Anatomical study of Tsushima Warm Current system: Determination of Principal Pathways and its Variation

The Tsushima Warm Current (TWC) forms a chaotic picture of surface currents in the Sea of Japan. This study, based on satellite-based sea surface topography, was conducted to clarify the complicated figures by identifying the main pathways of the TWC system. We specifically examine four main branches based on the initial position at the entrance region and their downstream trajectories. In regions west of 133 degrees E, the four currents mutually flowed independently, whereas the streamlines became scrambled at eastern longitudes. Our analyses revealed that the three branches of TWC, excluding the Subpolar Front Current, showed a confluence in the regions around the Oki Islands and off the Noto Peninsula. The seasonality of those current pathways is also addressed by this study. In the Yamato Basin, the TWC pathways, particularly offshore branches, were affected strongly by the existence and the location of developed mesoscale eddies, where basin-wide anticyclone during winter and cyclone during summer are frequently observed. In the eastern area of the Sea of Japan, the TWC branches showed notable features of meandering during winter, but it was straightforward during summer, mostly exiting towards the Pacific Ocean through the Tsugaru Strait.

Automated summary

This study, based on satellite data, clarifies the complex ocean currents in the Sea of Japan, identifies the main pathways of the Tsushima Warm Current system, and explores the seasonal variations of the currents. The characteristics and behaviors of the currents vary in different regions, with the offshore branches in the Yamato Basin strongly affected by mesoscale eddies, and the branches in the eastern Sea of Japan meandering during winter.