- Rotation of the Earth
- Air pressure and wind
- Density of ocean water
- Revolution of the Earth
Which of the above factors influence the ocean currents?
(a) 1 and 2 Only
(b) 1, 2 and 3
(c) 1 and 4
(d) 2, 3 and 4
Answer: (b)
Oceanic currents describe the movement of water from one location to another. Currents are generally measured in metres per second or in knots (1 knot = 1.85 kilometres per hour or 1.15 miles per hour). Oceanic currents are driven by the following factors:
Option (b) is correct: The rise and fall of the tides: Tides create a current in the oceans, which are strongest near the shore, and in bays and estuaries along the coast. These are called “tidal currents.” Tidal currents change in a very regular pattern and can be predicted for future dates. In some locations, strong tidal currents can travel at speeds of eight knots or more. Wind: Winds drive currents that are at or near the ocean’s surface. Near coastal areas winds tend to drive currents on a localised scale and can result in phenomena like coastal upwelling. On a more global scale, in the open ocean, winds drive currents that circulate water for thousands of miles throughout the ocean basins. Thermohaline circulation: This is a process driven by density differences in water due to temperature (thermo) and salinity (haline) variations in different parts of the ocean. Currents driven by thermohaline circulation occur at both deep and shallow ocean levels and move much slower than tidal or 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. 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.
