1. Chapter 16
The Dynamic Ocean

2. Section 16.1
Ocean Circulation

3. 16.1 The Composition of Seawater
Surface Circulation
 Ocean current is the mass of ocean water that flows from one place to another.
 Surface Currents
• Surface currents are movements of water that flow horizontally in the upper part of the ocean’s surface.
• Surface currents develop from friction between the ocean and the wind that blows across its surface.

4. Ocean Surface Currents
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5. 16.1 The Composition of Seawater
Surface Circulation
 Gyres
• Gyres are huge circular-moving current systems that dominate the surfaces of the oceans.
• The Coriolis effect is the deflection of currents away from their original course as a result of Earth’s rotation.

6. 16.1 The Composition of Seawater
Surface Circulation
 Ocean Currents and Climate
• When currents from low-latitude regions move into higher latitudes, they transfer heat from warmer to cooler areas on Earth.
• As cold water currents travel toward the equator, they help moderate the warm temperatures of adjacent land areas.

7. False-Colored Satellite Image of the Gulf Stream
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8. What causes ocean surface currents?
Gravitational attraction
Friction between the ocean and wind on its surface
Ocean movements associated with earthquakes
Changes in water density

9. Currents affect climate by
Making ocean water evaporate
Transferring heat and cold between the tropics and polar regions
Changing the density of water in the tropics
Transferring heat from the polar regions to the tropics

10. 16.1 The Composition of Seawater
Surface Circulation
 Upwelling
• Upwelling is the rise of cold water from deeper layers to replace warmer surface water.
• Upwelling brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the ocean surface.

11. Effects of Upwelling
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12. 16.1 The Composition of Seawater
Deep-Ocean Circulation
 Density Currents
• Density currents are vertical currents of ocean water that result from density differences among water masses.
• An increase in seawater density can be caused by a decrease in temperature or an increase in salinity.

13. What is the importance of upwelling?
It brings warm water from the tropics to the poles.
It decreases winds along exposed coastlines.
It helps warm the North Atlantic gyre.
It brings dissolved nutrients to the ocean’s surface.

14. A decrease in seawater temperature or an increase in salinity causes
Upwelling along tropical coast.
An increase in seawater density.
The circulation of ocean gyres.
A decrease in seawater density.

15. 16.1 The Composition of Seawater
Deep-Ocean Circulation
 High Latitudes
• Most water involved in deep-ocean currents begins in high latitudes at the surface.
 Evaporation
• Density currents can also result from increased salinity of ocean water due to evaporation.
Example: The Mediterranean Sea

16. 16.1 The Composition of Seawater
Deep-Ocean Circulation
 A Conveyor Belt
• In a simplified model, ocean circulation is similar to a conveyor belt that travels from the Atlantic Ocean, through the Indian and Pacific Oceans, and back again.

17. Conveyor Belt Model
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18. Cross Section of the Arctic Ocean
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19. What causes density currents to form in the Mediterranean Sea?
Freezing
Evaporation
Melting Ice
Upwelling