Modeling Lagrangian residual velocity in a tide-dominated long-narrow bay: case study of the inner Xiangshan Bay

Many tide-dominated long-narrow bays worldwide face marine pollution because of their semi-enclosed nature. The Lagrangian residual velocity (LRV) characterizes the mass transport in shallow seas. Therefore, studying LRV is helpful for solving marine environmental problems. In this study, the inner Xiangshan Bay along the coast of the East China Sea was used as an example to study 3D LRVs in a tide-dominated long-narrow bay. The LRV pattern and its dynamic mechanism were analyzed. The LRV flowed outward in the deep central area and inward in the shallow areas along the bank, with no apparent variation in the vertical direction. Study results indicated that the main controlling dynamics of the LRV were the balance of the tidal-averaged barotropic gradient force and the tidal body force. Additionally, the LRV showed good correspondence with mass transport and previous study in an ideal tide-dominated long-narrow model bay, which provides a reference for pollution control.