ADCP Observation and Numerical Model Prediction of Tidal Currents Near Kozu Island

Izu island chain south of Tokyo, Japan has been considered as a prospective area for ocean renewable energy development because of relatively strong tidal currents, and the Kuroshio current. An Acoustic Doppler Current Profiler (ADCP) measurement near one of the islands, Kozu island, was conducted to know ocean current variability. The ADCP, Signature500, was installed 700m away from the coast and the water depth is 32m there. The observation period is for a month from January 8th, 2017. Vertical profile of the currents was recorded every 1 m at 1 minute interval. Based on the observation, the peak tidal currents were often more than 1m/s, and the maximum total speed exceeded 2m/s. The maximum flow is probably related to the Kuroshio intrusion because temperature increased abruptly. Typical vertical profile of the current follows the logarithmic law except for the near surface area. To study the spatial distribution of the current around Kozu island, a numerical model is developed based on MIT General Circulation Model (MITgcm). The model prediction of tidal sea surface variation is in a good agreement with the observation. The model underestimated the tidal currents, but the phase is in a reasonable agreement with the ADCP observation result.