Ocean Currents

Ocean waters are constantly being pushed around the earth by currents. A current is a stream of water that flows through the ocean like a river. Some of the currents are on the surface of the ocean while others are deeper beneath the surface. Each is equally important.

Surface currents are driven by the wind. As the wind begins to steadily blow across the surface of the ocean, the top layer of the ocean begins to move in a circular motion causing a current to build. This momentum may move the water hundreds of miles across the ocean each day.

The rotation of the earth also affects surface currents. Each day as the earth rotates it pulls large bodies of water along with it. This causes currents to build and to bend to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. As a result, the currents begin to flow in huge circles. This builds a force that can move of up to 137 miles every day. A surface current can carry more water than the Amazon River.

The Gulf Stream is a surface current that begins near the equator and flows north past the United States. As it moves it brings warm waters to the east coast.

There are also deep water currents that flow far beneath the surface of the ocean. The water in these deep currents moves much slower than the surface water currents. They are set into motion by either differences in the water temperature or by the saltiness of the water. Unlike the surface currents, deep water currents only move a few miles a day.

The water on the surface loses its heat to the atmosphere. It also becomes saltier as water evaporates leaving the salt. The salt does not evaporate. Instead the salt falls to the lower water causing the colder saltier to be denser. The less dense water flows upward and replaces the water at the surface. As a result, the deep water currents move much slower than the surface currents because it is denser. It may take up to 500 years for the deep water to resurface.

Dense water forms mainly in Antarctica and in North Atlantic Ocean. From there the water sinks and slowly spreads outward to the equator.

As the surface current moves, waves are formed. The waves carry energy from place to place. As the wind blows this process picks up force and waves are continually passing energy across the ocean.

When a wave approaches the shore it slows down and at the same time it begins to get higher. The tall wave reaches a point where it has to collapse against the shore. The force of this collapsing can be powerful.

Currents are formed both on the surface and deep beneath the ocean. The surface currents move faster and are more easily formed by the wind whereas the deep currents take much longer to form and more much slower due the denseness. However, each current is equally important serves a valuable purpose to the many oceans throughout the world.