Physical Oceanography The Motion of the Ocean

Unit 5: Physical OceanographyThe Motion of the OceanMarine Science

Day 1: Atmospheric Circulation Objectives:What is physical oceanography?What are the layers of the atmosphere?Explain how the surface of the Earth is heated.What are convection cells?What is the Coriolis Effect?Explain the affect of the Coriolis Effect on global wind patterns.Explain how land masses affect global wind patterns Explain the difference between anabatic and katabatic winds.Physical OceanographyThe study of physics within the marine environment.This includes:SoundWavesCurrentsTidesLight How the oceans influence weather and climate

AtmosphereThe atmosphere is a mixture of gasses that extends about 90 km from the Earths surfaceDifferences in the heating of the atmosphere at different latitudes sets the gasses in motion creating windLayers of the atmosphere:TrophosphereStratosphereMesosphereThermosphereThe atmosphere is composed of:Nitrogen 78%Oxygen 21 %Inert Gasses (argon, helium, neon) 1%Carbon Dioxide (0.03)

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http://forces.si.edu/atmosphere/04_00_01.htmlTroposphereLowest LayerExtends from the surface of the earth to an altitude of about 12 kmTemperature decreases with altitude at a rate of approximately -10oC for each 1000m of elevationWhere weather happens

StratosphereWhere the ozone layer floatsOzone Layer: Layer of O3 in the stratosphere that shields life from harmful ultraviolet radiation from the sunCommercial airliners fly in this layerFrom 12 to 50 km above Earths surfaceTemperature increases with altitude because the ozone layer (O3) absorbs UV radiation from the sun (heat)

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MesosphereFrom 50-80 km above Earths surfaceTemperature decreases as altitude increasesSpace debris begins to burn as it enters the mesosphere shooting stars blaze

ThermosphereFrom 82-640 km above the Earths surfaceTemperature risesNorthern and Southern lights occur here

greenlandkid.comHeating of the Earths SurfaceSolar radiation from the sun heats the Earths surfaceWhen the radiation hits Earth it is reflected, absorbed, or reradiated.

Heating of the Earths SurfaceThe intensity of solar radiation varies with latitude

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Heat BudgetMore intense sunlight reaches the equator and the intensity of solar radiation decreases towards to the polesAt high latitudes the same amount of sunlight passes through the atmosphere but the same amount of sunlight is spread over a larger areaTo maintain a stable long term temperature, the Earth must loose as much heat as it gainsExcessive heat from the tropics tends to move to higher latitudes by winds and ocean currentsHeat Budget

Formation of Convection CellsNon-Rotating EarthEquator receives more heat and has more warm moist air (less dense)As this moist air rises this creates an area of low pressureWhen moist air rises it condenses forming precipitationThe now dry air flows north or south (depending on the hemisphere) and sinks back down at the poles . Then back to the equator creating a large convection cells

Formation of Convection CellsRotating EarthThe Earth rotates and moves in an easterly direction at a speed of 1674km/hr at the equatorThe rotation of the Earth affects the movements of the atmosphere, the ocean, and any other object not directly attached to EarthCoriolis Effect: Deflection of objects in movement not directly attached to Earth

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mind42.comSurface Wind Bands

oneonta.eduEffects of Continents and Seasons Large land masses modify the atmosphereLand masses have a lower heat capacity than water so they absorb and lose heat faster changes temperature faster70% of land masses are in the northern hemisphereDuring the summer, land is warmer than the ocean, causing a low pressure area over land (hot air rises) so there is a continuous low pressure area between 0-60 degrees north During the winter, land is cooler than the oceans, causing a high pressure area over land (cold air sinks)

Local EffectsLand warms faster during the day and as this warm air rises it is replaced by air from over the ocean creating an on-shore breeze / sea breeze (anabatic wind)At night, the air over land cools faster (sinks) than the ocean, and air flows out toward the ocean creating an off-shore breeze (katabatic wind)This typically creates rain on the windward side of islands

nc-climate.ncsu.eduAtmosphere Video ClipDay 2: HurricanesObjectives:What are hurricanes?Explain hurricane formation?How are hurricanes measured?Where do hurricanes get their name?

HurricanesHurricanes are low pressure systems with winds greater than 74mphNamed for the location in which they are occurring:Hurricanes are defined as storms over the North Atlantic or the CaribbeanIn the western Pacific Ocean, hurricanes are known as typhoons.Cyclones are hurricanes over the Indian Ocean.Hurricane FormationForm over warm tropical waters ( sea surface temps greater than 27oC)Low pressure cells that occur in latitudes higher than 5o are set into a circular motion by the Coriolis Effect this causes a circular pattern (counterclockwise in the northern hemisphere)As the storm grows, the winds evaporate more water (and heat) which fuels the storm and creates a column of fast moving airHurricanes dissipate/stop when they travel over land because they lose energy

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spaceplace.nasa.govHurricane DevelopmentTropical Disturbance: Group of thunderstorms with very little wind circulationTropical Depression: Storm with wind speeds up to 20 to 34 miles per hourTropical Storm: Storm with wind speeds reach 35-64 miles per hour. Hurricane: When wind speeds reach 74 miles per hour or greaterHurricane Formation= http://news.bbc.co.uk/2/hi/science/nature/4588149.stm Hurricane Development

bom.gov.auMeasuring HurricanesSaffir-Simpson Scale. Scale that measures wind speed and air pressure of a hurricane.Category 1- winds 74-95 mph, 64-82 kt, 119-153 km/h Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Branches of trees will snap, shallowly rooted trees may be uprooted. Power outages could last a few to several days.Category 2 - winds 96-110 mph, 83-95 kt, 154-177 km/h Extremely dangerous winds will cause extensive damage: Well-constructed frame homes could sustain major roof and siding damage. Shallowly rooted trees will be uprooted and block numerous roads. Near-total power loss is expected - outages that could last from several days to weeks. Category 3 (major)- winds 111-129 mph, 96-112 kt, 178-208 km/h Devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes.Category 4 (major) winds 130-156 mph, 113-136 kt, 209-251 km/h Catastrophic damage will occur: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months. Category 5 (major) - winds 157 mph or higher, 137 kt or higher, 252 km/h or higher Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months.Hurricane FactsHurricanes may have a diameter of 400 to 500 miles (640-800 kilometers).The eye (center) of a hurricane can be up to 20 miles (32 km) across. The weather in the eye is surprisingly calm with low winds and clear skies. Hurricanes hit land with tremendous force, bringing huge waves and heavy rain. Many hurricanes cause severe flooding.About 90 percent of the deaths that occur during hurricanes result from drowning in floods. The worlds worst hurricane (for loss of life) took place in 1970 in Bangladesh. That hurricane created a flood that killed more than one million people.Thunderstorms often form within hurricanes and produce tornadoes.

Damage from Hurricanes

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boston.comHurricanes in Media LiteracyMovieRaging Planet HurricaneHurricane Katrina - National Geographic

geology.comTracking Hurricanes Hugo and KatrinaHurricane Tracking Video ClipHurricane Lab

Day 3: Oceanic CirculationObjectives:What are the two main types of ocean circulations?Explain the difference between upwelling and downwelling.What are eddies?What is a wave?Label the parts of a wave.Explain the difference between deep and shallow water waves.What is a tsunami?Ocean CurrentsOcean Currents: Continuous, directed movement of ocean water generated by forces such as breaking waves, wind, Coriolis Effect, tides, temperature, density and salinity differencesMajor ocean currents are predictable they have been described as rivers without banksTypes of Currents:Surface 0-400 meters deep 10% of ocean currentsDeep below 400 meters 90% of ocean currentsThree major factors set ocean currents in motion:Thermohaline Circulation (density driven) Wind Driven Circulation Changes in Sea Level

Thermohaline/Density Driven CirculationAffect deep ocean currentsDensity differences are occur as a result of temperature and salinity. Warm water holds less salt than cold water so it is less dense and rises toward the surface while cold, salt laden water sinks. As the warm water rises though, the cold water is forced to rise through upwelling and fills the void left by the warm water. When cold water rises, it too leaves a void and the rising warm water is then forced, through downwelling, to descend and fill this empty space, creating thermohaline circulation.Coldest water is at the poles and have higher salinities because of low precipitation and the formation of sea ice Minute changes in density cause large changes in circulation for this reason, oceanographers measure density to 5 decimal placesDemonstration - http://www.divediscover.whoi.edu/circulation/demonstration.html Wind-Driven CirculationWind transfers energy to the water it blows across by the force of friction on the waters surfaceWinds cause both surface currents and wavesCause horizontal flow of water.If the wind blows long enough in the same direction, it will cause a water current to developWhat happens if the wind then stops blowing? - The current continues to flow until internal friction, or friction with the sea floor, dissipates its energyGlobal Wind Patterns

GyresGyres: Large system of rotating ocean currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis EffectThere are five major gyres:North AtlanticSouth AtlanticNorth Pacific South PacificIndian

Upwelling versus DownwellingUpwellingDownwellingUpward vertical current that brings deep water to the surfaceTends to bring deepwater nutrients up into the shallow water increasing biological productivitySometimes upwelling occurs when a wind blowing parallel to shore pushes surface water out to sea due to Ekman TransportEkman Transport: The net motion of water column down to friction depthNorthern Hemisphere =90o to the rightSouthern Hemisphere = 90o to the left

A downward vertical current that pushes surface water deep into the oceanCarry nutrients and other essential materials out to the deep ocean have no dramatic effect on biological productivity

Upwelling and Downwelling - Deep Ocean

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Coastal Upwellings and Downwellings

eeb.ucla.eduEddiesGyres flow in a general area but they dont flow within perfectly defined paths they can vary due to wind strengthEddies: Swirling currents Caused by friction with adjacent water Can form large circular loops that can temporarily break away:Coldcore eddies flow counter clockwise in the northern hemisphereWarm-core eddies flow clockwise in the northern hemisphereBoth types can travel slowly for weeks, months, and even yearsEddies are important because:they can affect local temperatures and weather conditions by redistributing heat.commercial fishing boats use eddies to located fish.they can affect ship speeds.The Ocean Conveyor BeltThe Ocean Conveyor Belt: The interconnected flow of currents that redistribute heat - AKA the Earths Air conditionerIt would take one to two thousand years for a drop of water to complete a cycle on the ocean conveyer belt

Changes in Sea LevelSea level: the Average level of the seas surface at its mean height between high and low tideChanges in sea level occur in horizontal distancesOcean circulation causes slopes to developEx. when a land mass interrupts a currents flow, water mounds up against the landThe slope in the water surface causes a horizontal difference in water pressureThe water will tend to flow out due to this difference creating a pressure gradientThe steeper the mound of water, the larger and faster the current will be

sealevel.jpl.nasa.govImportance of Ocean CirculationOcean circulation affects the Earth in many ways:Circulates nutrients and energy throughout the oceanAffects the Earths climateAffects the transport and shipping industries.Transport living things like seeds and actual organisms around the globe.

Studying Ocean CurrentsDifferent Approaches:Lagrangian Method (AKA the Float Method): Studies currents by tracking and drifting an object floating something in the current that records information as it driftsEulerian Method (AKA the Flow Method): Studies currents by staying in one place and measuring the velocity of water as it flows past.Flotsam Method: Scientists also take advantage of accidental opportunities to study currentsIn 1992 a cargo carrier lost its cargo 30,000 athletic shoes while en-route to Seattle from Korea. Oceanographers asked the public to report the time, date, and place they found the shoes. Using this info they were able to improve current models in the north pacificIn 1992 a ship lost 29,000 rubber ducks, frogs, and turtles while sailing from China to Seattle. The toys washed up along the north pacific coast at various location from Oregon to Alaska eventually drifting through the Bering Strait they are expected to make it New England none of washed up yet.

Ocean Currents Songhttp://safeshare.tv/w/HfLljJafyJ Day 4: WavesWhat is a wave?What are the three types of waves?What are the crest, trough, height, wavelength, period, and frequency of a wave?How do wave length and period relate to a waves speed?What disturbing forces cause waves?What restoring forces resist waves?Compare shallow water and deep water wavesWhat three factors affect maximum wave size?What causes internal waves?WaveWave: Transmission of energy through matterWhen energy moves through matter as a wave, the matter moves back and forth but then it returns to its original positionIt transmits energy to the adjacent matter (next thing) allowing the energy to continueExample: Dropping a stone in water Waves ripple away from the splash the water doesnt move away only the energy

Types of Progressive WavesProgressive Wave: Wave in which energy progresses from one point to another Progressive waves are waves in which there is a direction to the transmission of the waveCan be created by a variety of disturbing forces including: wind, seismic activity, volcanic eruptions, landslides, gravity, or a change in atmospheric pressure3 Types of Progressive Waves:LongitudinalTransverseOrbital

Longitudinal WaveLongitudinal Wave: Matter moves back and forth in the same direction that the energy travelsCan move through all states of matterEnergy is transmitted through the compression and decompression of particles like a spring or slinkyExample: Sound travels in longitudinal waves

spot.pcc.eduTransverse WaveTransverse Wave: Motion of the matter is perpendicular to the direction in which the wave as a whole is movingExample: Ripple in pond

Orbital WavesOrbital Waves: Transmit only through fluids as energy moves through the fluid in a circular motion as it passesWaves in the ocean are orbital waves

kingfish.coastal.eduWave TerminologyWavelength: The horizontal distance between two successive crests or troughsCrest: Highest part of the waveTrough: Lowest part of the waveHeight: Vertical distance between 2 successive crests or troughs Period: The time it takes for 2 troughs or 2 crests to pass a fixed pointFrequency: The number of waves or crests/troughs that pass a fixed point each secondCelerity: Speed of the wave - equal to the wavelength period

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asdk12.orgWaves and Mathematics Wave characteristics can be expressed mathematicallySpeed = wavelength period or S = L TRatio of wave height to wavelength H:LWavelength (L: Depth in meters)Period (T: Time in seconds)Speed (S: Speed in meters per second)Wave Height (H: Height in meters)Example: If in a given wave, T=20s and L=200m, what is the speed of the wave?S=200m 20s + 10m/s

Wave FormationDisturbing Forces: Forces that cause wavesRestoring Forces: Forces that resist wavesThe intensity and duration of a disturbing force and the interaction of restorative forces give waves their characteristicsFluids tend to remain at rest they only move when something imparts energy on them disturb themDisturbing forces that cause ocean waves include wind, changes in gravity, and seismic activity (volcanoes and earthquakes)Restorative forces include gravity, Coriolis effect, and surface tension

Wave Classification Based on Resisting ForcesCapillary Waves: Primary force acting on them is surface tensionFirst to form when wind blows across still waterGravity Waves: Waves in which the weight of the wave is pulled by gravityMost waves that concern us in oceanography are gravity wavesWave PatternsWaves tends to organize themselves into patternsWaves that are not organized travel at different speeds and longer waves outrun the shorter waves eventually only waves of the same length are left travelling togetherSwell: The rise and fall of a uniform wave pattern on the seaWave Trains: Groups of swells with similar characteristics that tend to travel together in groups The first wave gradually looses energy, which is picked up by new waves forming in the trailing portion of the train When wave trains reach shallow water, the individual and group speeds become the same

Waves at Different DepthsDepth affects wave characteristicsDeepwater Waves: Occur in water that is deeper than half their wavelength No interaction from the bottom can affect the wave characteristicsTheir orbital motion progresses unaffectedCapillary waves are almost always deep water waveMostly wind drivenTransitional Waves: Occur in depths between one-half and one-twentieth the wavelengthAt depths that are one-fourth the wavelength, the bottom of the ocean creates a drag that affects the orbital motion flattens the circular motion into an ellipse

Shallow-water Waves: Occur in waters that are shallower than one-twentieth the wavelengthWavelength and speed are dependent on depth, as friction with the sea floor slows down the wave the wave behind continues at the original speed and the wavelength decreases this causes the height of the wave to increaseWaves break when they reach a height of 1:7 (height: length)Tides are usually shallow water wavesWaves at Different Depths

Factors Affecting Wind Wave GrowthWind SpeedWind must be blowing faster than the wave to give it energyDurationLength of time wind blows in a single directionFetchSurface over which the wind blowsLarge the surface area, the greater the energy transfer, the bigger the wavesFully Developed Sea: Maximum wave size has been reached (disturbing and restoring forces counterbalance)Rouge Wave: Theorized to result from the interaction of two closely related wave trainsDeadliest Catch Rogue WaveRogue Wave Deadliest CatchInteraction of Wave TrainsIn-Phase: Crest and troughs of different trains coincide and make larger wavesIf this happens against the current REALLY LARGE waves like rogue waves can formAKA Constructive InterferenceOut-of-Phase: Crest of one train coincides with troughs of others the waves cancel each other outThis is how calm seas can occur during strong windsAKA Destructive Interference

teachgreenbk.wordpress.comBreaking WavesAs a wave approaches shore, the bottoms of ocean begins to affect to orbit of the waveAs the wave continues to move forward the friction with the bottom causes the wave to slow down and the wavelength decreases and wave height increaseWaves break when they reach a height of 1:7 (height to length) because the crest is travelling faster than the trough making the wave unstable and its crest topples forward

Types of Breaking WavesType of breaker depends on slope of shore and speedSpilling Breakers: Occur on wide flat beaches and lose energy gradually(longer ride for surfers)Plunging Breakers: Occur on narrow steep beach slopes and loose energy faster have a characteristic curl(more exciting ride for surfers)Surging Breakers: Occur on very abrupt shores with no opportunity for break no surfing very destructive

booksite.academicpress.comWave Deformation: RefractionRefraction: Bending of waves as they approach shore at an angle Crest closest to shore slows sooner creating uneven slowing and the waves refract or bend until they face the shore more squarely slowly and evenly

answers.comWave Deformation: DiffractionDiffraction: When waves pass an obstacle and energy shifts in the wave allowing a new wave pattern to form past the obstacle or through an openingExample: Waves in well protected harbor

geographyfieldwork.comWave Deformation: ReflectionReflection: Occurs when waves hit an obstacle and the wave retains most of its energy and bounces back toward the open waterExamples of obstacles include cliffs or seawallsCan cause standing waves when water rocks back and forth on the edges but remains motionless in the center or node (like when you bump a cup of liquid like a coffee cup)

Destructive Waves3 Types of waves are noted for their destructive power:Storm Surge: Destructive wave or wall of water that forms when high winds push water up against the shore where it piles up.The shallower the water offshore and further it extends offshore, the greater the surge (this is why the Gulf Coast has the biggest storm surges) common with hurricanesSeiche: Standing wave that forms in large bays and lakes as a wave rocks back and forthCan result from strong winds that push water levels up one side of a bay (this is actually common in the great lakes)Tsunami: Sudden water displacement caused by landslide, volcanic eruption, iceberg calving, or most commonly an earthquakeThese are also called tidal waves (even though their not caused by tides)Not that large at sea but as they approach shoe it becomes much higher

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SeicheTsunamiStorm SurgeDay 5 TidesObjectives:What causes tides?How does Newtons Equilibrium Theory of Tides differ from Laplaces Dynamic Theory?What factors influences/affect tides?What are diurnal, semidiurnal, and mixed tides?What are tidal currents and a tidal bore?What are the relative positions of the sun and moon during spring tides and neap tides?TidesTides: Daily variations in the oceans sea levelResult from the gravitational pull of the moon, the sun, and the rotation of the EarthThose forces pull ocean water into a huge wave with a wavelength the size of the ocean basin (or half the circumference of the Earth) therefore, the waves are always shallow water and their speed is controlled by the depth of the waterThey are forced waves as they are always under the forces from which they were generated

Tides SimplifiedThe sun and the moon create two bulges on opposite sides of the Earth. The relative positions of the sun and moon change slowly so the bulge rotates around the Earth.As a coastline rotates into the bulge, the tide rises as it rotates out, the tide falls.

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Tidal Theories Equilibrium TheoryDynamic TheoryProposed by Isaac NewtonThe gravitational pull of the sun and moon create two bulges of water on either side of the Earth.Assumes the Earth is perfectly uniform, that the water is VERY deep, and that there are no land massesProblem = too simple

Proposed by Pierre-Simon Laplace and modified Newtons theoryThere are several tidal bulges because in addition to lunar and solar gravity the imperfect sphere of the Earth, the season, the time of the month, the shape of the ocean basin, the Coriolis effect all influence tides.web.vims.eduTidal PatternsThe shape and depth of the ocean basins affect tidal patterns. Large wide basins tend to have a smaller tidal range than narrow, shallower basins.Diurnal Tides: Single high and low tide dailyEx. Gulf of MexicoSemidiurnal Tides: Roughly two high and low tides dailyEx. East CoastMixed Tides: Two unequally high and low tides dailyEx. West Coast

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tideclocks.comTidal CurrentsDaily tides create a current that flows into and out of bays, rivers, harbors and other restricted spacesInflow is called flood currentOuttflow is called slack currentMidpoint between high and low tide creates a slack tide (where little water is moving) These currents are very important to the people in live in or around these areasFor example:large ships may only enter or leave some harbors at high tide.sailing vessels often use slack currents to take advantage of the flow carrying them seaward.Tidal BoreTidal Bore: Incoming tide produces a wave that flows into a river, bay, or other narrow openingThis is a true tidal waveCan be several meters highExample: Happens in the Amazon River and Severn River in Englad

voyagner.comSurfer on the Amazon Tidal Bore The Sun, Moon, and Types of TidesSolar and lunar gravity affect the tides differently, depending on the positions of the sun and moon relative to the EarthThe moon has twice the influence of the sun on the tidesSun has a greater gravity but is farther away than the moonSpring Tides: When the sun, the moon, and the Earth are in-line it creates the highest and lowest tidesThis occurs during a new moon (no moon visible) and a full moonNeap Tides: Weak tides created when the moon is in quarter phase and the lines from the moon and the sun to the Earth form a right angle. The suns gravitation pulls to the side of the moons tidal bulge which tends to raise the low tide and lower the high tide.

Solar and Lunar TidesAnimation

iupui.eduSpring Tide vs. Neap Tide

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