This study examines the expansion of the Pearl River diluted waters in the Northern South China Sea (NSCS) in summer, with a particular emphasis on the characteristics of buoyant water expansion and water age. Employing a process-oriented simulation and applying the Constituent-oriented Age and Residence Time Theory, we illustrate the three-dimensional distribution and the temporal evolution of the mean age of the diluted waters. We identify two principal expansion pathways for the diluted waters across the continental shelf: a northeastward surface-advected plume propelled by monsoonal winds, and an offshore southwestward current influenced by tides and riverine discharges. The surface waters, influenced by active upwelling and mixing, are characterized by shorter mean ages, whereas the bottom waters show longer mean ages. The buoyant plume tends to follow the northeastward pathway, dispersing towards the Taiwan Strait within approximately 30 days. The southwestward pathway requires a more extended period for the buoyant waters to disperse. Sensitivity experiments further reveal that tidal forces establish a buoyance runoff in the spring-neap tidal cycle along the edge of the buoyant plume. Meanwhile, the general characteristics of the mean age are predominantly determined by the monsoonal winds and riverine discharges.

Water Age,Pearl River Estuary