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Ocean Currents

Ocean Currents. Chapter 16. Surface Currents. A current is the flow of water moving through the ocean. Surface currents (flow in the upper 1000 m) are caused by wind. . Surface Currents in the Ocean.

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Ocean Currents

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  1. Ocean Currents Chapter 16

  2. Surface Currents • A current is the flow of water moving through the ocean. • Surface currents (flow in the upper 1000 m) are caused by wind.

  3. Surface Currents in the Ocean • Warm currents flow from the equator to the poles, and cold currents flow from the poles to the equator • Surface currents form a circular pattern called a gyre.

  4. Surface Currents in the Ocean • Gyres in the Northern Hemisphere flow clockwise, gyres in the Southern Hemisphere flow counterclockwise.

  5. Surface Currents in the Ocean • West sides of oceans have warm ocean currents that flow away from the equator. • East sides of oceans have cold ocean currents that flow to the equator.

  6. Surface Currents & Wind • The earth rotates in an easterly direction. • This makes the winds blowing toward the equator curve westward, and the winds blowing toward the poles curve eastward.

  7. Surface Currents and Winds • Trade winds drive the equatorial part of the ocean currents. • They blow from the east, towards the west. • The westerly winds drive the polar part of the ocean currents. • They blow from the west, towards the east.

  8. Surface Currents and Winds

  9. Deep Currents • Because the warm surface water and cold deep waters don’t mix, surface currents have little effect on the deep ocean water. • Deep currents are caused by density differences. • Remember, cold water is more dense than warm water!

  10. Deep Current Movement • The densest water is at the poles. • As ice forms, the salt is left behind, leading to high-salinity, dense water. • This water sinks to the deep ocean (deep water masses). • Water flows from high density to low density, and moves from the poles toward the equator.

  11. Upwelling • When wind blows parallel to a shoreline, surface currents and deep currents can mix. • The wind pushes the warm water away from the coast, and cold deep water takes its place. • This upward movement of cold water is called upwelling. • Where upwelling occurs, the water is rich with nutrients that it brings up from the ocean floor.

  12. Upwelling

  13. Shoreline Currents • A longshore current forms when waves approach a shore at an angle.

  14. Rip Currents • A rip current forms when water that is built up behind a sandbar due to a longshore current finally breaks through.

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