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Ocean Currents

Ocean Currents. Why is Ocean Circulation Important?. Transport ~ 20% of latitudinal heat Equator to poles Transport nutrients and organisms Influences weather and climate Influences commerce. Non-rotating Earth. Convection cell model. Add rotation and add landmasses

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Ocean Currents

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  1. Ocean Currents

  2. Why is Ocean Circulation Important? • Transport ~ 20% of latitudinal heat • Equator to poles • Transport nutrients and organisms • Influences weather and climate • Influences commerce

  3. Non-rotating Earth Convection cell model

  4. Add rotation and add landmasses unequal heating and cooling of the Earth

  5. Physical properties of the atmosphere: Density • Warm, low density air rises • Cool, high density air sinks • Creates circular- moving loop of air (convection cell)

  6. Physical properties of the atmosphere: Water vapor • Cool air cannot hold much water vapor, so is typically dry • Warm air can hold more water vapor, so is typically moist • Water vapor increases the density of air

  7. Physical properties of the atmosphere: Pressure

  8. 90o High pressure, dry climate 60o Low pressure, wet climate High pressure, dry climate 30o ITCZ intertropical convergence zone= doldrums Low pressure, wet climate 0o 30o 60o 90o

  9. The Coriolis effect • The Coriolis effect • Is a result of Earth’s rotation • Causes moving objects to follow curved paths: • In Northern Hemisphere, curvature is to right • In Southern Hemisphere, curvature is to left • Changes with latitude: • No Coriolis effect at Equator • Maximum Coriolis effect at poles

  10. Idealized winds generated by pressure gradient and Coriolis Force.  • Actual wind patterns owing to land mass distribution..

  11. Ocean Currents Surface Currents The upper 400 meters of the ocean (10%). Deep Water Currents Thermal currents (90%)

  12. Surface Currents Forces • Solar Heating (temp, density) • Winds • Coriolis

  13. Gyres are surface currents that form a circular pattern due to prevailing winds, the Coriolis effect and landmasses. They will effect the climate of coastal regions. If the current is warm, it will keep the land by the coast warmer than inland areas. If it is a cold current the coast will be cooler. Gyres

  14. Upwelling and downwelling Vertical movement of water () • Upwelling = movement of deep water to surface • Hoists cold, nutrient-rich water to surface • Produces high productivities and abundant marine life • Downwelling = movement of surface water down • Moves warm, nutrient-depleted surface water down • Not associated with high productivities or abundant marine life

  15. upwelling downwelling

  16. El Niño-Southern Oscillation (ENSO) • El Niño = warm surface current in equatorial eastern Pacific that occurs periodically around Christmas time • Southern Oscillation = change in atmospheric pressure over Pacific Ocean accompanying El Niño • ENSO describes a combined oceanic-atmospheric disturbance

  17. El Niño • Oceanic and atmospheric phenomenon in the Pacific Ocean • Occurs during December • 2 to 7 year cycle Can affect • Sea Surface Temperature • Atmospheric Winds • Upwelling

  18. Normal conditions in the Pacific Ocean

  19. El Niño conditions (ENSO warm phase)

  20. La Niña conditions (ENSO cool phase; opposite of El Niño)

  21. Non El Niño El Niño 1997

  22. Non El Niño upwelling El Niño thermocline

  23. World Wide Effects of El Niño • Weather patterns • Marine Life • Economic resources El Nino Animation http://esminfo.prenhall.com/science/geoanimations/animations/26_NinoNina.html

  24. Effects of severe El Niños

  25. Surface and Deep-Sea Current Interactions Unifying concept: “Global Ocean Conveyor Belt” http://seis.natsci.csulb.edu/rbehl/ConvBelt.htm

  26. Thermohaline Circulation White sections represent warm surface currents. Purple sections represent deep cold currents

  27. Inquiry • What is a convection cell? • Which direction do currents get deflected in the Southern Hemisphere? • How are surface currents created? • What is a gyre? • How can an El Nino impact upwelling? • Coriolis Effect is strongest near the _____?

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