UPSC Previous Year Questions:
- “The relationship between the winds and the currents is best seen in the Indian Ocean.” Justify. ( 2016)
Ocean Currents:
Ocean currents are streams of water( like river flow) flowing on the ocean surface in a definite direction.
Ocean currents are influenced by two forces.
- Primary forces that initiate the movement of water.
- The secondary force that influences the current to flow
Primary forces:
The following are primary forces:
Heating by Solar Energy:
- Heating by solar energy causes the water to expand. Ocean water at equators is about 8 cm higher than the middle latitude level of the ocean. This creates a gradient to water flow down the slope.
Winds:
- Winds create friction on the ocean surface between air and water that affects the movement of the ocean current.
Gravity:
- Gravity tends to pull the water down and high saline cold water sinks in the bottom of the ocean.
Coriolis forces:
- Coriolis forces intervene and cause water to move to the right in the northern hemisphere and left in the southern hemisphere.
Characteristics of ocean currents:
- Current speed s largest on the surface and speed get decreases with depth.
- Differences in water density affect the vertical movability of the ocean current.
- High saline and cold water are relatively denser and they sink and relatively low saline water tends to rise.
- Coldwater ocean current originated when cold water at poles sinks and slowly moves towards equators.
- Warm water currents travel from the equator along the surface and replace the sinking cold water at poles.
Types of Ocean currents:
Based on the depths:
Surface current
- It is about 10 % of all ocean water.
It is about 90 % of ocean water. Due to gravity, cooler saline water, and density, water at higher and latitudes sinks and move from the bottom.
Based on the temperatures:
- Cold currents
- Warm currents
Cold ocean current:
- Coldwater brings cold water into a warm water ocean. Cold ocean currents are generally found on the west coast of the continents in the lower ( excluding near equators) and middle latitudes in both hemispheres.
- It is also found east coast of the continents in the higher latitudes.
Warm Ocean current:
- It brings warm water into cold water areas and usually observe on the east coast of continents on the low and middle latitudes in both hemispheres and also found on the west coast of higher latitudes in the northern hemisphere.
Major Ocean Currents:
- Major ocean currents are greatly influenced by prevailing winds and Coriolis forces.
- Oceanic circular pattern roughly synchronous with atmosphere circulation pattern.
- The air circulation over the middle latitude is anticyclone and oceanic circulation patter also the same.
- At higher latitudes, winds flow mostly cyclonic in nature and the ocean circulation follows the same.
- Monsoon winds influence the current movement.
- Due to Coriolis forces, warm ocean flow from low latitudes tends to move in the right direction in the northern hemisphere and left to the southern hemisphere.
Effects of Ocean current:
Ocean currents have a number of direct and indirect influences on human activities
The cold currents:
- Cold ocean currents originated near the poles and move towards the equators.
- The West Coast of the continents in tropical and subtropical latitudes excluding near equator is bordered by cool water.
- Their average temperatures are relatively low and narrow diurnal and annual range.
- These regions experience fog.
- Surround regions are arid.
The impacts of Warm currents:
Warm ocean currents originated near equators and move towards poles.
West Coast of Continents in the middle and higher latitudes are bordered by warm ocean current and warm ocean current flow parallel to the east coast of continents in the tropical and subtropical latitudes.
Characterized by:
- Cool Summer
- Mild Winter
- The narrow annual range of temperature.
- Warm and rainy climate.
Meeting Point of Warm and Cold Current:
- The areas where warm and cold current meets enable the best fishing ground in the world. It replenishes the oxygen and nutrients that enable the growth of plankton.
- Meeting points of warm and cold ocean currents create foggy weather that makes it difficult for navigation.
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