[A-OS16] 沿岸域の海洋循環と物質循環

[AOS16-P12] Sea surface signature of incoherent semidiurnal internal tides revealed by a tide-resolving OGCM

*WANG SHUYA¹、郭 新宇^1,2、宮澤 泰正²、古惠 亮²、Sergey M. Varlamov² (1.愛媛大学沿岸環境科学研究センター、2.海洋研究開発機構アプリケーションラボ)

キーワード：内部潮汐、海面シグネチャー 、海洋大循環モデル

The Northwestern Pacific is a hotspot of internal tides due to the complex bottom topographies. As the internal tides are radiated away from the generation sites, they become incoherent under the influence of varying background fields. In this study, based on a high-resolution tide-resolving numerical model, we investigate the sea surface signature of incoherent semidiurnal internal tides, including its variability and mechanism. The model results indicate strong incoherent semidiurnal internal tides in the Japan Sea, south of Japan, the Philippine Sea, and the Northern South China Sea, whose SSH variance reaches approximately 2 cm². The fraction of incoherent variance is regionally dependent, approaching nearly 100% in the Japan Sea and south of Japan but remaining at 30% in the Philippine Sea and Northern South China Sea. Spectral analysis reveals different modal contents of incoherent internal tides in these subdomains: Incoherent semidiurnal internal tides in the Japan Sea and south of Japan are controlled by mode-1 but show multi-modal features in the Phillippine Sea. By calculating the relative change of wave speed, we find that it is largely correlated with the incoherent SSH variance, implying that it could be considered as an indicator of the incoherence of internal tides. Further examination on the terms in the relative change of wave speed demonstrates the important contribution of the advection of background currents. The results of this study provide essential implications for the SWOT mission, in which internal tidal signals should be removed to better resolve submesoscale features in the ocean.