On the interaction between the nonlinear internal waves and the Pearl River plume

In late July of 2016, a temperature mooring deployed north of Dongsha Atoll has recorded the enhancement of nonlinear internal waves (NIWs) associated with regionally environmental variability. Observations revealed large daily temperature fluctuations of 10-14 °C at depths of 80-100 m, with peak variations occurring after spring tides and showing an increasing trend, indicative of intensified NIW activity. This study investigates the uncertainties regarding the influence of river flux, precipitation, and other environmental factors on the short-term intensification of NIWs. Through the analysis of multiple independent oceanic and atmospheric datasets, we identified significant variations in zonal oceanic currents and the advection of low-salinity water discharged from the Pearl River to the Dongsha mooring (DSM), which enhanced in situ stratification. The analysis of buoyancy frequency squared (N²) indicates favorable conditions for westward NIW propagation from DSM toward the Pearl River Estuary. These findings highlight the critical role of river flux in shaping NIW dynamics by creating a pathway that enhances the concentration and propagation of NIWs. Given the rising frequency of extreme summer precipitation events associated with global warming and climate change, this study suggests an increased likelihood of NIWs in the northern South China Sea directly reaching the southeastern mainland coast from the Luzon Strait.