Unit 10 Lesson 5 Ocean Currents Copyright © Houghton Mifflin Harcourt Publishing Company 1

Unit 10 Lesson 5 Ocean Currents Florida Benchmark SC.6.E.7.3 Describe how global patterns such as the jet stream and ocean currents influence local weather in measureable terms such as temperature, air pressure, wind direction and speed, and humidity and precipitation. Copyright © Houghton Mifflin Harcourt Publishing Company 2

Remember the essential question… By the end of this lesson, you should be able to describe the movement of ocean water, and explain what factors influence this movement, and explain why ocean circulation is important in the Earth system.

Going with the Flow What are ocean currents? Unit 10 Lesson 5 Ocean Currents Going with the Flow What are ocean currents? Ocean currents are streamlike movements of water in the ocean. Surface currents are ocean currents that occur at or near the surface of the ocean. The Gulf Stream is a surface current. The sequence that produces movement of ocean water is the sun->wind in the atmosphere->surface currents in the ocean Copyright © Houghton Mifflin Harcourt Publishing Company 4

What affects surface currents? Unit 10 Lesson 5 Ocean Currents What affects surface currents? Surface currents are affected by continental deflections, the Coriolis effect, and global winds. When surface currents meet continents, they are deflected and change direction. The deflection of moving objects from a straight path due to Earth’s rotation is the Coriolis effect. If Earth did not have continents surface currents would travel in regularly shaped curves Copyright © Houghton Mifflin Harcourt Publishing Company 5

What affects surface currents? Unit 10 Lesson 5 Ocean Currents What affects surface currents? In the Northern Hemisphere, currents are deflected to the right. In the Southern Hemisphere, currents are deflected to the left. Therefore, they flow in a counterclockwise direction. Global winds can push ocean water across Earth’s surface to create surface currents. Copyright © Houghton Mifflin Harcourt Publishing Company 6

What powers surface currents? Unit 10 Lesson 5 Ocean Currents What powers surface currents? The major source of energy that powers surface currents is the sun. The sun causes differences in temperature across Earth, which causes differences in air pressure. Winds form as a result of differences in air pressure and create surface currents. The role that heat plays in the formation of convection currents is when water loses heat, it becomes denser and sinks Copyright © Houghton Mifflin Harcourt Publishing Company 7

Current Events How do deep currents form? Unit 10 Lesson 5 Ocean Currents Current Events How do deep currents form? Deep currents are movements of ocean water below the surface caused by differences in density. Density is the amount of matter in a given space or volume. Salinity and temperature of water are the two factors that are responsible for the formation of deep currents. Copyright © Houghton Mifflin Harcourt Publishing Company 8

How do deep currents form? Unit 10 Lesson 5 Ocean Currents How do deep currents form? Salinity is a measure of the amount of dissolved salts or solids in a liquid. Higher salinity makes water more dense. Dense water sinks and can form deep water currents that flow along the ocean floor or on another layer of denser water. Copyright © Houghton Mifflin Harcourt Publishing Company 9

What are convection currents? Unit 10 Lesson 5 Ocean Currents What are convection currents? Convection currents in the ocean are the movement of water that results from density differences. Convection currents can be vertical, circular, or cyclical. Copyright © Houghton Mifflin Harcourt Publishing Company 10

How do convection currents transfer energy? Unit 10 Lesson 5 Ocean Currents How do convection currents transfer energy? Water at the ocean’s surface absorbs energy from the sun, which can be carried to colder regions. As water reaches a colder region, it cools and sinks. As warm water moves away, cold water can rise from the bottom of the ocean, and the cycle continues. Copyright © Houghton Mifflin Harcourt Publishing Company 11