The Dynamic Ocean
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Surface Circulation
 Surface Currents
 movements of water that flow horizontally near the
surface
 develop from friction between the ocean and the wind
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Surface Circulation
 Gyres
 huge circular-moving current
systems that dominate the
surfaces of the oceans.
 Coriolis effect
 deflection of currents away
from their original course as a
result of Earth’s rotation
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Ocean Currents and Climate
 Currents from low-latitude
regions moving into higher
latitudes transfer heat from
warmer to cooler areas
 Upwelling
 rise of cold water from deeper
layers to replace warmer
surface water
 brings greater concentrations
of dissolved nutrients to the
surface
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Deep Ocean Circulation
 Density currents
 Vertical currents of ocean water that result from
density differences among water masses
 Increases in seawater density can be caused by a
decrease in temperature or an increase in salinity
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Conveyor Belt Model
 Ocean circulation is similar to a conveyor belt that
travels from the Atlantic Ocean, through the Indian
and Pacific Oceans, and back again.
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Waves
 Most ocean waves obtain their energy and motion from
the wind.
 wave height - vertical distance between the trough and crest.
 Wavelength - horizontal distance between two successive crests
or two successive troughs.
 wave period - time it takes one full wave to pass a fixed position.
 Fetch - distance that the wind has traveled across open water.
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Tides
 Daily changes in the elevation of the ocean
surface
 Result from the gravitational attraction exerted
upon Earth by the moon
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Tides
 Tidal range - difference in height between
successive high and low tides
 Spring tides - have the greatest tidal range due to
the alignment of the Earth–moon–sun system
 Neap tides - have the lowest tidal range, occurring
near the times of the first-quarter and third-quarter
phases of the moon.
9
Forces Acting On The Shoreline
 Waves along the shoreline are constantly
eroding, transporting, and depositing sediment.
 Wave Impact
 Abrasion - the sawing and grinding action of rock
fragments in the water
 Wave Refraction - the bending of waves
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Forces Acting On the Shoreline
 Wave Refraction
 Because of refraction, wave energy is concentrated against the
sides and ends of headlands that project into the water, whereas
wave action is weakened in bays.
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Forces Acting On The Shoreline
 Longshore Current - a near-shore current that flows
parallel to the shore
 Turbulence allows longshore currents to easily move fine
suspended sand and to roll larger sand and gravel particles along
the bottom.
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