Dynamics of Flow in the Region of the Tsugaru Strait

摘要

The Tsugaru Strait is one of four straits that connect the Sea of Japan to adjacent oceans. Flow dynamics in the Tsugaru Strait region are closely tied to the dynamics of the Tsushima Current, a branch of the Kuroshio that enters the Sea of Japan through the Korea Strait and exits through the Tsugaru and Soya Straits. This research concentrates on the dynamic interplay of the Tsushima Current and the Tsugaru Strait in three regions: the inflow region (Sea of Japan side), the strait itself, and the outflow region (North Pacific side). Dynamic calculations and steric sea leveling in the inflow region indicate that transport into the Tsugaru Strait is principally governed by the geostrophically balanced Tsushima Current. Setup generated south of the strait by the Tsushima Current cannot be maintained at the entrance to the strait; the resulting northward drop in coastal sea level is balanced by a net loss of transport into the strait. Within the strait, the flow is geostrophically balanced in the cross-stream direction. In the long stream direction, the barotropic pressure gradient is chiefly balanced by the longitudinal baroclinic pressure gradient and friction. Application of the Hansen-Rattray (1966) estuarine classification scheme to several straits shows that the Tsugaru Strait displays dynamics similar to that of a well-mixed estuary. The outflow jet emerging from the eastern mouth of the strait is governed by inertial-rotational dynamics; two distinct circulation modes, which behave in a manner consistent with the laboratory findings of Whitehead and Miller (1979), are seen.