PADI Divemaster Certification Practice Exam

What primarily drives the occurrence of upwelling and downwelling in ocean currents?

1. Temperature changes in the ocean

2. Gravitational pull of the moon

3. Wind and deep currents interacting with the bottom

4. Earth's rotation only

The correct answer is: Wind and deep currents interacting with the bottom

The occurrence of upwelling and downwelling in ocean currents is primarily driven by the interaction of wind with surface waters and the subsequent effects on deeper water layers. Upwelling typically occurs when winds blow across the ocean surface, pushing warm surface water away from an area. This movement allows nutrient-rich water from the deeper layers to rise and replace the surface water, fueling marine ecosystems. Conversely, downwelling occurs when surface waters converge, causing them to sink. This is often a result of the wind patterns that compress the water and push it downward. The relationship between the wind and the movement of the deeper currents plays a crucial role in these processes. As surface winds push water, they can also indirectly influence the flow of deep ocean currents, maintaining the overall circulation patterns in the ocean. While temperature changes, the gravitational pull of the moon, and Earth's rotation have roles in ocean dynamics, they do not primarily drive the processes of upwelling and downwelling. Temperature influences water density and movements over time, and gravitational forces contribute to tides rather than direct upwelling or downwelling events. Earth's rotation does affect current patterns through the Coriolis effect but is not the primary driver of the vertical movements seen in upwelling and