gulf stream, enso, climate, and up and downwelling
TRANSCRIPT
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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
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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
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El Nino – Southern Oscillation (ENSO)High pressure in
eastern Pacific weakens
Weaker trade windsWarm pool migrates
eastwardThermocline deeper in
eastern PacificDownwellingLower biological
productivityPeruvian fishing
suffers
Downwelling
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ENSO Conditions in the Pacific Ocean
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La Nina – ENSO Cool PhaseIncreased pressure
difference across equatorial Pacific
Stronger trade winds
Stronger upwelling in eastern Pacific
Shallower thermocline
Cooler than normal seawater
Higher biological productivity
Stronger upwelling
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La Nina Conditions
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Occurrence of ENSO EventsEl Niño warm phase about every
2–10 yearsHighly irregularPhases usually last 12–18 months10,000-year sediment record of eventsENSO may be part of Pacific Decadal
Oscillation (PDO) Long-term natural climate cycleLasts 20–30 years
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ENSO Occurrences
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ENSO has Global Impacts
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Notable ENSO Events1982 – 19831997 – 1998 Flooding,
drought, erosion, fires,tropical storms, harmful effects on marine life
Unpredictable
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Predicting El Nino Events Tropical Ocean−Global Atmosphere (TOGA)
program1985Monitors equatorial South PacificSystem of buoys
Tropical Atmosphere and Ocean (TOA) projectContinues monitoring
ENSO still not fully understood
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Ocean Currents and ClimateWarm ocean currents
warm the air at the coast.Warm, humid airHumid climate on
adjoining landmassCool ocean currents
cool the air at the coast.Cool, dry airDry climate on
adjoining landmass
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Upwelling and DownwellingUpwelling – Vertical
movement of cold, nutrient-rich water to surfaceHigh biological
productivity
Downwelling – Vertical movement of surface water downward in water column
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Coastal UpwellingEkman transport
moves surface seawater offshore.
Cool, nutrient-rich deep water comes up to replace displaced surface waters.
Example: U.S. West Coast
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Other Types of UpwellingOffshore windsSeafloor
obstruction Coastal geometry
change
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Coastal DownwellingEkman transport
moves surface seawater toward shore.
Water piles up, moves downward in water column
Lack of marine life