open access

https://doi.org/10.14943/bull.fish.76.10

https://hdl.handle.net/2115/100328

The Reason Why only the Winter Intensification of the Tsushima Warm Current Can Penetrate into the Tsugaru Strait

日本語

Hydrographic observation

2026-09-01

北海道大学大学院水産科学研究院

Bulletin of Fisheries Sciences, Hokkaido University

76

10-23

14

It is known that the Tsushima Warm Current (TWC), which flows northward as a coastal boundary current along the Japanese islands, intensifies twice a year ─ in summer (August to September) and winter (November to December). Based on seasonal variations in the sea level difference across the Tsugaru Strait (assuming a surface geostrophic flow), it was inferred that only the sea level disturbance associated with the winter intensification is capable of penetrating into the strait. In this study, we clarified its reason through analyses of hydrographic observation data (collected approximately monthly) off Aomori, spatiotemporal distributions of freshwater content in the Japan Sea, and numerical experiments. The TWC that intensifies in summer is a warm-water-driven density current that extends deeper than the strait. Consequently, the sea level disturbance associated with this summer intensification cannot enter the strait. In contrast, the TWC that intensifies in winter is a low-salinity-driven density current caused by freshwater supply from rivers north of the Noto Peninsula. Since this low-salinity density current is shallower than the depth of the strait, it can penetrate into the strait as a Kelvin-type coastal trapped disturbance.

紀要論文

Version of Record

2435-3353