Dominant factors responsible for wave modulation in the macro-tidal Gyeonggi Bay of the Yellow Sea

Surface gravity waves, crucial for sediment transport in coastal regions, undergo wave modulation owing to local hydrodynamic conditions. However, the cause of the spatial and temporal distribution of the dominant factors in wave modulation remains vague. This study was aimed at identifying the causes of tidal modulation of waves in Gyeonggi Bay, which exhibits shallow water and macro-tidal environment, and estimating site-specific dominant factors using numerical modeling. The results indicated that tides significantly impact wave dynamics at semi -diurnal tidal frequencies, with spatiotemporal variability. The most dominant factor in wave modulation in the nearshore region is the depth change caused by tides, and the most notable impact was found in tidal flats. Depth dependence is mainly evident in surf zones, with a clear distinction at locations where the wave height to water depth ratio reaches 0.2. While idealized studies highlight the significant role of wind in governing incoming waves, it is not the primary cause of modulation. Nevertheless, stronger tidal strength can lead to more pro-nounced modulation, which is further amplified when accompanied by strong wind conditions. This finding indicates that the spatiotemporal distribution of wave modulation in macro-tidal regions may have a significant impact on various estuarine dynamics including sediment transport.