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Ocean Currents. Ocean water circulates in currents caused by wind and by density differences Currents are the flow of water between areas of different surface levels or different densities. Ocean Currents. Ocean water moves constantly sideways, up, down because it is: Blown by wind - PowerPoint PPT Presentation
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Ocean CurrentsOcean water circulates in currents caused by wind and by density differences
Currents are the flow of water between areas of different surface levels or different densities
Ocean CurrentsOcean water moves constantly sideways, up, down because it is:
Blown by windMoved by density differencesHeated unevenly Evaporated unevenlyAffected by Earth’s rotation (Coriolis)Pulled by sun & moon
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CURRENTSCurrents are important because they:- moderate climates (transfer
heat)- mix nutrients and gases- transport larvae and nektonWarm air from equator flows toward poles, drives air circulation, makes wind, moves waterContinents deflect east-west water movement, but not air
NOAA
NASA
Coriolis EffectWater near ocean surface moves to the right of wind direction in Northern Hemisphere
Water near ocean surface moves to the left of wind direction in Southern Hemisphere
Coriolis EffectCauses currents to move
Clockwise in the Northern Hemisphere
Counterclockwise in the Southern Hemisphere
http://www.youtube.com/watch?v=mcPs_OdQOYU
Surface CurrentsAffect the uppermost 10% of world oceanSome rapid & riverlike, some slow and diffuse
Largest organized into gyres
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The circular patterns of surface water currents are called gyres. The characteristics of a current depend upon where the water is coming from in the gyre.
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Eastern boundary currents are located on the eastern side of the OCEAN - not the continent.
Gulf Stream in red
Florida
East Coast of United States
Western boundary currents are located on the western side of oceans.
Comparison of Boundary CurrentsWestern Eastern
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1. currents bring warm water from the equator
2. high salinity; low oxygen content
3. nutrient poor, infrequent upwelling
4. lower biomass
1. currents bring cold water from the poles
2. low salinity; high oxygen content
3. nutrient rich due to upwelling
4. high biomass
Effect of Surface Currents on ClimateSurface currents distribute heat
worldwideWarm water flows to higher latitudes
transfers heat to the air and coolsMoves back to low latitudesAbsorbs heatRepeats
Vertical MovementUpwelling – upward movement of water
Can be caused by wind blowing parallel to shore or offshore (Coastal Upwelling)
Brings nutrients
Vertical MovementDownwelling – downward movement of water – caused by:
Increase in surface water densityWind blowing parallel to shore or onshore (Coastal Downwelling)
Brings dissolved gases and nutrients to deeper ocean