UPSC Prelims 2012 · Question 45 of 98
UPSC Prelims 2012 question on Ocean Current Factors
- ExamUPSC CSE
- Year2012
- PaperGeneral Studies Paper I
- SubjectGeography
- TopicOceanography
- DifficultyMedium
- TypeStatement
Consider the following factors:
1. Rotation of the Earth
2. Air pressure and wind
3. Density of ocean water
4. Revolution of the Earth
Which of the above factors influence the ocean currents?
Show answer
Answer: B. 1, 2 and 3
Verdict
Correct Answer: 1, 2 and 3
Analysis
Ocean currents are influenced mainly by Earth’s rotation, winds, pressure differences and density variations in seawater.
Revolution of the Earth causes seasons, but it is not a direct factor controlling ocean currents.
Statement by statement
1. Rotation of the Earth — Correct
Earth’s rotation causes the Coriolis effect.
It deflects ocean currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, helping form large circular current systems called gyres.
2. Air pressure and wind — Correct
Winds are the main drivers of surface ocean currents.
Prevailing winds such as Trade Winds and Westerlies drag surface water and influence the direction of currents.
3. Density of ocean water — Correct
Density differences drive deep ocean currents.
Density depends mainly on temperature and salinity; colder and saltier water becomes denser and sinks, creating thermohaline circulation.
4. Revolution of the Earth — Incorrect
Revolution means Earth’s annual movement around the Sun.
It causes seasons but does not directly push, pull or deflect ocean water like wind, rotation or density differences.
Extra UPSC info
* Surface currents are mainly driven by winds and Earth’s rotation.
* Deep ocean currents are driven by density differences caused by temperature and salinity.
* Warm currents generally move from equatorial regions towards higher latitudes.
* Cold currents generally move from polar regions towards lower latitudes.
* Gulf Stream and Kuroshio are examples of warm currents.
* Labrador Current and Canary Current are examples of cold currents.
* Indian Ocean currents show seasonal reversal due to monsoon winds.
How to crack it
Rotation of the Earth, air pressure and wind, and density of ocean water influence ocean currents, but revolution of the Earth does not directly control them.