Ocean Circulation Concepts 16.1

What is upwelling in the context of ocean circulation?

• The process of warm water moving towards the ocean surface

• The movement of cold, nutrient-rich water from the deep ocean to the surface

• The horizontal movement of water across the ocean surface

• The sinking of warm water to the ocean floor

Answer explanation

Upwelling is the movement of cold, nutrient-rich water from the deep ocean to the surface, which supports marine life. This process contrasts with warm water rising, making the second option the correct choice.

Which factor primarily drives density currents in the ocean?

• Wind patterns

• Temperature and salinity differences

• Tidal forces

• Earth's rotation

Answer explanation

Density currents in the ocean are primarily driven by temperature and salinity differences, which create variations in water density. These differences lead to the movement of water masses, unlike wind patterns or tidal forces.

Explain how upwelling affects marine life in coastal regions.

• It decreases the availability of nutrients, leading to less marine life.

• It brings nutrient-rich water to the surface, supporting abundant marine life.

• It causes water temperatures to rise, reducing marine biodiversity.

• It leads to the formation of dead zones due to lack of oxygen.

Answer explanation

Upwelling brings nutrient-rich water from the ocean depths to the surface, which supports phytoplankton growth. This, in turn, attracts a variety of marine life, making coastal regions highly productive and biodiverse.

Describe the role of density currents in global ocean circulation.

• They primarily influence surface currents and weather patterns.

• They are responsible for the vertical mixing of ocean layers.

• They have no significant impact on global ocean circulation.

• They contribute to the horizontal movement of water across the ocean.

Answer explanation

Density currents play a crucial role in global ocean circulation by facilitating the vertical mixing of ocean layers. This mixing helps distribute heat and nutrients, impacting marine ecosystems and climate.

Which of the following is a direct consequence of upwelling?

• Increased surface water temperatures

• Decreased salinity levels

• Enhanced primary productivity

• Reduced oceanic carbon dioxide levels

Answer explanation

Upwelling brings nutrient-rich waters to the surface, which enhances primary productivity by supporting the growth of phytoplankton, the foundation of the marine food web.

How do density currents contribute to the thermohaline circulation?

• By creating surface currents that distribute heat globally

• By transporting warm water from the equator to the poles

• By moving cold, dense water from the poles to the equator

• By facilitating the exchange of gases between the ocean and atmosphere

Answer explanation

Density currents contribute to thermohaline circulation by moving cold, dense water from the poles towards the equator, which helps regulate global climate and oceanic heat distribution.

Evaluate the impact of upwelling on local fisheries.

• Upwelling decreases fish populations by reducing available nutrients.

• Upwelling increases fish populations by providing more nutrients.

• Upwelling has no impact on fish populations.

• Upwelling leads to the migration of fish away from coastal areas.

Answer explanation

Upwelling brings nutrient-rich waters to the surface, enhancing primary productivity. This increase in nutrients supports larger fish populations, making upwelling crucial for local fisheries.

Analyze how changes in temperature and salinity can alter density currents.

• Increased temperature and decreased salinity make water denser, strengthening currents.

• Decreased temperature and increased salinity make water less dense, weakening currents.

• Increased temperature and increased salinity make water denser, strengthening currents.

• Decreased temperature and increased salinity make water denser, strengthening currents.

Answer explanation

Decreased temperature increases water density, while increased salinity also contributes to higher density. This combination strengthens density currents, making the correct choice: 'Decreased temperature and increased salinity make water denser, strengthening currents.'

What is the primary cause of coastal upwelling?

• The Coriolis effect

• Wind blowing parallel to the coast

• Tidal forces

• Underwater volcanic activity

Answer explanation

The primary cause of coastal upwelling is wind blowing parallel to the coast. This wind pushes surface water away, allowing deeper, nutrient-rich water to rise and replace it, promoting marine productivity.

How does the Coriolis effect influence density currents?

• It causes density currents to move in a straight line.

• It deflects density currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

• It has no effect on density currents.

• It reverses the direction of density currents.

Answer explanation

The Coriolis effect causes moving fluids, like density currents, to be deflected: to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, influencing their direction and flow patterns.