What term describes the increase in speed of geostrophic currents as they pass along the western boundary of an ocean basin?

• A. Eastward Intensification
• B. Polar Intensification
• C. Mixed-Layer Acceleration
• D. Westward Intensification

Answer: (D)

In rotating oceans, the flow that returns the interior Sverdrup-driven transport concentrates into a very fast, narrow current along the western boundary of a basin. This happens because of how potential vorticity and the beta effect force the system to balance the interior flow with a strong boundary current on the western side. As the wind-driven interior circulation sets up, the need to conserve vorticity means the western boundary current must speed up and become tighter to carry the same transport, producing noticeable speeding up as you move along the western edge. That’s why the term is westward intensification—the current intensifies on the western boundary. The other ideas don’t describe this basin-wide, boundary-focused acceleration: eastward intensification would imply the opposite side; mixed-layer acceleration refers to depth-dependent mixing processes rather than boundary current speed changes; polar intensification points to polar regions and different dynamics.