background image ocean currents & climate the ocean and its currents have a major influence on...
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Ocean Currents & ClimateOcean Currents & Climate
•The ocean and its currents have a major influence on weather and climate on Earth.•In this unit we will see how interactions among the hydrosphere, lithosphere, atmosphere, and the ocean produce weather and climate changes. •On the following slides, the green sections are the most important.Underline words = vocabulary!
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Global Warming Pre-TestGlobal Warming Pre-Test
• Last week you took a global warming pre-test to test your prior knowledge on the subject of global warming.
• Let’s review your scores!
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CurrentsCurrents
• The major landmasses on Earth are connected by moving water called ocean currents.
• A current is a large mass of continuously moving ocean water.
• The largest currents that move across the ocean are called global ocean currents. These currents are like rivers that travel great distances.
• Ocean currents are affected by global temperature, freshwater glacial ice melt, and density differences due to salt concentrations and temperature differences.
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Greenhouse EffectGreenhouse Effect• The atmosphere of our Earth acts
like a greenhouse that traps heat; the energy from the sun also heats up the oceans.
• 50% of radiation from the sun is absorbed by the Earth’s surface and then “bounces” back into the earth’s atmosphere.
• Gases, such as carbon dioxide and water vapor, can stop this energy from escaping into space by keeping it here on Earth.
• As a result, the Earth’s atmosphere stays warm, this is termed the greenhouse effect. Image
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Global WarmingGlobal Warming
• Scientists have noticed that the Earth is experiencing a warming trend.
• In the past 100 years, the Earth’s mean global temperature has increased more than 1 degree Celsius and ocean levels have risen approximately 10 cm.
• Global warming is the result, the gradual increase in Earth’s temperature.
• Scientists are trying to measure polar ice caps to determine if their rate of melting continues to increase.
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Measuring the MeltMeasuring the Melt• Scientists around the world provide research
based data on the effects of increased global temperatures.
• Specific data includes measuring the levels of artic ice.
• The graph below shows total ice coverage since 1973.
• As glacial ice melts, sea levels rise and ocean currents can change.
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Carbon Dioxide levelsCarbon 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.
• Air pollution produces by humans is adding to the problem of global warming.
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Natural Air PollutionNatural 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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Natural Cycle?Natural Cycle?
• Throughout the history of Earth the climate has gone through periods of warmth and periods of extreme cold (often known as an Ice Age). This is a natural phenomenon.
• 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 Earth’s atmosphere is a real problem that can be reduced by decreasing the use of fossil fuels and finding alternative energy sources.
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Water’s DensityWater’s Density• Density is the process by which molecules are
packed closely together. • Warm water has a higher density than cold water
due to the increased kinetic energy of the molecules (they are moving fast, creating more pace – thus, they rise).
• Fresh water is less dense than salty water.
• Density is important to the currents which shape the planet’s climate.
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• Salinity, or the amount of salt within a solution, changes the density of the water.
• Salty water will sink while fresh water will rise because of differences in density.
Effect of SalinityEffect of Salinity
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In the MediterraneanIn 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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Global Ocean CurrentsGlobal Ocean Currents
• Observe the Image of the major global currents.
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Radiant EnergyRadiant Energy• The sun, the
source of all energy on Earth, gives off radiant energy and influences the climate that we experience.
• The amount of radiant (or solar) energy that reaches any part of the planet depends on the angle at which the rays of the sun strike the surface. (Angle of Isolation)
• The Earth’s curved surface and the tilt of its axis causes areas farthest away from the sun’s rays (the poles) to receive slanted rays with a smaller angle, and are therefore less intense.
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Ocean TemperatureOcean 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 EffectCoriolis Effect
• The coriolis effect states that the spinning Earth causes the winds and surface waters to move in a specific directions.
• In the northern hemisphere, the currents deflect clockwise to the east.
• In the southern hemisphere currents move in the opposite direction, counter clockwise to the west.
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GyresGyres• The water moves and hits the continent which
deflect the currents, causing them to move in giant circles called gyres.
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Gulf StreamGulf 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.
• You can see that the gulf stream flows northeast up the coast of the United States. The satellite image shows it carries with it very warm water.
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HurricanesHurricanes• A hurricane is a coastal
storm with a wind velocity exceeding 120 km per hour.
• Hurricanes form in warm tropical seas where there is hot, moist air. Such conditions contain the heat needed to fuel a hurricane.
• 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.
• View the animation from NASA by clicking the graphic.
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El NinoEl Nino• Droughts in Australia,
famine in Africa, floods in California, and other climate disturbances in recent years have all been caused by changes in the warm ocean currents around the globe.
• Oceanic warming is called El Nino.
• El Nino 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 and causes a change in the climate of South America (bringing floods and stormy weather).
• Follow the arrows in the image above.
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La NinaLa Nina• Unusually cold currents causing cooler surface
temperatures is known as La Nina. • During La Nina years (when ocean currents are unusually
cool in the mid-Pacific) 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.
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ConclusionConclusion
• Ocean currents on planet Earth drive the weather and stabilize the climate.
• Changing of ocean currents and related factors such as trade winds can have devastating effects (El Nino, La Nina, rising sea levels, etc).
• In order to understand the complex factors that create Earth’s climate you need to understanding the forces of density, salinity, and Earth’s temperature as they relate to ocean currents.
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Possible EffectsPossible Effects
Journal: Future of Global WarmingUsing the political cartoon at the left, predict earth in the future and explain why the cartoonist chose to use the image to image a future earth after global warming. Is this a possible effect of an increase in global temperatures?
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