Surface Ocean Currents
Dana Desonie, Ph.D.
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Printed: June 19, 2014
AUTHOR
Dana Desonie, Ph.D.
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C HAPTER
Chapter 1. Surface Ocean Currents
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Surface Ocean Currents
• Define major and local surface currents.
• Explain how major and local surface currents are created.
What can debris tell us about surface currents?
The surface of the ocean is on the move. One way to see this is when something is dumped in the ocean. Where will
it end up? The tsunami that struck Japan in March 2011 pulled a lot of material into the ocean. The image above is a
model created in April 2012. The orange and red are where floating debris might be. Scientists are creating models
of where the debris will go. But no one knows for sure where it will go or when it will get there.
Surface Currents
Like air in the atmosphere, ocean water moves in currents. A current is a stream of moving water that flows through
the ocean. Surface currents are caused mainly by winds but not daily winds. Surface currents are caused by the
major wind belts. These winds blow in the same direction all the time. So they can keep water moving in the same
direction.
Surface currents are created by three things:
• global wind patterns
• the rotation of the Earth
• the shape of the ocean basins
Surface currents are extremely important because they distribute heat around the planet. Surface currents also have
a tremendous influence on climate around the globe.
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Global Wind Patterns
Winds on Earth are either global or local. Global winds blow in the same directions all the time. They are created
when more solar energy strikes the Equator than the polar regions. More about global wind patterns is described in
detail in the concept "Global Wind Belts."
The major wind belts push the water in the surface currents. The water moves in the direction of :
• trade winds: east to west between the Equator and 30°N and 30°S.
• westerlies: west to east in the middle latitudes.
• polar easterlies: east to west between 50° and 60° north and south of the Equator and the North and South
Poles.
Earth’s Rotation
The rotation of the Earth—that is, the Coriolis effect—causes the ocean currents to turn. More information about
the phenomenon can be found in the concept "Coriolis Effect."
Shape of the Ocean Basins
A surface current move across the ocean. Eventually, the current runs into land ( Figure 1.1). When it does, it turns
right in the Northern Hemisphere and left in the Southern Hemisphere. The direction is due to Coriolis effect.
FIGURE 1.1
The major surface ocean currents.
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Chapter 1. Surface Ocean Currents
Gyres
The major surface currents are pictured below ( Figure 1.2). They flow in a clockwise direction in the Northern
Hemisphere. In the Southern Hemisphere, they flow in the opposite direction. These loops are called gyres. Only
the Antarctic Circumpolar Current flows nonstop around the globe.
FIGURE 1.2
Earth’s surface currents flow in the patterns shown here.
This video shows the surface ocean currents set by global wind belts: http://www.youtube.com/watch?v=Hu_Ga
0JYFNg (1:20).
MEDIA
Click image to the left for more content.
Local Surface Currents
Currents are also found along shorelines ( Figure 1.3). They are not related to the global wind belts. Two are
longshore currents and rip currents.
Rip currents are very dangerous currents! Rip currents move large amounts of water offshore quickly. Look at the
rip-current animation to determine what to do if you are caught in a rip current: http://www.onr.navy.mil/focus/oc
ean/motion/currents2.htm . Each summer in the United States, at least a few people die when they are caught in rip
currents.
This animation shows the surface currents in the Caribbean, the Gulf of Mexico, and the Atlantic Ocean off of the
southeastern United States: http://polar.ncep.noaa.gov/ofs/viewer.shtml?-gulfmex-cur-0-large-rundate=latest .
Vocabulary
• Coriolis effect: Apparent deflection of a freely moving object like water or air because of Earth’s rotation.
• gyre: Five seawater loops created by surface ocean currents.
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FIGURE 1.3
Longshore currents move water and sediment parallel to the shore. They move in
the direction of the prevailing local winds.
• longshore current: Local surface currents that move along a shoreline in the direction of prevailing winds.
• rip current: Strong surface current that returns to the ocean from the shore.
• surface current: Horizontal movement of ocean water, caused by surface winds.
Summary
• Major surface ocean currents are the result of global wind patterns, Earth’s rotation, and the shape of the ocean
basins.
• Major surface currents circle the oceans in five gyres.
• Local surface currents, like longshore and rip currents, move near shorelines.
Practice
Use the resource below to answer the questions that follow.
• Ocean Odyssey-Surface Current: http://www.youtube.com/watch?v=YCorkyBe66o (4:27)
MEDIA
Click image to the left for more content.
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2.
3.
4.
5.
6.
7.
8.
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What is a surface current?
What is a thermocline?
Where is the thermocline?
How do surface currents form?
What factors determine the movement of surface currents?
Why are currents different temperatures?
How do surface currents affect climate?
How are the currents monitored by NASA?
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Chapter 1. Surface Ocean Currents
Review
1. Why does the North Pacific gyre move the way it does?
2. What should you do if you get stuck in a rip current? Why?
3. Why is the Antarctic Circumpolar Current different from other surface currents? What would surface currents
look like if there were no continents?
References
1. Courtesy of Rick Lumpkin, NOAA/AOML. Map of the major surface ocean currents. Public Domain
2. Map: courtesy of Wereon and US Geological Survey; modified by CK-12 Foundation. Map of the ocean
gyres. CC BY-NC 3.0 (map available in the public domain)
3. User:Yefi/Wikimedia Commons. Diagram of longshore currents. Public Domain
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