Everything about Ocean Circulation totally explained
An
ocean current is continuous, directed movement of
ocean water. Ocean currents are rivers of hot or cold water within the ocean. The currents are generated from the forces acting upon the water like the planet rotation, the wind, the
temperature and
salinity (hence
isopycnal) differences and the
gravitation of the moon. The
depth contours, the
shoreline and other currents influence the current's direction and strength.
Important currents
Ocean
currents can flow for thousands of kilometers. They are very important in determining the
climates of the
continents, especially those regions bordering on the ocean. Perhaps the most striking example is the
Gulf Stream, which makes northwest
Europe much more temperate than any other region at the same latitude. Another example is the
Hawaiian Islands, where the
climate is cooler (sub-tropical) than the tropical latitudes in which they're located because of the
California Current.
Background
Surface ocean currents are generally wind driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere because of the imposed wind stresses. In wind driven currents, the
Ekman spiral effect results in the currents flowing at an angle to the driving winds. The areas of surface ocean currents move somewhat with the
seasons; this is most notable in equatorial currents.
Deep ocean currents are driven by density and temperature gradients.
Thermohaline circulation, also known as the ocean's conveyor belt, refers to the deep ocean density-driven
ocean basin currents. These currents, which flow under the surface of the ocean and are thus hidden from immediate detection, are called
submarine rivers. These are currently being researched by a fleet of underwater robots called
Argo.
Upwelling and
downwelling areas in the oceans are areas where significant vertical movement of ocean water is observed.
Surface currents make up about 10% of all the water in the ocean. Surface currents are generally restricted to the upper 400 meters of the ocean. The movement of deep water in the ocean basins is by density driven forces and gravity. The density difference is a function of different temperatures and salinity. Deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase. The main causes of currents are: solar heating, winds and gravity.
Ocean currents are measured in
Sverdrup with the symbol Sv, where 1 Sv is equivalent to a volume flow rate of 10
6 cubic meters per second.
Significance to people and sea life
Knowledge of surface ocean currents is essential in reducing costs of shipping, since they reduce fuel costs. In the sail-ship era knowledge was even more essential. A good example of this is the Agulhas current, which long prevented Portuguese sailors from reaching India. Even today, the round-the-world sailing competitors employ surface currents to their benefit.
Ocean currents are also very important in the dispersal of many life forms. A dramatic example is the
life-cycle of the eel.
Important currents
Further Information
Get more info on 'Ocean Circulation'.
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