UPSC Prelims 2015·GS1·geography·oceanography

What explains the eastward flow of the equatorial counter-current?

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Last updated 23 May 2026, 3:31 pm IST
  1. AThe Earth's rotation on its axis
  2. BConvergence of the two equatorial currentsCorrect
  3. CDifference in salinity of water
  4. DOccurrence of the belt of calm near the equator

Explanation

The Equatorial Counter-Current, or Equatorial Undercurrent, is an eastward-flowing current found near the equator in the Pacific, Atlantic, and Indian Oceans. This current flows against the prevailing westward flow of the North and South Equatorial Currents. Its eastward flow is primarily explained by the accumulation of water in the western part of the ocean basin due to the continuous push of the westward-flowing equatorial currents by the trade winds. This piling up of water creates a hydrostatic pressure gradient, where the sea level is slightly higher in the west. This pressure gradient then drives the water back eastward as a counter-current in the absence of strong Coriolis deflection at the equator. While other factors might subtly influence ocean currents, the convergence and resulting pressure gradient due to the two equatorial currents is the primary mechanism for the eastward counter-current.
geography: What explains the eastward flow of the equatorial counter-current?

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