How the Sun Drives Winds and Ocean Currents

0:00How does the Sun make winds blow and ocean currents flow?

0:05Here is Earth, with the equator, the North Pole and the South Pole.

0:10Energy from the Sun is solar radiation. Here are three equal beams.

0:16Near the equator, a beam hits almost straight on, concentrating its energy on a small area.

0:23Near the poles, the same beam hits at a low angle and spreads over a larger area.

0:29So the equator warms more than the poles. This is unequal heating.

0:35The equator is not hotter because it is closer to the Sun. It is only about 6,400 kilometres closer, out of about 150 million.

0:46Air over the equator heats up, expands and becomes less dense, so it rises.

0:53High up, it spreads toward the poles, cools, becomes denser and sinks.

1:00Surface air flows back to the equator. This loop is a convection current, and the moving surface air is wind.

1:08Winds drag surface water along, making surface currents, steady flows of seawater.

1:15Warm currents carry heat toward the poles, and cold currents bring cooler water back.

1:21Along some coasts, winds push surface water offshore, and cold deep water rises in its place. This is upwelling.

1:31Deep water carries nutrients that feed plankton, tiny drifting living things. Plankton feed fish, making rich fishing grounds.

1:40So unequal heating by the Sun drives the winds and the ocean currents.