Water on the Move    

The Water PlanetOceans in MotionLife in the SeaScientist at SeaResources


Clouds flow through the atmosphere just as water flows across the land.

The Earth is surrounded by two great oceans: an ocean of air and an ocean of water. Both are in constant motion, driven by the energy of the sun and the gravity of the Earth. Their motions are linked; the winds give energy to the sea surface and ocean currents are the result. The currents carry heat from one location to another, altering the Earth's surface temperature patterns and modifying the air above.

Out in the open sea, ocean waters are driven by two great wind systems. Close to the equator the Trade Winds blow the surface waters westward. In the temperate zone, the Westerlies blow the surface waters back toward the east. The result is that in each great ocean basin there is roughly circular movement of the surface waters. In the northern hemisphere these wind driven currents move clockwise and in the southern hemisphere they move counter clockwise. Both surface and deep-water currents affect the world's climate by moving cold water from the poles toward the tropics and vice versa.

Ocean waters are always in motion. Currents flow like rivers, waves crash against seashores and tides rise and fall.

Current Events

Currents are created by the sun warming ocean layers in certain areas like at the equator. The warmer water expands slightly, creating a slope, and the warm water runs downhill toward the poles.

Wind and Waves

Ocean waves are created by wind. Energy in the form of waves moves across the ocean surface but the water itself moves in a circular motion beneath the surface.

The Ebbs and Flows of the Sea

Tides are rhythmic, predictable and are affected by the gravitational pull of the sun and moon. Tidal range can vary dramatically depending on the shape of the water basin that the tides flow through.

Science Learning Network | email: sln@mos.org | © 1998 The Museum of Science