13 Feb 2024 : Daily Answer Writing
Q1) With the help of a map, show major ocean currents of the world. Explaining the factors driving the ocean currents, highlight their effects on human activities. (250 Words/15 Marks)
ANSWER
Ocean currents are continuous movement of oceanic water in a definite path and direction driven under the influence of wind, gravity, Coriolis force and heating by solar energy. They are streams of water circulating along ocean margins and circumnavigate the whole earth.
On the basis of Temperature, ocean currents are classified into Warm Current and Cold Current. On the basis of depth, ocean currents are classified into Surface current and deep-water current.
Figure: Map depicting ocean currents
The factors that drive the ocean currents can be studied under the following heads:
Primary forces:
- Incoming Insolation/Solar energy causes the water to expand and causes a very slight gradient due to this water usually flows down the slope.
- Planetary winds provide the driving force by friction drag on the water surface.
E.g., the North East trade wind between equator and tropic move the North Equatorial currents in Pacific Ocean to warm the eastern coast of Japan as the Kuroshio Current.
- Gravity tends to pull the water down to pile and create gradient variation.
- Coriolis force changes the direction of water toward right in the Northern Hemisphere and left in the southern hemisphere which results in formation of gyres and give directional orientation to the ocean currents.
Secondary forces:
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- Salinity difference and temperature difference are the secondary forces as they create density difference.
- Denser water (cooler or more saline) tends to sink, while relatively lighter water tends to rise.
E.g., Weak current across the Strait of Gibraltar between the Atlantic Ocean and Mediterranean Sea.
Ocean currents are significant for human activities because of the impacts they have on climate, navigation, and economic activities:
- Ocean current plays an important role in determining the climate of a region. E.g., the climate of Florida becomes warm due to the Gulf Stream; similarly, the otherwise hot climate of Peru is cooled by cold Peru current.
- Warm Ocean currents increase precipitation whereas Cold current reduces it:
- Warm currents such as North Atlantic drift and Kuroshio current bring in sufficient rainfall along the western coast of Europe and eastern coast of Japan respectively.
- Mohajve desert in North America and Atacama Desert along the Western coast of South America owe their existence to some extent to California current and Peru Current respectively.
- Benguela current and the canaries current are partially responsible for the existence of Kalahari Desert along the western coast of South Africa and Sahara Desert in the north-west part of Africa.
- Convergence of warm and cold current replenish oxygen levels and boost phytoplankton growth, enhancing the potential for fishing industry.
E.g., rich fishing ground at Newfoundland (convergence of Labrador current and Gulf Stream).
- On the account of influence of warm currents, ports and harbours are kept open in winters, thus facilitating trade throughout the year.
E.g., Impact of North Atlantic Drift on the ports of Western Europe.
- Ocean currents help in international navigation and ships follow the route which is aided by ocean currents.
- West coasts of the continents in the middle and higher latitudes are bordered by warm waters giving the region a distinct marine climate suitable for tourism activities.
In the contemporary times, the nature and pattern of ocean currents are being affected and modified by climate change. In this regard a moderation in anthropogenic influences on environment is an imperative.
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