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How Do We Measure Currents (Currently)?

A partnership between the USA (NASA) and France (CNES) led to the launching of a satellite to study ocean currents. Since its launch into Earth orbit during August 1992, the TOPEX/Poseidon satellite has mapped ocean topography--the barely perceptible liquid "hills" and "valleys" that make up the ocean's surface. Oceanographers use ocean topography to study and monitor the currents. One full cycle of data is taken every 10 days. 

The World Ocean Circulation Experiment (WOCE) is a global observation program. Their goal is to develop improved ocean circulation models for climate prediction. If you have already visited our web page "The Role of the Ocean in Weather," you know that the ocean plays a central role in determining Earth's climate.

The following link takes you to a movie made using a simplified ocean model by Professor Chelton at Oregon State University. The model shows how the oceans respond to winds. The ocean model starts off revolving in the center of the model basin but gradually the center of the spinning shifts to the west. This shift is a result of the westward intensification of the currents along the western edge of the model basin. This same westward intensification occurs along the western edges of the Pacific, the Atlantic and the Indian oceans. The theory for this intensification was worked out by a famous Oceanographer, Dr Stommel in 1948. An example of this intensification is the Gulf Stream off the coast of North America. The movie file is very large (12 MB) so it will take quite some time to download Currents Model 

We've only touched the "surface" here you might say. But if you wish to dive deeper, watch out for the undercurrents, and explore more about ocean currents. Here are some topics to look up: undercurrents, countercurrents, upwellingdownwellinggyreswind beltseddies, and deep ocean circulation.

Questions that come to mind are:

1. Why does a wind-driven current not flow in the same direction as the wind that causes it? 

2. Why do subtropical gyres (pronounced jires) rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere? 

3. Why are temperature and salinity the two most important tracers of water masses? 

4. What are the factors that affect coastal currents but not deep ocean currents? 

5. Why are the deepest water masses in the oceans formed at high latitudes? Why are they not formed in the Indian and North Pacific Oceans?

Critical Thinking Questions:

6. If we were to build a solid causeway across the Pacific Ocean (I can't imagine this, but just pretend..) from Seattle (USA) to Tokyo (Japan), how would the surface currents in the North Pacific Ocean be affected and how might this affect the climate of Japan, Alaska, and California?

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