Long-term direct current velocity (GEK and ADCP), wind, coastal sea level, coastal water temperature and snapshot hydrographic data were used to describe the typical seasonal variations of surface flow patterns in the Nemuro Strait. At the southern end of the Strait, we find a remarkable seasonal change with a c1ear one-year cycle in the inflow into the Strait (May to August) and the outflow to the North Pacific (other months). However, it seems that such in/outflow variation never synchronize with the seasonal flow patterns in the Strait. During the wInter season when the northwesterly wind brows, we Infer that the southward wind-induced passage-flow through the Strait may transiently connect to the outflow at the southern end of the Strait. During the other seasons when the south-westerly wind is intensified at two times in spring and autumn, stable bifurcation flow (i.e., the northern northward and southern southward branch flows) forms around the deeper area at the northern part of the Strait (i.e., south of the Shiretoko peninsula). Since the northward branch flow strengthens at the corresponding season of intensified southwesterly wind, one possible mechanism of bifurcation flow is the wind-driven current. On the other hand, the southward branch flow is gradually interrupted by the westward flow, which begins to appear around the shallower area at the central part of the Strait in summer and dominates at the southern Strait in autumn.

Subtropical fromt that is one of the most distinct features in the upper ocean of the North Pacific subtropical gyre has been studied from comprehensive analyses of various data from satellite and hydrographic observations and atmospheric reanalysis. This article reviews the author's studies on physical properties and generation processes of mesoscale eddy in the subtropical front region, on detailed distribution and structure of the subtropical front, on frontogenesis due to mode waters in the thermocline north of the subtropical front，and on atmospheric influence of subtropical front through sea surface temperature front.