Is the small-scale turbulence an exclusive breaking product of oceanic internal waves |
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Authors: | FAN Zhisong |
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Institution: | College of Physical and Environmental Oceanography, Ocean University of China, Qingdao 266100, China |
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Abstract: | On the basis of the theoretical research results by the author and the literature published up to date, the analysis and the
justification presented in this paper show that the breaking products of oceanic internal waves are not only turbulence, but
also the fine-scale near-inertial internal waves (the oceanic reversible finestructure) for inertial waves and the internal
solitary waves for internal tides respectively. It was found that the oceanic reversible finestructure may be induced by the
effect of the horizontal component (f)\tilde]((f)\tilde] = 2Wcosj)\tilde f(\tilde f = 2\Omega cos\varphi ) of the rotation vector on inertial waves. And a new instability of the theoretical shear and strain spectra due to the effect
of (f)\tilde]\tilde f occurs at critical vertical wavenumber β
c≈0.1 cpm. It happens when the levels of shear and strain of the reversible finestructure are higher than those of inertial
waves, which is induced by the effect of (f)\tilde]\tilde f along an “iso-potential-pycnal” of internal wave. If all breaking products of internal waves are taken into account, the
average kinetic energy dissipation rate is an order of magnitude larger than the values of turbulence observed by microstructure
measurements. The author’s theoretical research results are basically in agreement with those observed in IWEX, DRIFTER and
PATCHEX experiments. An important impersonal fact is that on the mean temporal scale of thermohaline circulation these breaking
products of internal waves exist simultaneously with turbulence. Because inertial waves are generated by winds at the surface,
and internal tides are generated by strong tide-topography interactions, the analysis and justification in this paper support
in principle the abyssal recipes II: energetics of tidal and wind mixing by Munk &; Wunsch in 1998, in despite of the results
of microstructure measurements for the turbulent kinetic energy dissipation rate and the diapycnal turbulent eddy diffusivity. |
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Keywords: | internal waves inertial waves internal tides turbulence oceanic interior mixing |
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