The Effect of Typhoon Passage on Northern South China Sea Coastal Waters: Modulation by Pearl River Plume

Abstract Estuarine plumes enriched with nutrients and contaminants significantly influence coastal stratification and nearshore ecosystem dynamics. Despite extensive research on their formation mechanisms and environmental impacts, their direct responses to typhoons and modulation of typhoon-driven coastal ocean processes remain elusive. Using observational data and numerical simulations, this study analyzes the response of the Pearl River Plume (PRP) and its modulating effects on shelf waters in the northern South China Sea during Typhoon Hato (2017). Results show that intense typhoon-induced vertical mixing rapidly eroded the shelf plume structure, increasing upper-layer salinity by up to 10 psu. In the middle and lower estuaries, the typhoon-modified currents elevated salinity in the eastern deep channel by 1~4 psu, while the upper estuary remained unaffected. A comparative numerical experiment without river discharge shows that the PRP suppresses typhoon-induced sea surface cooling in certain coastal zones (up to 2 °C) and enhances cross-shore two-layer circulation (onshore surface, offshore bottom currents) on the typhoon’s right-hand side. These findings characterize the influence of plume-typhoon interactions and have potential implications for improving typhoon intensity forecasts in estuarine-influenced coastal regions.