Ocean Currents

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Ocean Currents

• Chapter 5
• Notes

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Ocean Currents

• Movement of ocean water that follows a regular
  pattern

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First Explorer

• 1940 Thor Heyerdahl theorized that humans
  migrated across oceans using currents
• 1947 he left Peru in a sail boat sailed for 97
  days until he reached the island of Polynesia.

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Surface Currents

• Horizontal movement caused by winds near the
  oceans surface
• Two examples Gulf Stream and Brazil Current
• Three Factors global winds, Coriolis effect,
  continental deflections

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Global Winds

• Winds cause the currents to flow in different
  directions
• Equator east to west
• Poles west to east

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Coriolis Effect

• Curving of moving objects from a straight path
  due to Earths rotation
• Northern hemisphere- clockwise
• Southern hemisphere-counterclockwise

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Continental Deflections

• Currents change directions by hitting the
  continents or landmasses

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Deep Currents

• A stream like movement of ocean water far below
  the surface
• Form where water density increases
• Decreasing water temperature and increasing water
  salinity increase density.
• Examples North Atlantic Deep Water and Antarctic
  Bottom Water

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Deep Currents can form by

• Decreasing temperature
• Increasing salinity through freezing
• Increasing salinity through evaporation

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Currents and Climates

• Surface currents gently cool or warm the coastal
  areas year round
• Some surface currents change their circulation
  pattern causing changes in the atmosphere that
  affect the climate in many parts of the world.

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Warm Water Currents and Climates
Warm water currents create warmer climates in
coastal areas.
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Cold Water Currents and Climates
Cold water current bring cooler climates into
areas.
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Upwelling

• An upwelling is the movement of deep, cold, and
  nutrient rich water to the surface of the ocean
• This is important for organisms. Allows for the
  plankton and zooplankton to feed fish and other
  organisms.

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El Nino

• El Nino a change in the water temperature in the
  Pacific Ocean that produces a warm current
• Occurs ever 2-12 years
• Can last a year or longer

• La Nina A change in the eastern Pacific Ocean
  in which the surface water temperature becomes
  usually cool
• Usually follows El Nino

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Effects of El Nino

• Flash floods
• Mudslides in the United States and Peru
• Droughts in Indonesia and Australia
• Lack of upwelling off the coast of South America

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El Nino
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Wave

• Parts of a Wave

• Picture of a wave

• Trough lowest point on a wave
• Crest highest point on a wave
• Wavelength distance between two crests
• Wave height the vertical distance between the
  crest and the trough

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Types of Waves

• Wind forms MOST ocean waves
• Waves can move in one direction and can generate
  many different events that can be dangerous to
  humans.

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Deep water waves and Shallow water waves

• Deep water waves are waves that move in water
  deeper than one-half their wavelength.
• As these waves turn into shallow water waves the
  waves start to interact with the ocean floor.

This interaction allows the wave to increase in
height. Eventually gravity will pull the crests
downward at the Breaker zone. Waves continue
to break until they reach the surf or beach.
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Shore Currents

• Undertow when waves crash on the beach head on,
  the water flows back to the ocean underneath new
  incoming waves

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Long shore Currents

• Waves that hit the shore at an angle cause the
  water to move along the shore in a current that
  is near and parallel to the shoreline
• Down side spreads trash and erodes the sand.

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Open Ocean Waves

• Whitecaps Bubbles in the crests of breaking
  waves
• Form during storms
• Very short lived

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Open Ocean Waves

• Swells Rolling waves that move steadily across
  the ocean
• Have longer wavelengths
• Travel for thousands of kilometers

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Tsunamis

• Waves that form when a large volume of ocean
  water is suddenly moved up or down
• Causes Underwater Earthquakes, Volcanic
  Eruptions, landslides, underwater explosions,

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Tsunamis
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Storm Surges

• A local rise in sea level near the shore that is
  caused by strong winds from a storm
• Contain a lot of energy
• Follow a hurricane
• Can be 8 m in height