Internal Tides in the Southwestern East/Japan Sea from Observation and Simulation

Abstract

Energetic internal tides were observed near the continental slope of the southwestern East/Japan Sea. We investigated the energetics of the internal tides using two data sets of 25-hour-long hourly CTD and LADCP profiles and idealized numerical modeling. The energy level during spring tide was about five times stronger than that of neap. During both observation periods the semi-diurnal M-2 constituent was dominant. Internal tide energy flux peaked at about 150 m level where the amplitude of the internal tide was largest. During spring tide the energy flux directed to the deeper part of the East/Japan Sea across the continental slope, while it was mainly along the slope during neap. The modeling results showed that semi-diurnal internal tides are generated mostly on the continental slope near the observation site. It is also suggested by modeling study that thermocline depth is one of important factors controlling the generation of the internal tide. When the thermocline is deeper (shallower) the internal wave becomes stronger (weaker). The response of the internal tide to the thermocline depth is not symmetric. It also showed most of the energy propagates toward the deeper sections.