1. Ocean currents are either
There are more than 20 major currents which move large amounts of water predictably around the oceans.
Currents move large quantities of water, minerals, solar energy, oxygen and carbon dioxide, plankton and fish.
Currents are caused and driven by water
density and salt content, the wind, the
spin of Earth, coastlines and the moon.
Largest current is the Antarctic
Circumpolar Current in the
Southern Ocean, at km long
Ocean currents are either
Surface currents ( m)
Deep water currents (200 m and deeper)
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3. What Makes Surface Currents Move?
Wind
As air warms from solar energy, it rises, and cooler air rushes to replace it. This creates wind.
As the wind passes along the surface of the water, it bumps the water molecules and moves them along in the same direction.
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4. What Makes Surface Currents Move?
Spin of the Earth
Earth spins from West to East (counter clockwise)
The Coriolis effect deflects winds and currents to
the right/East in the Northern hemisphere
(opposite in the Southern hemisphere)
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5. What Makes Surface Currents Move?
Shape of continents
Currents move through the oceans and around
the continents like rocks in a stream.
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6. What Makes Deep Currents Move?
Water temperature
Like air, warm water rises, and cool water falls
Density current = cool, dense water moving on an ocean floor.
Three layers of water dependent on temperature:
Surface: m, warmest
Thermocline: 200 m - 1 km, rapidly cools
Deep water: 1 km and deeper, just above freezing
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7. What Makes Deep Currents Move?
Water salinity
Adding fresh water decreases salinity
Evaporation and freezing increases salinity
Densest ocean waters at the poles
Upwelling occurs when nutrient-rich cold water finally moves up to the surface
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8. Ocean Waves and Their Effect on Shaping Land
Most waves are created by wind.
In open ocean, waves are called swells.
Swells “break” in shallow water, show characteristic curl.
The largest waves are tsunamis, caused by undersea earthquakes, landslides or volcanic eruptions.
Waves erode coastal areas based on the force of the waves, and the composition of the shoreline.
Headlands made up of harder rock, and erode less, but absorb most wave force.
Bays occur between headlands, are generally calm.
Sea stacks are extra-hard rock left behind
from eroded headlands.
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10. Tides are caused by gravities of Earth and the Moon.
High tides occur where the Moon is
closest to Earth (and opposite side)
Low tides occur at 90º to the high tides.
Tidal range (difference between
high and low) averages 3 m in BC.
The Sun’s gravity, when lined up
properly, can produce extreme tides.
These are called spring tides
When the Sun, Moon and Earth are not lined up,
the tides are called neap tides.
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Take the Section 11.2 Quiz
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