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Ocean Currents

Ocean Currents. Some key questions: What causes the ocean currents? What are the global ocean current patterns? How do ocean currents interact with climates? https://mediaplayer.pearsoncmg.com/assets/4ALEUTqaD5kmQVbrebIXu_pvWObSSpIz. Ocean Currents. Ocean currents are generated by

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Ocean Currents

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  1. Ocean Currents • Some key questions: • What causes the ocean currents? • What are the global ocean current patterns? • How do ocean currents interact with climates? https://mediaplayer.pearsoncmg.com/assets/4ALEUTqaD5kmQVbrebIXu_pvWObSSpIz

  2. Ocean Currents • Ocean currents are generated by • surface winds • differences in surface water density, due to salinity and temp. diff. (thermohaline circulations) • evaporation-induced sea level gradients   • Surface Currents:  • generally flow in sub-basin scale circulations known as gyres • deflected by Coriolis Force, so surface current differs up to 45° from overlying wind (apparent deflection to the _ in the N. Hem, to the _ in S. Hem. See next slide) • E. margins of oceans: are cool for their latitude (eg. Humbolt, California, Benguelan Currents). Flow equatorward. Coolness adjacent to continents is accentuated by coastal upwelling (explained later). • W. margins of ocean basins are warm for their latitude (eg. Gulf Stream, Kuroshio Currents), & flow poleward

  3. winds & ocean currents

  4. Major Ocean Currents Figure 4.21

  5. Pacific Ocean Currents Figure 1

  6. Deep Thermohaline Currents Figure 4.22

  7. Coastal Upwelling • driven by winds that induce near-surface water currents to have an offshore component (Coriolis Effect) • significant on west coasts, particularly high sun season • Oregon Coast example: upwelling causes cool surface temperatures, is often associated w/ fogs • also observed anywhere where wind has an offshore component (Central American example) Equatorial Upwelling Pacific Equatorial Region (Equatorial upwelling) http://oceanmotion.org/html/background/upwelling-and-downwelling.htm Sea floor topography-induced upwelling

  8. Ocean Currents and Climate • El Niño/Southern Oscillation (ENSO): A weakening or reversal of the normal east-to-west flow of the trade winds and surface ocean currents in the tropical Pacific. Sea surface temps. rise in eastern Pacific, coastal upwelling and marine productivity diminished. • La Niña: An unusually strong east-to-west flow of the trade winds in surface ocean currents in the tropical Pacific, associated with cooler water temps. • Enormous amounts of heat are transferred between tropics and higher latitudes via the ocean currents, moderating climates in both regions. • The Gulf Stream and World History…

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