Typhoon-induced variation of semidiurnal internal tides along the southeastern coast of Korea

초록

Typhoon-induced strong winds can change the oceanic environments dramatically, which sometimesdamage the fisheries and power plants located along the coast. In July 2015, two consecutive typhoons,Chanhom and Nangka, passed over the Yellow and East/Japan Seas within a week. The temperatureobserved near the southeastern coast of Korea fluctuates with the typhoon-induced upwelling anddownwelling events interrupting the typical stratification condition. In addition, the energy of semidiurnalinternal tides from observed temperature and current data variates depending on changes ofstratification condition. Data-assimilated numerical simulation results reveal that the generation ofsemidiurnal internal tide energy from a region north of the Tsushima Island is dependent on thebarotropic tides. However, during the typhoon-induced downwelling event, the energy of semidiurnalinternal tides near the southeastern coast of Korea varies much different from the barotropic tidalforcing. The sloped pycnocline near the southeastern coast in the typical condition enables the internaltidal energy to be transmitted toward a shallow region from the generated region. The downwellingevent deepens the pycnocline and makes the internal tide energy reflected and concentrated in theadjacent sea. This result presents a case study showing that typhoon-induced stratification changes canmodify propagation of internal tides, which charge a large portion of the ocean mixing processes.