Ocean Currents

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Ocean Currents

• the motion of water

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Can you think of some currents you have
experienced?
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Can you think of some currents you have
experienced?
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Factors that affect currents

• Tides (near coasts, bays, and estuaries)
• Wind
• Thermohaline circulation

Thermo heat density differences Haline -
salinity
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Surface Ocean Current

• Coastal currents
• Driven by local winds
• Open ocean
• Driven by global wind systems

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Coriolis Effect

• Due to spinning of the earth
• Air deflected
• Right in northern hemisphere
• Left in southern hemisphere
• Result curved paths

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Trade Winds

• Northern Hemisphere
• Warm air moves away from equator
• Deflected right
• About 30 North, some cools and decends
• Cooled air blows northeast to southwest (back
  toward equator)
• Southern Hemisphere same in reverse (southeast
  to northwest)

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Doldrums

• Cooled air masses meet again around 5 North and
  South
• Cancel each other out
• Result calm winds

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Westerlies

• Winds that did not cool and return to the
  equator, continue on to the poles

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Result of the Winds

• Winds drag on waters surface
• Push water in direction wind is blowing
• Coriolis effect occurs on water just as it does
  on wind
• Gyres major spirals of ocean-circling current
• No circling at the equator
• 5 major ocean-wide gyres North Atlantic, South
  Atlantic, North Pacific, South Pacific, Indian
  Ocean

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Ekman Spiral

• Wind effect decreases with depth
• Lower layers move more slowly
• Ekman layer upper part of water column affected
  by the wind
• Ekman layer moves 90 from direction of the wind

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Thermohaline Currents

• The Global Conveyor Belt

What do you think happens to water in the North
Atlantic near the pole?
Coolsfreezesice forms
Saltier because salt does not freeze
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Thermohaline Currents

• What happens to colder, denser water?

It sinks!
Surface water moves in to replace it, creates a
current.
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Thermohaline Currents

• The Global Conveyor Belt

What do you think happens to water at the poles?
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Thermohaline Current

• Much slower than surface currents.
• Estimate 1 particle of water would take 1,000
  years to completely circle the earth on the
  Global Conveyor Belt
• Illustrates the importance of One World Ocean