Q. Which of the following is/are correct inference/inferences from isothermal maps in the month of January?
1. The isotherms deviate to the north over the ocean and to the south over the continent.
2. The presence of cold ocean currents, Gulf Stream and North Atlantic Drift make the North Atlantic Ocean colder and the isotherms bend towards the north.
Select the answer using the code given below:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Correct answer: (a) 1 only
Question from UPSC Prelims 2024 GS Paper
Explanation:
1. “The isotherms deviate to the north over the ocean and to the south over the continent.”
This statement is correct. In January (winter in the Northern Hemisphere), isotherms generally bend northward over oceans and southward over continents. This is due to the different heat capacities of land and water. Oceans retain heat longer than land, so they tend to be warmer relative to their latitude in winter. This causes the isotherms to bend northward over oceans. Conversely, land cools faster, causing isotherms to dip southward over continents.
2. “The presence of cold ocean currents, Gulf Stream and North Atlantic Drift make the North Atlantic Ocean colder and the isotherms bend towards the north.”
This statement is incorrect. The Gulf Stream and North Atlantic Drift are warm ocean currents, not cold ones. These currents actually bring warm water from the tropics to the North Atlantic, making it warmer than it would be otherwise. This warmth causes the isotherms to bend northward over the North Atlantic Ocean, not because it’s colder.