Variation of volume transport in the Tsugaru Strait; An Estimation based on ADCP observation in the period of 2002-2004

Ito, Toshimichi ; Kawamura, Hideyuki  ; Nakayama, Tomoharu*; Shima, Shigeki*; Onishi, Mitsuyo*; Isoda, Yutaka*

We had measured the 3-D velocity distribution of throughflow in the Tsugaru Strait during Nov. 1999 and Dec. 2007. In this observation, an ADCP (RDI, 150 kHz) had been mounted on the bottom of voluntary ferry (VIRGO, Higashi-nihon Ferry co. ltd.,) regularly operated in the strait. Main results of the observation for the period of Apr. 2002-Mar. 2004 are as follows; (1) velocity distribution was elucidated, (2) volume transport of the throughflow ranged 0.77-1.80 Sv (1Sv=110 ms) and its mean was 1.30 Sv with standard deviation 0.24 Sv, (3) the volume transport showed relatively weak seasonal variation and relatively strong periodicity with period of 20-30 days, (4) the variation was controlled by sea level difference around the strait, and (5) mean volume transport for in this period, in which missing data were filled using sea level difference data around the strait, was estimated to be 1.340.24 Sv.