Ocean currents

Ocean surface currents are like giant rivers, often tens of kilometres wide, 100m deep and flowing at 15 km/h. The major currents are split on either side of the Equator into giant rings called gyres.

In the Northern Hemisphere the gyres flow round clockwise; in the south they flow anticlockwise.

Ocean currents are driven by a combination of winds and the Earth's rotation.

Near the Equator water is driven by easterly winds to make westward-flowing equatorial currents. When equatorial currents reach continents, the Earth's rotation deflects them polewords as warm currents.

As warm currents flow polewards, westerly winds drive them east back across the oceans. When the currents reach the far side, they begin to flow towards the Equator along the west coasts of continents as cool currents.

The North Atlantic Drift brings so much warm water from the Caribbean to SW England that is warm enough to grow palm trees, yet it is as far north as Newfoundland.

By drying out the air cool currents can create deserts, such as California's Baja and Chile's Atacama deserts.