Currents and Waves. Surface Currents Ocean Circulation Patterns –Winds are the primary driving...
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Transcript of Currents and Waves. Surface Currents Ocean Circulation Patterns –Winds are the primary driving...
Currents and Waves
Surface Currents
• Ocean Circulation Patterns– Winds are the primary
driving force– Relationship between
oceanic circulation and atmospheric circulation
Surface Currents
– Coriolis effect• Currents are
deflected due to the Earth’s rotation
• To the right in the Northern Hemisphere
• To the left in the Southern Hemisphere
Surface Currents
• Ocean Currents and Upwelling– Upwelling
• Rising of cold water from deeper layers to replace warmer surface water—vertical movement
• Brings up concentrated nutrients
Surface Currents
• The Importance of Ocean Currents– Affect time to reach a destination– Affect climates—moderate temperatures– Helps maintain Earth’s heat balance
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
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 tide—higher crests and lower troughs
– During 1st and 3rd quarters of the moon
• Neap tide—daily tidal range is less
Tides
• Types of Tides– Semidiurnal
• Twice daily
– Diurnal• Single high and low water height each day
– Mixed• Inequality of tides
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
Tides
– Tidal flats• Areas affected by flood and ebb currents
– Tidal deltas• Deposits created by tidal currents
Waves Modify the Shoreline
• Characteristics of Waves– Crest—top of a wave– Trough—bottom of a wave– Wave height—length
between crest and trough– Wavelength—length
between two crests– Wave period—time
interval between successive crests
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
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
Wave Refraction
• Bending of waves• Affects distribution of
energy• Influences erosion,
sediment transport, and deposition