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The Ocean General Circulation

The Ocean General Circulation. Gulf Stream. Mean Circulation in the Ocean. Gulf Stream. Mean Circulation in the Ocean. California Current. Oceans are filled with energetic eddies!!!. Gulf Stream, Plankton Bloom. Gulf Stream Spiral Eddies. Mediterranean Sea, Shear Wall Spiral Eddies.

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The Ocean General Circulation

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  1. The Ocean General Circulation

  2. Gulf Stream Mean Circulation in the Ocean

  3. Gulf Stream Mean Circulation in the Ocean California Current Oceans are filled with energetic eddies!!!

  4. Gulf Stream, Plankton Bloom

  5. Gulf Stream Spiral Eddies

  6. Mediterranean Sea, Shear Wall Spiral Eddies

  7. Tropical Atlantic, Spiral Eddy

  8. Greek Island, Spiral Eddies and Wakes

  9. Strait of Gibralter, Solitons

  10. Eastern Pacific Internal Waves

  11. Kelvin Wakes, from Ships

  12. Coastal Dynamics California Filaments and Phytoplankton Hawaiian Island Wakes

  13. Ocean wind driven circulation Key questions: How does the wind drive surface currents? What drives oceanic gyres? What is Ekman transport? What drives upwelling and downwelling?

  14. Atmospheric winds “Eddy” regime Variable weather Westerly wind Subtropical high “Hadley” regime Intertropical convergence zone (ITCZ)

  15. How is the energy of the winds transferred to the ocean? Ekman Theory …

  16. How does wind force propagate in the ocean? surface balance between friction and rotation

  17. Ekman transport: Balance between wind and Coriolis force FWIND Wind direction Ekman transport FCoriolis • Surface water is pushed by the atmospheric wind • Coriolis force acting on surface current balances the wind stress • Surface current (averaged over tens of meters) points to the right of the direction of the wind

  18. What would happen to the Ekman transport under the cyclonic atmospheric circulation? Wind stress Ekman transport L Ekman upwelling under cyclonic circulation

  19. What would happen to the Ekman transport under the anti-cyclonic atmospheric circulation? Wind stress Ekman transport H Ekman pumping under anti-cyclonic circulation

  20. Ocean temperature structure Atlantic Ocean Temperature structure in the top 1,000m What controls this structure? H L H

  21. Ekman Theory …and vertical advection in the ocean COASTAL UPWELLING and DOWNWELLING OPEN OCEAN EKMAN PUMPING

  22. Subtropical “ocean gyre” is a geostrophic circulation • Atmospheric high pressure  Anti-cyclonic wind stress • Ekman transport converges toward the middle, raising up the sea surface slightly • Pressure force drives the geostrophic gyre circulation

  23. Balance of forces: geostrophic balance Applies to the Ocean same as Atmosphere! Fpressure Low Pressure High Pressure FCoriolis • Particle will have the Coriolis force 90 degrees to the right • Particles will tend to move along line of constant pressure • Particles will have the high pressure on their right (same as Coriolis)

  24. Effects of Ekman Currents

  25. Ocean general circulation

  26. Heat transport by the ocean circulation

  27. Regional circulation: Coastal upwelling

  28. Equatorial upwelling

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