by the US Office of Naval Research and the Taiwan National Science Council. We are indebted to the captains and crew of all of the research vessels that supported this work, as well as to the technical staff of the seagoing institutions. Without the skill and hard work of all of these people, these observations would not have been possible.

Author information

Authors and Affiliations

Authors

Contributions

All authors contributed to the paper in multiple ways. Primary writing: M.H.A., T. Peacock, J.A.M. & J.D.N. Synthesis and overall coordination: T. Paluszkiewicz & T.-Y.T. Energy flux calculations: M.H.A. & A.I.P. Energy budget calculation: M.H.A., M.C.B., M.-H.C., R.-C.L., J.M.K. & L.C.S.L. Near-field moorings and calculations: M.H.A., A.I.P., L.R., J.D.N., J.N.M. & M.-H.C. Far-field moorings and calculations: L.R.C., M.-H.C., R.-C.L., S.R.R., Y.J.Y. & T.-Y.T. Near-field CTD measurements (Fig. 2d): R.P. & R.M. Near-field lowered acoustic Doppler current profiler measurements: M.H.A., J.D.N., J.A.M., L.R., H.L.S., A.I.P & R.M. Pressure inverted echo sounder measurements: D.M.F., J.-H.P., Y.J.Y. & M.H.A. Microstructure measurements: L.C.S.L., K.-H.F., H.L.S. & Y.-H.W. Remote sensing: C.R.J. & H.C.G. Theory: K.R.H. & D.M.F. Glider measurements: T.M.S.J. & D.L.R. Regional contextualization and logistical support: S.-Y.C., I-H.L., S.R.R., J.W., Y.J.Y. & T.-Y.T. Far-field modelling: S.J. & H.L.S. Two-dimensional modelling: J.M.K., S.S., S.M.J., A.S., R.M. & K.V. Near-field modelling: M.C.B., O.B.F., S.L. & S.M.J. Kuroshio modelling: P.C.G., S.J. & D.S.K. Laboratory measurements: T. Peacock & M.J.M.

Corresponding author

Correspondence to Matthew H. Alford.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Comparison of observed and model energy flux.

Left, Scatter plot of flux magnitude F from observations (x axis) and far-field (UAF; University of Alaska Fairbanks) model (y axis). Error bars are ±20% for observed values and ±10% for model values (see Methods). Right, As for the left panel, but for direction θ; error bars are ±30°. See source data and ref. 15 for station locations. Black, semi-diurnal; red, diurnal.

Source data

Extended Data Table 1 Conversion and radiated flux integrated over the region 19° to 21.5° N, 120° to 122.5° E.

PowerPoint slides

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Alford, M., Peacock, T., MacKinnon, J. et al. The formation and fate of internal waves in the South China Sea. Nature 521, 65–69 (2015). https://doi.org/10.1038/nature14399

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature14399

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing