By: Jason LaFloreBy: Jason LaFloreJacquelyn MatiaJacquelyn MatiaMatt MiddendorfMatt Middendorf

John OnsaJohn Onsa

Ocean Circulation is the large scale Ocean Circulation is the large scale movement of waters in the ocean basins.movement of waters in the ocean basins.

Winds drive surface circulation, and the Winds drive surface circulation, and the cooling and sinking of waters in the polar cooling and sinking of waters in the polar regions drive deep circulationregions drive deep circulation

http://www.tsgc.utexas.edu/topex/http://www.tsgc.utexas.edu/topex/ocean.htmlocean.html JM

Ocean currents are Ocean currents are constantly in motion as constantly in motion as

shown below:shown below:

• Ocean currents move in many different Ocean currents move in many different patterns affected by: wind, salinity in patterns affected by: wind, salinity in the water, heat, the earths rotation, etc. the water, heat, the earths rotation, etc. JM

Ocean Circulation Ocean Circulation Patterns effect:Patterns effect:

• The climateThe climate

• Living conditions for plants and Living conditions for plants and animals in the ocean and on landanimals in the ocean and on land

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This map shows the major This map shows the major movements of water in movements of water in

oceans of the world.oceans of the world.

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Two Primary Types of Two Primary Types of Ocean CirculationOcean Circulation

• Wind Driven CirculationWind Driven Circulation – (which – (which involves the surface)involves the surface)

• Thermohaline Circulation-Thermohaline Circulation- (which (which involves density and depth)involves density and depth)

-caused by density differences-caused by density differences

- such as temperature and - such as temperature and salinitysalinity

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Ocean currents are Ocean currents are affected by two types of affected by two types of

forces:forces:

• Primary forces-Primary forces- which are forces that which are forces that start the motion of the waterstart the motion of the water

• Secondary forces-Secondary forces- which influence which influence the direction in which the currents the direction in which the currents flowflow

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Some of these forces Some of these forces include:include:

– Solar heating- causes the water Solar heating- causes the water to expandto expand

– Winds- push the ocean waterWinds- push the ocean water– Gravity- tends to pull water (for Gravity- tends to pull water (for

example down a hill)example down a hill)– Coriolis Force- which causes Coriolis Force- which causes

water to move to the right water to move to the right around gyresaround gyres

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The Corolis EffectThe Corolis Effect

• The Corolis Effect is the deflection of The Corolis Effect is the deflection of objects, winds, and currents on the objects, winds, and currents on the surface of the earth owing to the planet’s surface of the earth owing to the planet’s rotation.rotation.

• This plays a major role in the temperature This plays a major role in the temperature and weather patterns of the earthand weather patterns of the earth

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The Coriolis Effect cont.The Coriolis Effect cont.

• As a result of the Coriolis Effect, north-As a result of the Coriolis Effect, north-flowing currents in the Northern flowing currents in the Northern hemisphere deflect to the east, while south-hemisphere deflect to the east, while south-flowing currents deflect to the west. The flowing currents deflect to the west. The opposite is true for the Southern opposite is true for the Southern Hemisphere.Hemisphere.

• This plays a major role in ocean currents This plays a major role in ocean currents and circulation.and circulation.

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Demonstration of the Coriolis Demonstration of the Coriolis EffectEffect

• This shows how the This shows how the prevailing surface winds prevailing surface winds flow.flow.

• As you can see, it is As you can see, it is rather interesting how rather interesting how the warmer westerly the warmer westerly winds flow north and the winds flow north and the trade winds from the trade winds from the northeast as well as the northeast as well as the polar easterlies flow polar easterlies flow south.south.

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The Ocean’s Conveyor BeltThe Ocean’s Conveyor Belt

The Oceanic Circulation The Oceanic Circulation CycleCycle• Near surface seawater begins its travel deep into the ocean Near surface seawater begins its travel deep into the ocean

in the North Atlantic. The downwelling of this water is in the North Atlantic. The downwelling of this water is caused by high levels of evaporation which cools and caused by high levels of evaporation which cools and increases the salinity of the seawater located here. increases the salinity of the seawater located here.

• This seawater then moves south along the coast of North This seawater then moves south along the coast of North and South America until it reaches Antarctica and South America until it reaches Antarctica

• At Antarctica, the cold and dense seawater then travels At Antarctica, the cold and dense seawater then travels eastward. During this part of its voyage the flow splits off eastward. During this part of its voyage the flow splits off into two currents that move northward. into two currents that move northward.

• In the North Pacific (off the coast of Asia) and in the Indian In the North Pacific (off the coast of Asia) and in the Indian Ocean (off the coast of Africa), these two currents move Ocean (off the coast of Africa), these two currents move from the ocean floor to its surface creating upwellings. from the ocean floor to its surface creating upwellings.

• The flow then becomes near surface moving back to the The flow then becomes near surface moving back to the starting point in the North Atlantic. One complete circuit of starting point in the North Atlantic. One complete circuit of this flow of seawater is estimated to take about 1,000 this flow of seawater is estimated to take about 1,000 years. M.M.years. M.M.

ConclusionsConclusions

• The Coriolis Effect stems from the fact that at different The Coriolis Effect stems from the fact that at different latitudes on the earth, different points experience latitudes on the earth, different points experience different rates of rotation. This causes certain objects different rates of rotation. This causes certain objects to be “deflected” from their original path.to be “deflected” from their original path.

• As we can see, the Coriolis Effect has a large impact As we can see, the Coriolis Effect has a large impact on the the patterns of ocean circulationon the the patterns of ocean circulation

• This effects the weather and climate of the world by This effects the weather and climate of the world by directing winds and warm or cold ocean currents to directing winds and warm or cold ocean currents to certain parts of the globecertain parts of the globe

• This process takes a long time however, often up to This process takes a long time however, often up to 1,000 years. M.M. 1,000 years. M.M.

The Historical Foundations:

• Earliest knowledge of Ocean Currents came from various ship captains and explorers

•Matthew Fontaine Maury - Maury was the first person to use large amounts of ocean data in a study of surface currents. He also was responsible for publishing the first pilot charts and sailing directions for all the oceans of the world.

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Taken from the Website: http://www.utexas.edu/depts/grg/hudson/grg301c/hudson_grg_301c/schedule/2_sun_earth_images/4_circulation/10.htm

•Surface Circulation

•Thermohaline Circulation

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• One of two Circulation Patterns found in all Oceans across the world.

• Surface Circulation is the Horizontal movement of water that is driven by the force of winds at the surface.

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• Surface Circulation is driven by winds.Surface Circulation is driven by winds.

• These winds are determined by the These winds are determined by the Earth’s radiation budget which Earth’s radiation budget which determine net heat gain at low determine net heat gain at low latitudes and net heat loss at high latitudes and net heat loss at high latitudes.latitudes.

• Sets up hemispheric and atmospheric Sets up hemispheric and atmospheric circulation cells which breaks up into circulation cells which breaks up into three main cells pre hemisphere: the three main cells pre hemisphere: the Hadley cell, Ferrell cell, and polar Cell.Hadley cell, Ferrell cell, and polar Cell.

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Taken from the Website: http://www.bigelow.org/virtual/handson/current2_lg.gif

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• Thermohaline Circulation is the second of Thermohaline Circulation is the second of Circulation patterns that effects the earth’s Circulation patterns that effects the earth’s oceans.oceans.

• The pattern is made up of the vertical The pattern is made up of the vertical movement of water which is driven by the movement of water which is driven by the density differences from variations in density differences from variations in water. water.

• These Variations include temperature and These Variations include temperature and Salinity Salinity

• Three main processes make up the Three main processes make up the Thermohalne CirculationThermohalne Circulation PatternPattern

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•Processes that Make up the Processes that Make up the Thermohaline Pattern:Thermohaline Pattern:

•Tidal Forces, Wind Stress, and Tidal Forces, Wind Stress, and Density differences.Density differences.

-The density of the sea water is -The density of the sea water is controlled by temperature (Thermo) controlled by temperature (Thermo) and salinity (Haline), and the and salinity (Haline), and the circulation which is driven by density circulation which is driven by density differencesdifferences

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Taken form the website: http://www.gcrio.org/ocp99/ch2.htmlJ.O.

La NinaLa Nina

•Means the Little Girl Means the Little Girl •Also known as El ViejoAlso known as El Viejo•Refers to cooler than normal sea-Refers to cooler than normal sea-surface temperatures in the central and surface temperatures in the central and eastern tropical Pacific Ocean that eastern tropical Pacific Ocean that impact global weather patternsimpact global weather patterns•Conditions recur every few years and Conditions recur every few years and can persist as long as 2 yearscan persist as long as 2 years

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CausesCauses

• Preceded by a buildup of cooler-than-normal Preceded by a buildup of cooler-than-normal subsurface waters in the Tropical Pacific subsurface waters in the Tropical Pacific

• Eastward-moving atmospheric and oceanic Eastward-moving atmospheric and oceanic waves help bring the cold water to the waves help bring the cold water to the surfacesurface

• Easterly trade winds strengthen and sea-Easterly trade winds strengthen and sea-surface temperatures (SST) drop below surface temperatures (SST) drop below normalnormal

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Difference Between El Nino and La NinaDifference Between El Nino and La Nina

• Both refer to large-scale changes in sea-surface Both refer to large-scale changes in sea-surface temperature across the eastern tropical Pacifictemperature across the eastern tropical Pacific

• Sea surface readings off South America’s west coast Sea surface readings off South America’s west coast range from the 60s to the 70s in degrees Fahrenheit, range from the 60s to the 70s in degrees Fahrenheit, while they exceed 80 degrees Fahrenheit in the while they exceed 80 degrees Fahrenheit in the “warm pool” located in the central and western “warm pool” located in the central and western PacificPacific

• The “warm pool” expands to cover the tropics during The “warm pool” expands to cover the tropics during El Nino, but during La Nina, the easterly trade winds El Nino, but during La Nina, the easterly trade winds strengthen and cold upwelling along the equator and strengthen and cold upwelling along the equator and west coast of South America intensifieswest coast of South America intensifies

• Sea-surface temperatures along equator can fall to 7 Sea-surface temperatures along equator can fall to 7 degrees below normaldegrees below normal

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El Nino (December 1997)El Nino (December 1997)

La Nina (December 2000)La Nina (December 2000)

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Global ImpactsGlobal Impacts

• Produces opposite climate variations Produces opposite climate variations from El Nino from El Nino

• Parts of Australia and Indonesia are Parts of Australia and Indonesia are prone to drought during El Nino, but prone to drought during El Nino, but are typically wetter than normal are typically wetter than normal during La Ninaduring La Nina

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U.S. ImpactsU.S. Impacts

• Often features drier than normal conditions in the Often features drier than normal conditions in the Southwest in late summer through the Southwest in late summer through the subsequent wintersubsequent winter

• Drier than normal conditions also typically occur Drier than normal conditions also typically occur in the Central Plains in the fall and in the in the Central Plains in the fall and in the Southeast in the winter Southeast in the winter

• The Pacific Northwest is more likely to be wetter The Pacific Northwest is more likely to be wetter than normal in the late fall and early winter with than normal in the late fall and early winter with the presence of a well-established La Nina the presence of a well-established La Nina

• La Nina winters are usually warmer than normal La Nina winters are usually warmer than normal in the Southeast and colder than normal in the in the Southeast and colder than normal in the NorthwestNorthwest

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Occurrence and Length Occurrence and Length

• El Nino and La Nina occur on average every 3 El Nino and La Nina occur on average every 3 to 5 years to 5 years

• However, in the historical record, the interval However, in the historical record, the interval between events has varied from 2 to 7 yearsbetween events has varied from 2 to 7 years

• La Ninas have been half as frequent as El Ninos La Ninas have been half as frequent as El Ninos • Conditions typically last approximately 9 to 12 Conditions typically last approximately 9 to 12

monthsmonths• Some episodes may persist as long as 2 yearsSome episodes may persist as long as 2 years

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