Revisiting the tidal dynamics in the complex Zhoushan Archipelago waters: A numerical experiment

Abstract

A complex archipelago exhibits high velocity shear, strong advection, and significant nonlinearity for tides, overtides, tidal currents, and subtidal hydrodynamics. Here, a high-resolution regional ocean modeling system with two-way nesting is applied to the coastal Zhoushan Archipelago in the East China Sea. After validation for the M2, S2, K1, and O1 tidal constituents, the spatial structures of tides and tidal currents are presented. The features of these constituents and two significant overtides of M2 (M4 and M6) are discussed. The M2 tide is dominant in the study domain, followed by the S2, K1, and O1 tides in amplitude in that order. Tidal energy budget analysis shows that about 46.4% of the incoming energy is dissipated inside the study area and 67.3% of the dissipated energy is consumed by the bottom friction, while the remainder passes through the study domain. Jetlike flows in the channels are among the most remarkable features. Analysis of momentum balance terms averaged over the flood or ebb period demonstrates that the primary balance near the islands is between the horizontal advection and the pressure gradient force, suggesting a predominant Bernoulli-type motion with strong nonlinearity. However, in the area away from the islands, the horizontal advection becomes less important. The M4 and M6 tides are mainly generated by nonlinear advection, bottom friction plays a minor role, and the interactions between different constituents also have some influence.