Q.11 During El Niño,
(A) cold water of the north flowing Peru current is displaced by a low-nutrient warm
southward current
(B) warm water of the north flowing Peru current is displaced by a low-nutrient cold
southward current
(C) cold water of the south flowing Peru current is displaced by a warm northward current
rich in nutrients
(D) warm water of the south flowing Peru current is displaced by a cold northward current
rich in nutrients
During El Niño, the cold water from the north-flowing Peru Current (also called Humboldt Current) gets displaced by low-nutrient warm water from a southward-flowing equatorial current, disrupting coastal upwelling and fisheries off Peru.
Option Analysis
Option (A): Correct. The Peru Current flows northward along South America’s west coast, bringing cold, nutrient-rich waters that support plankton and fish. El Niño weakens trade winds, pushing warm, nutrient-poor waters southward from the equator, replacing the cold upwelling and causing ecological shifts.
Option (B): Incorrect. The Peru Current carries cold water northward, not warm; no low-nutrient cold southward current displaces it during El Niño.
Option (C): Incorrect. While warm northward currents displace cold Peru water, they are nutrient-poor due to lack of upwelling, not rich in nutrients; this harms Peru’s fisheries.
Option (D): Incorrect. Peru Current is cold, not warm; no nutrient-rich cold northward current replaces it.
El Niño disrupts ocean currents along Peru’s coast, where the cold water of the north-flowing Peru Current is displaced by a low-nutrient warm southward current. This phenomenon, part of the El Niño-Southern Oscillation (ENSO), occurs every 2-7 years when trade winds weaken, allowing warm equatorial Pacific waters to shift east.
Key Mechanisms
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Normal Conditions: Humboldt (Peru) Current flows north, upwelling nutrient-rich cold water for rich marine life.
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El Niño Shift: Warm pool from west Pacific advances, suppressing upwelling; waters warm 4-8°C, reducing oxygen and nutrients.
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Impacts: Fish like anchovovy migrate or decline, costing Peru’s economy up to 5% GDP; floods hit Ecuador/Peru coasts.
Exam Relevance for CSIR NET
This MCQ tests oceanography in environmental biology. Option A matches as warm waters are explicitly low-nutrient, contrasting La Niña’s cold enhancements. Practice similar questions on ENSO-fisheries links for competitive exams.
