Summer behavior of the Changjiang diluted water to the East/Japan Sea: A modeling study in 2003

The summer behavior of Changjiang diluted water (CDW) toward the East/Japan Sea (EJS) is investigated by using a numerical ocean model. The present study focuses on the summer 2003, in which significant low salinity water is observed in the southwestern EJS in spite of similar amount of Changjiang discharge to the normal year. This paper mainly compares two experimental results for the summer 2003 (Exp. Y2003) and the normal year (Exp. NML). The simulated CDW in summer 2003 reveals remarkable changes in the pathway toward the Tsushima/Korea (T/K) Strait. The northeastward CDW behavior to the Jeju Strait, a major pathway in the normal year, is significantly reduced, while an intense southeastward extension to the along-shelf current (i.e., Taiwan–Tsushima Warm Current System) is dominant, similar to the field observation in July 2003. It is suggested that the Ekman dynamics plays an active role in remarkable changes of the CDW behavior. Namely, the reduction of northeastward behavior is associated with the dominance of strong northerly wind anomaly where the fresher bulge develops. On the other hand, the strengthened southwesterly wind over the southern region off the river mouth reinforces the extension to the along-shelf current. In consequence, the CDW below 28.0 psu joins the along-shelf current in the central East China Sea, and a passage of significant low salinity water is resulted at the T/K Strait in August 2003 due to the advection by along-shelf current. The additional experiment also exhibits that the strength of along-shelf current has an impact on the passage of CDW via the T/K Strait.