movements of masses of water in the ocean

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Movements of masses of water in the ocean. Formation of Surface Currents. The forces that move water to produce ocean currents are caused by: Rotation of the earth Winds Water density Differences. Effect of a Rotating Earth. Turns from west to east . - PowerPoint PPT Presentation


  • Movements of masses of water in the ocean

  • Formation of Surface CurrentsThe forces that move water to produce ocean currents are caused by:Rotation of the earthWindsWater density Differences

  • Effect of a Rotating EarthTurns from west to east.Velocity of rotation at its surface is greatest at the equator and least at the poles.This is called the Coriolis effect.

  • Find city of Quito, capital of EcuadorPut a sticker on itFind Buffalo, NYPut a sticker on it

    Use a string to measure the distance around the earth beginning and ending at the same city (do not cut the string, just mark with your finger)

    Speed = distance/time (24 hrs)Effect of Rotating Earth

  • Understanding the Coriolis EffectRead pp. 164 to first paragraph on pp. 167 under The Coriolis EffectDiscuss with your partner until you both understand. Read pp. 189 (Western Boundary Currents) to pp. 191 and look at Figure 9.8.On a piece of paper, describe the coriolis effect and draw a pictureWhich direction does it turn in N. Hemisphere?Which direction does it turn in the S. Hemisphere?

  • Coriolis EffectEarth spins counterclockwiseDeflection will always be to the right (looking south from N. Pole)Air turns to the right in the Northern HemisphereAir turns to the left in the Southern Hemisphere

  • CirculationGlobal circulation of airUneven solar heatingRotation of the Earth (Coriolis effect)

    Areas near equator wherewind converges is known asintertropical convergencezone (ITCZ)Doldrums

  • Wind PatternsTrade WindsSurface winds that move from latitudes where dry air sinks toward latitudes at the equator****Winds are named by the direction from which they blowIn the N. Hemisphere they are the northeast tradesIn the S. Hemisphere they are the southeast trades

    WesterliesSurface winds that flow between areas where dry air sinks toward the latitudes at polar cellsIn N. Hemisphere they approach from the southwestIn the S. Hemisphere they approach from the northwest

  • MonsoonsA monsoon is a pattern of wind circulation that changes with the seasonAreas that experience monsoons typically have wet summers and dry wintersLand changes temperature more rapidly than the oceanIn spring, land heats faster than the oceanAir above the land becomes warmer and risesRelatively cool air flows from over the ocean to the land to take the place of the warm air, which then heats, rises, and forms clouds and rain

  • JanuaryJuly

  • BreezesBreezes are small, daily mini-monsoonsSea breezesMorning sunlight warms the land, which then warms the air above itWarm air expands and risesCooler air from over the sea moves toward landLand breezesAfter sunset, the land loses heat quickly.The air over the still-warm ocean will be warmer than air over the cooling landThe air over the ocean will rise and cooler air from the land will move over the ocean

  • ReviewDifferentiate between trade winds and westerlies. (i.e. Where are they located and in what direction do they flow...from _____to _____?)

    Diagram and label sea and land breezes.

  • STOPBegin and Finish Storm PowerpointThen continue

  • Ocean CirculationPrimary forces start water moving and determine velocity (speed and direction).Thermal expansion and contractionStress of wind blowing over the waterDensity differencesSecondary forces influence the direction and nature of the flow.Coriolis effectGravityFrictionShape of the ocean basins (floor)

  • Surface Currents Solar heatingSolar (sun) heating causes water to expand slightly.Sea level near equator is about 8 cm higher than sea level moving toward poles.This global difference creates a very slight slope, and warm equatorial water flows downhill toward poles.

  • Surface CurrentsBecause the earth is turning west to east, the water is deflected to the westWaters travel is influenced by the Coriolis effect which starts a circular flow

  • Surface Currents - WindPrimary force responsible for surface currents

    Trade winds and Westerlies tug on the surface of the water

    Water is deflected to the right of the wind direction (Coriolis Effect)

    As a rule, the friction of wind blowing for at least 10 hours will cause surface water to flow at about 2% of wind speed a surface current

  • Ekman TransportCoriolis effect spinning of the earth Water flows to the right of the direction of the windWater in each layer flows a little more to the right as you go downA down flowing spiral occursEventually water in one layer will flow in the opposite direction of the surface water

  • Gyres circular flow of waterCoriolis effect deflects water to the right of wind directionClockwise in the northern hemisphereCounterclockwise in the southern hemisphere5 Major GyresNorth AtlanticSouth AtlanticSouth Pacific North Pacific Indian

  • Western and EasternBoundary Currents5 major ocean gyres flow in relation to the spin of the earth geostrophic currents.Currents on the western boundary of the ocean flow from the equator to the polesCurrents on the eastern boundary of the ocean flow from the poles to the equator

  • Western Boundary CurrentsFastest and deepest currents

    Move warm water poleward in each hemisphere

    Examples:Gulf Stream (largest)Japan or Kuroshio CurrentBrazil CurrentAqulhas CurrentEast Australian Current

  • Eastern Boundary CurrentsCarry cold water toward equator

    Shallow, broad, and slower than western boundary currents

    Examples:Canary CurrentBenguela CurrentCalifornia CurrentWest Australian CurrentPeru or Humboldt Current

  • Countercurrents and UndercurrentsCountercurrent - Surface water at the equator where lack of wind allows it to flow in the opposite direction of the main current. Without the wind driving the water to the west, some backward flow of water occurs here

    Undercurrent water flows beneath and opposite of the current over it.Undercurrents are why the Galapagos islands are in cold water even though they are in the tropics near Equator

  • UpwellingsForm when winds parallel to shore force water away from shore; west coast of continents.Water from the bottom is brought up to replace the moved waterWater brings with it nutrients from the ocean bottomCooler water brought upward can create fog banks and cool summers (San Francisco)

  • DownwellingsForm when winds parallel to shore force water into shore; east coast of continents

    Extra water is forced down towards the bottom

    Helps supply deeper ocean with dissolved gases and nutrients

  • Heat transport and ClimateCurrents redistribute heat throughout the globe

    Without these, Earth would have more extreme weather.

    Cold water from the poles keeps the Galapogos Islands cool even though they are in the tropics

    Warm water from Gulf Stream, warms the air above and keeps much of Europe warmer than other places at similar latitudes.

  • Galapagos IslandsFROM:

  • El Nio Southern Oscillation (ENSO)

    ENSO is a reoccurring natural phenomenon in which the Eastern Pacific is warmer than usual causing global weather changes.Trade winds weaken and warm equatorial water that would normally flow west-ward backs up to flow eastUpwellings in California and Peru decrease or stopIncreases Pacific tropical cyclone activityOccurs every 3-8 years

  • La NiaLa Nina is a intense return to the normal conditions following strong ENSOColder than normal conditions in California and Peru

  • Deep Ocean Currents

  • Gravitational CurrentsTwo forces that explain vertical movement in the ocean:Gravitational Force (G)Buoyant Force (B)G > B downward movement = sinkingB >G upward movement = risingG = B no movement = floating at surfaceG = B no movement = floating neutrally bouyant

  • Thermohaline CirculationWater movement caused by differences in temperature and salinity.Processes that decrease salinity:PrecipitationFreshwater run-offProcesses that increase salinity:EvaporationFreezing

  • Thermohaline Circulation continued . . .*What is the Coriolis Effect? Winds BBC*What's the Coriolis Effect? - Winds - BBC Four

    *;_ylu=X3oDMTBpcGszamw0BHNlYwNmcC1pbWcEc2xrA2ltZw--/SIG=1289tgeqm/EXP=1321268685/**http%3a//*Sailors outbound from Europe to the New World learned to drop south to catch the trades and to return home by a more northerly route to take advantage of the westerlies.

    Pic:******Undercurrents are why the galapogos islands are in cold water even though they are in the**


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