Ocean currents — Geography, 11–13
Learn how moving seawater redistributes heat and helps explain why nearby coasts can have different climates.
The ocean moves heat
Ocean currents are large, organised movements of seawater. Some carry warm water away from the tropics; others bring colder water towards lower latitudes or up from the deep ocean. They move heat, nutrients and sometimes floating material around the planet.
Why currents matter
A map of air temperature alone cannot explain every coastal climate. Geographers study currents because the sea stores and transports huge amounts of heat, changing the air above it. This helps explain mild western European coasts, cold desert coasts and rich fishing grounds.
A current changes a coast
Compare two coasts at about 25° north. Coast A has a warm current from the tropics: warmer sea water adds heat and moisture to the air, so the coast is relatively mild. Coast B has cold water rising from below: the air is cooled, evaporation is lower, and a dry coastal climate is more likely.
A current is not just a wave
It is easy to think all ocean water moves randomly like waves at the beach. Waves mostly pass energy through water, while currents move water itself over long distances. Currents can change direction or strength, too, so a single arrow on a map is a useful model, not the whole ocean.
Currents in real decisions
Ships use current forecasts to save fuel and time, while search teams use them to estimate where a drifting object may go. Fishers track currents because they carry nutrients that support plankton and fish. Scientists also monitor them to understand changing ocean temperatures and ecosystems.
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