Currents

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Currents

• Oceans 11

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Essential Questions

• What are ocean currents?
• What is the purpose / role of ocean currents?
• What is the Coriolis Effect?
• What are thermohaline currents?
• What are the major global gyres?
• What are the major currents affecting Atlantic
  Canada?

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What are ocean currents?
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What is a current?

• A continuous, directed movement of ocean water
  generated by the forces acting upon this mean
  flow, such as
• breaking waves,
• wind,
• Coriolis force,
• Temperature,
• salinity differences, and
• tides caused by the gravitational pull of the
  Moon and the Sun.

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What is a gyre?

• Gyres are any large system of rotating ocean
  currents, particularly those involved with large
  wind movements.
• Gyres are caused by the Coriolis Effect
  planetary vorticity (tendency for elements of
  fluid to spin) along with horizontal and vertical
  friction.

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What is the purpose / role of ocean currents?
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Purpose

• to carry heat from place to place in the Earth
  system
• affects regional climates
• they transport creatures around the world and
  affect the water temperature in ecosystems

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Anomalies of Surface Currents

• Ocean Eddies
• form when a bend in a surface ocean current
  lengthens and eventually makes a loop, which
  separates from the main current.
• the swirling waters last for at least a few
  months
• Warm water eddies are sparse in marine life
  because the water does not have many nutrients
• Cold water eddies are usually full of nutrients
  and marine life.
• Upwelling
• where water from the deep sea travels up to the
  surface
• often happens where wind blows along a coastline
• upwelling areas are full of marine life

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What is the Coriolis Effect?
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Who discovered the Coriolis Effect?

• Gustave-Gaspard Coriolis
• in 1835
• he was a French engineer-mathematician

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Coriolis Effect explained

• The rotation of the Earth causes an interesting
  phenomena on free moving objects on the Earth.
• Objects in the Northern Hemisphere are deflected
  to the right, while objects in the Southern
  Hemisphere are deflected to the left.
• The Coriolis effect, thus tries to force winds to
  shift towards the right or left. The Coriolis
  effect can at times cause winds to blow back up
  the pressure gradient.

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Why does this happen?

• There are two reasons for this phenomenon
• the Earth rotates eastward
• the tangential velocity (speed along a curve) of
  a point on the Earth is a function of latitude
  (the velocity is essentially zero at the poles
  and it attains a maximum value at the Equator)

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What does the Coriolis Effect affect?

• it affects the rotation of the oceanic currents
• it affects prevailing winds and the rotation of
  storms

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What are thermohaline currents?
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How does it work?

• Thermohaline currents are driven by density
  differences in the water
• density depends on its temperature (thermo) and
  salinity (haline)
• At the earth's poles, when water freezes, the
  salt doesn't necessarily freeze with it, so a
  large volume of dense cold, salt water is left
  behind.
• When this dense water sinks to the ocean floor,
  more water moves in to replace it, creating a
  current.

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• This current begins with the cold water near the
  North Pole and heads south between South America
  and Africa toward Antarctica, partly directed by
  the landmasses it encounters.
• In Antarctica, it gets recharged with more cold
  water and then splits in two directions -- one
  section heads to the Indian Ocean and the other
  to the Pacific Ocean.
• As the two sections near the equator, they warm
  up and rise to the surface as an upwelling.
• When they can't go any farther, the two sections
  loop back to the South Atlantic Ocean and finally
  back to the North Atlantic Ocean, where the cycle
  starts again.

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Interesting details

• An underwater current circles the globe with a
  force 16 times as strong as all the world's
  rivers combined
• Moves much more slowly than surface currents -- a
  few centimeters per second, compared to tens or
  hundreds of centimeters per second.

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Purpose

• It is crucial to the base of the world's food
  chain
• transports water around the globe
• enriches carbon dioxide-poor, nutrient-depleted
  surface waters by carrying them through the
  ocean's deeper layers where those elements are
  abundant
• nutrients and carbon dioxide from the bottom
  layers are brought up to the surface
• allows algae and seaweed to grow
• also helps to regulate temperatures.

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The Endless Voyage Series - Deep Connections -

• http//learning.aliant.net/Player/ALC_Player.asp?P
  rogIDINT_ENDVOY08

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What are the major global gyres?
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Major gyres

• North Atlantic Gyre
• South Atlantic Gyre
• Indian Ocean Gyre
• North Pacific Gyre
• South Pacific Gyre

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North Atlantic Gyre

• located in the Atlantic Ocean
• contains the Sargasso Sea
• circulates clockwise
• traps man-made ocean debris in the North Atlantic
  Garbage Patch

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South Atlantic Gyre

• the southern branch of the subtropical gyre in
  the south Atlantic
• circulates counter-clockwise
• this current allows Antarctica to maintain its
  huge ice sheet by keeping warm ocean waters away
• is the largest ocean current

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Indian Ocean Gyre

• is located in the Indian Ocean
• circulates counter-clockwise

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North Pacific Gyre

• located in the northern Pacific Ocean
• comprises most of the northern Pacific Ocean
• circulates clockwise
• is the largest ecosystem on our planet
• an accumulation of man-made marine debris, known
  as the Great Pacific Garbage Patch

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South Pacific Gyre

• located south of the equator between South
  America and Australia
• circulates counter-clockwise
• is the Earth's biggest system of ocean currents
• it is mostly inactive and contains little marine
  life

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What are the major currents affecting Atlantic
Canada?
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The currents of the North Atlantic

• The Gulf Stream
• The North Atlantic Current
• The Irminger Current
• The Labrador Current
• The Greenland Current

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The Gulf Stream

• is a powerful, warm, and swift Atlantic ocean
  current
• it originates at the tip of Florida, and follows
  the eastern coastlines of the United States and
  Newfoundland before crossing the Atlantic Ocean
• The Gulf Stream influences the climate of the
  east coast of North America from Florida to
  Newfoundland, and the west coast of Europe
• is also a significant potential source of
  renewable power generation

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The North Atlantic Current

• is a powerful warm ocean current
• it continues the Gulf Stream northeast.
• West of Ireland it splits in two.
• one branch (the Canary Current) goes south
• the other continues north along the coast of
  northwestern Europe where it has a considerable
  warming influence on the climate.

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The Irminger Current

• is a north Atlantic ocean current setting
  westward off the southwest coast of Iceland

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The Labrador Current

• is a cold current in the North Atlantic Ocean
• it flows from the Arctic Ocean south along the
  coast of Labrador and passes around Newfoundland,
  continuing south along the east coast of Nova
  Scotia
• It meets the warm Gulf Stream at the Grand Banks
  southeast of Newfoundland and again north of the
  Outer Banks of North Carolina. The combination of
  these two currents produces heavy fogs and also
  created one of the richest fishing grounds in the
  world.

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The Greenland Current

• is a weak cold water current that flows to the
  north along the west coast of Greenland