Ocean Current Explorer: Wind, Spin and the Great Loops
See that surface currents are driven by wind, bent into loops (gyres) by Earth’s rotation and closed by the coasts, and that they carry warm water toward the poles on one side and cold water back on the other.
Before you try
What if Earth stopped spinning? Which way would the ocean flow?
Try it out
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What happened?
Move a control to see what changes and why.
One idealised northern-hemisphere basin with relative speeds; real oceans have many gyres, eddies and seasons.
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Try these ideas
- Switch Earth’s rotation off. What happens to the loop and the coastal temperatures?
- Set the wind to zero and see how much flow the deep circulation alone gives.
- Drop the bottle and time how long one trip round the gyre takes at 1× and 2× wind.
Why it works
Winds blow steadily across the oceans: trade winds toward the west near the equator, westerlies toward the east farther north. They drag the surface water along, and Earth’s rotation bends the moving water to the right in the northern hemisphere (the Coriolis effect). Hemmed in by the continents, the flow closes into an enormous clockwise loop called a gyre.
Warm equatorial water rides poleward on the western side of the gyre; cold water returns toward the equator on the eastern side. That is why a coast can be several degrees warmer than another at the same latitude. A slower, deeper circulation, driven by cold salty water sinking near the poles, moves heat too. In this explorer you set the wind, switch rotation on or off, and drop a bottle to trace the loop.
Check your understanding
Question 1 of 4
Surface ocean currents are mainly driven by
Currents in the northern hemisphere loop clockwise because of
A warm current flowing past a coast makes that coast
The deep ocean circulation starts when
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Put a drop of food colouring in a bowl of water and blow gently across it.
- Ask: why is London milder in winter than places at the same latitude in Canada?
- Trace the path of a message in a bottle on a world map.