Currents and Waves

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Currents and Waves
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Surface Currents

• Ocean Circulation Patterns
• Winds are the primary driving force
• Relationship between oceanic circulation and
  atmospheric circulation

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Surface Currents

• Coriolis effect
• Currents are deflected due to the Earths
  rotation
• To the right in the Northern Hemisphere
• To the left in the Southern Hemisphere

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Surface Currents

• Ocean Currents and Upwelling
• Upwelling
• Rising of cold water from deeper layers to
  replace warmer surface watervertical movement
• Brings up concentrated nutrients

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Surface Currents

• The Importance of Ocean Currents
• Affect time to reach a destination
• Affect climatesmoderate temperatures
• Helps maintain Earths heat balance

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Deep-Ocean Circulation

• Gravity and density differences
• Temperature and salinity create a dense mass of
  water
• Thermohaline circulation
• Water is made colder and saltier at the surface,
  becomes more dense, and sinks
• Arctic and Antarctic mainly affected

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Tides

• Causes
• Gravity
• Bulge toward and away from the moon
• Two high tides and two low tides per day
• During new and full moons, moon and sun affect
  tides
• Spring tidehigher crests and lower troughs
• During 1st and 3rd quarters of the moon
• Neap tidedaily tidal range is less

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Tides

• Types of Tides
• Semidiurnal
• Twice daily
• Diurnal
• Single high and low water height each day
• Mixed
• Inequality of tides

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Tides

• Tidal Currents
• Horizontal flow of water accompanying the rise
  and fall of the tide
• Flood currents
• Advance into the coastal zone as the tide rises
• Ebb currents
• Water retreats during low tide
• Slack water
• Between flood and ebb

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Tides

• Tidal flats
• Areas affected by flood and ebb currents
• Tidal deltas
• Deposits created by tidal currents

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Waves Modify the Shoreline

• Characteristics of Waves
• Cresttop of a wave
• Troughbottom of a wave
• Wave heightlength between crest and trough
• Wavelengthlength between two crests
• Wave periodtime interval between successive
  crests

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Waves Modify the Shoreline

• Types of Waves
• Energy
• Move through the nearly stationary medium of the
  water
• Oscillation
• Waves in the open sea
• Translation
• Water advances up the shore because of a break

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Wave Erosion

• Pressure from waves can exceed 2000 lb/ft2
• Causes air in cracks to compress and then expand
  as the wave recedes
• Abrasion
• Sawing and grinding of water with rock fragments

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Wave Refraction

• Bending of waves
• Affects distribution of energy
• Influences erosion, sediment transport, and
  deposition