Physical Oceanography

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Chapter 15

• Physical Oceanography

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Chapter 15

• Section 15.1
• The Oceans

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Section 15.1 Learning Goal

• I will.
• Identify methods scientists use to study Earths
  oceans.
• Discuss the origin and composition of the oceans.
• Describe oceans and major seas.

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• Oceanography- The scientific study of the Earths
  oceans.

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Background Brief History of Oceanography

• The ancient Egyptians were the first to build
  seafaring ships, around 4000 b.c.
• Oceans were used for travel, recreation and to
  obtain food.

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Oceans

• 71 of Earths surface covered by oceans
• vast bodies of water affect
• Weather
• Climate
• Food supplies
• Recreation
• Global trade
• And marine life (such as humpback whales)

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British Challenger (first research ship)

• In the late 1800s, Challenger used measuring
  devices to investigate
• ocean currents
• water temperature
• chemical composition
• seafloor sediments
• topography

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SONAR

• German ship Meteor 1920s used sonar for first
  time
• Sound Navigation and Ranging
• Uses the return time of an echo and the known
  velocity of sound in water to determine water
  depth.
• Velocity of sound in water is 1500m/s
• Velocity of sound in air is 334m/s
• Calculation
• Ocean depth sonar signal and time it returns or
  echo
• Distance to the ocean floortime x 1500m/s
  divided by 2.

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ADVANCED TECHNOLOGY

• Satellites (Topex/Poseidon) monitor oceans
  surface temperature
• Submersibles (underwater vessels) investigates
  deep trenches
• Side-scan sonar (for mapping)- directs sound
  waves to the seafloor at an angle

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ORIGIN OF THE OCEANSWere did the water come from?

• Earth is about 4.6 billion years old.
• Scientists hypothesize that Earths water could
  have originated from 2 sources
• Comets- (dust, rock particles mixed with frozen
  water and gases)
• Gases-water vapor, methane, ammonia
• Volcanoes-(water vapor, carbon dioxide and other
  gasses)

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DISTRIBUTION OF EARTHS WATER

• 97 Oceans (salt water)
• 3 Fresh water (frozen ice caps, rivers, lakes,
  underground sources)
• Sea Level- is the level of the oceans surface.
• Affected by
• Melting of ice caps
• Tectonic forces
• Trivia avg. global sea level rising 1 -2mm/yr
  due to melting glaciers

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THE BLUE PLANET - Earth

• 71 of the surface is covered with oceans.
• Avg. depth is 3800m
• All the oceans are interconnected, continents act
  as huge islands.
• There are 5 oceans
• Pacific Ocean contains ½ Earths seawater
• Atlantic Ocean extends 20,000km
• Indian Ocean located mainly in southern
  hemisphere
• Antarctic Ocean covered by sea ice
• Arctic Ocean covered by sea ice

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SEAS

• Smaller than oceans
• Mostly landlocked
• Exp
• Aral Sea
• Mediterranean Sea first sea to be mapped by
  Egyptians, Phoenicians, Greeks, Romans
• Gulf of Mexico
• Caribbean Sea
• Bering Sea

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MISCONCEPTIONS

• We can usually see through the water in a glass,
  sink, bucket, or bathtub.
• Thus, many people have the impression that water
  is transparent.
• In reality, however, all water absorbs light.

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Misconceptions

• In fact, a layer of ocean water 100m thick
  absorbs more than 99 percent of light.
• This means that the oceans are essentially dark
  below a depth of 100m.

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Video- Discovering the seas

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