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Ocean Currents

March 2nd, 2010 in Geography by Fario

Ocean currents are continuous, directed movements of ocean water. These smooth movements of water follow a specific course; they proceed either in a cyclical pattern or as a continuous stream. These movements can be caused by the gravitational pull of the moon, sun, the wind, the temperature, salinity, and the Coriolis force. The Coriolis effect is what happens with the wind because the earth is rotating. The wind in the Northern Hemisphere turns clockwise and the wind in the Southern Hemisphere turns anti-clockwise. There are different types of ocean currents.

Main Surface Currents

Surface ocean currents are created by the wind. A current moving in the top 400 metres of the ocean is considered as a surface ocean current. The Gulf Stream is an example of a surface ocean current. Not all these currents are the same, some are wide and slow, while others are fast and narrow. Some carry heat, and others are cold. The currents are heated at the equator by the sun and then the heat is transported to higher latitudes.

Deep Ocean Currents

Deep ocean currents are like great big rivers on the ocean bed. These use thermohaline circulation. This is when the current passes by Greenland or Antartica and they fill up with cold water. In those cold regions, ice is always being made, but the salt in the water cannot come into the ice, so it stays in the water. When the current passes, it picks up cold, extremely salty water, making it more dense, and it therefore sinks. As it moves along, it loses it cold salty water and starts to come back up. This is called upwelling. Of course it still stays under the ocean surface, because by the time it upwells, it passes by Antartica and fills up with the cold, salty water again and it downwells, the opposite of upwelling.
The Great Conveyer Belt is all the ocean currents (surface and deep) merged together to create a main current to show the general direction of currents.