쿠로시오와 중규모 와류의 영향에 의한 남중국해 비선형내부파의 변동성

Abstract

Barotropic tides in Luzon Strait are the primary forcing determining the variability of internal waves in the South China Sea. The SUNTANS model is implemented in the northern South China Sea to analyze the tidal effect on the nonlinear internal wave generation and propagation. However, the inverted echo sounder observations during two selected segments reveal that the nonlinear internal waves have very different amplitudes even though the tidal forcing is almost identical. On the base of the SUNTANS model simulation, which uses the horizontally uniform stratification, the effects of the Kuroshio and mesoscale eddies are individually investigated. The Kuroshio can enhance the zonal tilt of the thermocline and induce intruding flow in Luzon Strait, hence affecting the generation of internal tides. During the two selected segments, different thermocline slopes do not significantly change the internal tide generation, but the intruding flow may result in a 10% difference in the amplitude of generated M2 internal tides. Mesoscale eddies change local stratification and induce additional background currents, affecting the nonlinear evolution of internal tides. In addition, wavefront steering due to the mesoscale eddies dramatically affected the observed amplitude changes of the nonlinear internal waves: the edge, rather than the center, of the nonlinear internal wavefront passed through the observational stations, resultinernal wave generation and propagation. However, the inverted echo sounder observations during two selected segments reveal that the nonlinear internal waves have very different amplitudes even though the tidal forcing is almost identical. On the base of the SUNTANS model simulation, which uses the horizontally uniform stratification, the effects of the Kuroshio and mesoscale eddies are individually investigated. The Kuroshio can enhance the zonal tilt of the thermocline and induce intruding flow in Luzon Strait, hence affecting the generation of internal tides. During the two selected segments, different thermocline slopes do not significantly change the internal tide generation, but the intruding flow may result in a 10% difference in the amplitude of generated M2 internal tides. Mesoscale eddies change local stratification and induce additional background currents, affecting the nonlinear evolution of internal tides. In addition, wavefront steering due to the mesoscale eddies dramatically affected the observed amplitude changes of the nonlinear internal waves: the edge, rather than the center, of the nonlinear internal wavefront passed through the observational stations, resultin