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Ocean · 5 min · 4 steps

The warm sea and its currents

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Goal. Read a sea temperature map, find the warm pool, upwelling and warm currents, and explain why the sea changes temperature slowly.

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Steps

  1. Predict

    Where do you expect the warmest open sea on Earth?

    • Near the poles
    • In the western tropical Pacific and Indian Ocean
    • Off the coast of Peru
    Show the answer

    In the western tropical Pacific and Indian Ocean. In the western tropical Pacific and eastern Indian Ocean, the Warm Pool, often above 29 °C.

    This map is about two days old, built from several satellites, ships and buoys. The warmest water, the Warm Pool, lies around Indonesia and the Philippines.

  2. Off Peru the sea is much cooler than you might expect so close to the equator. Winds push the surface water away from the coast and cold water rises from below: upwelling.

  3. Zoom in on the Kuroshio, the warm current flowing north past the east coast of Taiwan towards Japan. It carries tropical heat towards the pole and keeps the sea east of Taiwan warm in winter. It shows most clearly in winter, as a tongue of warm water.

  4. The Gulf Stream does the same in the Atlantic. Tap the sea anywhere to read its temperature, then compare places at the same latitude on either side of the ocean.

The common mistake

Myth

The Gulf Stream alone keeps Europe's winters mild.

Fact. It helps, but much of the effect comes from westerly winds blowing off an ocean that stores summer heat. The Rocky Mountains also bend the winds so that Europe gets mild sea air.

Check yourself

Question 1

Why is the sea off Peru cool so close to the equator?

  • Melting ice from Antarctica
  • Cold water rises from below (upwelling)
  • The Andes shade it
Show the answer

Cold water rises from below (upwelling). Winds push the surface water away from the coast and cold, nutrient-rich water rises to replace it.

Question 2

Which current flows north past the east coast of Taiwan?

  • The Gulf Stream
  • The Kuroshio
  • The Humboldt Current
Show the answer

The Kuroshio. The Kuroshio, the Pacific's equivalent of the Gulf Stream.

Question 3

Why does the sea warm and cool more slowly than land?

  • Water needs much more heat to change temperature, and it mixes
  • Water reflects all sunlight
  • Salt makes heat
Show the answer

Water needs much more heat to change temperature, and it mixes. Water needs four to five times more heat than dry soil or rock to warm by the same amount, and waves and currents mix the heat down through many metres.

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Curriculum

Taiwan 12-year curriculum (108 課綱), natural science
Ic-Ⅳ-2 · EFa-Vc-5 · EIc-Vc-1
US Next Generation Science Standards
MS-ESS2-6
England national curriculum
KS3 Geography: weather and climate