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Observations of the Internal Wave to Turbulence Cascade.

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Title: Observations of the Internal Wave to Turbulence Cascade.
Authors: Northcott, Devon1 (AUTHOR) dnorthco@ucsd.edu, Le Boyer, Arnaud1 (AUTHOR), MacKinnon, Jennifer1 (AUTHOR), Alford, Matthew H.1 (AUTHOR), Lucas, Andrew J.1 (AUTHOR)
Source: Journal of Physical Oceanography. Apr2026, Vol. 56 Issue 4, p839-853. 15p.
Subjects: Internal waves, Turbulence, Oceanic mixing, Oceanographic observations, Nonlinear waves, Energy transfer, Canyons, Fluid dynamics
Geographic Terms: Southern California, La Jolla (San Diego, Calif.)
Abstract: Shear spectral energy density (shear spectra) is measured across three decades in vertical wavenumber using a Wirewalker profiler equipped with a microstructure instrument and a pulse-coherent Doppler sonar. We identify the features of the canonical ocean vertical shear spectrum, including an internal wave band, an intermediate saturation band whose spectral level is independent of turbulent dissipation, and a three-dimensional turbulence band. The internal wave band and saturation band of the spectrum scale as Φ IW ∼ ε 1 / 2 N 1 f − 1 / 2 and Φ sat ∼ N 2 k z − 1 , respectively. These scalings hold despite the deployment location at the head of a La Jolla Canyon, a deep canyon incising the shelf off La Jolla, California, where weakly nonlinear wave–wave interaction is not the primary physical process driving the forward energy cascade. In La Jolla Canyon, high-amplitude tidally driven internal waves generate significant strain, resulting in turbulent events that cover a majority of the water column. During these events, we observe shear spectra with energy above the saturation level, which we interpret as a sign of the wave–turbulence transition. Finestructure parameterizations developed to predict mixing from shear spectra in the open ocean thermocline continue to predict average mixing well. The success of finestructure parameterizations implies a rate of downscale energy transfer consistent with the rate predicted from weakly nonlinear wave–wave interactions and suggests that the theoretical framework of the canonical shear spectrum can be used to make useful predictions in shallow, high-energy environments. Significance Statement: Internal waves with vertical scales from tens to hundreds of meters provide much of the energy that drives irreversible turbulent mixing at centimeter scales in the ocean. The pathways energy follows from internal wave scales to mixing scales depend on the internal wave energy and the water depth. Energy pathways in high-energy coastal systems are dominated by highly nonlinear dynamics, while energy at middepths in the open ocean moves between scales via weakly nonlinear interactions. Our observations show that predictions made about the rate of energy transfer from internal wave to mixing scales formulated for the open ocean work surprisingly well in a coastal marine canyon with a high-energy nonlinear internal wave field. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Physical Oceanography is the property of American Meteorological Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Observations of the Internal Wave to Turbulence Cascade.
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  Data: <searchLink fieldCode="AR" term="%22Northcott%2C+Devon%22">Northcott, Devon</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> dnorthco@ucsd.edu</i><br /><searchLink fieldCode="AR" term="%22Le+Boyer%2C+Arnaud%22">Le Boyer, Arnaud</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22MacKinnon%2C+Jennifer%22">MacKinnon, Jennifer</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Alford%2C+Matthew+H%2E%22">Alford, Matthew H.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Lucas%2C+Andrew+J%2E%22">Lucas, Andrew J.</searchLink><relatesTo>1</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Physical+Oceanography%22">Journal of Physical Oceanography</searchLink>. Apr2026, Vol. 56 Issue 4, p839-853. 15p.
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  Data: <searchLink fieldCode="DE" term="%22Internal+waves%22">Internal waves</searchLink><br /><searchLink fieldCode="DE" term="%22Turbulence%22">Turbulence</searchLink><br /><searchLink fieldCode="DE" term="%22Oceanic+mixing%22">Oceanic mixing</searchLink><br /><searchLink fieldCode="DE" term="%22Oceanographic+observations%22">Oceanographic observations</searchLink><br /><searchLink fieldCode="DE" term="%22Nonlinear+waves%22">Nonlinear waves</searchLink><br /><searchLink fieldCode="DE" term="%22Energy+transfer%22">Energy transfer</searchLink><br /><searchLink fieldCode="DE" term="%22Canyons%22">Canyons</searchLink><br /><searchLink fieldCode="DE" term="%22Fluid+dynamics%22">Fluid dynamics</searchLink>
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  Label: Geographic Terms
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  Data: <searchLink fieldCode="DE" term="%22Southern+California%22">Southern California</searchLink><br /><searchLink fieldCode="DE" term="%22La+Jolla+%28San+Diego%2C+Calif%2E%29%22">La Jolla (San Diego, Calif.)</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Shear spectral energy density (shear spectra) is measured across three decades in vertical wavenumber using a Wirewalker profiler equipped with a microstructure instrument and a pulse-coherent Doppler sonar. We identify the features of the canonical ocean vertical shear spectrum, including an internal wave band, an intermediate saturation band whose spectral level is independent of turbulent dissipation, and a three-dimensional turbulence band. The internal wave band and saturation band of the spectrum scale as Φ IW ∼ ε 1 / 2 N 1 f − 1 / 2 and Φ sat ∼ N 2 k z − 1 , respectively. These scalings hold despite the deployment location at the head of a La Jolla Canyon, a deep canyon incising the shelf off La Jolla, California, where weakly nonlinear wave–wave interaction is not the primary physical process driving the forward energy cascade. In La Jolla Canyon, high-amplitude tidally driven internal waves generate significant strain, resulting in turbulent events that cover a majority of the water column. During these events, we observe shear spectra with energy above the saturation level, which we interpret as a sign of the wave–turbulence transition. Finestructure parameterizations developed to predict mixing from shear spectra in the open ocean thermocline continue to predict average mixing well. The success of finestructure parameterizations implies a rate of downscale energy transfer consistent with the rate predicted from weakly nonlinear wave–wave interactions and suggests that the theoretical framework of the canonical shear spectrum can be used to make useful predictions in shallow, high-energy environments. Significance Statement: Internal waves with vertical scales from tens to hundreds of meters provide much of the energy that drives irreversible turbulent mixing at centimeter scales in the ocean. The pathways energy follows from internal wave scales to mixing scales depend on the internal wave energy and the water depth. Energy pathways in high-energy coastal systems are dominated by highly nonlinear dynamics, while energy at middepths in the open ocean moves between scales via weakly nonlinear interactions. Our observations show that predictions made about the rate of energy transfer from internal wave to mixing scales formulated for the open ocean work surprisingly well in a coastal marine canyon with a high-energy nonlinear internal wave field. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Physical Oceanography is the property of American Meteorological Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1175/JPO-D-25-0114.1
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 15
        StartPage: 839
    Subjects:
      – SubjectFull: Internal waves
        Type: general
      – SubjectFull: Turbulence
        Type: general
      – SubjectFull: Oceanic mixing
        Type: general
      – SubjectFull: Oceanographic observations
        Type: general
      – SubjectFull: Nonlinear waves
        Type: general
      – SubjectFull: Energy transfer
        Type: general
      – SubjectFull: Canyons
        Type: general
      – SubjectFull: Fluid dynamics
        Type: general
      – SubjectFull: Southern California
        Type: general
      – SubjectFull: La Jolla (San Diego, Calif.)
        Type: general
    Titles:
      – TitleFull: Observations of the Internal Wave to Turbulence Cascade.
        Type: main
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            NameFull: Northcott, Devon
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            NameFull: Le Boyer, Arnaud
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            NameFull: MacKinnon, Jennifer
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            NameFull: Alford, Matthew H.
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            NameFull: Lucas, Andrew J.
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            – D: 01
              M: 04
              Text: Apr2026
              Type: published
              Y: 2026
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              Value: 56
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            – TitleFull: Journal of Physical Oceanography
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