The canonical Ekman transport is 90 degrees to the right of the wind in which hemisphere?

• A. Southern Hemisphere
• B. Equator
• C. Northern Hemisphere
• D. None

Answer: (C)

Ekman transport comes from wind-driven movement of the surface layer being deflected by the Coriolis effect. The wind drags the top water, and as water layers move, the Coriolis force turns their motion. In the Northern Hemisphere, the Coriolis force deflects moving water to the right, and when you average all the layers with depth, the net transport ends up 90 degrees to the right of the wind. That’s why the canonical statement is that Ekman transport is 90 degrees to the right of the wind in this hemisphere. In the Southern Hemisphere the deflection is to the left, and at the equator the Coriolis effect is effectively zero, so the simple 90-degree rule doesn’t apply there. So the Hemisphere in which Ekman transport is 90 degrees to the right is the Northern Hemisphere.