Currents

Currents By: Michelle Johnson



Currents are the movement of water in a certain direction in oceans. There are two which are called __surface currents__ and __deep water currents.__

__Surface Currents__ make up the upper 400 meters of the ocean and 10% of all the ocean's waters. They are moved by winds that blow in ceratin patterns because of the Earth's spin and the Coroilis effect. Although the wind and the Corolis effect move the water around, surface currents are not formed in this way. They are instead formed by large circular patterns called gyres. __Gyres__ are large mounds of water and the flow around them. They flow counterclockwise in the Northern Hemisphere oceans while the Corolis effect causes the waters in the Southern Hemisphere to flow counterclockwise. With this happening surface ocean currents are formed.

Surface Currents also differentiate in size. although they all flow in a regular pattern some currents may be steep and narrow while other currents may be shallow and wide. The reason they are created like this is often because of the shape of the ocean floor.

Currents can also carry heat from one place to another on Earth. This process occurs because the Sun warms water at the equator more than it does at around colder regions. The heat then travels in surface currents to areas with higher latitudes.

__Deep Water Currents__ make up the other 90% of the ocean and are the deep waters that sink into the deep ocean basins at high latitudes where temperatures are very cold. These waters move around ocean basins by gravity and density driven forces.

Ocean currents are influenced by two types of forces, primary forces and secondary forces.

The primary forces are solar heating, winds, gravity, and the Coriolis effect. __Solar heating__ causes the ocean water to expand. This heating causes a slight slope and water to flow down it. __Winds__ that blow on the surface of the ocean push the water. How this happens is that water will pile up and the wind blows it and pushes it around. __Gravity__ pulls water or piles of water down against the pressure gradient, or the Coriolis effect. The pressure gradient intervenes and causes the water to move around a mound of water. These larges mounds of water and the flow around them can also be identified as __gyres__.

The secondary force are the influence in which currents flow.