1. Ocean Currents “Rivers in the Ocean”

2. Currents Current – a large stream of moving water that flows through the ocean. Capable of moving large amounts of water long distances. Current – a large stream of moving water that flows through the ocean. Capable of moving large amounts of water long distances. Surface Currents Surface Currents –Affect water to a depth of several hundred meters and are driven mainly by wind. –Currents move in circular patterns in each of the five major ocean basins.

3. Currents Factors that affect currents Factors that affect currents –Sun’s heat –Earth’s winds –Earth’s rotation (please add this to your list) –Earth’s rotation (please add this to your list) Coriolis effect – the effect of Earth’s rotation on the direction of winds and currents Coriolis effect – the effect of Earth’s rotation on the direction of winds and currents –This is why currents in the Northern Hemisphere are clockwise, and those in the Southern Hemisphere run counter-clockwise

4. Currents The largest and most powerful current in the North Atlantic Ocean is the Gulf Stream. The largest and most powerful current in the North Atlantic Ocean is the Gulf Stream. –Caused by strong winds coming from the west (the same ones that move weather fronts from west to east) –More than 30 km wide and 300 m deep –Carries warm water up the East Coast

5. Currents Deep Currents – caused by differences in density rather than by surface winds Deep Currents – caused by differences in density rather than by surface winds Density of ocean water depends on two factors Density of ocean water depends on two factors –Temperature (cold water = more dense = sinks to bottom) –Salinity (amount of salt, more salt = more dense = sinks to bottom) Warm water surface currents move water from the equator toward the poles, where the water gets very cold. Warm water surface currents move water from the equator toward the poles, where the water gets very cold.

6. Currents As ice forms at the poles, the salinity of the water increases. As ice forms at the poles, the salinity of the water increases. When temperature decreases and salinity increases, the density of the water increases. When temperature decreases and salinity increases, the density of the water increases. This causes the water to sink to the bottom of the ocean floor. This causes the water to sink to the bottom of the ocean floor. Deep currents move much more slowly than surface currents. Deep currents move much more slowly than surface currents.

7. Currents Upwelling – the upward movement of colder water from the ocean depths. Upwelling – the upward movement of colder water from the ocean depths. Caused by the winds. Caused by the winds. –Wind blows the warm surface water away, causing cold water to rise up to replace it.

8. Currents Upwelling also brings up Upwelling also brings up –Tiny ocean organisms –Minerals –Other nutrients Without this, the surface waters would have very little nutrients. Without this, the surface waters would have very little nutrients. Upwelling zones are typically home to enormous schools of fish Upwelling zones are typically home to enormous schools of fish

9. Currents One major area of upwelling is in the Pacific Ocean off of South America. One major area of upwelling is in the Pacific Ocean off of South America. Upwelling occurs when strong winds from the Andes Mountains sweep across the ocean. Upwelling occurs when strong winds from the Andes Mountains sweep across the ocean. –This creates a fishing area that is important to millions of people who depend on it for food and jobs.

10. Quick Check Review What are the two types of currents found in the ocean? What are the two types of currents found in the ocean? What type of current did our model represent yesterday? What type of current did our model represent yesterday? What is the Coriolis Effect? What is the Coriolis Effect? What three things does upwelling bring to the surface? What three things does upwelling bring to the surface?