UPSC CSE Prelims
Ocean Currents Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 3 — Both 1 and 2

Both statements correctly describe the influence of prevailing winds on ocean temperature distribution. Trade winds in tropical zones and westerlies in temperate zones drive warm surface currents in their respective directions, creating distinct temperature patterns across ocean basins.

✅ Statement 1 – Correct: Trade winds (blowing east to west) in tropical zones push warm surface waters westward, making western sections of tropical oceans warmer than eastern sections (e.g., warm Western Pacific versus cool Eastern Pacific).

✅ Statement 2 – Correct: Westerlies (blowing west to east) in temperate zones drive warm waters eastward, making eastern sections warmer than western sections (e.g., warm North Atlantic Drift warming Western Europe).

📝 Short Notes: Ocean Temperature Distribution and Wind Patterns

• Trade Winds mechanism: Push warm equatorial waters westward, causing warm water accumulation on western ocean boundaries and upwelling of cold water on eastern boundaries
• Westerlies mechanism: Drive warm currents from west to east, transferring heat from lower latitudes to higher latitudes on eastern ocean sides
• Western boundary currents: In tropical zones (e.g., Gulf Stream, Kuroshio) are warm, narrow, and fast-flowing
• Eastern boundary currents: In tropical zones (e.g., California Current, Peru Current) are cold, wide, and slow-flowing
• Climate impact: These patterns significantly influence coastal climates, with western tropical coasts being warmer and wetter, while eastern tropical coasts are cooler and drier

Detailed Explanation:

The North and South Equatorial Currents flow westward due to Trade Winds, causing water to accumulate on the western sides of ocean basins and creating a higher sea level in the west.

This convergence and water pile-up generates a pressure gradient that drives the Equatorial Counter-Current to flow eastward between the two equatorial currents in the Doldrums region (where surface winds are weak), restoring oceanic equilibrium.

Detailed Explanation:

The world's most productive fishing grounds are located where warm and cold oceanic currents converge. This mixing creates nutrient-rich waters and ideal conditions for phytoplankton growth, which forms the base of the marine food chain.

Grand Banks (Newfoundland): Cold Labrador Current meets warm Gulf Stream, creating one of the world's richest fishing zones.

North-West Pacific (Japan): Cold Oyashio Current meets warm Kuroshio Current, supporting highly productive fisheries.

Detailed Explanation:

✅ Statement 1 – Correct: Rotation of the Earth causes the Coriolis effect, which deflects ocean currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

✅ Statement 2 – Correct: Air pressure and wind generate wind-driven currents by exerting friction on the ocean surface; prevailing winds like Trade Winds and Westerlies drive major surface currents.

✅ Statement 3 – Correct: Density of ocean water, determined by temperature and salinity, drives thermohaline circulation (deep ocean currents).

❌ Statement 4 – Incorrect: Revolution of the Earth (orbit around the Sun) causes seasonal changes but does not directly influence ocean currents.