Unit 2 Lesson 3 Ocean Currents
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Unit 2 Lesson 3 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, caused by
wind.
• The Gulf Stream is one of the strongest surface
currents on Earth.
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Unit 2 Lesson 3 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 called the Coriolis
effect.
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Unit 2 Lesson 3 Ocean Currents
What affects surface currents?
• How does a continent change surface currents on
Earth? Could a small island change surface
currents?
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Unit 2 Lesson 3 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.
• Global winds can push ocean water across Earth’s
surface to create surface currents.
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Unit 2 Lesson 3 Ocean Currents
What powers surface currents?
• The major source of energy that powers surface
currents is the sun.
• The sun heats air near the equator more than it
heats air at other latitudes. As a result, there are
differences in pressure in the atmosphere.
• Winds form as a result of differences in air
pressure and create surface currents.
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Unit 2 Lesson 3 Ocean Currents
Current Events
How do deep currents form?
• Deep currents are movements of ocean water far
below the surface. They are caused by differences
in water density.
• Density is the amount of matter in a given space or
volume.
• Salinity and temperature cause differing ocean
water densities.
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Unit 2 Lesson 3 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.
• Cold water is denser than warm water.
• Dense water sinks and can form deep water
currents that flow along the ocean floor or on
another layer of denser water.
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Unit 2 Lesson 3 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.
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Unit 2 Lesson 3 Ocean Currents
How do convection currents transfer
energy?
• Water at the ocean’s surface absorbs energy from
the sun, and surface currents carry this energy to
colder regions.
• As warm water reaches a colder region, it cools,
becomes denser, and sinks.
• As warm surface water moves away, cold water
rises to the surface. The cold water absorbs the
sun’s energy, and the cycle continues.
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Unit 2 Lesson 3 Ocean Currents
That’s Swell
What is upwelling?
• Upwelling is the process by which winds blow
warm water away from a shore, allowing cool,
nutrient-rich water to rise to the surface.
• Upwelling supplies the nutrients that support the
growth of phytoplankton and zooplankton.
• These tiny organisms are food for larger
organisms, such as fish and seabirds.
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Unit 2 Lesson 3 Ocean Currents
What is upwelling?
• What would happen to ocean life if upwelling did
not occur?
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Unit 2 Lesson 3 Ocean Currents
Hitching a Ride!
• Ocean currents can transport various living
organisms to different parts of the world.
• Turtles, coconuts, and phytoplankton all ride the
ocean’s surface currents.
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Unit 2 Lesson 3 Ocean Currents
Traveling the World
What do ocean currents transport?
• Convection currents in the ocean transport energy
in the form of heat.
• Ocean currents can release energy into the
atmosphere, making currents an important
influence on climate.
• Ocean water also transports dissolved solids,
including nutrients, and dissolved gases that
support the growth of many marine organisms.
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Unit 2 Lesson 3 Ocean Currents
What do ocean currents transport?
• Trace pathways on the map to show how nutrients
can be transported by ocean currents.
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