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Ocean Circulation

Ocean Circulation. Ocean Circulation. Key Points: I can discuss the importance of ocean circulation. I can describe the circulation of wind in a non-rotating vs. a rotating Earth. I can discuss the physical properties of the atmosphere. I can begin to understand the Coriolis effect.

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Ocean Circulation

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  1. Ocean Circulation

  2. Ocean Circulation • Key Points: • I can discuss the importance of ocean circulation. • I can describe the circulation of wind in a non-rotating vs. a rotating Earth. • I can discuss the physical properties of the atmosphere. • I can begin to understand the Coriolis effect.

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

  4. Non-rotating Earth Convection cell model

  5. Add rotation and add landmasses unequal heating and cooling of the Earth You Tube Link YouTube Link #2

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

  7. 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 decreases the density of air

  8. Physical properties of the atmosphere: Pressure

  9. The Coriolis effect http://www.youtube.com/watch?v=Wda7azMvabE http://www.youtube.com/watch?v=i2mec3vgeaI http://www.youtube.com/watch?v=XiYs4QBWTOo • 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. The Coriolis effect on Earth • As Earth rotates, different latitudes travel at different speeds • The change in speed with latitude causes the Coriolis effect

  11. Ocean Currents • Recap Key Points: • I can discuss the importance of ocean circulation. • I can describe the circulation of wind in a non-rotating vs. a rotating Earth. • I can discuss the physical properties of the atmosphere. • I can begin to understand the Coriolis effect.

  12. Ocean Currents • Key Points: • I can describe how the Coriolis effect influences surface winds. • I can explain the difference between factors affecting surface circulation vs. deep ocean circulation. • I can describe oceanic gyres & their rotations.

  13. Idealized winds generated by pressure gradient and Coriolis Force.  • Actual wind patterns owing to land mass distribution.. http://www.youtube.com/watch?v=aeY9tY9vKgs&feature=youtube_gdata_player

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

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

  16. Wind-driven surface currents

  17. Current Gyres Gyres are large circular-moving loops of water Five main gyres (one in each ocean basin): • North Pacific • South Pacific • North Atlantic • South Atlantic • Indian • Generally 4 currents in each gyre • Centered about 30o north or south latitude

  18. Surface and Deep-Sea Current Interactions Unifying concept: “Global Ocean Conveyor Belt” http://www.youtube.com/watch?v=6vgvTeuoDWY http://seis.natsci.csulb.edu/rbehl/ConvBelt.htm

  19. Heat Transport by Currents • Surface currents transport heat energy from equator towards the poles • Currents also involved with gas exchanges, especially O2 and CO2 • Nutrient exchanges important within surface waters (including outflow from continents) and deeper waters (upwelling and downwelling) • Pollution dispersal • Impact on fisheries and other resources

  20. Thermohaline Circulation Global ocean circulation that is driven by differences in the density of the sea water which is controlled by temperature and salinity.

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

  22. Thermohaline Circulation

  23. Ocean Currents • Recap the Key Points: • I can describe how the Coriolis effect influences surface winds. • I can explain the difference between factors affecting surface circulation vs. deep ocean circulation. • I can describe oceanic gyres & their rotations.

  24. Ocean Currents • Key Points:

  25. 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

  26. upwelling downwelling

  27. Satellite Observations • TOPEX/Poseidon, Jason 1, and other satellites have observed patterns of change over the past few years • Animation of seasonal and climatically-influence shifts available at http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/MOVIES/Topex_Dynamic_Ocean_Topography.mpg

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

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

  30. Normal conditions in the Pacific Ocean

  31. El Niño conditions (ENSO warm phase)

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

  33. Non El Niño El Niño 1997

  34. Non El Niño upwelling El Niño thermocline

  35. El Niño events over the last 55 years El Niño warmings (red) and La Niña coolings (blue) since 1950. Source: NOAA Climate Diagnostics Center

  36. 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

  37. Effects of severe El Niños

  38. Inquiry • What is a convection cell? • Which direction do currents get deflected in the Southern Hemisphere? • What depth should the water be for an Ekman spiral to occur? • 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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