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How Ocean Currents Moderate Climate

Ocean currents transfer heat around the globe; the Gulf Stream is a great example.

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How Ocean Currents Moderate Climate

Why is northwestern Europe relatively warm?

The Gulf Stream waters do a lot for Europe. The equatorial warmth this current brings to the North Atlantic moderates temperatures in northern Europe. In a satellite image of water temperature in the western Atlantic it is easy to pick out the Gulf Stream, which brings warmer waters from the Equator up the coast of eastern North America.

Effect on Global Climate

Surface currents play an enormous role in Earth’s climate. Even though the Equator and poles have very different climates, these regions would have more extremely different climates if ocean currents did not transfer heat from the equatorial regions to the higher latitudes.

The Gulf Stream is a river of warm water in the Atlantic Ocean, about 160 kilometers wide and about a kilometer deep. Water that enters the Gulf Stream is heated as it travels along the Equator. The warm water then flows up the east coast of North America and across the Atlantic Ocean to Europe (see opening image). The energy the Gulf Stream transfers is enormous: more than 100 times the world's energy demand.

The Gulf Stream's warm waters raise temperatures in the North Sea, which raises the air temperatures over land between 3 to 6°C (5 to 11°F). London, U.K., for example, is at about six degrees further south than Quebec, Canada. However, London’s average January temperature is 3.8°C (38°F), while Quebec’s is only -12°C (10°F). Because air traveling over the warm water in the Gulf Stream picks up a lot of water, London gets a lot of rain. In contrast, Quebec is much drier and receives its precipitation as snow.

London during the winter

London, England in winter.

Quebec during the winter

Quebec City, Quebec in winter.


  • Water in the Gulf Stream travels along the Equator and is heated as it goes.
  • The Gulf Stream brings warm water north along the Atlantic coast of the United States and then across the northern Atlantic to the British Isles.
  • A tremendous amount of energy is transferred from the equatorial regions to the polar regions by ocean currents.


  1. Explain why England is relatively mild and rainy in winter but central Canada, at the same latitude and during the same season, is dry and frigid.
  2. Where else do you think ocean currents might moderate global climate?
  3. What would Earth be like if ocean water did not move?

Explore More

  1. What drives ocean and atmospheric circulation? What does the ocean store more of than the atmosphere?
  2. What are surface ocean currents driven by? What are deeper ocean currents driven by?
  3. What is the importance of upwelling nutrients in the ocean?
  4. What causes El Nino and La Nina? What happens during these events?
  5. How does heat exchange between ocean surface and atmosphere influence climate?
  6. How do hurricanes form in the oceans? Where does the heat come from to power them?
  7. What kind of life would be on Earth if there were no oceans?

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