The Annual Cycle of the Japan Sea Throughflow

The mechanism responsible for the annual cycle of the flow through the straits of the Japan Sea is investigated using a two-layer model. Observations show maximum throughflow from summer to fall and minimum in winter, occurring synchronously at the three major straits: Tsushima, Tsugaru, and Soya Straits. This study finds the subpolar winds located to the north of Japan as the leading forcing agent, which first affects the Soya Strait rather than the Tsushima or Tsugaru Straits. The subpolar winds generate baroclinic Kelvin waves along the coastlines of the subpolar gyre, affect the sea surface height at the Soya Strait, and modify the flow through the strait. This causes barotropic adjustment to occur inside the Japan Sea and thus affect the flow at the Tsugaru and Tsushima Straits almost synchronously. The barotropic adjustment mechanism explains well why the observations show a similar annual cycle at the three straits. The annual cycle at the Tsugaru Strait is further shown to be weaker than that in the other two straits based on frictional balance around islands, that is, frictional stresses exerted around an island integrate to zero. In the Tsugaru Strait, the flows induced by the frictional integrals around the northern (Hokkaido) and southern (Honshu) islands are in opposite directions and tend to cancel out. Frictional balance also suggests that the annual cycle at the Tsugaru Strait is likely in phase with that at the Soya Strait because the length scale of the northern island is much shorter than that of the southern island.

Description of appendages from three marine trachyleberidid species (Ostracoda, Crustacea) from Japan

Three living trachyleberidid ostracod species, Acanthocythereis munechikai Ishizaki, Actinocythereis kisarazuensis Yajima and Hirsutocythere hanaii Ishizaki, were discovered in the Tsushima Straits, c. 120 km east of Tsushima Island (north Island), N 34° 46′ E 130° 46′ at a depth of 116 m. This is the first description of complete appendages for these genera.

The Tsushima Warm Current through Tsushima Straits Estimated from Ferryboat ADCP Data

Current structures across the Tsushima Straits are studied using results from long-term acoustic Doppler current profiler (ADCP) observations by a ferryboat between Hakata and Pusan conducted since February 1997. Two maxima of the northeastward current are observed in the central parts of the eastern and western channels, and the maximum velocity in the western channel is stronger than that of the eastern channel. Downstream of the Tsushima Islands, a southwestward countercurrent is observed associated with a pair of cyclonic and anticyclonic eddies. In the western channel, the deep countercurrent is observed pronouncedly on the bottom slope of the Korean side from summer to winter. The volume transport of the Tsushima Warm Current through the straits has strong seasonal variation with a minimum in January and two maxima from spring to autumn (double peaks). The spring peak of the volume transport through the eastern channel is more pronounced than the autumn peak, and the autumn peak of the western channel is more pronounced than the spring peak. The inflow volume transport into the Japan Sea through the western channel significantly increases in autumn because of an incrementation of the freshwater transport. The total volume transport averaged over the observation period (5.5 yr) is 2.64 Sv (Sv ≡ 106 m3 s−1). The average volume transports through the eastern and western channels are 1.10 and 1.54 Sv, respectively.