Oceanography The Official Magazine of
The Oceanography Society
Volume 25 Issue 02

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Volume 25, No. 2
Pages 160 - 165

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Breaking Topographic Lee Waves in a Tidal Channel in Luzon Strait

By Robert Pinkel , Maarten Buijsman , and Jody M. Klymak 
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Article Abstract

Barotropic tides generate energetic internal tides, smaller-scale waves, and turbulence as they flow through Luzon Strait, between Taiwan and the Philippines. Three-dimensional numerical simulations of this process suggest that small-scale lee waves will form and break preferentially in “outflow channels,” trough-like depressions that descend the strait’s flanks. In the simulations, these sites are the locations of the most intense dissipation in the eastern strait. To investigate this numerical prediction, an 11-day cruise on R/V Roger Revelle was devoted to exploring an outflow channel on the eastern slope of the strait, north of Batan Island. Using a rapidly profiling conductivity-temperature-depth sensor and shipboard Doppler sonars, observations of velocity and density fields were made at four sites in the channel. At Site III, approximately 4 km offshore the crest, the generated lee wave was found to occupy much of the water column. It expanded upward from the seafloor as an irregular disturbance with a dominant vertical scale of 250 m. Sea-surface horizontal currents exceeded 1.5 m s–1 and were sufficient to cause surface waves to break at 1,300 m above the local topography. Widespread internal wave breaking appeared initially at the seafloor and spread to much of the water column during the outflow phase of the tide. Breaking was also seen to a lesser extent on the inflow phase, as Pacific waters were advected westward toward the crest. The average dissipation rate at Site III, 8 W m–2, exceeds typical wind energy input rates by four orders of magnitude.

Citation

Pinkel, R., M. Buijsman, and J.M. Klymak. 2012. Breaking topographic lee waves in a tidal channel in Luzon Strait. Oceanography 25(2):160–165, https://doi.org/10.5670/oceanog.2012.51.

References
    Alford, M.H., and R. Pinkel. 2000. Observations of overturning in the thermocline: The context of ocean mixing. Journal of Physical Oceanography 30:805–832, https://doi.org/10.1175/1520-0485(2000)030<0805:OOOITT>2.0.CO;2.
  1. 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. 2011. Energy flux and dissipation in Luzon Strait: A tale of two ridges. Journal of Physical Oceanography 41:2,211–2,222, https://doi.org/10.1175/JPO-D-11-073.1.
  2. Aucan, J., M.A. Merrifield, D.S. Luther, and P. Flament. 2006. Tidal mixing events on the deep flanks of Kaena Ridge, Hawaii. Journal of Physical Oceanography 36:1,202–1,219, https://doi.org/10.1175/JPO2888.1.
  3. Dillon, T.M. 1982. Vertical overturns: A comparison of Thorpe and Ozmidov scales. Journal of Geophysical Research 87:9,601–9,613, https://doi.org/10.1029/JC087iC12p09601.
  4. 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.
  5. Klymak, J.M., R. Pinkel, and L. Rainville. 2008. Direct breaking of the internal tide near topography: Kaena Ridge, Hawaii. Journal of Physical Oceanography 38:380–399, https://doi.org/10.1175/2007JPO3728.1.
  6. Klymak, J.M., S. Legg, and R. Pinkel. 2010. A simple parameterization of turbulent tidal mixing near supercritical topography. Journal of Physical Oceanography 40:2,059–2,074, https://doi.org/10.1175/2010JPO4396.1.
  7. Legg, S., and J.M. Klymak. 2008. Internal hydraulic jumps and overturning generated by tidal flow over a tall steep ridge. Journal of Physical Oceanography 38:1,949–1,964, https://doi.org/10.1175/2008JPO3777.1.
  8. Nash, J., M.H. Alford, E. Kunze, K. Martini, and S. Kelly. 2007. Hotspots of deep ocean mixing on the Oregon continental slope. Geophysical Research Letters 34, L01605, https://doi.org/10.1029/2006GL028170.
  9. Nikurashin, M., and R. Ferrari. 2010. Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography: Application to the Southern Ocean. Journal of Physical Oceanography 40:2,025–2,042, https://doi.org/10.1175/2010JPO4315.1.
  10. Pinkel, R., W. Munk, P. Worcester, B.D. Comuelle, D. Rudnick, J. Shearman, J.H. Filloux, B.D. Dushaw, B.M. Howe, T.B. Sanford, and others. 2000. Ocean mixing studies near the Hawaiian Ridge. Eos, Transactions American Geophysical Union 81(46):545, https://doi.org/10.1029/EO081i046p00545-02.
  11. Thorpe, S.A. 1977. Turbulence and mixing in a Scottish loch. Philosophical Transactions of the Royal Society of London A 28:125–181, https://doi.org/10.1098/rsta.1977.0112.
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