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Oceanography Orals Review

Oceanography Orals Review. Allegra LeGrande. Some Generals. TOA rad in Tropics >> Poles than outgoing LWR  atm & ocean heat transport Old ½ ocean New 1/6 ocean Atm circulation cells set up Hadley Cells Ferrel Cells. High & Low Pressure in Atm  Winds

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Oceanography Orals Review

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  1. Oceanography Orals Review Allegra LeGrande

  2. Some Generals

  3. TOA rad in Tropics >> Poles than outgoing LWR  atm & ocean heat transport Old ½ ocean New 1/6 ocean Atm circulation cells set up Hadley Cells Ferrel Cells High & Low Pressure in Atm  Winds Coriolis Force  Winds along isobars High Pressure  Anticyclonic Flow (clockwise in NH) Surface Wind into ocean Windstress ~ drag times velocity2 Ekman transport Moving Heat drives Circulation

  4. Geostrophic Balance • Pressure Gradient • Horizontal pressure gradient per unit mass • Coriolis Force • m x 2 Ω sin Φ x u • Ω = 2π/84600 = 7.27 x 10-5 rad/sec • Fcx = + 2 Ω v sin Φ = + f v • Fcy = - 2 Ω u sin Φ = - f u • f ~ 10-4 in mid-latitudes Momentum equation Rossby Number Small (drop 1st RHS) Ekman Number Small (drop 2nd LHS)

  5. Thermal Wind (Vertical shear and horizontal density gradient) • Geostrophic Balance • Vertical gradient • Simplify • Hydrostatic Balance • Thermal Wind

  6. Atmosphere to Ocean • Wind Stress • τ = cW2 (drag coefficient c ~ 2x10-3) • Wind of 10 m/s  τ 0.2 N/m2 • ‘Rule of Thumb’ • Surface current speed ~ 3% Wind speed • Ekman Spiral • Surface 45° to the right (NH) wind • Net 90° to the right (NH) wind

  7. Low High

  8. Coastal Upwelling

  9. SSH : If winds STOPPED blowing, PE in SSH would mean ocean kept circulating for 10 years

  10. Surface Currents Subtropical Gyres Subpolar Gyres Equation of State ρ= ρ0(1-α(T-T0)+β(S-S0)) α ~ 2X10-4 K-1 β ~ 8X10-4 Meridional Overturning Deep water formation Upwelling (out of order) Coastal Divergences Special Stuff El Nino Nutrients Circulation Is Going

  11. Average surface salinity

  12. August SSTs

  13. Deep Water • Diffusivity Salt 10-5 cm2/sec • Diffusivity Heat 10-3cm2/sec • NADW: Water loses Heat faster than Salt, denser water forms as Salty water cooled • Polyna: Surface water loses latent heat  surface water cools AND becomes saltier  cold salty water is denser and sinks

  14. Latitude-Depth Potential Temp. (°C)and Salinity (p.s.u.) Profiles

  15. Atlantic Ocean Circulation

  16. Why is there a Gulf Stream? • Conservation of Potential Vorticity • Sverdrup Balance: negative wind stress curl (as in the subtropics) tends to generate negative vorticity propelling fluid into lower latitudes • Stommel: only bottom friction as a sink for vorticity. Solution decaying into interior possible only on Western Boundary • Monk: Also Horizontal viscous terms call for western intensification • Rossby Waves • Propogate west to east • Reflect & dissipate • Western boundary is a collection of energy from incoming waves

  17. Profile Knowledge • Just in case you are asked about nutrients, temperature, salinity, etc., etc…

  18. Identify Water Masses (1,2,3,4)

  19. Plot Profile on T-S Diagram Antarctic Intermediate Water Shallow Salinity Maximum North Atlantic Deep Water Antarctic Bottom Water

  20. Atlantic Ocean Salinity

  21. Atlantic Ocean Temperature

  22. Atlantic Ocean Nutrients

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