Author(s): Zhiguo He; Haoxuan Weng; Kailong Huangfu; Dan Song; Weifeng Zhang
Keywords: Macro-tidal estuary; Salinity; Tidal current; Frequency variation; Hangzhou Bay
Abstract: Coastal field surveys were conducted in a tidal channel of a macro-tidal estuary, Hangzhou Bay to understand the coastal dynamics in this mainly island-occupied estuarine area. The surveys covered a spring-neap tidal period in summer, and current, salinity, temperature, and turbidity were measured during the surveys. The salinity and temperature data show that the water in the channel is weakly stratified during both spring and neap tides. The Acoustic Doppler Current Profiler measurements show that the strong tidal current with an average velocity of around 2 m/s comes in along the northern side of the waterway during the flood tide and retreats along the southern side during the ebb tide, creating a lateral density gradient near the bottom. As the current relaxes from flood to ebb or vice versa, the lateral density gradient may force a lateral exchange flow. Based on the wavelet analysis, the time-series mooring data near the bottom demonstrated that the salinity and temperature in this region vary in a higher frequency than the dominant M2 tidal frequency. It is plausible that the salinity and temperature variation at this higher frequency is mainly impacted by the tidal current and the lateral exchange flow.