Spatially Broad Observations of Internal Waves in the Upper Ocean at the Hawaiian Ridge

Joseph P. Martin Scripps Institution of Oceanography, La Jolla, California

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Daniel L. Rudnick Scripps Institution of Oceanography, La Jolla, California

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Robert Pinkel Scripps Institution of Oceanography, La Jolla, California

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Abstract

The density and current structure at the Hawaiian Ridge was observed using SeaSoar and Doppler sonar during a survey extending from Oahu to Brooks Banks. Across- and along-ridge changes in internal wave statistics in the upper ocean within 200 km of the ridge are investigated. Internal waves with trough-to-crest amplitude as large as 60 m and horizontal wavelength of about 50 km are observed repeatedly in across-ridge sections of potential density. Within 150 km of the ridge, kinetic and potential energy density exceed open-ocean values with maxima about 10 times Garrett–Munk levels. In the Kauai Channel (KC), the kinetic energy density is largest along an M2 internal tide ray. The ray originates at the northern edge of the ridge peak at a large across-ridge change in topographic slope and terminates at the ocean surface about 30–40 km south of the ridge peak. Kinetic and potential energy density are larger on the south side of the ridge at KC, the side with larger topographic slope. Energy density is also larger on the south side of the ridge at KC in numerical model results and on the side of steeper topographic slope in analytical model results. Along the ridge, the largest observed values of mean-square shear and mean-square slope of isopycnal depth are collocated with the largest energy density in numerical model results. Mean-square shear and mean-square slope increase with decreasing bottom depth and with increasing M2 barotropic tidal forcing.

Corresponding author address: Joseph Martin, Applied Physics Laboratory, University of Washington, 1013 NE 40th St., Seattle, WA 98105-6698. Email: martin@apl.washington.edu

Abstract

The density and current structure at the Hawaiian Ridge was observed using SeaSoar and Doppler sonar during a survey extending from Oahu to Brooks Banks. Across- and along-ridge changes in internal wave statistics in the upper ocean within 200 km of the ridge are investigated. Internal waves with trough-to-crest amplitude as large as 60 m and horizontal wavelength of about 50 km are observed repeatedly in across-ridge sections of potential density. Within 150 km of the ridge, kinetic and potential energy density exceed open-ocean values with maxima about 10 times Garrett–Munk levels. In the Kauai Channel (KC), the kinetic energy density is largest along an M2 internal tide ray. The ray originates at the northern edge of the ridge peak at a large across-ridge change in topographic slope and terminates at the ocean surface about 30–40 km south of the ridge peak. Kinetic and potential energy density are larger on the south side of the ridge at KC, the side with larger topographic slope. Energy density is also larger on the south side of the ridge at KC in numerical model results and on the side of steeper topographic slope in analytical model results. Along the ridge, the largest observed values of mean-square shear and mean-square slope of isopycnal depth are collocated with the largest energy density in numerical model results. Mean-square shear and mean-square slope increase with decreasing bottom depth and with increasing M2 barotropic tidal forcing.

Corresponding author address: Joseph Martin, Applied Physics Laboratory, University of Washington, 1013 NE 40th St., Seattle, WA 98105-6698. Email: martin@apl.washington.edu

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  • Althaus, A. M., E. Kunze, and T. B. Sanford, 2003: Internal tide radiation from Mendocino Escarpment. J. Phys. Oceanogr., 33 , 15101527.

    • Search Google Scholar
    • Export Citation
  • Balmforth, N. J., G. R. Ierley, and W. R. Young, 2002: Tidal conversion by nearly critical topography. J. Phys. Oceanogr., 32 , 29002914.

    • Search Google Scholar
    • Export Citation
  • Bendat, J. S., and A. G. Piersol, 2000: Random Data: Analysis and Measurement Procedures. Wiley-Interscience, 594 pp.

  • Boyd, T., M. D. Levine, S. R. Gard, and W. Waldorf, 2002: Mooring observations from the Hawaiian Ridge, Nov.2000–Jan.2001. Tech. Rep. 2002-1, Data Rep. 185, Oregon State University, Corvalis, OR.

  • Chiswell, S. M., 1994: Vertical structure of the baroclinic tides in the central North Pacific subtropical gyre. J. Phys. Oceanogr., 24 , 20322039.

    • Search Google Scholar
    • Export Citation
  • Chiswell, S. M., 2002: Energy levels, phase, and amplitude modulation of the baroclinic tide off Hawaii. J. Phys. Oceanogr., 32 , 26402651.

    • Search Google Scholar
    • Export Citation
  • Egbert, G. D., 1997: Tidal data inversion: Interpolation and inference. Progress in Oceanography, Vol. 40, Pergamon. 5380.

  • Egbert, G. D., and R. D. Ray, 2000: Significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data. Nature, 405 , 775778.

    • Search Google Scholar
    • Export Citation
  • Egbert, G. D., and R. D. Ray, 2001: Estimates of M2 tidal energy dissipation from TOPEX/Poseidon altimeter data. J. Geophys. Res., 106 , C10. 2247522502.

    • Search Google Scholar
    • Export Citation
  • Egbert, G. D., and S. Y. Erofeeva, 2002: Efficient inverse modeling of barotropic ocean tides. J. Atmos. Oceanic Technol., 19 , 183204.

    • Search Google Scholar
    • Export Citation
  • Ferrari, R., and D. L. Rudnick, 2000: Thermohaline variability in the upper ocean. J. Geophys. Res., 105 , C7. 1685716883.

  • Fofonoff, N. P., 1969: Spectral characteristics of internal waves in the ocean. Deep-Sea Res., 16 , (Suppl.). 5871.

  • Gill, A. E., 1982: Atmosphere–Ocean Dynamics. Academic Press, 662 pp.

  • Gregg, M. C., T. B. Sanford, and D. P. Winkel, 2003: Reduced mixing from the breaking of internal waves in equatorial waters. Nature, 422 , 513515.

    • Search Google Scholar
    • Export Citation
  • Holloway, P. E., and M. A. Merrifield, 2003: On the spring–neap variability and age of the internal tide at the Hawaiian Ridge. J. Geophys. Res., 108 .3126, doi:10.1029/2002JC001486.

    • Search Google Scholar
    • Export Citation
  • Katz, E. J., and M. G. Briscoe, 1979: Vertical coherence of the internal wave field from towed sensors. J. Phys. Oceanogr., 9 , 518530.

    • Search Google Scholar
    • Export Citation
  • Khatiwala, S., 2003: Generation of internal tides in an ocean of finite depth: Analytical and numerical calculations. Deep-Sea Res., 50 , 321.

    • Search Google Scholar
    • Export Citation
  • Klymak, J. M., and Coauthors, 2006: : An estimate of tidal energy lost to turbulence at the Hawaiian Ridge. J. Phys. Oceanogr., 36 , 11481164.

    • Search Google Scholar
    • Export Citation
  • Kunze, E., and J. M. Toole, 1997: Tidally driven vorticity, diurnal shear, and turbulence atop Fieberling Seamount. J. Phys. Oceanogr., 27 , 26632693.

    • Search Google Scholar
    • Export Citation
  • Levine, M. D., 2002: A modification of the Garrett–Munk internal wave spectrum. J. Phys. Oceanogr., 32 , 31663181.

  • Lien, R-C., and P. Müller, 1992: Consistency relations for gravity and vortical modes in the ocean. Deep-Sea Res., 39 , 15951612.

  • Lien, R-C., and M. C. Gregg, 2001: Observations of turbulence in a tidal beam and across a coastal ridge. J. Geophys. Res., 106 , 45754591.

    • Search Google Scholar
    • Export Citation
  • Llewellyn Smith, S. G., and W. R. Young, 2002: Conversion of the barotropic tide. J. Phys. Oceanogr., 32 , 15541566.

  • Llewellyn Smith, S. G., and W. R. Young, 2003: Tidal conversion at a very steep ridge. J. Fluid Mech., 495 , 175191.

  • Merrifield, M. A., and P. E. Holloway, 2002: Model estimates of M2 internal tide energetics at the Hawaiian Ridge. J. Geophys. Res., 107 .3179, doi:10.1029/2001JC000996.

    • Search Google Scholar
    • Export Citation
  • Merrifield, M. A., P. E. Holloway, and T. M. S. Johnston, 2001: The generation of internal tides at the Hawaiian Ridge. Geophys. Res. Lett., 28 , 559562.

    • Search Google Scholar
    • Export Citation
  • Munk, W., 1981: Internal waves and small scale processes. Evolution of Physical Oceanography, B. A. Warren and C. Wunsch, Eds., The MIT Press, 264–291.

    • Search Google Scholar
    • Export Citation
  • Munk, W., and C. Wunsch, 1998: Abyssal recipes II: Energetics of tidal and wind mixing. Deep-Sea Res., 45 , 19772010.

  • Pinkel, R., and J. A. Smith, 1992: Repeat-sequence coding for improved precision of Doppler sonar and sodar. J. Atmos. Oceanic Technol., 9 , 149163.

    • Search Google Scholar
    • Export Citation
  • Pinkel, R., J. Sherman, J. Smith, and S. Anderson, 1991: Strain: Observations of the vertical gradient of isopycnal vertical displacement. J. Phys. Oceanogr., 21 , 527540.

    • Search Google Scholar
    • Export Citation
  • Rainville, L., 2004: Propagation of the internal tide from the Hawaiian Ridge. Ph.D. thesis, University of California, San Diego, 161 pp.

  • Rattray, M., J. G. Dworski, and P. E. Kovala, 1969: Generation of long internal waves at the continental slope. Deep-Sea Res., 16 , (Suppl.). 179195.

    • Search Google Scholar
    • Export Citation
  • Ray, R. D., and G. T. Mitchum, 1997: Surface manifestation of internal tides in the deep ocean: Observations from altimetry and island gauges. Progress in Oceanography, Vol. 40, Pergamon. 135162.

    • Search Google Scholar
    • Export Citation
  • Roden, G. I., 1991: Effects of the Hawaiian Ridge upon oceanic flow and thermohaline structure. Deep-Sea Res., 38 , (Suppl. 1). S623S654.

    • Search Google Scholar
    • Export Citation
  • Rudnick, D. L., and J. R. Luyten, 1996: Intensive surveys of the Azores Front 1. Tracers and dynamics. J. Geophys. Res., 101 , C1. 923939.

    • Search Google Scholar
    • Export Citation
  • Rudnick, D. L., and Coauthors, 2003: From tides to mixing along the Hawaiian Ridge. Science, 301 , 355357.

  • Simmons, H. L., R. W. Hallberg, and B. K. Arbic, 2004: Internal wave generation in a global baroclinic tide model. Deep-Sea Res. II, 51 , 30433068.

    • Search Google Scholar
    • Export Citation
  • Smith, W. H. F., and D. T. Sandwell, 1997: Global seafloor topography from satellite altimetry and ship depth soundings. Science, 277 , 19571962.

    • Search Google Scholar
    • Export Citation
  • St. Laurent, L., and C. Garrett, 2002: The role of internal tides in mixing the deep ocean. J. Phys. Oceanogr., 32 , 28822899.

  • St. Laurent, L., S. Stringer, C. Garrett, and D. Perrault-Joncas, 2003: The generation of internal tides at abrupt topography. Deep-Sea Res., 50 , 9871003.

    • Search Google Scholar
    • Export Citation
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