Ocean Currents

The hydrosphere, including all the water on the planet, is constantly moving. This motion on a grand scale is called current. Current is caused by differences in temperature, differences in salinity, the motion of the Earth, and wind.

Water moves in large circles around the oceans. When water is near the hot equator, the water is warmed by the Sun. It carries this warmth with it toward the north and south poles, where it cools, and begins the process again.

Thought Questions

• Is there an ocean near your home town? Is the water there cool or warm?
• If you go swimming in an ocean, can you feel a current moving you in one main direction?
• How do you think the world would change if there were no current?
• Look at this map (78 k). Which oceans are mainly warm? Which are mainly cold?