Ocean currents

Steady flows driven by wind and by differences in sea temperature and saltiness.

Natural sources · Solar-derived flows · No. 5

• Natural sources
• Origin: Indirect solar
• Renewable: Yes

Unlike wind or tides, the Gulf Stream never stops, so a turbine placed in it could run about 70% of the time.

Chart: Illustration: Ocean currents

Where it comes from

Chart: Map of where it comes from

Wind drags the sea surface and the Earth's spin organises the flow, putting about 0.8 TW of work into the ocean circulation.

Three things to know

1. About 80% of the wind's work on the ocean circulation enters over the remote, stormy Southern Ocean.
2. The Gulf Stream off the south-eastern US averages about 6.4 km/h, far faster than most currents.
3. Most other US coastal waters have non-tidal currents of only about 0.2 m/s or less.

The journey

1. 1 Wind stressSurface winds drag the sea along
2. 2 Earth's rotationSpin shapes flows into basin-wide circulations
3. 3 Boundary currentsFast narrow jets like the Gulf Stream
4. 4 TurbinesUnderwater prototypes, no commercial plants yet
5. 5 ElectricitySteady output, if the technology matures

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