INFLUENCES OF THE KUROSHIO ON THE SALINITY BUDGET OF THE SETO INLAND SEA

Abstract

 The hydrodynamics and water quality of the Seto Inland Sea (SIS) are strongly influenced by oceanic waters. In this study, we aimed to precisely extract oceanic influences by focusing on salinity as a conservative tracer and conducted a salinity budget analysis for the entire SIS using a long-term reanalysis data set based on a 3D ocean circulation model. The salinity fluxes through the strait transects were influenced by the Kuroshio path and exhibited a high degree of correlation with volume flux. This resulted in an increase in inflow from the Bungo Channel during winter and a decrease or outflow in summer. The changes in total salinity in the eight sub-basins also demonstrated a pronounced correlation with salinity fluxes. In particular, in the sub-basins west of Hiuchi-nada Sea, total salinity was found to increase with the salinity influx at Bungo Channel and decrease with the outflux. In contrast, in the eastern sub-basins, the salinity flux fluctuations were weaker than in the western sub-basins, indicating a notable east-west deviation. This includes smaller tidal residual currents and a lesser influence from the Kuroshio.