Ask a Biology Tutor: What Causes Ocean Currents?

Ocean Currents by Nicole Rhodes, Lead STEM (Science Technology Engineering Math) Tutor at The Community Classroom

Oceans play a vital role in our ecosystem, serving as a source of food and transportation, and supporting diverse marine life. All of Earth’s oceans are interconnected through what is known as the global ocean conveyor belt. Think of it like a conveyor belt in a factory—a continuous loop that moves water, nutrients, plants, and animals around the globe. This ocean conveyor is composed of a mix of warm, shallow currents and deeper, colder currents.

Ocean currents play a vital role in:

– Climate Regulation: They help transfer heat across the globe, influencing weather patterns and temperatures in different regions.

– Nutrient Distribution: Currents transport essential nutrients, supporting marine ecosystems and the food chain.

– Migration and Breeding: Many marine species rely on currents for migration and reproductive cycles, ensuring the survival of their populations.

At the heart of this system is the Gulf Stream, which is influenced by the freezing cold waters of the North Pole and Greenland. Warm water from the equator rises and remains near the surface, while the cold water from the north sinks, creating space for the warm water to flow north along the eastern coasts of North America. As the warm water travels, it gradually loses heat to the atmosphere, cools, and sinks as it moves toward Southern Europe and Northern Africa. 

By studying a map of ocean currents, you can observe how this interconnected cycle drives ocean currents worldwide.

Ocean Current Experiment

To better understand how cold and warm water interact, try this simple experiment at home—no stirring required! 

Ocean Currents Experiment

To model the movement of warm and cold water in the Earth’s oceans, gather the following materials:

– 1 large, shallow tray (preferably white or clear for better visualization)

– About 2 cups of ice cubes

– A small pitcher of freezing cold water with 1-2 drops of blue food coloring

– A small pitcher of warm water mixed with 4-8 drops of red food coloring

– Sea shells or rocks to represent islands in the ocean (ensure they are heavy enough to sink firmly in place)

1. Prepare the Tray: Pour the ice-cold water into the tray, until it is about 2-3 inches deep. The colder the water, the better the experiment will work. 
2. Add Ice: Then add 2-3 cups of ice cubes, and mix well. The ice represents the Arctic and Antarctic oceans, which are covered in ice at opposite poles of the Earth. 
3. Introduce Islands: Add shells or rocks to represent ocean islands near the middle of the tray. This will help you see how ocean currents behave when encountering an island in the middle of the ocean. The sides of your tray represent large continents, so you can also notice what the ocean currents do in response to the coastlines. To best visualize the movement of the water, it’s best to clear obstacles from a portion of the tray. 
4. Pour Warm Water: Now you will introduce warm red water coming from the warmest part of the Earth, at the equator. This is where the heat from the Sun warms the ocean surface. Slowly pour about ½ cup of the warm water into one part of your tray. 
5. Observe and Record: Watch how the red water interacts with the blue cold water. Take notes on the shapes or patterns you see—look for swirling motions, shape formations, or eddies.

What’s Happening?

You may notice that the warm water creates currents as it moves through the cold water. These currents are the steady, predictable movement of one fluid within another. Observing the interaction between the warm and cold water, you might see spirals forming at their meeting point—these spirals are called eddies. If you examine a thermal image of the ocean, you’ll observe similar patterns in nature.

By conducting this experiment, you’ll deepen your understanding of ocean currents and how they function in our global ecosystem. Happy experimenting!

Have fun with this experiment? Try some more biology and science experiments!

• Popcorn Science
• Winter Solstice Science
• Want to book a biology tutor? We can help with that too!