Gulf Stream, ENSO, Climate, and up and downwelling
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Gulf Stream, ENSO, Climate, and up and downwelling

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    Gulf Stream, ENSO, Climate, and up and downwelling Gulf Stream, ENSO, Climate, and up and downwelling Presentation Transcript

    • Gulf Stream Best studied of all ocean currents Meanders and loops Merges with Sargasso Sea  Circulates around center of North Atlantic Gyre  Unique biology – Sargassum© 2011 Pearson Education, Inc.
    • Gulf Stream Meanders or loops may cause loss of water volume and generate:  Warm-core rings – warmer Sargasso Sea water trapped in loop surrounded by cool water  Cold-core rings – cold water trapped in loop surrounded by warmer water Unique biological populations © 2011 Pearson Education, Inc.
    • El o – Southern Oscillation (ENSO) High pressure in eastern Pacific weakens Weaker trade winds Warm pool migrates eastward Thermocline deeper in eastern Pacific Downwelling Downwelling Lower biological productivity  Peruvian fishing suffers © 2011 Pearson Education, Inc.
    • ENSO Conditions in the Pacific Ocean© 2011 Pearson Education, Inc.
    • La a – ENSO Cool Phase Increased pressure difference across equatorial Pacific Stronger trade winds Stronger upwelling in eastern Pacific Shallower thermocline Cooler than normal seawater Higher biological productivity Stronger upwelling © 2011 Pearson Education, Inc.
    • a Conditions© 2011 Pearson Education, Inc.
    • Occurrence of ENSO Events  El Niño warm phase about every 2–10 years  Highly irregular  Phases usually last 12–18 months  10,000-year sediment record of events  ENSO may be part of Pacific Decadal Oscillation (PDO)  Long-term natural climate cycle  Lasts 20–30 years© 2011 Pearson Education, Inc.
    • ENSO Occurrences© 2011 Pearson Education, Inc.
    • ENSO has Global Impacts© 2011 Pearson Education, Inc.
    • Notable ENSO Events 1982 – 1983  1997 – 1998  Flooding, drought, erosion, fires, tropical storms, harmful effects on marine life  Unpredictable© 2011 Pearson Education, Inc.
    • Predicting El o Events  Tropical Ocean−Global Atmosphere (TOGA) program  1985  Monitors equatorial South Pacific  System of buoys  Tropical Atmosphere and Ocean (TOA) project  Continues monitoring  ENSO still not fully understood© 2011 Pearson Education, Inc.
    • Ocean Currents and Climate Warm ocean currents warm the air at the coast.  Warm, humid air  Humid climate on adjoining landmass Cool ocean currents cool the air at the coast.  Cool, dry air  Dry climate on adjoining landmass © 2011 Pearson Education, Inc.
    • Upwelling and Downwelling Upwelling – Vertical movement of cold, nutrient-rich water to surface  High biological productivity © 2011 Pearson Education, Inc.
    • Downwelling – Vertical movement ofsurface water downward in water column
    • Coastal Upwelling Ekman transport moves surface seawater offshore. Cool, nutrient-rich deep water comes up to replace displaced surface waters. Example: U.S. West Coast © 2011 Pearson Education, Inc.
    • Other Types of Upwelling Offshore winds Seafloor obstruction Coastal geometry change © 2011 Pearson Education, Inc.
    • Coastal Downwelling Ekman transport moves surface seawater toward shore. Water piles up, moves downward in water column Lack of marine life © 2011 Pearson Education, Inc.