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Contrasted turbulence intensities in the Indonesian Throughflow: a challenge for parameterizing energy dissipation rate
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 (đ) and vertical eddy diffusivities (K z ) were obtained with depth-averaged ranges of âŒ[9Ă10â10â10â5] W kgââ1 and of âŒ[1Ă10â5â2Ă10â3] m2 sââ1, respectively. Similarly, turbulence intensity, I=Ï”/(ÎœN2) with Îœ the kinematic viscosity and N the buoyancy frequency, was found to vary seven orders of magnitude with values up to 107. 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 đ induced by the breaking of weakly nonlinear internal waves were only relevant in regions located far from any generation area (âfar fieldâ), at the deep Banda Sea station. Closer to generation areas, at the âintermediate fieldâ 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 ânear fieldâ stations within strait and passages, đ is most adequately inferred from horizontal velocities provided that part of the inertial subrange is resolved, according to Kolmogorov scaling.
Keyword(s)
Turbulence, Internal tides, Vertical mixing, Parameterization, Indonesian seas, Microstructure measurements
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File | Pages | Size | Access | |
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Publisher's official version | 22 | 11 Mo | ||
Author's final draft | 71 | 11 Mo |