Residual circulations and associated water mass transport in the South China sea analyzed with a coupled HYCOM-ROMS downscaling ocean model

Abstract

A high-resolution, high-precision downscaling oceanic circulation model for the Southern China Sea (SCS) was developed based on the Regional Oceanic Modeling System (ROMS) at a lateral resolution of 5 km, initialized and forced by the HYbrid Coordinate Ocean Model (HYCOM) global reanalysis product. A multi-year reanalysis was conducted with the HYCOM-ROMS system that properly accounts for wind stress and heat budget at surface, freshwater influences from the atmosphere and major rivers, and tidal variability. Prospective applications of the system include assessments of oceanic dispersal of wastewater, quantification of marine ecosystem network, analyses of micro plastic transport and its coastal accumulation, etc. In prior to applied studies, we extensively investigated the validity and performance of the developed system. We found that it successfully reproduced primary dynamics of the SCS in many aspects such as the transient Kuroshio path in the south of Taiwan prominently affecting the circulation of the northern SCS through the Luzon Strait. The North Equatorial Current (NEC) drifting near Bismarck Archipelago, New Guinea, sporadically intrudes into the Indonesian water and adjacent seas to invoke bifurcating northward and westward currents. This intrusion promotes the northwestward mass transport into the Celebes Sea and further into the Sulu Sea, and then enters the SCS through the Palawan Strait.