UPSC Prelims 2015 Question:

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

Explanation:

Ocean currents are the directional movement of seawater caused by gravity, wind (Coriolis Effect), and water density. Water in the ocean flows in two directions: horizontally and vertically. Currents are horizontal movements, while upwellings and downwellings are vertical changes.

• The equatorial counter currents are major surface flows that carry water eastward in the Atlantic, Indian, and Pacific Oceans. They are located near the equator and are sandwiched between two westward-flowing currents, the North Equatorial Current and the South Equatorial Current. The equatorial counter currents are driven by a distinct surface wind pattern in the tropics. Strong westward trade winds result in westward surface flow in most of the tropical Atlantic and Pacific Oceans.
  
  
• Equatorial counter-currents are unique, in that they flow in the opposite direction of the surface winds. Winds are significantly weaker several hundred kilometers north of the equator. Where the winds are weaker to the south, the stronger winds pile up water. As a result, the ocean's surface can rise higher and the thermocline can be deeper than it is directly to the north. The excess water flows eastward due to the rotation of the Earth, causing equatorial countercurrents.
  
  

Therefore, option (2) is the correct answer.

Subject: Geography | Oceanography