tidalcurrent

A tidal current is the horizontal movement of seawater driven by the tides. It consists of alternating flood currents, which move water toward the coast or estuary as the tide rises, and ebb currents, which move water away from the coast as the tide falls. Tidal currents are most pronounced in constricted coastal areas, straits, channels, and estuaries, where bathymetry and coastline shape the flow.

Causes and dynamics: Tidal currents arise from the gravitational pull of the Moon and the Sun, which causes the adjoining water to bulge and recede. The interaction of these tidal bulges with coastlines and seabed friction produces horizontal flow. The timing and strength of tidal currents depend on tidal type (semidiurnal with two almost equal high tides per day, diurnal with one high tide per day), local bathymetry, tidal harmonic constituents, and coastal geometry. In narrow passages and over platforms, currents can become relatively fast, while in open sea they are typically weaker.

Measurement and forecasting: Tidal currents are monitored with instruments such as Acoustic Doppler Current Profilers, current meters, and high-frequency radar systems. Predictions rely on tidal constituents and hydrodynamic models that incorporate bathymetry, coastal topography, and external forcing, enabling forecasts of current speed and direction for navigation, coastal engineering, and offshore operations.

Impacts and applications: Tidal currents influence navigation and harbor operations, sediment transport, and coastal erosion. They also play a role in marine ecosystems by promoting mixing and transport of nutrients and organisms. Tidal energy projects seek to harness strong, predictable tidal currents in suitable locations.