What Is the Difference Between Currents, Waves & Tides?

Waves

• A wave is a forward motion of energy in water. As the wind blows across the ocean's surface, it pushes on the water, causing it to ripple. A wave's size and speed depends on the wind's strength, the length of its gusts and how far it blows. The greater these three are, the larger the wave. Steady winds produce a series of waves called a wave train, where one wave follows another in the same direction. The energy moves forward through the water, but the water itself does not move forward. As a wave approaches land, the ocean floor affects its shape and speed, causing it to become unstable before it finally pitches forward and breaks on the shore.

Tides

• A tide is the daily rise and fall of ocean waters caused by the Earth's rotation and the moon's gravitational pull. This gravitational pull causes the ocean water closest to the moon to bulge out from the Earth, creating a high tide. On the opposite side of the globe, the moon's gravitational pull forms a second bulge of water, creating a second high tide. Low tides lay in the shallow areas found halfway between the two high tides. A particular tide returns about every 24 hours and 50 minutes.

Ocean Currents

• Ocean currents are like highways or rivers of continuously moving water that travel great distances. Large surface currents are primarily driven by year-round winds and flow horizontally across the ocean's surface, spinning in large loops called gyres that rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Subsurface currents may move vertically and are caused when cold or very salty water, which is denser, sinks below warm or less-salty water, which is less dense.

Coastal Currents

• Some currents occur only along the coast, and are caused by wave and tidal action. After a wave breaks on the beach, momentum carries water across the sand, and an undertow current returns it to the ocean. Longshore currents occur when waves strike the beach at an angle, causing a current that runs parallel to the shore. Tidal currents also run parallel to the shore, and occur when the tide enters and leaves bays and inlets as it is changing from high to low and vice versa.