Atmospheric and Oceanic CirculationAtmospheric and Oceanic Circulation

Atmospheric circulation transfers energy and mass over the Atmospheric circulation transfers energy and mass over the EarthEarth Redistributes surplus energy along the tropics to deficit areasRedistributes surplus energy along the tropics to deficit areas Generates weather patternsGenerates weather patterns Produces ocean currentsProduces ocean currents Spread natural and anthropogenic pollutionSpread natural and anthropogenic pollution

What is atmospheric pressure?What is atmospheric pressure?

Atmospheric PressureAtmospheric PressureAir pressureAir pressure – pressure exerted on the surface of the – pressure exerted on the surface of the

earth by the atmosphere.earth by the atmosphere.

Motion, size and number of air molecules within the Motion, size and number of air molecules within the atmosphere determine the temperature and density of airatmosphere determine the temperature and density of air

Temperature and density of air determine the pressure it Temperature and density of air determine the pressure it exerts on the surfaceexerts on the surface

Air pressure is caused by the force of gravity pulling the Air pressure is caused by the force of gravity pulling the mass of the atmosphere toward the surface of the earthmass of the atmosphere toward the surface of the earth

What determines atmospheric pressure?What determines atmospheric pressure?

Atmospheric PressureAtmospheric Pressure

-Pressure = force per unit area

-Due to gravity the atmosphere exerts a force

According to the According to the Ideal Gas LawIdeal Gas Law: density (: density (ρρ) and ) and temperature (T) control atmospheric pressure (P)temperature (T) control atmospheric pressure (P)

P = P = ρρRTRT

R = a constantR = a constant

Pressure, Density & TemperaturePressure, Density & Temperature

Density (Density (ρρ))

Amount of matter (mass) per unit volume (kg/mAmount of matter (mass) per unit volume (kg/m33))

Density (of a gas) is directly proportional to pressureDensity (of a gas) is directly proportional to pressure

Density varies with altitudeDensity varies with altitude

Pressure, Density & TemperaturePressure, Density & Temperature

Temperature (T)Temperature (T) Molecules move faster in hot air than cold airMolecules move faster in hot air than cold air

Faster = more collisions (more force) and therefore higher pressureFaster = more collisions (more force) and therefore higher pressure

Temperature is directly proportional to pressureTemperature is directly proportional to pressure

Pressure, Density & TemperaturePressure, Density & Temperature

In the atmosphere density and temperature do not change In the atmosphere density and temperature do not change independentlyindependently

Example:Example:

When air in the atmosphere is heated it expands and causes a decrease When air in the atmosphere is heated it expands and causes a decrease in density and pressurein density and pressure

How is atmospheric pressure measured?How is atmospheric pressure measured?

Atmospheric PressureAtmospheric Pressure

Atmospheric pressure is often measured in Atmospheric pressure is often measured in millibars (mb)millibars (mb)

Atmospheric pressure at sea level is 1013.25 millibars (standard Atmospheric pressure at sea level is 1013.25 millibars (standard pressure)pressure)

At the earth’s surface, pressure varies from 980 mb to 1030 mb (about At the earth’s surface, pressure varies from 980 mb to 1030 mb (about 5%)5%)

Atmospheric Pressure:Atmospheric Pressure:In 1643, a student of Galileo, Evangelista Torricelli developed a In 1643, a student of Galileo, Evangelista Torricelli developed a method for measuring air pressure while trying to drain mines.method for measuring air pressure while trying to drain mines.

Noticed that water levels within mines varied dailyNoticed that water levels within mines varied daily Arrived at the theory that the downward force of the atmosphere on Arrived at the theory that the downward force of the atmosphere on

the water surface also fluctuatedthe water surface also fluctuated→→days of higher air pressure caused lower water levels within minesdays of higher air pressure caused lower water levels within mines

Measurement of Atmospheric Pressure:Measurement of Atmospheric Pressure:

Atmospheric pressure is measured using and instrument called a Atmospheric pressure is measured using and instrument called a barometerbarometer

A A mercurial barometermercurial barometer measures atmospheric pressure with a column measures atmospheric pressure with a column of mercuryof mercury

Sea-level pressure (1013mb) also can be defined as 29.92 inches of Sea-level pressure (1013mb) also can be defined as 29.92 inches of mercury (in. Hg)mercury (in. Hg)

Atmospheric PressureAtmospheric Pressure

A more common type of barometer is the A more common type of barometer is the aneroid barometeraneroid barometer

It uses the pressure exerted against a partial vacuum to measure air It uses the pressure exerted against a partial vacuum to measure air pressurepressure

Note:Note: decrease in air pressure with increase in elevation decrease in air pressure with increase in elevation

- Decrease boiling point of waterDecrease boiling point of water- 0 m 0 m 100 C100 C- 3000 m 3000 m 90 C90 C- 5000 m 5000 m 80 C80 C

- Increase in cooking times at higher elevationsIncrease in cooking times at higher elevations

WindWind

Wind –Wind – horizontal movement of air horizontal movement of air Produced by differences in air pressure from one location to Produced by differences in air pressure from one location to

anotheranother Air moves from locations of high pressure to locations of low Air moves from locations of high pressure to locations of low

pressurepressure

Measurement:Measurement: wind has two principal components wind has two principal components- Speed (anemometer)Speed (anemometer)- Directions (wind vane)Directions (wind vane)

Wind Vane:

-Points in the direction air is moving

-Wind is named based on the direction from which it originated

-Designated by compass directions

Forces Driving Atmospheric MotionForces Driving Atmospheric Motion

Four Four forcesforces affect the direction and speed of air (wind) as it affect the direction and speed of air (wind) as it moves throughout the atmosphere:moves throughout the atmosphere:

3.3. Gravitational forceGravitational force4.4. Pressure gradient force Pressure gradient force 5.5. Coriolis forceCoriolis force6.6. FrictionFriction

1) Gravity:1) Gravity: Draws the mass of the atmosphere towards the surface of the earthDraws the mass of the atmosphere towards the surface of the earth Causes decrease in pressure and mass with increasing elevationCauses decrease in pressure and mass with increasing elevation Would not have an atmosphere or air pressure without itWould not have an atmosphere or air pressure without it

2) Pressure Gradient Force:2) Pressure Gradient Force: air moves from high pressure air moves from high pressure regions to low pressureregions to low pressure

Variations in air pressure are caused by uneven heating of the Variations in air pressure are caused by uneven heating of the earth’s surface.earth’s surface.

Uneven heating of the earth’s surfaceUneven heating of the earth’s surface

Warm surfaces encourage upward vertical motionWarm surfaces encourage upward vertical motion

Warm Surface

Converging Horizontal Air

Converging Horizontal Air

Upward airflow

Low pressure area

Uneven heating of the earth’s surfaceUneven heating of the earth’s surface

As air molecules cool, they condense and decend towards the surfaceAs air molecules cool, they condense and decend towards the surface

Diverging Horizontal Air

Diverging Horizontal Air

Air Cools

High pressure area

Lines of equal pressure are isobars:Lines of equal pressure are isobars:

- b/c air moves from high to low pressure, the PGF is exerted at 90b/c air moves from high to low pressure, the PGF is exerted at 90º º angles from the isobarsangles from the isobars

- When isobars are close together the pressure gradient is higher When isobars are close together the pressure gradient is higher → stronger winds→ stronger winds

- When isobars are farther apart the pressure gradient is lower When isobars are farther apart the pressure gradient is lower → weaker winds→ weaker winds

3) Coriolis Force:3) Coriolis Force: air flow is deflected from a straight path by air flow is deflected from a straight path by the rotation of the earththe rotation of the earth

Earth’s rotational speed increases from the poles toward the Earth’s rotational speed increases from the poles toward the equatorequator 0km /hr at the poles, 1675km /hr at equator0km /hr at the poles, 1675km /hr at equator Deflection increases north and south of the polesDeflection increases north and south of the poles No deflection at the equatorNo deflection at the equator

3) Coriolis Force:3) Coriolis Force:- The earth rotates The earth rotates eastwardeastward

- Deflection causes air motion to curve to the Deflection causes air motion to curve to the right right in thein the N Hem N Hem- Deflection causes air motion to curve to the Deflection causes air motion to curve to the left left in thein the S Hem S Hem

Geostrophic Wind –Geostrophic Wind – upper level winds that move parrallel to upper level winds that move parrallel to isolines b/c the coriolis force are equalisolines b/c the coriolis force are equal

Rather than air flowing from high to low pressure, air moves around Rather than air flowing from high to low pressure, air moves around high and low pressure areashigh and low pressure areas

Occurs within upper levels of the troposphereOccurs within upper levels of the troposphere

Northern HemisphereNorthern Hemisphere

Northern HemisphereNorthern Hemisphere

Northern HemisphereNorthern Hemisphere

Northern HemisphereNorthern Hemisphere

Northern HemisphereNorthern Hemisphere

4) Frictional force:4) Frictional force: drag (backward force) on wind as it moves drag (backward force) on wind as it moves over the earth’s surfaceover the earth’s surface

Extends to and elevation of about 500mExtends to and elevation of about 500m Decreases with increasing elevationDecreases with increasing elevation Varies with surface texture, wind speed, time of day/year, and Varies with surface texture, wind speed, time of day/year, and

atmos conditionsatmos conditions→ → Decreases speed of windDecreases speed of wind

Northern HemisphereNorthern Hemisphere

Summary of Forces:Summary of Forces:Gravity Gravity pulls atmosphere toward earth creating air pressurepulls atmosphere toward earth creating air pressure

PGF PGF air moves from high to low pressure perpendicular to isolinesair moves from high to low pressure perpendicular to isolines

Coriolis Coriolis deflects wind direction due to earth’s rotationdeflects wind direction due to earth’s rotation- zero at the equator- zero at the equator- right in N hem; left in S Hem- right in N hem; left in S Hem

Friction Friction backward force on air movement slowing it downbackward force on air movement slowing it down

Clouds, precipitationClear skies, sunshineWEATHER

Surface convergenceUpper-level divergence

Surface divergenceUpper-level convergence

HORIZONTAL MOTION

Rising AirSinking AirVERTICAL MOTION

Air spins in to centerAir spins out from centerSPIN

N Hem : ccw circulationS Hem : cw circulation

N Hem : cw circulationS Hem : ccw circulation

CIRCULATION

CycloneAnticycloneNAME

Low PressureHigh Pressure

Global Air Pressure Patterns:Global Air Pressure Patterns:

Temperature differences along the equator and at the poles Temperature differences along the equator and at the poles cause pressure differences:cause pressure differences:

Pressure differences cause air to flow Pressure differences cause air to flow Warm air along the equator rises creating low pressureWarm air along the equator rises creating low pressure Cold, more dense air over the poles sinks creating high pressureCold, more dense air over the poles sinks creating high pressure These pressure differences cause air to flow from the poles north These pressure differences cause air to flow from the poles north

and south to the equatorand south to the equator This This north-southnorth-south air flow is called air flow is called meridinal flowmeridinal flow

Four primary pressure areasFour primary pressure areas for each hemisphere: for each hemisphere:

- Equatorial low-pressure troughEquatorial low-pressure trough (10 N & S) (10 N & S)- Polar high-pressure cellsPolar high-pressure cells (90 N & S) (90 N & S)- Subtropical high-pressure cellsSubtropical high-pressure cells (20-35 N & S) (20-35 N & S)- Subpolar low-pressure cellsSubpolar low-pressure cells (60 N & S) (60 N & S)

- Equatorial low-pressure troughEquatorial low-pressure trough (10 N & S) (10 N & S)- Caused by intense heating of the earth’s surfaceCaused by intense heating of the earth’s surface- Warm air rises creating low pressure and associated weatherWarm air rises creating low pressure and associated weather- Characterized by warm, wet atmospheric conditionsCharacterized by warm, wet atmospheric conditions

- Polar high-pressure cellsPolar high-pressure cells (90 N & S) (90 N & S)- Subtropical high-pressure cellsSubtropical high-pressure cells (20-35 N & S) (20-35 N & S)- Subpolar low-pressure cellsSubpolar low-pressure cells (60 N & S) (60 N & S)

- Equatorial low-pressure troughEquatorial low-pressure trough (10 N & S) (10 N & S)- Polar high-pressure cellsPolar high-pressure cells (90 N & S) (90 N & S)

- Caused by sinking air over cold surfaceCaused by sinking air over cold surface- Characterized by cold, dry airCharacterized by cold, dry air

- Subtropical high-pressure cellsSubtropical high-pressure cells (20-35 N & S) (20-35 N & S)- Subpolar low-pressure cellsSubpolar low-pressure cells (60 N & S) (60 N & S)

- Equatorial low-pressure troughEquatorial low-pressure trough (10 N & S) (10 N & S)- Polar high-pressure cellsPolar high-pressure cells (90 N & S) (90 N & S)- Subtropical high-pressure cellsSubtropical high-pressure cells (20-35 N & S) (20-35 N & S)

- Caused by dry, sinking airCaused by dry, sinking air- Characterized by hot, dry airCharacterized by hot, dry air

- Subpolar low-pressure cellsSubpolar low-pressure cells (60 N & S) (60 N & S)

- Equatorial low-pressure troughEquatorial low-pressure trough (10 N & S) (10 N & S)- Polar high-pressure cellsPolar high-pressure cells (90 N & S) (90 N & S)- Subtropical high-pressure cellsSubtropical high-pressure cells (20-35 N & S) (20-35 N & S)- Subpolar low-pressure cellsSubpolar low-pressure cells (60 N & S) (60 N & S)

- Caused by the clash of warmer, wet maritime air and cold, dry polar Caused by the clash of warmer, wet maritime air and cold, dry polar airair

- The warmer marine air rises over colder, heavier polar airThe warmer marine air rises over colder, heavier polar air- Characterized by cool, wet airCharacterized by cool, wet air

Equatorial low-pressure trough:Equatorial low-pressure trough:

Long, narrow band of low pressure encircling the earthLong, narrow band of low pressure encircling the earth Air converges along the surface towards the centerAir converges along the surface towards the center

Creates trade winds (NE in N Hem; SE in S. Hem)Creates trade winds (NE in N Hem; SE in S. Hem) Air moves toward equator and is deflected wast by coriolisAir moves toward equator and is deflected wast by coriolis

Warm air rises along equator Warm air rises along equator →→ Intertropical Convergence Zone Intertropical Convergence Zone Surface flow along the ITCZ is minimal Surface flow along the ITCZ is minimal →→ Doldrums Doldrums

Air Characteristics:Air Characteristics:- constant altitude and consistent daylength result in large amounts of constant altitude and consistent daylength result in large amounts of

available energy available energy - Energy warms and lightens air near the surface causing it to riseEnergy warms and lightens air near the surface causing it to rise- Air is very moist; lots of evaporation from nearby oceansAir is very moist; lots of evaporation from nearby oceans

Equatorial low-pressure trough:Equatorial low-pressure trough:

Air rises into upper atmosphere moving away from equatorAir rises into upper atmosphere moving away from equator Air sinks and returns to surface and divergesAir sinks and returns to surface and diverges Some air moves back toward the ITCZ (Some air moves back toward the ITCZ (hadley cellhadley cell))

Process is repeatedProcess is repeated Results in band of tropical weather systemsResults in band of tropical weather systems

Warm, moist air massesWarm, moist air masses Precipitation Precipitation →→Amazon rainforestAmazon rainforest

Subtropical high-pressure cells:Subtropical high-pressure cells:

Broad zone of high pressure along subtropical latitudesBroad zone of high pressure along subtropical latitudes Upper-level air moves north and south of ITCZ and eventually sinks Upper-level air moves north and south of ITCZ and eventually sinks

along subtropical latitudesalong subtropical latitudes Moisture is removed by precipitation along the ITCZMoisture is removed by precipitation along the ITCZ Still within the area of energy surplusesStill within the area of energy surpluses Resulting in anticyclonic conditions characterized by hot, dry air Resulting in anticyclonic conditions characterized by hot, dry air →→ world’s world’s

desertsdeserts

Air circulation:Air circulation: Air diverges along surface:Air diverges along surface:

Moves toward equator Moves toward equator →→ easterly trade winds easterly trade winds Moves toward poles Moves toward poles →→ westerlies westerlies

Subtropical high-pressure cells:Subtropical high-pressure cells:

Anticyclonic circulation (cw in N Hem)Anticyclonic circulation (cw in N Hem)- drier land conditions and cool ocean currents along eastern edgedrier land conditions and cool ocean currents along eastern edge- Wetter land conditions and warm ocean currents along wester edgeWetter land conditions and warm ocean currents along wester edge

- surface winds along high pressure zones are calmsurface winds along high pressure zones are calm- Horse latitudes (sailing)Horse latitudes (sailing)

Subpolar low-pressure cells:Subpolar low-pressure cells:

Occur along the boundary midlatitude air masses and polar airOccur along the boundary midlatitude air masses and polar air Boundary called the polar frontBoundary called the polar front Midlatitude air is warm/cool and moistMidlatitude air is warm/cool and moist Polar air is cold and dryPolar air is cold and dry

Air converges along Polar Front and risesAir converges along Polar Front and rises Warmer midlatitude air rises above colder polar airWarmer midlatitude air rises above colder polar air Moisture within warmer air mass is condensedMoisture within warmer air mass is condensed Results in cyclonic conditions Results in cyclonic conditions →→ precipitation precipitation Westerlies and roaring fortiesWesterlies and roaring forties

Polar high-pressure cells:Polar high-pressure cells:

Occur over poles, poleward of the polar frontOccur over poles, poleward of the polar front Anticyclonic circulation of cold, dry air around polesAnticyclonic circulation of cold, dry air around poles

Weak, polar easterliesWeak, polar easterlies

Upper Atmospheric CirculationUpper Atmospheric Circulation

Upper level atmospheric circulation is monitored on a constant pressure Upper level atmospheric circulation is monitored on a constant pressure surface or a surface or a constant isobaric surfaceconstant isobaric surface

The height of the 500mb pressure surface:The height of the 500mb pressure surface:- This height variesThis height varies- The layer of air under an upper-level high pressure system are The layer of air under an upper-level high pressure system are

thickerthicker- 500mb isobar is at a higher elevation500mb isobar is at a higher elevation- 500mb isobars bend poleward on map 500mb isobars bend poleward on map →→ ridge ridge

- The layer of air under an upper-level low pressure system are The layer of air under an upper-level low pressure system are thinnerthinner

- 500mb isobar is at a higher elevation500mb isobar is at a higher elevation- 500mb isobars bend equatorward on map 500mb isobars bend equatorward on map →→ trough trough

Upper atmospheric circulation generate surface pressure systemsUpper atmospheric circulation generate surface pressure systems

Divergence of upper-level air results in a voidDivergence of upper-level air results in a void Surface air will rise to fill upper level voidSurface air will rise to fill upper level void Rising air at the surface results in Rising air at the surface results in surface low pressure cyclonessurface low pressure cyclones

Convergence of upper-level air results in build up of airConvergence of upper-level air results in build up of air Air will be pushed down toward the surfaceAir will be pushed down toward the surface Sinking air at the surface results in Sinking air at the surface results in surface high pressure surface high pressure

anticyclonesanticyclones

Rossby Waves-Rossby Waves- undulations within the smooth westerly flow undulations within the smooth westerly flow of geostrophic windsof geostrophic winds Cold air poleward of polar front; warm air equatorwardCold air poleward of polar front; warm air equatorward Develop along the polar jet streamDevelop along the polar jet stream Waves send cold polar air equatorward and warm midlatitude air Waves send cold polar air equatorward and warm midlatitude air

polewardpoleward Distinct cyclonic and anticyclonic systems form as warm air is Distinct cyclonic and anticyclonic systems form as warm air is

pushed closer to the poles and cold air is squeezed toward equatorpushed closer to the poles and cold air is squeezed toward equator Cold, cyclonic systems can be squeezed out and move even Cold, cyclonic systems can be squeezed out and move even

further southfurther south

Jet StreamJet Stream: irregular, concentrated band of wind at several locations that : irregular, concentrated band of wind at several locations that supports surface weather systemssupports surface weather systems 160-480 km wide, 900-2150 m thick, with core velocities exceeding 160-480 km wide, 900-2150 m thick, with core velocities exceeding

300 kmph300 kmph Weaken during summer and strengthen in winterWeaken during summer and strengthen in winter

Polar jet streamPolar jet stream - located along the tropopause along the polar front - located along the tropopause along the polar front Elevation of 7600-10,700m, between 30-70 N and SElevation of 7600-10,700m, between 30-70 N and S

Subtropical jet streamSubtropical jet stream - along the boundary btw tropical and - along the boundary btw tropical and midlatitide air midlatitide air 20-50 N and S20-50 N and S

The polar and subtropical jet streams can flow over N. America at the The polar and subtropical jet streams can flow over N. America at the same time and can even mergesame time and can even merge

Local WindsLocal Winds

A Sea BreezeA Sea Breeze

Sea breezeSea breeze - - during the day the land heats faster than the oceanduring the day the land heats faster than the ocean Air over the land is warmer than that over oceanAir over the land is warmer than that over ocean Warmer air is less dense and rises leaving a void over landWarmer air is less dense and rises leaving a void over land Cooler ocean air flows laterally over land to fill voidCooler ocean air flows laterally over land to fill void

A sea breeze is strongest in mid-afternoon!A sea breeze is strongest in mid-afternoon! Why?….. Why?…..

A Land BreezeA Land Breeze

Land BreezeLand Breeze: at night land cools faster than ocean: at night land cools faster than ocean Air over land is cooler than that over oceanAir over land is cooler than that over ocean Warmer, less dense air over ocean rises leaving a voidWarmer, less dense air over ocean rises leaving a void Cooler air over land flow laterally over oceanCooler air over land flow laterally over ocean

Mountain-valley breezesMountain-valley breezes - breezes created by the exchange of cool - breezes created by the exchange of cool mountain air and warmer valley airmountain air and warmer valley air Valley air gains heat rapidly during the dayValley air gains heat rapidly during the day

Warmer valley air rises moving upslopeWarmer valley air rises moving upslope Mountain air loses heat rapidly at nightMountain air loses heat rapidly at night

Cooler mountain air sinks downslopeCooler mountain air sinks downslope

Katabatic windsKatabatic winds - cold dense air from elevated terrain flows downslope - cold dense air from elevated terrain flows downslope Larger regional scale than mountain valley breezesLarger regional scale than mountain valley breezes Generally form along an elevated highland or plateauGenerally form along an elevated highland or plateau

Also very common over ice sheetsAlso very common over ice sheets

Monsoonal Winds -Monsoonal Winds - shifting wind system seasonally b/c of regional scale shifting wind system seasonally b/c of regional scale pressure changespressure changes Typical of SE Asia but also occurs over SW U.S.Typical of SE Asia but also occurs over SW U.S. Large seasonal temp difference occur over SE Asia b/c of its Large seasonal temp difference occur over SE Asia b/c of its

continentalitycontinentality In winter, ITCZ is over Indian Ocean and Asia dominated by In winter, ITCZ is over Indian Ocean and Asia dominated by

subtropical high pressure cellsubtropical high pressure cell Region characterised by dry, cool air with very little precipRegion characterised by dry, cool air with very little precip

Monsoonal Winds -Monsoonal Winds - shifting wind system seasonally b/c of regional scale shifting wind system seasonally b/c of regional scale pressure changespressure changes Typical of SE Asia but also occurs over SW U.S.Typical of SE Asia but also occurs over SW U.S. Large seasonal temp difference occur over SE Asia b/c of its Large seasonal temp difference occur over SE Asia b/c of its

continentalitycontinentality In winter, ITCZ is over Indian Ocean and Asia dominated by In winter, ITCZ is over Indian Ocean and Asia dominated by

subtropical high pressure cellsubtropical high pressure cell Region characterised by dry, cool air with very little precipRegion characterised by dry, cool air with very little precip

In summer, ITCZ is over SE Asia, which is dominated by tropical In summer, ITCZ is over SE Asia, which is dominated by tropical low pressure, and subtropical high pressure is centered over Indian low pressure, and subtropical high pressure is centered over Indian OceanOcean Results in world record rainfall amountsResults in world record rainfall amounts

Ocean CirculationOcean Circulation

Ocean currentsOcean currents are driven by the frictional drag of wind and are driven by the frictional drag of wind and their direction is affected by:their direction is affected by:

- the coriolis forcethe coriolis force- Water density differences caused by temperature and salinityWater density differences caused by temperature and salinity- Configuration of land masses and the ocean floorConfiguration of land masses and the ocean floor- Astronomical forces (tides)Astronomical forces (tides)

Surface Currents –Surface Currents – ocean currents are driven by the ocean currents are driven by the circulation around high pressure systems and deflected by circulation around high pressure systems and deflected by the coriolis force.the coriolis force.

Gyres: circulation patterns caused by circulation around high Gyres: circulation patterns caused by circulation around high pressure systemspressure systems

Equatorial CurrentsEquatorial Currents – ocean currents that are driven – ocean currents that are driven westward by the trade windswestward by the trade winds

Located near the equatorLocated near the equator Are not deflected by coriolis force b/c it is zero along the equatorAre not deflected by coriolis force b/c it is zero along the equator Such currents push water west toward the eastern shores of land Such currents push water west toward the eastern shores of land

massesmasses Causes water to pile up along eastern coasts of continentsCauses water to pile up along eastern coasts of continentsWestern Intensification (15cm)Western Intensification (15cm)

The case of the rubber duck!The case of the rubber duck!- Jan 1994, a large container ship from Hong KongJan 1994, a large container ship from Hong Kong- Loaded with toys and other goodsLoaded with toys and other goods- One container split off Japanese coast (30,000 rubber ducks, turtles One container split off Japanese coast (30,000 rubber ducks, turtles

and frogs)and frogs)- Similar thing happened with 60,000 pairs of athletic shoesSimilar thing happened with 60,000 pairs of athletic shoes- Trip of the floating ducks took over a decade!Trip of the floating ducks took over a decade!

Deep Water Circulation –Deep Water Circulation – ocean water also moves along the ocean water also moves along the ocean floor in distinct patterns resulting from vertical ocean floor in distinct patterns resulting from vertical motionmotion

Upwelling currents:Upwelling currents: occur where surface water is swept away from the occur where surface water is swept away from the coast by surface divergence (coriolis and offshore winds)coast by surface divergence (coriolis and offshore winds) this allows cold, deep ocean water to move up from the ocean floor toward this allows cold, deep ocean water to move up from the ocean floor toward

the surface the surface → → nutrients for fishingnutrients for fishing

Downwelling currents:Downwelling currents: occur where excess water accumulation along a occur where excess water accumulation along a coast causes surface water to be pushed to greater ocean depths coast causes surface water to be pushed to greater ocean depths (west end of the equatorial currents)(west end of the equatorial currents) This allows surface ocean water to move down to the ocean floorThis allows surface ocean water to move down to the ocean floor Warmer surface water is cooledWarmer surface water is cooled Water flows along the ocean floor until it is upwelledWater flows along the ocean floor until it is upwelled

This continuous flow of surface water to the bottom and bottom water to This continuous flow of surface water to the bottom and bottom water to the surface transports heat and energy around the globe:the surface transports heat and energy around the globe:

- Water that moves along the equator is warmed and transports that heat to Water that moves along the equator is warmed and transports that heat to the poles where it loses heat as it cools, sinks, and flows back to the ocean the poles where it loses heat as it cools, sinks, and flows back to the ocean floorfloor

- That cold bottom water eventually upwells and is warmed and continues That cold bottom water eventually upwells and is warmed and continues circulatingcirculating

- Process takes about Process takes about 1,0001,000 years years- Currents have shifted throughout geologic historyCurrents have shifted throughout geologic history