Tidal Currents

currents that are caused by the tide-generating forces of the moon and sun and that periodically change direction and speed. The basic components of tidal currents have periods of 12 and 24 hours. In the open sea, tidal currents are rotatory, or circular, with speeds up to 0.5 knot (25 cm/sec). Near shore, in narrow gulfs, and in straits, they approach and recede and may reach speeds exceeding 10 knots (500 cm/sec).