On leakage of energy from turbulence to internal waves in the oceanic mixed layer |
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| Authors: | Lakshmi H Kantha Carol Anne Clayson |
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| Institution: | (1) Department of Aerospace Engineering Sciences, CB 431, University of Colorado, Boulder, CO 80309, USA;(2) Department of Meteorology, Florida State University, Tallahassee, FL 32306, USA |
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| Abstract: | In this paper, we address the question of energy leakage from turbulence to internal waves (IWs) in the oceanic mixed layer
(OML). If this leakage is substantial, then not only does this have profound implications as far as the dynamics of the OML
is concerned, but it also means that the equation for the turbulence kinetic energy (TKE) used in OML models must include
an appropriate sink term, and traditional models must be modified accordingly. Through comparison with the experimental data
on grid-generated turbulence in a stably stratified fluid, we show that a conventional two-equation turbulence model without
any IW sink term can explain these observations quite well, provided that the fluctuating motions that persist long after
the decay of grid-generated turbulence are interpreted as being due to IW motions generated by the initial passage of the
grid through the stably stratified fluid and not during turbulence decay. We conclude that there is no need to postulate an
IW sink term in the TKE equation, and conventional models suffice to model mixing in the OML. |
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| Keywords: | Turbulence Turbulent mixing Oceanic mixed layer Stably stratified fluid Internal waves Turbulence kinetic energy |
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