Currents and Climate

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Currents and Climate
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Currents

• A current is a large stream of moving water that
  flows through the oceans.
• Currents carry water great distances and some
  currents move water at the surface of the ocean,
  while others move the deep water.
• Currents move the Suns energy from the equator
  to the poles.
• They also move cold water from the poles towards
  the equator.
• This moderates the climate of our planet.

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One Way to Explore Currents

• Norwegian explorer Thor Heyerdahl proved his
  theory that ocean currents influenced human
  migration by using a raft that was powered only
  by wind and ocean currents.
• He showed that Polynesia could have been settled
  from people migrating from South America.

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Surface Currents

• The wind mainly drives surface currents, which
  affects water to the depth of several hundred
  meters.
• If Earth were not rotating, winds and currents
  would only flow in straight lines to the north
  and south poles.
• This Coriolis effect causes the winds to curve.

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Coriolis Effect

• The Earths rotation causes the winds and
  currents to curve in relation to Earths surface.
• In the northern hemisphere the Coriolis effect
  causes the currents to curve to the left.

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The Gulf Stream

• The largest and most powerful surface current is
  the Gulf Stream in the North Atlantic Ocean.
• It is caused by strong winds from the west.
• The Gulf Stream carries warm water from the Gulf
  of Mexico to the Caribbean Sea, then northward
  along the coast of the United States.
• This current keeps Northern Europe much warmer in
  the winter than it would otherwise be.

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Ocean Current Map
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How Surface Currents Affect Climate

• Climate is a pattern of temperature and
  precipitation, typical for an area over a long
  period of time.
• Currents affect the climate by moving cold and
  warm water around the globe.
• A surface current warms or cools the air above
  it, affecting the climate of the land near the
  coast.

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Deep Currents

• Streamlike movements of ocean water located far
  below the surface are called deep currents. Deep
  currents are not controlled by wind.
• Deep currents form in parts of the ocean where
  water density increases. The density of the ocean
  is affected by temperature and salinity.

Deep currents are caused by changes in density.
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Deep Currents, continued

• Formation and Movement of Deep Currents
  Differences in water density cause variations in
  the movement of deep currents.

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Surface Currents and Climate

• Warm-Water Currents and Climate Warm-water
  currents create warmer climates in coastal areas
  that would otherwise be much cooler.

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Surface Currents and Climate, continued

• Cold-Water Currents and Climate Cold-water
  currents keep climates along a coast cooler than
  the inland climate year-round.

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Surface Currents and Climate, continued

• Upwelling is the movement of deep, cold, and
  nutrient-rich water to the surface of the ocean.
• The nutrients that are brought to the surface
  support the growth of plankton. Plankton support
  larger organisms, such as fish and seabirds.
• Upwelling is shown on the next slide.

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El Nino

• El Nino is an abnormal climate event that occurs
  every two to seven years in the Pacific Ocean.
• It begins when an unusual pattern of winds form
  over the western Pacific.
• This causes fast sheets of warm water to move
  eastward to the south American coast.
• It can last one to two years.

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El Ninocontinued

• Effects of El Niño
• El Niño alters weather patterns enough to cause
  disasters, including flash floods, mudslides, and
  droughts. El Niño also prevents upwelling off the
  coast of South America.

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El Nino Impact (Western Coast of South America)

• El Nino can have disastrous consequences.
• Warm surface water prevents upwelling off of the
  western coast of South America.
• Without nutrients brought up by upwelling, fish
  die or go somewhere else to find food.
• Sea birds have no fish to eat, and also must
  leave the area or die.

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El Nino (On Land)

• El Nino causes shifts in weather patterns around
  the world, bringing severe conditions to
  different areas.
• El Nino caused an unusually warm winter in
  northeastern U.S.
• It also brought heavy rains, flooding, and mud
  slides in California.
• It also brought a string of deadly tornadoes in
  Florida.

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Surface Currents and Climate, continued

• Studying and Predicting El Niño Learning as
  much as possible about El Niño is important
  because of its effects on organisms and land.
• To study El Niño, scientist use a network of
  buoys located along the equator. The buoys
  collect data about surface temperature, air
  temperature, currents, and wind.

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Forecasting El Nino

• Scientist dont fully understand the conditions
  that create El Nino
• They can predict its occurrence by using computer
  models of the world climate
• Knowing when El Nino will strike, officials will
  give notice and can plan for unusual weather
  patterns.

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El Nino (2006 hurricane season)

• Why hasnt there been many hurricanes in the 2006
  hurricane season?
• The seasonal activity was lower than expected
  because of the rapid development of El Nino.
• This year there were only 9 named storms, 5
  became hurricanes, and 2 became major hurricanes
  in Category 3 or higher.
• 2005 was the most active season on record, with
  28 named storms, of which 15 became hurricanes.
• Five of the seven major storms hit the US,
  including Katrina.