• Alford, M. H., , and M. C. Gregg, 2001: Near-inertial mixing: Modulation of shear, strain and microstructure at low latitude. J. Geophys. Res., 106 , 1694716968.

    • Search Google Scholar
    • Export Citation
  • Aucan, J., , M. A. Merrifield, , D. S. Luther, , and P. Flament, 2006: Tidal mixing events on the deep flanks of Kaena Ridge, Hawaii. J. Phys. Oceanogr., 36 , 12021219.

    • Search Google Scholar
    • Export Citation
  • Batchelor, G. K., 1959: Small-scale variation of convected quantitites like temperature in turbulent fluid. J. Fluid Mech., 5 , 113139.

    • Search Google Scholar
    • Export Citation
  • Cairns, J. L., , and G. O. Williams, 1976: Internal wave observations from a midwater float, II. J. Geophys. Res., 81 , 19431950.

  • D’Asaro, E. A., 1995: Upper-ocean inertial currents forced by a strong storm. Part II: Modeling. J. Phys. Oceanogr., 25 , 29372952.

  • D’Asaro, E. A., , and R-C. Lien, 2000: The wave-turbulence transition for stratified flows. J. Phys. Oceanogr., 30 , 16691678.

  • Desaubies, Y. J. F., , and M. C. Gregg, 1981: Reversible and irreversible finestructure. J. Phys. Oceanogr., 11 , 541556.

  • Dugan, J. P., , W. D. Morris, , and B. S. Okawa, 1986: Horizontal wave number distribution of potential energy in the ocean. J. Geophys. Res., 91 , 1299313000.

    • Search Google Scholar
    • Export Citation
  • Gardner, C. S., 1996: Testing theories of atmospheric gravity wave saturation and dissipation. J. Atmos. Terr. Phys., 58 , 15751589.

  • Gargett, A. E., 1985: Evolution of scalar spectra with the decay of turbulence in a stratified fluid. J. Fluid Mech., 159 , 379407.

  • Gargett, A. E., , P. J. Hendricks, , T. B. Sanford, , T. R. Osborn, , and A. J. Williams III, 1981: A composite spectrum of vertical shear in the upper ocean. J. Phys. Oceanogr., 11 , 12581271.

    • Search Google Scholar
    • Export Citation
  • Garrett, C., , and W. Munk, 1972: Space-time scales of internal waves. Geophys. Fluid Dyn., 2 , 225264.

  • Garrett, C., , and W. H. Munk, 1975: Space-time scales of internal waves: A progress report. J. Geophys. Res., 80 , 291297.

  • Gregg, M. C., 1989: Scaling turbulent dissipation in the thermocline. J. Geophys. Res., 94 , 96869698.

  • Gregg, M. C., , and E. Kunze, 1991: Shear and strain in Santa Monica Basin. J. Geophys. Res., 96 , 1670916719.

  • Gregg, M. C., , E. A. D’Asaro, , T. J. Shay, , and N. Larson, 1986: Observations of persistent mixing and near-inertial waves. J. Phys. Oceanogr., 16 , 856885.

    • Search Google Scholar
    • Export Citation
  • Gregg, M. C., , D. Winkel, , and T. Sanford, 1993: Varieties of fully resolved spectra of vertical shear. J. Phys. Oceanogr., 23 , 124141.

    • Search Google Scholar
    • Export Citation
  • 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
  • Hebert, D., , and J. Moum, 1994: Decay of a near-inertial wave. J. Phys. Oceanogr., 24 , 23342351.

  • Henyey, F. S., , J. Wright, , and S. M. Flatté, 1986: Energy and action flow through the internal wave field. J. Geophys. Res., 91 , 84878495.

    • Search Google Scholar
    • Export Citation
  • Hines, C. O., 1991a: The saturation of gravity waves in the middle atmosphere. Part I: Critique of linear-instability theory. J. Atmos. Sci., 48 , 13481360.

    • Search Google Scholar
    • Export Citation
  • Hines, C. O., 1991b: The saturation of gravity waves in the middle atmosphere. Part II: Development of Doppler-spread theory. J. Atmos. Sci., 48 , 13601379.

    • Search Google Scholar
    • Export Citation
  • Katz, E. J., 1975: Tow spectra from Mode. J. Geophys. Res., 80 , 11631167.

  • 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
  • Klymak, J. M., , and J. N. Moum, 2007: Oceanic isopycnal slope spectra. Part II: Turbulence. J. Phys. Oceanogr., 37 , 12321245.

  • 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 T. B. Sanford, 1996: Abyssal mixing: Where it is not. J. Phys. Oceanogr., 26 , 22862296.

  • Kunze, E., , E. Firing, , J. M. Hummon, , T. K. Chereskin, , and A. M. Thurnherr, 2006: Global abyssal mixing inferred from lowered ADCP shear and CTD strain profiles. J. Phys. Oceanogr., 36 , 15531576.

    • Search Google Scholar
    • Export Citation
  • Lee, C. M., , E. Kunze, , T. B. Sanford, , J. D. Nash, , M. A. Merrifield, , and P. E. Holloway, 2006: Internal tides and turbulence along the 3000-m isobath of the Hawaiian Ridge. J. Phys. Oceanogr., 36 , 11651183.

    • Search Google Scholar
    • Export Citation
  • Levine, E. R., , and R. G. Lueck, 1999: Turbulence measurements with an autonomous underwater vehicle. J. Atmos. Oceanic Technol., 16 , 15331544.

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

  • McKean, R. S., , and T. E. Ewart, 1974: Temperature spectra in the deep ocean off Hawaii. J. Phys. Oceanogr., 4 , 191199.

  • Moum, J. N., , M. C. Gregg, , R. C. Lien, , and M. Carr, 1995: Comparison of turbulence kinetic energy dissipation rate estimates from two ocean microstructure profilers. J. Atmos. Oceanic Technol., 12 , 346366.

    • Search Google Scholar
    • Export Citation
  • Moum, J. N., , D. R. Caldwell, , J. D. Nash, , and G. D. Gunderson, 2002: Observations of boundary mixing over the continental slope. J. Phys. Oceanogr., 32 , 21132130.

    • Search Google Scholar
    • Export Citation
  • Mudge, T. D., , and R. G. Lueck, 1994: Digital signal processing to enhance oceanographic observations. J. Atmos. Oceanic Technol., 11 , 825836.

    • Search Google Scholar
    • Export Citation
  • Müller, P., , D. J. Olbers, , and J. Willebrand, 1978: The IWEX spectrum. J. Geophys. Res., 83 , 479500.

  • Munk, W. H., 1981: Internal waves and small-scale processes. Evolution of Physical Oceanography, B. A. Warren and C. Wunsch, Eds., MIT Press, 264–291.

    • Search Google Scholar
    • Export Citation
  • Nagasawa, M., , T. Hibiya, , Y. Niwa, , M. Watanabe, , Y. Isoda, , S. Takagi, , and Y. Kamei, 2002: Distribution of fine-scale shear in the deep waters of the North Pacific obtained using expendable current profilers. J. Geophys. Res., 107 .3221, doi:10.1029/2002JC001376.

    • Search Google Scholar
    • Export Citation
  • Naveira Garabato, A. C., , K. I. C. Oliver, , A. J. Watson, , and M-J. Messias, 2004: Turbulent diapycnal mixing in the Nordic seas. J. Geophys. Res., 109 .C1201, doi:10.1029/2004JC002411.

    • Search Google Scholar
    • Export Citation
  • Polzin, K. L., 2004: A heuristic description of internal wave dynamics. J. Phys. Oceanogr., 34 , 214230.

  • Polzin, K. L., , J. M. Toole, , and R. W. Schmitt, 1995: Finescale parameterizations of turbulent dissipation. J. Phys. Oceanogr., 25 , 306328.

    • Search Google Scholar
    • Export Citation
  • Polzin, K. L., , E. Kunze, , J. Toole, , and R. Schmitt, 2003: The partition of finescale energy into internal waves and subinertial motions. J. Phys. Oceanogr., 33 , 234248.

    • Search Google Scholar
    • Export Citation
  • Riley, J. J., , and S. M. deBruynKops, 2003: Dynamics of turbulence strongly influenced by buoyancy. Phys. Fluids, 15 , 20472059.

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

  • Sherman, J. T., , and R. Pinkel, 1991: Estimates of the vertical wavenumber–frequency spectra of vertical shear and strain. J. Phys. Oceanogr., 21 , 292303.

    • Search Google Scholar
    • Export Citation
  • Smith, S. A., , D. C. Fritts, , and T. E. VanZandt, 1987: Evidence for a saturated spectrum of atmospheric gravity waves. J. Atmos. Sci., 44 , 14041410.

    • 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.

  • Sun, H., , and E. Kunze, 1999: Internal wave–wave interactions. Part I: The role of internal wave vertical divergence. J. Phys. Oceanogr., 29 , 28862904.

    • Search Google Scholar
    • Export Citation
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Oceanic Isopycnal Slope Spectra. Part I: Internal Waves

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  • 1 Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California
  • | 2 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon
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Abstract

Horizontal tow measurements of internal waves are rare and have been largely supplanted in recent decades by vertical profile measurements. Here, estimates of isotherm displacements and turbulence dissipation rate from a towed vehicle deployed near Hawaii are presented. The displacement data are interpreted in terms of horizontal wavenumber spectra of isopycnal slope. The spectra span scales from 5 km to 0.1 m, encompassing both internal waves and turbulence. The turbulence subrange is identified using a standard turbulence fit, and the rest of the motions are deemed to be internal waves. The remaining subrange has a slightly red slope (ϕk−1/2x) and vertical coherences compatible with internal waves, in agreement with previous towed measurements. However, spectral amplitudes in the internal wave subrange exhibit surprisingly little variation despite a four-order-of-magnitude change in turbulence dissipation rate observed at the site. The shape and amplitude of the horizontal spectra are shown to be consistent with observations and models of vertical internal wave spectra that consist of two subranges: a “linear” subrange (ϕk0z) and a red “saturated” subrange (ϕk−1z). These two subranges are blurred in the transformation to horizontal spectra, yielding slopes close to those observed. The saturated subrange does not admit amplitude variations in the spectra yet is an important component of the measured horizontal spectra, explaining the poor correspondence with the dissipation rate.

Corresponding author address: J. Klymak, School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, STN CSC, Victoria, BC V8W 3P6, Canada. Email: jklymak@uvic.ca

Abstract

Horizontal tow measurements of internal waves are rare and have been largely supplanted in recent decades by vertical profile measurements. Here, estimates of isotherm displacements and turbulence dissipation rate from a towed vehicle deployed near Hawaii are presented. The displacement data are interpreted in terms of horizontal wavenumber spectra of isopycnal slope. The spectra span scales from 5 km to 0.1 m, encompassing both internal waves and turbulence. The turbulence subrange is identified using a standard turbulence fit, and the rest of the motions are deemed to be internal waves. The remaining subrange has a slightly red slope (ϕk−1/2x) and vertical coherences compatible with internal waves, in agreement with previous towed measurements. However, spectral amplitudes in the internal wave subrange exhibit surprisingly little variation despite a four-order-of-magnitude change in turbulence dissipation rate observed at the site. The shape and amplitude of the horizontal spectra are shown to be consistent with observations and models of vertical internal wave spectra that consist of two subranges: a “linear” subrange (ϕk0z) and a red “saturated” subrange (ϕk−1z). These two subranges are blurred in the transformation to horizontal spectra, yielding slopes close to those observed. The saturated subrange does not admit amplitude variations in the spectra yet is an important component of the measured horizontal spectra, explaining the poor correspondence with the dissipation rate.

Corresponding author address: J. Klymak, School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, STN CSC, Victoria, BC V8W 3P6, Canada. Email: jklymak@uvic.ca

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