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Ch. 24 The Moving Ocean

Ch. 24 The Moving Ocean. 24.1 Surface Currents. flow in the upper 1,000 meters of ocean driven by global winds N. and S. hemispheres each have two circulations caused by the Coriolis Effect clockwise in N. hemisphere counterclockwise in S. hemisphere. Current Temperature.

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Ch. 24 The Moving Ocean

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  1. Ch. 24 The Moving Ocean

  2. 24.1 Surface Currents • flow in the upper 1,000 meters of ocean • driven by global winds • N. and S. hemispheres each have two circulations • caused by the Coriolis Effect • clockwise in N. hemisphere • counterclockwise in S. hemisphere

  3. Current Temperature • cold currents- move towards the Equator • Eastern sides of ocean basins • warm currents- move towards poles • Western sides of ocean basins

  4. Winds Currents Currents & Winds • 2 sets of global winds drive currents • Trade winds- blow from NE in N. hemisphere; SE in S. hemisphere • Westerlies- blow from SW in N. hemisphere; NW in S. hemisphere • Earth’s rotation & continents push currents along path of travel

  5. Important Currents to Know • Gulf Stream • N. Atlantic • Canary • N. Equatorial • California • Labrador • West Wind Drift

  6. Countercurrents • flow in opposite direction of wind-related currents • return water taken away from one side of the ocean basin to the opposite side • EX: Equatorial Countercurrents

  7. 24.2 Currents Under the Surface • driven by gravity & differences in density • Density current= heavier & denser than surrounding water • Sink to bottom from surface • move very slowly • Circulate for 500-2000 years

  8. Global Conveyor Belt • global circulation of deep ocean currents • transports warm water to colder areas & cold water to warmer areas • efficient heat-transport system drives Earth’s climate

  9. Importance of Density Currents • carry oxygen absorbed from surface for deep sea life • retain same temperature, salinity, & density as surface • turbidity currents are an example of VERTICAL density currents!

  10. Density Currents from Polar Water • polar water is the most dense because it’s cold • when water freezes, it leaves behind salt • both of these factors increase density • depth of a water mass or current depends on its density

  11. Density Currents from Evaporation • increased evaporation leaves salt behind, which increases the density • dense water sinks and is replaced with less dense water • Example: Mediterranean

  12. Upwelling • vertical density currents that occur when cold deep water comes to the surface • can occur anywhere, prevalent along western coasts of continents

  13. Two Causes of Upwelling • surface winds push water away from continent • denser, salty water suddenly sinks

  14. Benefits of Upwelling • large amounts of nutrients come to surface • phytoplankton populations cultivate and provide food for marine life • Large-scale fishing areas • Examples: California, Morocco, southwestern Africa, Peru, western Australia

  15. 24.3 TIDES • twice-daily rise and fall of Earth’s oceans • result of gravitational pulls from moon and sun • reach different levels depending on Earth’s location in relation to moon and sun • Moon has a greater effect since it is closer • The closer an object is to another the greater the gravitational pull.

  16. Low tide Indirect high tide Direct high tide Moon’s orbit Moon Uniform water level Low tide 24.3 TIDES • Moon’s effect on the tides: • The moon orbits around Earth causes bulges to rotate around the Earth over the lunar month (~29 days). • The moon rises about 50 minutes later each days so do the tides.

  17. 24.3 TIDES • sun can enhance or detract from the moon’s effects • Spring Tides occur when the sun and moon are in alignment (enhances tides) • High tides are higher and low tides are lower

  18. 24.3 TIDES • Neap Tides occur when the sun and moon are at right angle (sun detracts from moon’s pull) • High tides are not as high and low tides are not as low

  19. 24.3 TIDES • Tidal Range is the difference between high and low tides. • more noticeable on oceans than lakes • Small lakes show no tides at all • Great Lakes have tides with ranges of just a few centimeters • Ocean tidal ranges can vary greatly • closer to the poles the greater the tidal range

  20. Bay of Fundy, High tide Bay of Fundy, Low tide 24.3 TIDES • The shapes of individual shorelines influence the tidal range • A narrow bay has a greater tidal range than a wide coastal area.

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