Tide observations in the Korea-Tsushima Strait

Abstract

Tides are analyzed in the Korea-Tsushima Strait using measurements from 11 moorings, each containing an acoustic Doppler current profiler (ADCP) and a pressure gauge. These instruments were bottom moored at depths ranging from 59 to 142 m from May 1999 until October 1999 along two lines across the Strait, northeast and southwest of Tsushima Island. Tide amplitudes range over 3 m along the southern line but only range about 0.7 m along the northern line. Maximum total current velocities exceed 100 cm/s in the surface layers and typically exceed 50 cm/s at mid-depths along both lines. These data are analyzed for eight tidal constituents, which are found to account for about 88% of the sea surface height variability along the southern line and 70% along the northern line. M2, S2, K1, and O1 are the dominant constituents. Their amplitudes are generally 10–20% smaller than amplitudes from tide charts. M2 tidal velocities range from 17 to 25 cm/s along the line northeast of Tsushima Island, and are largest at the mooring on the western side of the Strait, nearest to Korea. Southeast of Tsushima Island, either M2 or K1 dominates the tidal contribution to the current, with tidal velocities ranging between 13 and 23 cm/s. Tidal velocities are fairly depth independent at mid-depths but exhibit varying degrees of depth dependence in the near-surface and near-bottom layers. While tidal currents are responsible for about 25% of the eddy kinetic energy in the near surface layer, they account for more than 50% of the eddy kinetic energy at mid-depths and about 70% near the bottom.