| Demand of the question Introduction. Contextual introduction. Body. Discuss various factors are responsible for the origin and modification of ocean currents. Explain how ocean current currents affect the climate of surrounding regions. Conclusion. Way forward. |
Ocean currents represent a regular volume of water in a definite path and direction. They are like river flow in oceans. They are the most important ocean movements because of their influence on climatology of various regions.
Factors responsible for the origin and modifications of ocean currents:
| Primary forces | Secondary forces |
| Insolation: Heating by solar energy causes the water to expand. This causes a very slight gradient and water tends to flow down the slope causing ocean current. The flow is normally from east to west. | Difference of density and salinity: It is attributed to density differences in different layers of ocean waters. Heavier water sinks and causes the overlying surface water to move in its space. This gives rise to global oceanic circulation. |
| Planetary winds: Planetary winds are the principal cause of the origin of ocean currents. Such winds drive surface water along with them. | Coastline shape: The shape of coastline is also an important factor that affects the current in the oceans. |
| Earth rotation and gravity: The rotation of the Earth causes Coriolis force which affects the direction of movement of water and leads to formation of ocean currents. Gravity tends to pull the water down to pile and create gradient variation.
| Other factors: Accumulation of water on east coasts leads to gravity induced movements down the slope. Wind, Coast line and inundation, large river discharge, presence of partially enclosed seas also modify ocean currents. |
| Coriolis force: This force intervenes and causes the water to move to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. These produce large circular currents in all the Ocean basins. One such circular current is in the Sargasso Sea. | Temperature difference: Cold-water ocean currents occur when the cold water at the poles sinks and slowly moves towards the equator. Warm-water currents travel out from the equator along the surface, flowing towards the poles to replace the sinking cold water. |
Effect of ocean currents on the climate of surrounding regions:
- Local Climate: Winds blowing over a warm current become warm and at the same time, pick up moisture. Thus, the wind that reaches the land brings down the temperature and causes heavy rainfall. The western coast of Europe is an example of such a region.
- Navigation: By using predicted, real-time and short-term forecasted currents, ships can be safely docked and undocked, maneuvered in confined waterways and safely navigate through coastal waters. Lack of this knowledge can lead to collisions and delayed arrivals.
- Fishing: Places where cold and warm currents meet are ideal for the growth of plankton which is food for fish. These regions thus have developed into major fishing grounds of the world. Newfoundland on the eastern coast of North America is the meeting point of the Gulf Stream and the Labrador Current. It is one of the major fishing centers of the world.
- Precipitation: Warm ocean currents bring rain to coastal areas and even interiors. For example, summer rainfall in British type of climate.
- Desert Formation: Cold ocean currents have a direct effect on desert formation in west coast regions of the tropical and subtropical continents. E.g. Peru Current, also called Humboldt Current, is a cold-water current of the southeast Pacific Ocean and a primary reason for the aridity of Atacama Desert (driest desert of the world).
- Tropical cyclones: They pile up warm waters in tropics and this warm water is the major force behind tropical cyclones.
- Moderating effect: They are responsible for moderate temperatures at coasts. For example, the North Atlantic Drift brings warmth to England, Canary cold current brings a cooling effect to Spain, Portugal etc.
Although there are a number of factors which impact the formation of ocean currents, the ocean current themselves play a major role in determining regional as well as global climate. Without currents in the ocean, regional temperatures would be more extreme- super hot at the equator and frigid toward the poles and much less of Earth’s land would be habitable.
