Surface Ocean Currents
Dana Desonie, Ph.D.
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Printed: January 7, 2015
AUTHOR
Dana Desonie, Ph.D.
www.ck12.org
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.
Why is so much trash so far from land?
The Great Pacific Garbage Patch is a region in the center of the north Pacific Ocean where plastic bits and chemicals
are concentrated. Trash from the countries bordering the region enters the oceans and is transported into the center
of the North Pacific Gyre, where it remains. Seabirds may get sick from ingesting so much plastic instead of food.
More about the patch can be found in the chapter Human Impacts on Earth’s Systems.
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Surface Currents
Ocean water moves in predictable ways along the ocean surface. Surface currents can flow for thousands of
kilometers and can reach depths of hundreds of meters. These surface currents do not depend on weather; they
remain unchanged even in large storms because they depend on factors that do not change.
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 and are a major factor
influencing climate around the globe.
Global Wind Patterns
Winds on Earth are either global or local. Global winds blow in the same directions all the time and are related to the
unequal heating of Earth by the Sun —that is, more solar radiation strikes the Equator than the polar regions —and
the rotation of the Earth —that is, the Coriolis effect. Coriolis was described in the chapter Earth as a Planet. The
causes of the global wind patterns will be described in detail in the chapter Atmospheric Processes.
Water in the surface currents is pushed in the direction of the major wind belts:
• trade winds: east to west between the Equator and 30o N and 30o S
• westerlies: west to east in the middle latitudes
• polar easterlies: east to west between 50o and 60o north and south of the Equator and the north and south pole
Shape of the Ocean Basins
When a surface current collides with land, the current must change direction. In the Figure 1.1, the Atlantic South
Equatorial Current travels westward along the Equator until it reaches South America. At Brazil, some of it goes
north and some goes south. Because of Coriolis effect, the water goes right in the Northern Hemisphere and left in
the Southern Hemisphere.
Gyres
You can see on the map of the major surface ocean currents that the surface ocean currents create loops called gyres
( Figure 1.2). The Antarctic Circumpolar Current is unique because it travels uninhibited around the globe. Why is
it the only current to go all the way around?
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 or use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/1629
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Chapter 1. Surface Ocean Currents
FIGURE 1.1
The major surface ocean currents.
FIGURE 1.2
The ocean gyres. Why do the Northern
Hemisphere gyres rotate clockwise and
the Southern Hemisphere gyres rotate
counterclockwise?
Local Surface Currents
The surface currents described above are all large and unchanging. Local surface currents are also found along
shorelines ( Figure 1.3). Two are longshore currents and rip currents.
Rip currents are potentially dangerous currents that carry large amounts of water offshore quickly. Look at the ripcurrent animation to determine what to do if you are caught in a rip current: http://www.onr.navy.mil/Focus/ocean/
motion/currents2.htm . Each summer in the United States at least a few people die when they are caught in rip
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FIGURE 1.3
Longshore currents move water and sediment parallel to the shore in the direction of the prevailing local winds.
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 .
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.
Making Connections
MEDIA
Click image to the left or use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/54192
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Chapter 1. Surface Ocean Currents
Explore More
Use this resource to answer the questions that follow.
https://www.youtube.com/watch?v=ZP5BtLSU9z4
1. Which direction do currents move across the equator both north and south? What direction does the counter
current flow?
2. What is unique about the Antarctic Circumpolar Current and why?
3. What are gyres?
4. Where are currents that move heat from the equator to the higher latitudes flowing relative to the continents?
5. Why is the Caribbean so hot and humid?
6. Why does the Gulf Stream cool before it reaches Europe?
7. Why is it warmer and more pleasant to swim off of the Eastern Seaboard than off of California?
8. What are the western boundary currents due to?
Review
1. Describe the motion of a water particle that is stuck in a gyre in the North Pacific.
2. What should you do if you get stuck in a rip current?
3. What would happen if a major surface current did not run into a continent? Note that this is what happens
with the Antarctic Circumpolar Current.
References
1. Courtesy of Rick Lumpkin, NOAA/AOML. Map of the major surface ocean currents . Public Domain
2. CK-12 Foundation, using map courtesy of User:Wereon/Wikimedia Commons and US Geological Survey.
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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