Wind and wave effects on the dispersal of the Pearl River-derived sediment over the Shelf

Abstract. The transport processes of suspended sediment from river sources to ocean sinks are vital for the global material cycle. This study quantitatively examines the effects of wind and wave dynamics on riverine sediment transport over a continental shelf throughout a typical year, utilizing the Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) model. After meticulous calibration, the model effectively replicates various fundamental marine environmental processes. Key findings reveal that over a typical year, approximately 62 % of riverine sediment is retained near the estuary, with sediments primarily transported southwestward and deposited in Beibu Gulf. During the wet summer, calm winds and waves lead to initial sediment deposition near the estuary via the river plume. In contrast, the dry winter sees stronger winds and waves resuspending and transporting these sediments. Analyses demonstrate that combined wind and wave action reduces proximal riverine sediment deposition levels to 83 % of those under No wind or wave conditions, resulting in a fivefold increase in westward alongshore sediment flux. Additionally, intensified cross-shore gradients of water level and density boost westward geostrophic flow and thermal wind shear, facilitating sediment transport to distant regions. This study offers valuable insights into the intricate interplay between winds, waves, and riverine sediment dynamics on continental shelves.