What is the name of the theoretical model describing how wind affects surface water and causes depth-varying flow?

• A. The Ekman Spiral
• B. Flow Method
• C. Equatorial Upwelling
• D. Gyre

Answer: (A)

The wind-driven layer of the ocean creates a vertical shear in current due to the balance between friction and the Coriolis force. As surface water is dragged by the wind, the Coriolis effect deflects it to the right in the Northern Hemisphere (and to the left in the Southern Hemisphere). That deflection isn’t confined to the top layer: the friction at the surface transmits the influence downward, but each deeper layer feels a weaker deflection and less wind stress. The result is a progressively turning flow with depth—the velocity magnitude decreases, and the direction rotates, forming a spiral pattern. This is the Ekman spiral.

This concept is the best answer because it specifically describes how wind affects surface water and produces depth-varying flow, including the characteristic spiral of current with depth and the overall transport being at a right angle to the wind when you consider the entire Ekman layer. The other terms refer to different phenomena: a general coastal-upwelling process near the equator, a large-scale circular ocean circulation, or an unnamed general method, none of which capture the wind-driven, depth-dependent spiral of currents.