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Data from: Observations of the internal wave to turbulence cascade

Northcott, Devon1

Published Mar 19, 2026 on Dryad. https://doi.org/10.5061/dryad.8sf7m0d44

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Mar 19, 2026 version files 16.50 MB

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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 $\Phi_{IW}\sim\varepsilon\frac{1}{2}N1f{- \frac{1}{2}}$ and $\Phi_{sat}\sim N2 k_z^{-1}$ 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 non-linear 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 non- linear 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.