12th February, 2016 (MAINS)


Q1. Explain the factors responsible for the origin of ocean currents. How do they influence regional climates, fishing and navigation?

[12.5marks/2015/GS-1] 200 words.

Please write answer in the comments section.

  • Aniruddh Shrivastava

    Factors responsible for the origin of ocean currents.

    Temperature Gradient : Earth receives maximum insolation at equator and minimum at poles. Consequently , oceanic water expands at equator and flows towards poles on surface level. Due to receiving less radiation, oceanic water on poles sinks down and flows towards equator at subsurface level to maintain the equilibrium of volume.

    Salinity : Salinity increases density of water.Due to high rainfall, equator region receives fresh water and is less saline .Whereas on poles, icebergs are made of fresh water results remaining water more saline , so denser water sinks at depth. Less saline water on equator moves towards more saline water on poles as outcome of osmosis.

    Effect on climate,fishing and navigation :

    Climate : Ocean currents act much like a conveyer belt, transporting warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics. Thus, currents regulate global climate, helping to counteract the uneven distribution of solar radiation reaching Earth’s surface. Without currents, 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.

    Fishing and Navigation : The place where cold and warm currents meet is very crucial for marine organism. The mixing of these waters and the shape of the ocean bottom lifts nutrients to the surface. These conditions helped to create one of the richest fishing grounds in the world.Also, Current plays dominant role in navigation. It ensures stability of ship. When ship is in harbors and inland water and the current is constant in strength and direction, Ship’s handling become much easier.

    • http://shashidthakur.com/ Shashi Thakur

      good answer. very nicely explained. your answer will be published as top answer by cutting it short to maintain word limit.

      • Aniruddh Shrivastava

        Thank you Sir. Keep guiding.

  • Ashi Agarwal

    Ans. Ocean currents result from two processes – the action of wind on the surface of the water, and from variation in water temperature that
    causes movement- a process known as convection. Convection occurs because the oceanic waters heat up becoming less dense. Winds
    blowing over a cold current help to bring down the temperatures in places, which would have been much hotter. Such winds are bereft of any
    moisture and bring little or no rainfall over the coastal regions where they blow. As most cold currents flow along the western coast of
    continents, some of the major deserts are found in such regions.
    Winds blowing over a warm current become warm and at the same time, pick up moisture, as warm winds are able to retain more moisture.
    Thus, the wind that reaches the land brings down the temperature and causes heavy rainfall. Places where cold and warm currents meet are
    ideal for the growth of Plankton. These regions support a great number of fish. They have developed into major fishing grounds of the world.
    Ships moving against a current lose speed. Â Ships sailing with a current gain the speed, which helps to save fuel and time. Warm currents
    keep the Arctic regions free from icebergs, which can be dangerous for ships.