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

Surface Currents

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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