Intrusion of the Oyashio water into the eastern mouth of Tsugaru Strait in early summer, 2003

► We examine hydrography around the eastern mouth of Tsugaru Strait in June 2003. ► The subarctic water inflows into the north of the strait from Hidaka Bay. ► The Tsugaru Warm Current (TWC) water outflows from the south of the strait. ► The subarctic water is modified by diapycnal mixing with the TWC water. ► The mixed water is inferred to outflow from the deepest part of the strait.