Tidal-driven variation of suspended sediment in Hangzhou Bay based on GOCI data

Abstract The variation of suspended sediment concentration (SSC) in coastal waters plays a key role in the marine physical and chemical processes. Hangzhou Bay is a macrotidal estuary in eastern China. Under the influence of trapped tides, the SSC of Hangzhou Bay responds significantly commensurate with tidal frequencies, which leads to considerable changes in the ocean physical and chemical regimes, such as the underwater light field and turbidity front. However, polar-orbiting imaging satellites are unable to monitor the rapid variation of the SSC due to insufficient temporal resolution. In this study, we used the Geostationary Ocean Colour Imager (GOCI) data and in situ data of Hangzhou Bay to develop an appropriate remote sensing model to quantify the SSC of Hangzhou Bay and analyzed the impact of tides on the SSC. The research revealed the following findings: (1) The exponential model based on B8/B6 is best suited to remotely estimating the SSC in Hangzhou Bay, and the Mean Relative Error (MRE) is only 15.21%, (2) the variation of SSC in Hangzhou Bay is related to tidal forcing, especially during the ebb tide and the middle of the rising tide, (3) The effect of tidal driven SSC changes is less than the effect of diurnal tidal level variation of the middle tide day and the spring tide day tidal type, and (4) The maximum variation of SSC under tidal forcing is in the coastal ocean near the south bank of Hangzhou Bay and Nanhui Spit, while the origin of the variation of the Zhapu deep trough and the northern estuary is not obvious, which is speculated to be mainly related to the terrain and runoff of Hangzhou Bay. Furthermore, this study established a new model to map SSC in turbid seas and contributes to our understanding of SSC variation in the Hangzhou Bay, driven by strong tidal dynamics.