Ocean currents are driven by various forces including winds, temperature and salinity gradients, Earth’s rotation and gravity. They transport heat, influence weather, distribute nutrients and support fishing activities around the world.
Forces influencing ocean currents:
- Earth’s rotational force: It moves ocean water in the opposite direction to the west to east rotation of the earth, generating the Equatorial currents. Coriolis force affects the direction of the currents towards right in northern hemisphere.
- Atmospheric forces: Winds drive the ocean current in the direction in which they move because of friction. Rainfall and evaporation create level differences and thus move the water.
- Gradient forces: Temperature, salinity and density differences create gradients leading to expansion, floatation and sinking of water. Eg. – Labrador current moves as subsurface currents from the pole towards equator.
- Direction, shape and configuration of coastline- currents flow parallel to the coastline. Equatorial current after being obstructed by Brazilian coast gets bifurcated into two branches and then moves along the coast.
- Bottom reliefs: North Atlantic drift is deflected to the right when it crosses Wyville Thomson ridge.
Role of ocean currents in fishing industry:
- Meeting of the cold and warm ocean currents make the ideal place for breeding of fishes. For eg- the Grand Banks area.
- Upwelling currents bring cold nutrient-rich waters and support the growth of phytoplankton which provide the energy base for fish. Eg- fishing grounds on west coast of Africa and America.
- Current motion aids navigation thereby helping global trade. This in turn develops forward-backwards linkages for fishing industries.
However, in addition to this, other factors like the availability of vast shelves, government policies, consumption patterns etc also affect fishing industries.