Shifting Dynamics for Coastal Upwelling and Surface Cold Water Patch: A Synergy of HF-Radar, In-Site Observation, Satellite, and Numerical Model

Coastal currents exhibit high spatial and temporal variability and are influenced by rapid shifts in dominant dynamics, posing great challenges for accurate observation and interpretation. This research combines multiple data methods and a well-validated numerical model to investigate the shifting dynamics of upwelling-favorable winds, topographic variations, and the extension of the low-salinity plume in the coastal region of the southwestern Yellow Sea. By utilizing ocean surface current data from high-frequency radar (HF-Radar), velocity profile data from bottom-mounted acoustic Doppler current profiler (ADCP), sea surface temperature (SST) data from satellite, and wind data from the European Centre for Medium-Range Weather Forecasts (ECMWFs), 3-D flow patterns in the southwestern Yellow Sea, particularly focusing on the surface currents, are revealed in detail. The HF-Radar provides sufficient spatial coverage, while the ADCP and numerical model supplement the vertical structure of ocean currents. In addition to the nearshore upwelling caused by strong alongshore winds through Ekman transport, topographic variation can also lead to site-specific upwelling that can markedly impact surface currents. On the other hand, these two types of upwellings may affect each other. The offshore transport of low-salinity coastal surface water as a result of nearshore upwelling can significantly counteract topography-driven upwelling. The extension of the low-salinity plume shows a mutually exclusive relation with the isolated surface cold water patch (SCP) induced by site-specific upwelling. Integrating multimethods observational data and numerical simulations improves our understanding of coastal currents and holds significant potential for studying other dynamic processes.