Contrasted turbulence intensities in the Indonesian Throughflow: a challenge for parameterizing energy dissipation rate |
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| Authors: | Pascale Bouruet-Aubertot Yannis Cuypers Bruno Ferron Denis Dausse Olivier Ménage Agus Atmadipoera Indra Jaya |
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| Institution: | 1.Sorbonne Université- UPMC Université Paris 06- LOCEAN,Paris,France;2.LOPS-Ifremer,Plouzané,France;3.IPB,Bogor,Indonesia |
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| Abstract: | Microstructure measurements were performed along two sections through the Halmahera Sea and the Ombai Strait and at a station in the deep Banda Sea. Contrasting dissipation rates (??) and vertical eddy diffusivities (K z ) were obtained with depth-averaged ranges of \(\sim 9 \times 10^{-10}-10^{-5}]\) W kg??1 and of \(\sim 1 \times 10^{-5}-2 \times 10^{-3}]\) m2 s??1, respectively. Similarly, turbulence intensity, \(I={\epsilon }/(\nu N^{2})\) with ν the kinematic viscosity and N the buoyancy frequency, was found to vary seven orders of magnitude with values up to \(10^{7}\). These large ranges of variations were correlated with the internal tide energy level, which highlights the contrast between regions close and far from internal tide generations. Finescale parameterizations of ?? induced by the breaking of weakly nonlinear internal waves were only relevant in regions located far from any generation area (“far field”), at the deep Banda Sea station. Closer to generation areas, at the “intermediate field” station of the Halmahera Sea, a modified formulation of MacKinnon and Gregg (2005) was validated for moderately turbulent regimes with 100 < I < 1000. Near generation areas marked by strong turbulent regimes such as “near field” stations within strait and passages, ?? is most adequately inferred from horizontal velocities provided that part of the inertial subrange is resolved, according to Kolmogorov scaling. |
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