Ocean Surface Circulation: Patterns, Speed & Direction

Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

The water on planet Earth is constantly moving around the globe. Learn about the five major circular swirls that move the waters around in our oceans.

What Is Ocean Circulation?

Ocean circulation is much more important than you think. It is this circulation that helps large boats travel the open seas. It is also this circulation that helps keep the ocean's water temperatures fairly steady, mixing the cooler waters from the north and south with the warmer waters near the equator.

Interestingly, there are patterns to this circulation that scientists and researchers have found and discovered. There are circulation patterns on the ocean's surface, as well as deeper currents that run below the water's surface. They are both equally important. In this lesson, we will look more closely at the circulation patterns on the water's surface.

Circulation Patterns

We begin by looking at the patterns that form on the water's surface from these circulations.

There are five major rotating ocean currents.
ocean circulation

The National Ocean Service, part of the National Oceanic and Atmospheric Administration (NOAA), has studied the circulation patterns of the currents that travel the world's oceans, and they have found five major rotating ocean currents. These five major ocean currents are actually a system, or collection, of smaller rotating currents. These larger systems are referred to as gyres. The five major gyres are named after their locations in respect to the world's oceans:

  • North Pacific Subtropical Gyre
  • South Pacific Subtropical Gyre
  • North Atlantic Subtropical Gyre
  • South Atlantic Subtropical Gyre
  • Indian Ocean Subtropical Gyre

Gyres spin clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere. An interesting thing about these gyres is they occur on either side of the equator; they do not occur on the equator.

At the equator, the currents are referred to as equatorial counter currents. There are two of them, the North Equatorial Counter Current and the South Equatorial Counter Current. Both flow toward the west, as they are both driven by the trade winds that blow westward. The South Equatorial Counter Current brings warm waters northward, crossing the equator when it reaches the Atlantic Ocean.

Each gyre is also bordered by two currents, one on the west and one on the east. These border currents are called boundary currents. The boundary current on the west is usually strong and narrow, while the boundary current to the east is broad and weak. One famous western boundary current is the Gulf Stream that borders the North Atlantic Subtropical Gyre. It is paired with the Canary Current and travels about 25 to 75 miles each day. These boundary currents are what keep the state of Florida warmer in the winter and slightly cooler in the summer. It also warms some countries in western Europe.

Speed and Direction

Now, did you notice the speed of the Gulf Stream and the Canary Current? Did you notice the speed can vary anywhere from 25 miles per day to 75 miles per day? Why is that? It is because the currents themselves are not self-driven. They do not have any speed on their own. Instead, they get their speed from the winds that blow over the ocean. The direction of these currents is also dependent on the direction of these winds.

The winds that have the biggest impact on the gyres and currents in the oceans are the trade winds. These blow constantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. Both blow toward the equator and converge in the Intertropical Convergence Zone, where winds are not as strong. Sailing captains call this area the doldrums and they do not like sailing through this area due to the lack of strong winds.

Ekman Transport

Here's an interesting tidbit. You would think that water would travel in the same direction as the wind. But, it doesn't. As it turns out, water actually travels at a right angle to the wind direction. So if the wind is blowing toward the north, then the water will travel toward the east.

This phenomenon was observed by a Norwegian explorer named Fridtjof Nansen when he attempted to travel to the North Pole by way of ocean currents. He found that when the wind blew, he went toward the right of the wind direction.

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