Ocean Currents
by Krysta CardinaleOcean currents can be simply defined as continuous flows of water in one of the Earth’s oceans. Major ocean currents can flow for thousands upon thousands of kilometers. These constantly moving waters have significant influences on the climate and living conditions for plant and animal life, even on land. Deep water currents make up about 90% of the ocean and are considered a Thermohaline circulation. These are waters driven by density and gravity forces and move around the ocean basins. Ocean surface currents have just a surface circulation. These currents make up the other 10% and are the upper 400 meters of the ocean. The major systems of water flow are found in the Atlantic Ocean currents, the Pacific Ocean currents, and the Indian Ocean currents
Causes of Ocean Currents
Ocean currents flow in complex patterns caused by the wind, bottom topography, the water’s salinity and heat content, and the earth’s rotation. Major ocean currents are created by the spin of the earth, and by the sun. This explains why the waters at the equator have a warm westward drift, and then move away to the poles. This cause of ocean currents produces vast ocean wide eddies that replicate the whirlpools of tidal rises, but on a scale that is thousands of miles across.
Ocean surface currents are usually driven by the wind and are generally subject to the Ekman spiral effect. The Ekman spiral effect is the flowing of water at an angle to the wind pushing it. In the northern hemisphere ocean surface currents generally flow clock-wise, whereas in the southern hemisphere they flow counter-clockwise.
On the other hand, deep water currents have a Thermohaline circulation, in comparison to the mainly wind driven ocean surface currents. Deep water currents are driven by density, gravity, and temperature gradients. These deep currents are created where the air temperatures are typically cold and the salinity of the surface waters is usually high. This combination makes the water dense, and thus, sink to the bottom. These currents, or submarine rivers, flow deep beneath the water (below 400 meters) and are hidden from immediate finding. Upwelling or downwelling in the ocean is where a considerable vertical movement in water flow is observed.
Major Ocean Currents
The major ocean currents can be divided into the oceans from which they are located. The five oceans include the Arctic, Atlantic, Pacific, Indian, and the Southern Ocean. The major ocean currents can also be divided into two categories based on whether it is a warm or cold current. The Atlantic Ocean currents, the Pacific Ocean currents, and the Indian Ocean currents make up all of the earth’s major ocean currents except for about four. The Pacific Ocean currents are divided by the equatorial current. In the south, it flows as far down as New Zealand. The southern Indian Ocean currents consist of the most circular system. On the other hand, the northern has to swirl around the great triangle of India. In the Atlantic there is the major ocean current called the Gulf Stream. It encloses in the center of the ocean, as all these great whirlpools do, in an area where the waters are almost still. This Atlantic Ocean current’s water is warm and is generally accompanied by a steady warm breeze. It typically meets with a cold current coming down from the arctic. The combination of the warm breezes and the cold from the arctic usually creates fog and moisture.The top eight major ocean currents include the North and South Equatorial Current, the Equatorial Counter Current, the North Atlantic Drift, the Gulf Stream, the Kuroshio Current (off of Japan), the Antarctic Circumpolar Current, and the East Australian Current.
