Volume, Heat, and Salt Transports through the Soya Strait and Their Seasonal and Interannual Variations

Volume, heat, and salt transports through the Soya Strait are estimated based on measurements from high-frequency ocean radars during 2003–15 and all available hydrographic data. The baroclinic velocity structure derived from the climatological geopotential anomaly is combined with the sea surface gradient obtained from radar-derived surface velocities to estimate the absolute velocity structure. The annual-mean volume, heat, and salt transports are 0.91 Sv (1 Sv ≡ 10 6 m 3 s −1 ), 25.5 TW, and 31.15 × 10 6 kg s −1 , respectively. The volume transport exhibits strong seasonal variations, with a maximum of 1.41 Sv in August and a minimum of 0.23 Sv in January. The seasonal amplitude and phase roughly correspond to those of the Tsushima–Korea Strait. Time series of the monthly transport is presented for the 12 yr, assuming that the baroclinic components are the monthly climatological values. In cold seasons (November to April), the monthly volume transport is strongly correlated with the sea level difference between the Japan and Okhotsk Seas, and an empirical formula to estimate the transport from the sea level difference is introduced. It is likely that the sea level setup by the wind stress along the east coast of Sakhalin determines the sea level difference, which explains the seasonal and interannual wintertime variations of transport through the strait. The annual flux of water through the Soya Strait with a density greater than 26.8 σ θ , a potential source of Okhotsk Sea Intermediate Waters, is estimated to be 0.18 Sv.