Measurements of the Turbulent Energy Dissipation Rate around the Shelf Break in the East China Sea |
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Authors: | Email author" target="_blank">Takeshi?MatsunoEmail author Manabu?Shimizu Yasuhiro?Morii Hideaki?Nishida Yasuaki?Takaki |
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Institution: | (1) Research Institute for Applied Mechanics, Kyushu University, Fukuoka 816-8580, Japan;(2) Kuroshio Research Laboratory, National Research Institute of Fisheries Science, Kochi 780-8010, Japan;(3) Faculty of Fisheries, Nagasaki University, Nagasaki 852-8521, Japan |
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Abstract: | Using the micro-structure profiler, TurboMAP, large values for the turbulent energy dissipation rate ε were found just above the bottom of the shelf and around the thermocline near the continental shelf break in the East China
Sea. The values found above the bottom are produced by the bottom stress due to tidal currents, resulting in a distinct bottom
mixed layer where the vertical eddy diffusivity Kz is also large. Distinct maxima in the values of ε detected around the thermocline are located at the depth of the fine-scale shear maxima detected with the moored ADCP. The
vertical profiles of ε were compared with those of the current velocity, and it was found that the maxima in ε appear to correspond to those of the shear with fine scale. The magnitude of the observed ε coincided approximately with the ε calculated from the fine-scale shear and the buoyancy frequency according to the parameterization proposed by Gregg (1989),
if the large-scale mean shear caused by the Kuroshio is subtracted. However, it is not clear whether the parameterization
for the internal wave fields in the open ocean is applicable to the estimation of ε in the shelf break. Whereas the most predominant value of ε was found just above the bottom and around the thermocline, the maxima of ε could be found in the internal area. They could have been caused by the propagation of the vertically high wave number internal
tides along the characteristic ray. |
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Keywords: | Turbulent energy dissipation rate micro-structure profiler internal waves vertical eddy diffusivity shelf break the East China Sea |
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