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1
Weather Circulation

• The ocean and its currents have a major influence
  on weather and climate on Earth.

2
Atmosphere

• Air composed mostly of nitrogen and oxygen
• Never dry always contains water vapor
• Airs density determined by
• Temperature
• Water content
• Weather - The state of the atmosphere at a given
  time and place, with respect to variables such as
  temperature, moisture, wind velocity, and
  barometric pressure.
• Climate - The meteorological conditions,
  including temperature, precipitation, and wind,
  that characteristically prevail in a particular
  region.

3
Greenhouse Effect

• Greenhouse effect - The atmosphere of our Earth
  traps heat
• the energy from the sun also heats up the oceans.
  
• 50 of radiation from the sun is absorbed by the
  Earths surface and then reflected back into the
  earths atmosphere.
• Gases (carbon dioxide and water vapor) can stop
  this energy from escaping into space by keeping
  it here on Earth.

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4
Global Warming

• Scientists have noticed that the Earth is
  experiencing a warming trend.
• In the past 100 years, the Earths mean global
  temperature has increased more than 1 degree
  Farenheit and ocean levels have risen
• Global warming is the result, the gradual
  increase in Earths temperature.
• Scientists measure polar ice caps to determine if
  their rate of melting continues to increase.

5
Measuring the Melt

• The graph below shows total ice coverage since
  1973.
• As glacial ice melts, sea levels rise and ocean
  currents can change.

6

• Average temperatures in the Arctic region are
  rising twice as fast as they are elsewhere in the
  world. Arctic ice is getting thinner, melting and
  rupturing.
• the largest single block of ice in the Arctic,
  the Ward Hunt Ice Shelf, had been around for
  3,000 years before it started cracking in 2000.
  Within two years it had split all the way through
  and is now breaking into pieces.
• The polar ice cap as a whole is shrinking.
• Images from NASA satellites show that the area of
  permanent ice cover is contracting at a rate of 9
  percent each decade.
• If this trend continues, summers in the Arctic
  could become ice-free by the end of the century.
• The melting of once-permanent ice is already
  affecting native people, wildlife and plants.
• When the Ward Hunt Ice Shelf splintered, the rare
  freshwater lake it enclosed, along with its
  unique ecosystem, drained into the ocean.
• Polar bears, whales, walrus and seals are
  changing their feeding and migration patterns,
  making it harder for native people to hunt them.

7
Carbon Dioxide levels

• The amount of carbon dioxide in the atmosphere
  has been steadily increasing.
• As we continue to cut down trees for paper
  production, we are decreasing the plants that
  convert CO2 to oxygen, causing an increase in CO2
  levels.
• The burning of fossil fuels (oil, coal, etc) also
  adds carbon dioxide to the environment.

8
Natural Air Pollution

• Even clean air is not perfectly clean.
• It contains many pollutants from natural sources
  like dust, volcanic gases and ash, smoke from
  forest fires, pollen, etc.
• Most of the air pollution mentioned in the news
  is a result of human activities.

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9
Natural Cycle?

• natural phenomenon - climate has gone through
  periods of warmth and periods of extreme cold
  (often known as an Ice Age).
• Some scientists claim that the warming trend is
  part of a natural cycle that will eventually
  reverse itself through CO2 uptake by
  photosynthetic marine and terrestrial plant life.
  
• Others claim that the warming of Earths
  atmosphere is a real problem that can be reduced
  by decreasing the use of fossil fuels and finding
  alternative energy sources.

10
Currents

• Ocean currents - moving water connecting major
  landmasses on Earth
• global ocean currents largest currents that
  move across the ocean (like rivers that travel
  great distances)
• affected by
• global temperature
• freshwater glacial ice melt
• density differences due to salt concentrations
  and temperature differences.

11
Waters Density

• Density is important to the currents which shape
  the planets climate.
• Fresh water is less dense than salty water.
• Warm water has a lower density than cold water

12
Effect of Salinity

• Salty water will sink while fresh water will rise
  because of differences in density.

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13
In the Mediterranean

• The Mediterranean Sea, for example, has a higher
  salinity than the Atlantic Ocean, creating a
  current south of Spain that moves salty water
  deep into the Atlantic Ocean.

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14
Global Ocean Currents
15
Radiant Energy

• The sun, the source of all energy on Earth, gives
  off radiant energy and influences the climate
  that we experience.
• Angle of Isolation - the angle at which the rays
  of the sun strike the surface of the earth.
• Determines the amount of radiant (or solar)
  energy that reaches any part of the planet
• Areas farthest away from the suns rays (the
  poles) receive slanted rays with a larger angle,
  and are therefore less intense
• Caused by
• The Earths curved surface
• the tilt of its axis

16
Ocean Temperature

• The uneven heating of the Earth due to the rays
  of the sun causes ocean temperatures to vary with
  latitude.
• The ocean is warmest at the equator.

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Coriolis Effect

• The coriolis effect - the spinning Earth causes
  the winds and surface waters to move in a
  specific directions.

• northern hemisphere - the currents deflect
  clockwise to the east.
• southern hemisphere - currents move in the
  opposite direction, counter clockwise to the
  west.

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Gyres

• Gyres - giant circles created when the water
  moves and hits the continent which deflect the
  currents

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19
Gulf Stream

• The gulf stream current flows from the
  southwestern Atlantic to the northeastern
• it is the major factor in favorable (warm)
  weather on the eastern coast of the United
  States.
• Benjamin Franklin was the first to chart the
  temperature and speed of the gulf stream back in
  the 1700s.

20
Subsurface Currents

• Subsurface currents - move because of differences
  in temperature and salinity.

21
Downwelling Upwelling

• Downwelling - After warm water has risen to the
  surface, it will eventually cool off and
  therefore sink again near the poles
• Upwelling - When currents rise to the surface,
  they bring nutrient-rich sediments from the
  bottom.
• Nutrients found on the floor of the ocean (such
  as phosphates nitrates) are important for all
  organisms in aquatic food webs.

22
Coastal Currents

• Waves when currents eventually meet coastal
  areas
• After a wave breaks on a beach, the forward
  momentum transports water up the slope of a
  beach.
• The returning current or backwash is called the
  undertow.
• Currents that move parallel to the beach are
  called longshore currents.
• Spaces between islands off the coast of a
  continent, like Galveston and South Padre, cause
  a rush of water called a rip current that moves
  quickly out into the ocean.

23
Tidal Currents
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• The movement of the moon around the Earth and
  its gravity causes tides
• the daily rise and fall of the ocean seen along
  the shore.
• When a tide enters and leaves and area, the tidal
  change produces swift-moving tidal currents that
  run parallel to the shore.
• important to aquatic food chains because they
  carry nutrients and small organisms back and
  forth between the bays and the offshore waters.

24
Ocean Wind

• Convection currents occur in many different media
  (liquid, air, magma).
• Day Time
• Often, the wind around the ocean creates a sea
  breeze
• due to differences in temperature of the air over
  the ocean versus over land.
• Water heats up slowly, while land heats up
  quickly.
• A convection current is created because the
  cooler air over the ocean sinks and travels
  inland while the warm air over the land rises up.
  
• Night Time
• The opposite occurs
• land cools very quickly, but water has a very
  high specific heat and takes longer to cool.
• The air over the water is warmer and wind travels
  out to the ocean in the reversed convection
  current.

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Humidity

• Humidity- amount of water vapor into the
  atmosphere
• Coastal regions often have a higher level of
  humidity than inland areas because they are
  exposed to the moisture that evaporates from the
  ocean.

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Fog Dew

• Fog - Air saturated with moisture creating clouds
  near the ground
• forms when warm, moist air makes contact with a
  cold surface.
• The mirror in your bathroom often fogs when
  warm moist air from the shower hits the cold
  surface of the mirror.
• Dew - When water condenses (changes from a vapor
  to a liquid) on a solid surface

27
Hurricanes

• A hurricane -a coastal storm with a wind velocity
  exceeding 120 km/hr
• Form in warm tropical seas where there is hot,
  moist air
• As hot, moist air rises, it cools in the upper
  atmosphere and condenses into ring shaped clouds.
  
• During condensation, a great deal of heat energy
  is released, which causes more hot air to rise
  even quicker.
• This whirlwind of rising air moves in a spiral
  direction around calm air knows as the eye of a
  hurricane.

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El Nino

• El Nino - Oceanic warming
• Begins in the western Pacific Ocean
• Warm currents are normally carried northwest due
  to trade winds.
• El Nino reverses the currents because of a
  decline in southeast trade winds
• causes a change in the climate of South America
  (bringing floods and stormy weather).

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La Nina

• La Nina - Unusually cold currents causing cooler
  surface temperatures
• winters are cooler than normal in the northwest
  United states and warmer than normal in the
  southeast.
• The cycles for El Nino/La Nina often last 1 to 2
  years and occur every 4 to 6 years.
• Click on the graphic to view an animation
  depicting the differences between El Nino and La
  Nina.