PADI Divemaster Certification Practice Exam

What primarily causes upwellings and downwellings in the ocean?

1. Wind

2. Temperature variations

3. Tidal forces

4. Water salinity

The correct answer is: Wind

Upwellings and downwellings in the ocean are primarily driven by wind, which affects the movement of surface water. When wind blows across the surface of the ocean, it causes the water to move. In areas where the wind blows parallel to the coastline, surface water may be pushed away from the shore, creating a void that deeper, nutrient-rich water can fill, leading to upwelling. This process is crucial for bringing nutrients to the surface, which supports marine life and enhances productivity in those areas. Conversely, downwelling occurs when the wind pushes surface water towards the shore or when surface water cools and becomes denser. This denser water sinks, contributing to downwelling. These movements are critical components of ocean circulation, affecting temperature distribution, nutrient cycling, and marine ecosystems. While temperature variations, tidal forces, and water salinity play significant roles in ocean dynamics, they do not primarily cause the upwellings and downwellings in the same direct manner that wind does. Temperature variations can influence water density and thus contribute to vertical movements, but the immediate driving force of the surface currents leading to upwellings and downwellings is primarily the wind.