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The Coriolis Effect and Ekman Transport

The Coriolis Effect and Ekman Transport. The tendency for the path of a moving object to deflect to the right in the Northern Hemisphere and to deflect to the left in the Southern Hemisphere Caused by the Earth’s rotation relative to an object in motion over its surface.

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The Coriolis Effect and Ekman Transport

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  1. The Coriolis Effectand Ekman Transport

  2. The tendency for the path of a moving object to deflect to the right in the Northern Hemisphere and to deflect to the left in the Southern Hemisphere • Caused by the Earth’s rotation relative to an object in motion over its surface.

  3. Apparent deflection of the path of an object • Object does not actually deviate from its path, but it appears to do so because Earth is moving underneath.

  4. MARINE ENVIRONMENT surface winds + coriolis effect  surface currents coriolis effect = curved deflection in the path of a fluid flowing linearly over a rotating sphere (the Earth)

  5. coriolis effect:

  6. Wind + coriolis causes Ekman transport velocity vectors: each layer of water drags on next deeper layer (friction) and coriolis operates on each layer 90° to right of downwind direction coriolis displacement to right in No. Hemisphere 50 m deep

  7. Coastal Upwelling Due to offshore Ekman transport off coast Nutrient rich water comes up from the bottom of the ocean

  8. coastal upwelling due to offshore Ekman transport along coast coriolis displacement to left in So. Hemisphere

  9. Which direction (N,S, E, or W) will the mass movement of water be directed from a westerly wind in the northern hemisphere? • Wind is coming from the west and blowing to the east • Therefore mass water movement will be 90 degrees to the right or to the south Wind direction Mass water movement due to Ekman transport

  10. U. S. West Coast cold cool warm coastal upwelling due to offshore Ekman transport along coast

  11. coastal upwelling due to offshore Ekman transport along Oregon coast Oregon coast: temperature: phytoplankton: upwelling  cooler deeper water to surface  more nutrients  more photo- synthesis

  12. coastal upwelling due to offshore Ekman transport along Oregon coast summer upwelling winter downwelling (north winds) (south winds) water temperature

  13. coastal upwelling due to offshore Ekman transport along Oregon coast summer upwelling winter downwelling (north winds) (south winds) coriolis displacement to right in No. Hemisphere

  14. greater reflection solar heat + atmosphere  surface winds

  15. solar heat + atmosphere  surface winds

  16. solar heat + atmosphere  surface winds atmospheric airpressure   high  dry Horse Latitudes (deserts)   low  wet   high  dry

  17. surface winds + coriolis effect  surface currents coriolis displacement to right in No. Hemisphere

  18. Measuring surface currents • The modern message in a bottle • Surface buoy designed to track ocean currents

  19. http://www.aoml.noaa.gov/phod/dac/dac_animations.html

  20. surface winds + coriolis effect  surface currents

  21. MARINE ENVIRONMENT • Equatorial Counter-Current • strong equatorial currents move water to west • sea surface is 0.5m higher on west side of equatorial seas • some water flows back east along calm doldrums

  22. boundary currents = north-south surface currents eastern western

  23. coriolis effect makes western boundary currents stronger than eastern boundary currents

  24. MARINE ENVIRONMENT boundary currents easternvs.western USA example: California C. Gulf Stream temperature: cool (NS) warm (SN) width: wide (~1000 km) narrow (~100 km) depth: shallow (~0.5 km) deep (~2 km) speed: slow (~10 km/day) fast (~100 km/day) upwelling: high low productivity: high low

  25. MARINE ENVIRONMENT surface + vertical currents  sea surface temperature (SST)

  26. MARINE ENVIRONMENT surface + vertical currents  sea surface temperature (SST)

  27. MARINE ENVIRONMENT surface + vertical currents  sea surface temperature (SST)

  28. thermocline pycnocline MARINE ENVIRONMENT thermocline depth zone of rapid change in water temperature

  29. thermocline pycnocline MARINE ENVIRONMENT thermocline  stratification  deep nutrients separated from shallow light  limits photosynthesis in about 90% of oceans light shallows: photosynthesis depletes nutrients barrier to vertical mixing dark depths: nutrients sink and accumulate

  30. MARINE ENVIRONMENT upwelling  vertical mixing removes thermocline and moves deep nutrients to well-lit shallows  fertilizes photosynthesis in about 10% of oceans, which accounts for about 50% of marine fisheries greener = more chlorophyll (phytoplankton)

  31. MARINE ENVIRONMENT upwelling coastal, and equatorial

  32. coriolis displacement to right in No. Hemisphere coriolis displacement to left in So. Hemisphere MARINE ENVIRONMENT equatorial upwelling due to Ekman transport in opposite directions on either side of equator and nutrients

  33. Limits on Marine Primary Productivity • Most autotrophs require: • Water • CO2 • Inorganic nutrients • Sunlight

  34. Light Zones • Euphotic zone (good light) • Sunlit zone • Enough sunlight for photosynthesis • Most marine lifer found here • Disphotic zone (bad light) • Twilight zone • Very little light • No photosynthesis • Aphotic zone (no light) • Midnight zone • Entirely dark

  35. Zonation of Pelagic Environment 0 m Euphotic Zone Region of sufficient light for photosynthesis Epipelagic 200 m Mesopelagic Depth varies due to water clarity, available light, etc. 1000 m Bathypelagic 4000 m Abyssopelagic

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