Small scale internal waves and turbulent fluctuations near the continental shelf break in the East China Sea

Short term current data with high vertical resolution were obtained from an array moored near the continental shelf break in the East China Sea in summer, 1992 and 1993. Six current meters were moored just above the sloping bottom with a vertical interval of 10 m. The data obtained with time interval of one or two minutes, clarify the characteristics of small scale phenomena generated around the shelf break. Short time scale fluctuations less than 10 minutes with large amplitude were observed intermittently under the lower thermocline. According to comparison with the Richardson number, it is concluded that the fluctuations often originate from the Kelvin-Helmholtz instability of the stratified fluid. Distinct small scale internal waves, having a time scale around the Brunt-Väisälä period, are also intermittently observed just around the bottom layer, accompanied by turbulent fluctuations. Considering the horizontal scale of the small scale internal waves, which is several tens or hundred of meters, such internal waves and turbulent fluctuations must be generated frequently near the continental shelf break, though they can be detected only intermittently.