Ocean Basics
The ocean's waters are dynamic and these movements influence weather and climate, as well as living conditions in the sea and on land for plants and animals. The water cycle, also called the hydrologic cycle, is the continuous movement of water on, above, and beneath Earth’s surface. Water can change from liquid, vapor, and ice at various stages in the water cycle. Ocean currents flow in complex patterns and are affected by wind, salinity, water temperature, bottom topography, and the Earth's rotation.
The Water Cycle
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Since the water cycle is truly a "cycle," there is no beginning or end. Water can change states among liquid, vapor, and ice throughout in the water cycle. Water evaporates from the ocean and the Earth’s surfaces, rises and cools as it moves higher in the atmosphere, condenses as rain or snow, and falls to the surface where it collects in lakes, ocean, soil, and underground.
Surface Ocean Currents
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Water flows in a circular pattern – clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Warm surface currents flow from the tropics to the higher latitudes, driven mainly by atmospheric winds, as well as the Earth's rotation. Cold surface currents come from polar and temperate latitudes. These currents tend to flow toward the equator.
Deep Ocean Currents
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Currents flow in complex patterns affected by wind, salinity and water temperature, bottom topography, and the Earth's rotation. The density of ocean water causes deep ocean currents. Sea water that flows in polar regions will cool or freeze, becoming saltier and denser. Cold or salt water tends to sink.
