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Ocean Currents

Ocean Currents. Ocean water circulates in currents caused by wind and by density differences Currents are the flow of water between areas of different surface levels or different densities. Ocean Currents. Ocean water moves constantly sideways, up, down because it is: Blown by wind

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Ocean Currents

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  1. Ocean Currents • Ocean water circulates in currents caused by wind and by density differences • Currents are the flow of water between areas of different surface levels or different densities

  2. Ocean Currents • Ocean water moves constantly sideways, up, down because it is: • Blown by wind • Moved by density differences • Heated unevenly • Evaporated unevenly • Affected by Earth’s rotation (Coriolis) • Pulled by sun & moon

  3. CURRENTS • Currents are important because they: • moderate climates (transfer heat) • mix nutrients and gases • transport larvae and nekton Warm air from equator flows toward poles, drives air circulation, makes wind, moves water Continents deflect east-west water movement, but not air NASA NOAA

  4. Coriolis Effect • Water near ocean surface moves to the right of wind direction in Northern Hemisphere • Water near ocean surface moves to the left of wind direction in Southern Hemisphere

  5. Coriolis Effect • Causes currents to move • Clockwise in the Northern Hemisphere • Counterclockwise in the Southern Hemisphere http://www.youtube.com/watch?v=mcPs_OdQOYU

  6. Surface Currents • Affect the uppermost 10% of world ocean • Some rapid & riverlike, some slow and diffuse • Largest organized into gyres

  7. The circular patterns of surface water currents are called gyres. The characteristics of a current depend upon where the water is coming from in the gyre.

  8. Eastern boundary currents are located on the eastern side of the OCEAN - not the continent. East Coast of United States Gulf Stream in red Western boundary currents are located on the western side of oceans. Florida

  9. Comparison of Boundary Currents • Western • Eastern • currents bring warm water from the equator 1. currents bring cold water from the poles 2. high salinity; low oxygen content 2. low salinity; high oxygen content 3. nutrient poor, infrequent upwelling 3. nutrient rich due to upwelling 4. lower biomass 4. high biomass

  10. Surface Currents

  11. Effect of Surface Currents on Climate • Surface currents distribute heat worldwide • Warm water flows to higher latitudes transfers heat to the air and cools • Moves back to low latitudes • Absorbs heat • Repeats

  12. Vertical Movement • Upwelling – upward movement of water • Can be caused by wind blowing parallel to shore or offshore (Coastal Upwelling) • Brings nutrients

  13. Vertical Movement • Downwelling – downward movement of water – caused by: • Increase in surface water density • Wind blowing parallel to shore or onshore (Coastal Downwelling) • Brings dissolved gases and nutrients to deeper ocean

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