Q: Explain the factors responsible for the origin of ocean currents? How do they influence regional climates, fishing and navigation?
Ocean currents are streams made up of horizontal and vertical components of the circulation system of ocean waters. The factors responsible for origin of ocean currents may be discussed as:
- Planetary winds: Planetary winds are the principal cause of the origin of ocean currents. Such winds drive surface water along with them.
- Difference of density and salinity: Difference of density and salinity in ocean water motivates denser waters to sink and move as undercurrents; whereas lighter waters move towards the denser water as surface currents.
- The rotation of the Earth: The rotation of the Earth causes Coriolis force which affects the direction of movement of water and leads to formation of ocean currents.
- The shape of coastline: The shape of coastline is also an important factor that affects the current in the oceans.
- Frictional force: Movement of water through the oceans is slowed by friction, with surrounding fluid moving at a different velocity which leads to a difference in the speed of water and generates current.
The influence of ocean currents can be discussed as:
- On regional 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. Such winds bring down the temperature of the land like the Kuroshio (warm) current, which flows along the east coast of Japan. Ocean currents also lower the temperature of a region. For eg, The California (cold) current, which flows along the western coast of USA, makes the region much cooler than other places in the west coast on the same latitude.
- Navigation: By using predicted, real-time and short-term forecasted currents, ships can be safely docked and undocked, maneuvered in confined waterways and safely navigated through coastal waters. Lack of this knowledge can lead to collisions and delayed arrivals. Ships sailing with a current gain speed which helps in saving fuel and time. Ships moving against a current lose speed.
- 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.