[A-OS20] Coastal physical processes associated with mixing, eddies, and internal waves

[AOS20-09] The decreasing trend of M₂ tidal amplitude observed along northwestern Kyushu

*Hiromi Matsuura¹, Katsuto Uehara², Shinichiro Kida², Toshiyuki Hibiya³ (1.Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 2.Research Institute for Applied Mechanics, Kyushu University, 3.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo)

Keywords:M2 tide, tide, Northwestern Kyushu Coast

Observations show that M₂ tidal amplitude is decreasing along the northwestern coast of Kyushu. Using JODC and JMA datasets, we found that this decrease in M₂ tidal amplitude from 1980 to 2018 is 4% on average and that the trend is stronger towards the northwest than the southwest. When we further investigated the M₂ tidal amplitude along the coast of the Japan Sea and the Pacific Ocean, we found the decreasing trend to continue along the coast of Japan Sea but not along the Pacific Ocean. The mechanism responsible for this decreasing trend is still unknown. In this presentation, we plan to show the observed spatial distribution in M₂ tidal amplitude trend and the possible mechanisms using a numerical model.