Question

Which one of the following statements regarding equatorial undercurrent (EUC) in the Pacific Ocean is correct?

• A. EUC flows from west to east.
• B. EUC flows from east to west.
• C. EUC flows from north to south.
• D. EUC flows from south to north.

Hint:

The Equatorial Undercurrent (EUC) flows from west to east beneath the surface due to the displacement caused by trade winds at the surface.

Answer 1

The Correct Option is A

The Equatorial Undercurrent (EUC) is a critical component of the Pacific Ocean's circulation system. It is a subsurface current that flows from the west to the east beneath the surface waters. This current is significant for the transport of heat, nutrients, and momentum across the equator.
The Mechanism Behind the EUC:
- Surface currents and pressure gradient: The EUC is primarily driven by the trade winds blowing from east to west, which push the surface waters westward. This creates a pressure gradient in the ocean. As the surface waters move west, the water at the equator is displaced, causing a downwelling that generates a subsurface current that flows eastward. The EUC forms in the subsurface, typically at depths between 50 to 100 meters, and flows eastward under the surface layer of the ocean.
- Role in ocean circulation: The EUC plays an essential role in ocean dynamics by transporting warm water and nutrients from the western Pacific toward the eastern Pacific. It is a key component of the oceanic conveyor belt, contributing to the vertical exchange of water masses and affecting regional climate patterns.
Why the EUC flows from west to east:
- The trade winds, which blow from the east to the west, cause the surface water to accumulate in the western part of the Pacific Ocean. This results in a higher sea surface height in the west. In response, the water from the western Pacific moves eastward beneath the surface, creating the Equatorial Undercurrent. The EUC then carries this water eastward, balancing out the water distribution across the equator.
Thus, the correct answer is (A) EUC flows from west to east.
Other Options Explained:
- Option (B): The EUC does not flow from east to west; rather, it is the surface currents driven by the trade winds that flow from east to west.
- Option (C): The EUC flows in the horizontal direction, not from north to south. It is a surface-driven subsurface current that moves along the equator, not in the meridional direction.
- Option (D): Similarly, the EUC does not flow from south to north. It is confined to the equatorial region and flows eastward under the surface.
Thus, the correct answer is (A) EUC flows from west to east.