Differences Between Gyres & Currents

Ocean Currents

• The two types of ocean currents cover thousands of miles and flow in reliable patterns. Surface currents occur in the upper 400 meters of the Earth's ocean --- about 10 percent of the world's water. They result most commonly from solar heating, winds, gravity and the Coriolis effect. Deepwater currents, also called thermohaline circulation, result from gravity and changes in density resulting from differences in temperature and salinity.

Coriolis Effect

• The Coriolis effect describes the manner in which the rotation of the earth forces wind movement to pull in patterns to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. It thus causes currents to churn clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. However, the phenomenon does not occur at the equator since the Coriolis only occurs above and below equatorial waters.

Gyres

• As the earth's rotation creates swirling wind patterns, the wind drags upon the water and influences it to move in a giant spiral. The effect creates a "mound" of water surrounded by a circular flow. These systems, including both the mounded water and the motion of the surrounding water together, are called gyres. Since gyres circle entire oceans, they are massive and contain several smaller currents within them. Five major gyres exist: one is in the Indian ocean, two in the Pacific and two in the Atlantic.

Example: The North Atlantic Gyre

• The North Atlantic Gyre contains four separate currents. The Gulf Stream runs from the south near Cuba toward the northeast along the North American coast until it meets the North Atlantic Current, which pulls it eastward. The North Atlantic then meets the Canary Current, which runs southward along the coast of Europe and Africa. There, it intersects with the North Equatorial Current