On M2 tidal amplitude enhancement in the Taiwan Strait and its asymmetry in the cross-strait direction

Abstract

Enhanced M2 tidal amplitude in the Taiwan Strait (TS) and asymmetric M2 tidal amplitude in the cross-strait direction have been found and reproduced in numerical simulations. In this study, Finite Volume Coastal Ocean Model (FVCOM) is applied to investigate the mechanisms behind these features. Model results show that the linear interaction of waves from the East China Sea (ECS) and the Luzon Strait (LS) can explain the formation of the co-amplitude and co-phase lines of the M2 tide in the nodal point area, while the waves from the ECS dominate the tidal motion in the TS according to a basic linear wave superposition. Model simulation also show that wave reflection and transition occur when the M2 tidal waves from the ECS propagate through the TS and encounter an sharply deepened topography. The interaction of these induced reflection waves and the incident waves from the ECS is the main cause for the enhanced M2 tidal amplitude in the TS. The distribution of the sharply deepened topography, rather than the Coriolis effect, is the main reason for the asymmetry of the M2 tidal amplitude in the cross-strait direction in the TS. These findings provide some references for tidal dynamics in other areas, especially where long waves propagate through the shallow water to the deep sea.