River plumes as a source of large-amplitude internal waves in the coastal ocean

Abstract

Satellite images have long revealed the surface expression of large amplitude internal waves that propagate along density interfaces beneath the sea surface1,2,3. Internal waves are typically the most energetic high-frequency events in the coastal ocean4,5,6, displacing water parcels by up to 100 m and generating strong currents and turbulence7 that mix nutrients into near-surface waters for biological utilization. While internal waves are known to be generated by tidal currents over ocean-bottom topography8,9,10,11,12,13, they have also been observed frequently in the absence of any apparent tide–topography interactions1,7,14. Here we present repeated measurements of velocity, density and acoustic backscatter across the Columbia River plume front. These show how internal waves can be generated from a river plume that flows as a gravity current into the coastal ocean. We find that the convergence of horizontal velocities at the plume front causes frontal growth and subsequent displacement downward of near-surface waters. Individual freely propagating waves are released from the river plume front when the front's propagation speed decreases below the wave speed in the water ahead of it. This mechanism generates internal waves of similar amplitude and steepness as internal waves from tide–topography interactions observed elsewhere11, and is therefore important to the understanding of coastal ocean mixing.

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Figure 1: Synthetic aperture radar (SAR) image of the Columbia River plume on 9 August 2002.
Figure 2: Progression of the Columbia River plume from satellite-derived SST images.
Figure 3: Three stages of a wave-generation event.
Figure 4: Time-evolution of plume front and wave packet.

References

  1. 1

    Fu, L. L. & Holt, B. Seasat Views Oceans and Sea Ice with Synthetic-Aperture Radar (JPL publication 81–120, NASA Jet Propulsion Laboratory, Pasadena, 1982)

    Google Scholar 

  2. 2

    Jackson, C. & Apel, J. An atlas of internal solitary-like waves and their properties. http://www.internalwaveatlas.com/Atlas2_index.html 2004.

  3. 3

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

    ADS  Article  Google Scholar 

  4. 4

    Huthnance, J. M. Internal tides and waves near the continental shelf edge. Geophys. Astrophys. Fluid Dyn. 48, 81–105 (1989)

    ADS  Article  Google Scholar 

  5. 5

    Osborne, A. R. & Burch, T. L. Internal solitons in the Andaman Sea. Science 208, 451–460 (1980)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Ostrovsky, L. & Stepanyants, Y. Do internal solitons exist in the ocean? Rev. Geophys. 27, 293–310 (1989)

    ADS  Article  Google Scholar 

  7. 7

    Moum, J. N., Farmer, D. M., Smyth, W. D., Armi, L. & Vagle, S. Structure and generation of turbulence at interfaces strained by internal solitary waves propagating shoreward over the continental shelf. J. Phys. Oceanogr. 33, 2093–2112 (2003)

    ADS  Article  Google Scholar 

  8. 8

    Maxworthy, T. A note on the internal solitary waves produced by tidal flow over a three-dimensional ridge. J. Geophys. Res. 84, 338–346 (1979)

    ADS  Article  Google Scholar 

  9. 9

    Lamb, K. G. Numerical experiments of internal wave generation by strong tidal flow across a finite amplitude bank edge. J. Geophys. Res. 99, 843–864 (1994)

    ADS  Article  Google Scholar 

  10. 10

    Chereskin, T. K. Generation of internal waves in Massachusetts Bay. J. Phys. Oceanogr. 88, 2649–2661 (1983)

    Google Scholar 

  11. 11

    Loder, J. W., Brickman, D. & Horne, E. P. W. Detailed structure of currents and hydrography on the northern side of Georges Bank. J. Geophys. Res. 97, 14331–14351 (1992)

    ADS  Article  Google Scholar 

  12. 12

    Farmer, D. M. & Smith, J. D. in Hydrodynamics of Estuaries and Fjords (ed. Nihoul, J.) 465–493 (Elsevier, Amsterdam, 1978)

    Google Scholar 

  13. 13

    Farmer, D. M. & Armi, L. The generation and trapping of solitary waves over topography. Science 283, 188–190 (1999)

    CAS  Article  Google Scholar 

  14. 14

    Stanton, T. P. & Ostrovsky, L. A. Observations of highly nonlinear internal solitons over the continental shelf. Geophys. Res. Lett. 25, 2695–2698 (1998)

    ADS  Article  Google Scholar 

  15. 15

    Sutherland, B. R. Interfacial gravity currents. I. Mixing and entrainment. Phys. Fluids 14, 2244–2254 (2002)

    ADS  MathSciNet  CAS  Article  Google Scholar 

  16. 16

    Simpson, J. E. Gravity Currents in the Environment and Laboratory (Cambridge Univ. Press, Cambridge, UK, 1987)

    Google Scholar 

  17. 17

    Christie, D. R., Muirhead, K. J. & Clarke, R. H. Solitary waves in the lower atmosphere. Nature 293, 46–49 (1981)

    ADS  Article  Google Scholar 

  18. 18

    Smith, R. K., Crook, N. & Roff, G. The Morning Glory: An extraordinary atmospheric undular bore. Q. J. R. Meteorol. Soc. 108, 937–956 (1982)

    ADS  Article  Google Scholar 

  19. 19

    Doviak, R. J., Chen, S. S. & Christie, D. R. Thunderstorm-generated solitary wave observation compared with theory for nonlinear waves in a sheared atmosphere. J. Atmos. Sci. 48, 87–111 (1991)

    ADS  Article  Google Scholar 

  20. 20

    Rao, M. P., Castracane, P., Casadio, S., Fua, D. & Fiocco, G. Observations of atmospheric solitary waves in the urban boundary layer. Boundary-Layer Meteorol. 111, 85–108 (2004)

    ADS  Article  Google Scholar 

  21. 21

    Rottman, J. W. & Simpson, J. E. The formation of internal bores in the atmosphere: A laboratory model. Q. J. R. Meteorol. Soc. 115, 941–963 (1989)

    ADS  Article  Google Scholar 

  22. 22

    Maxworthy, T., Leilich, J., Simpson, J. E. & Meiburg, E. H. The propagation of a gravity wave into a linearly stratified fluid. J. Fluid Mech. 453, 371–394 (2002)

    ADS  MathSciNet  CAS  Article  Google Scholar 

  23. 23

    Orton, P. M. & Jay, D. A. Observations at the tidal plume front of a high-volume river outflow. Geophys. Res. Lett. 32, L11605 doi:10.1029/2005GL02237 (2005)

    ADS  Article  Google Scholar 

  24. 24

    Britter, R. E. & Simpson, J. E. Experiments on the dynamics of a gravity current head. J. Fluid Mech. 88, 223–240 (1978)

    ADS  Article  Google Scholar 

  25. 25

    Luketina, D. A. & Imberger, J. Characteristics of a surface buoyant jet. J. Geophys. Res. 92, 5435–5447 (1987)

    ADS  Article  Google Scholar 

  26. 26

    Drazin, P. G. & Reid, W. H. Hydrodynamic Stability (Cambridge Univ. Press, Cambridge, 1981)

    Google Scholar 

  27. 27

    O'Donnell, J. & Garvine, R. W. A time dependant, two layer frontal model of buoyant plume dynamics. Tellus A 35, 73–80 (1983)

    ADS  Article  Google Scholar 

  28. 28

    Duda, T. F. et al. Internal tide and nonlinear internal wave behaviour at the continental slope in the Northern South China Sea. IEEE J. Ocean. Eng. 20, 1105–1130 (2004)

    Article  Google Scholar 

  29. 29

    Moum, J. N., Gregg, M. C., Lien, R. C. & Carr, M. Comparison of turbulence kinetic energy dissipation rate estimates from two ocean microstructure profilers. J. Atmos. Ocean. Technol. 12, 346–366 (1995)

    ADS  Article  Google Scholar 

Download references

Acknowledgements

We thank M. Neeley-Brown, R. Kreth and A. Perlin for their technical expertise. L. Kilcher, T. Kimura, R. Bjorkquist, A. Horner-Devine, T. Chisholm, and the captain and crew of the RV Pt. Sur made data collection possible. Satellite imagery was provided by P.T. Strub and P. Orton. Comments were provided by W.D. Smyth, G. Avicola and J. Klymak. This work was funded by the National Science Foundation and the Office of Naval Research.

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Correspondence to Jonathan D. Nash.

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Nash, J., Moum, J. River plumes as a source of large-amplitude internal waves in the coastal ocean. Nature 437, 400–403 (2005). https://doi.org/10.1038/nature03936

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