Impact of wind and wave on the expansion of the Changjiang River plume in winter

The expansion of river plumes is essential for coastal systems and inner-shelf biogeochemical processes. This investigation employs the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system to systematically analyze the governing mechanisms influencing the Changjiang River plume during winter conditions. Model validation through comparison with the observational datasets demonstrates the system’s capability to accurately reproduce hydrodynamic processes and thermohaline variability. A series of sensitivity experiments was implemented to quantify the relative contributions of distinct forcing mechanisms, including tidal dynamics, wind stress, and wave-induced processes on hydrodynamic patterns and associated temperature-salinity distributions. Numerical simulations reveal that wave-induced vertical mixing generates significant nearshore thermal elevation concurrent with salinity reduction. Tidal residual currents exhibit persistent onshore and northward components, potentially facilitating northward advection of the Changjiang River plume during winter months. Conversely, wind-driven currents impose a constraining effect on plume expansion through the establishment of downwelling-favorable circulation patterns. During extreme wave events, wave-driven current contributions to salinity variance account for 30%–90%, relative to tidal mixing effects. These findings collectively establish wave-current interaction as a critical mechanistic component governing wintertime Changjiang River plume dynamics, with particular relevance to stratification modification and cross-shelf transport processes.