9. Major Ocean Surface
Currents
Putting It All Together
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Compare your maps from the previous pages to the simplified map below.
Graphic from NOAA/AOML State of the Ocean - Global Surface Currents
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The major surface currents form big loops or gyres in each hemisphere. The gyre in the middle of the ocean basin in each hemisphere is known as the central gyre.
Here is a map showing the average mean speed of the drifters, regardless of the direction of the motion, which allows to locate the fastest currents (in red) and slowest currents (in blue) (from http://www.aoml.noaa.gov/phod/dac/dac_meanvel.php).
Expedition Menu
1. Introduction
2. Tracking Drifters
3. Drifters Pacific
4. Drifters Atlantic
5. Drifters Indian
6. Velocity Pacific
7. Velocity Atlantic
8. Velocity Indian
9. Global Circulation
10. Counter Currents
11. Boundary Currents
Also notice how your hand-drawn maps have somewhat more complicated patterns because the widespread occurrence of "eddy currents" which spin off in rings along the edges of the gyres, along the west and east sides of the gyres.
Pause the audio at the top of this webpage and take about three minutes to view a more realistic animation of ocean surface circulation around the world during the period from June 2005 through Decmeber 2007. This visualization was produced using NASA/JPL's computational model called Estimating the Circulation and Climate of the Ocean, Phase II or ECCO2..
The term "eddy current" refers to localised areas of turbulence that give rise to persistent vortices (for example, smaller-scale circular currents around the edges of the major surface currents), which we see very clearly in the animation above. We will see an animation in the next expedition showing eddy currents along the edges of the Gulf Stream, one of the major surface currents on the western side of the Atlantic Ocean.
Determine the answers to the following questions by examining the map of the world's surface circulation above.What direction do the central gyres flow in the northern hemisphere?
What direction do the central gyres flow in the southern hemisphere?
What direction do the gyres flow near the equator (i.e. the north and south equatorial currents)?
Which current encircles the entire globe and therefore affects every ocean?
The major ocean gyres, located in the northern hemisphere, flow in huge clockwise rotations that have no true beginning or end.
Let's catch the current near Taiwan and head northeast along the coast of Japan. The flow here is called the Kuroshio Current, and transports relatively warm water up from the equator.
In japanese, the Kuroshio means the Black Stream (like a stream within the ocean - black from the dark blue-colored backs of tuna that follow the Kuroshio).
Jim Bettinger writes "As the Kuroshio (in orange) swings east along the Aleutian Islands it becomes the North Pacific Current, and not so warm any more. The surface current then heads southeast along the Pacific Coast, where we greet it as the California Current.
Off the coast of Baja California it swings west across the Pacific. During that long flow the sun heats it, so it's warm when it gets back to Taiwan."
Watch the video on the North Pacific Gyre as it explains the formation of the North Pacific Garbage Patch, which has been received much media attention over the past couple of years..
Surface circulation, combined with the rotation of the earth, pushes the floating plastic debris into the middle of the North Pacific Gyre and keep is trapped there. Flaoting has been collecting in thre middle of the gyres for decades, but has only recently received much media attention over the past couple of years..
Last
Updated on
July 1, 2011
Send to Don Reed
Department of Geology
San José State University
In what direction do the major ocean (central) gyres rotate in the northern hemisphere?