Correct Option (b)
The primary factors influencing ocean currents are:
- Rotation of the Earth: The Coriolis effect, resulting from Earth's rotation, deflects moving ocean water. This deflection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, significantly shaping the direction of ocean currents.
- Air pressure and wind: Surface ocean currents are predominantly driven by prevailing wind systems, such as the trade winds and westerlies. These winds exert frictional drag on the ocean surface, transferring energy and momentum to the water.
- Density of ocean water: Differences in ocean water density, primarily caused by variations in temperature (thermo) and salinity (haline), drive deep ocean currents. Colder, saltier water is denser and sinks, leading to thermohaline circulation.
Incorrect Options
- Option (a) 1 & 2 only: This option is incomplete as it omits the crucial role of ocean water density in driving deep ocean currents (thermohaline circulation).
- Option (c) 1 & 4: This option incorrectly includes the revolution of the Earth, which does not directly influence ocean currents, while omitting air pressure and wind, which are significant drivers of surface currents.
- Option (d) 2, 3 & 4: This option is incorrect because it omits the rotation of the Earth (Coriolis effect), a fundamental factor influencing current direction, and wrongly includes the revolution of the Earth. The Earth's revolution around the Sun does not directly influence the formation or direction of ocean currents.