The Dynamic Ocean

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Lecture 15 The Dynamic Ocean
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• Outline

(1.) Ocean Currents
(2.) Ocean Waves
(3.) Wave Erosion
(4.) Coastal Features
(5.) Tides
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• Outline

(1.) Ocean Currents
(2.) Ocean Waves
(3.) Wave Erosion
(4.) Coastal Features
(5.) Tides
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Ocean Currents

• Ocean Surface Currents
• Ocean surface water that flows from one place to
  another
• Develop from friction between ocean water and
  the wind that blows across the surface

Wind
Surface Current
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Ocean Currents

• Gyres
• Large circular surface current patterns found in
  the oceans

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Ocean Currents
Map of Ocean Surface Currents
Warm Surface Current
Cold Surface Current
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Ocean Currents
Map of Ocean Surface Currents
Main Gyres
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Ocean Currents

• Deep-Ocean Circulation
• Movement of ocean water caused by density
  differences due to variations in water
  temperature and salinity
• Cold and/or high salinity water is denser so it
  sinks, which creates ocean circulation

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Ocean Currents
Map of Deep-Ocean Circulation
Warm Surface Flow
Cool Subsurface Flow
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• Outline

(1.) Ocean Currents
(2.) Ocean Waves
(3.) Wave Erosion
(4.) Coastal Features
(5.) Tides
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Wave Terminology
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Wave Terminology

• Wave Crests
• Tops of the waves

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Wave Terminology

• Wave Troughs
• Low points of the waves

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Wave Terminology

• Wave Height
• Vertical distance between between trough and
  crest of a wave

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Wave Terminology

• Wavelength
• Horizontal distance between crest and crest

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Wave Motion
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Wave Motion

• Circular Orbital Motion
• As a water wave travels, it passes along the
  energy of the wave by moving water in a circle

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Wave Motion

• Note that water particles only move in small
  circles they do not travel with the wave
• Wave energy is what is actually traveling

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Breaking Waves on Shore
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Breaking Waves on Shore
Deep Water Waves (i.) constant wave speed(ii.)
constant wavelength (iii.) constant wave height
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Breaking Waves on Shore
Waves Approaching Shore (i.) waves slow
down(ii.) wavelength decreases (iii.) wave
height increases
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Breaking Waves on Shore
Waves at Shore (i.) waves slow down(ii.)
wavelength decreases (iii.) wave height collapses
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Wave Refraction
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Wave Refraction

• Wave Refraction
• The process where the portion of a wave in
  shallow water slows, causing the wave to bend
• Tends to align waves with the contours of the
  shore line

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Wave Refraction
Wave refraction causes waves to violently
converge on headlands (land that sticks out into
the ocean)
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Wave Refraction
Wave refraction causes waves to gently
diverge in bays
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• Outline

(1.) Ocean Currents
(2.) Ocean Waves
(3.) Wave Erosion
(4.) Coastal Features
(5.) Tides
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Wave Erosion

• Abrasion
• The grinding and scraping of a rock surface by
  the friction and impact of rock particles carried
  by water, wind, or ice

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Wave Erosion

• Impact Erosion
• Rock erosion due to waves
• compressing water into rock cracks, which causes
  the cracks to grow larger until the rock breaks

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• Outline

(1.) Ocean Currents
(2.) Ocean Waves
(3.) Wave Erosion
(4.) Coastal Features
(5.) Tides
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Coastal Features (a.) Beach (b.) Wave-cut
Cliff (c.) Wave-cut Platform (d.) Marine
Terrace (e.) Headland (f.) Sea Arch (g.) Sea
Stack

• Beach
• An accumulation of sediment found along the
  landward margin of an ocean or lake

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Coastal Features (a.) Beach (b.) Wave-cut
Cliff (c.) Wave-cut Platform (d.) Marine
Terrace (e.) Headland (f.) Sea Arch (g.) Sea
Stack

• Wave-cut cliff
• A seaward facing cliff along a steep shoreline
  formed by wave erosion at its base and mass
  wasting

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Coastal Features (a.) Beach (b.) Wave-cut
Cliff (c.) Wave-cut Platform (d.) Marine
Terrace (e.) Headland (f.) Sea Arch (g.) Sea
Stack

• Wave-cut Platform
• A bench or shelf in the bedrock at sea level,
  cut by wave erosion

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Coastal Features (a.) Beach (b.) Wave-cut
Cliff (c.) Wave-cut Platform (d.) Marine
Terrace (e.) Headland (f.) Sea Arch (g.) Sea
Stack

• Marine Terrace
• A wave-cut platform that has been exposed above
  sea level

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Coastal Features (a.) Beach (b.) Wave-cut
Cliff (c.) Wave-cut Platform (d.) Marine
Terrace (e.) Headland (f.) Sea Arch (g.) Sea
Stack

• Headland
• A high, narrow strip of land that extends out
  into the ocean

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Coastal Features (a.) Beach (b.) Wave-cut
Cliff (c.) Wave-cut Platform (d.) Marine
Terrace (e.) Headland (f.) Sea Arch (g.) Sea
Stack

• Sea Arch
• An arch formed by wave erosion of a headland

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Coastal Features (a.) Beach (b.) Wave-cut
Cliff (c.) Wave-cut Platform (d.) Marine
Terrace (e.) Headland (f.) Sea Arch (g.) Sea
Stack

• Sea Stack
• An isolated mass of rock standing just offshore,
  produced by wave erosion of a headland

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• Outline

(1.) Ocean Currents
(2.) Ocean Waves
(3.) Wave Erosion
(4.) Coastal Features
(5.) Tides
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Tides

• The Moon gravitationally stretches the Earth and
  its Oceans to create Tides

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Tides

• The Moon gravitationally stretches the Earth and
  its Oceans to create Tides

( Actual change in ocean height is only about 2
meters )
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Tides