Tidal current

A tidal current is the horizontal movement of seawater driven mainly by the rise and fall of tides. Its direction and speed vary with the tidal cycle and local geography.

Tidal force: The difference in gravitational pull across an extended body, producing deformation or relative motion. The Moon’s and Sun’s differential gravity drives the tides that generate these currents.
Tidal stream generator: A turbine that converts the kinetic energy of moving tidal water into electricity. It extracts energy directly from the currents described on this page.
Ocean current: A persistent, directed flow of seawater driven by forces such as wind, density differences, and tides. Tidal current is one time-varying kind of the broader ocean-current phenomenon.
Bay of Fundy: An Atlantic inlet between New Brunswick and Nova Scotia, Canada, known for exceptionally large tides. Its large tidal range drives strong currents through narrow passages and channels.
Tidal range: The vertical difference between high water and low water during a specified period. A larger rise and fall of sea level can produce stronger flows through constrained passages.
Tidal stream power: Electricity generated by turbines placed in fast-moving tidal flows. It turns predictable current cycles into a renewable energy resource.
Wind-driven current: A seawater flow produced primarily by momentum transferred from wind at the ocean surface. Unlike tidal currents, its immediate driver is wind stress rather than the tidal cycle.
Saltstraumen: A narrow strait in northern Norway where powerful tidal currents form large whirlpools. The constricted passage makes tidal exchange unusually rapid and turbulent.
Tidal prism: The volume of water entering or leaving an estuary or embayment during one tidal cycle. This exchanged volume helps determine the current needed to fill and drain an inlet.
Tidal race: A fast, turbulent tidal current formed where water is forced through a narrow passage or around an obstruction. These concentrated flows are both hazards and promising turbine sites.

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