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SIO210FinalexaminationWednesday,December12,201811:30-2:30Eckart227 Name:____________________Pleaseputyourinitialsornameoneachpage,especiallyifyoupullpagesapart.Turnoffallphones,iPods,etc.andputthemaway.Thisisaclosedbookexam.Youmayusetwopagesofnotes,bothsides,writtenorprinted.Youmayuseanon-communicatingcalculator.Checkwhichyoupreferregardingthereturnofthisexamandothergradedmaterials_______Iwillpickuptheexam(afterJan.2)_______Returntheexametctomeviacampusmail(orfulladdress)

Mailcode__________________________Possiblyusefulexpressionsandvalues;youwillnotneedallofthese.r:use1025kg/m3forgenericcalculationscp=4000J/kg°CrcpT1PW=1015W=1015J/secEarth’sradius:6371kmVEk=-t(x)/(rf)f=2Wsin(latitude)W=0.73x10-4/secsin(30°)=0.5sin(50°)=0.771°latitude=111km1Sv=1x106m3/secg=9.8m/sec2Multiplechoice(2pointseach;20pointstotal)Foreachmultiplechoiceproblem,circleONECORRECTanswer.1) InthetropicalPacific,theWalkercirculation

(a)weakensduringElNinoevents(b)strengthensduringElNinoevents(c)causesthesurfacewateralongtheequatortofloweastward(d)isassociatedwithexcessrainfallnearEcuadorandPeru

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2) Theclimateinteractionbetweenseasurfacetemperature,seaiceextent,andsolarradiation(reflectivity)showninthefigureisanexampleofa) stableequilibriumb) negativefeedbackc) neutralstabilityd) positivefeedback

3) NorthAtlanticDeepWaterisformedmostlyby

a) Downwarddiffusionofheataccompaniedbydeepupwellingb) BrinerejectionduetoseaiceformationintheGreenlandSeac) Openoceanconvectioninlimitedlocationsd) InflowofArcticwatersthroughtheCanadianarchipelagobetweenCanadaandGreenland

4) Geostrophicbalance

(a) Resultsfromtilting(sloping)ofisopycnals(b) IntheBrazilCurrentisassociatedwithhighsurfaceheightinthecenterofthegyre(mid-

Atlanticridgeregion)andlowsurfaceheightalongtheBraziliancoastline(c) ResultsfromEkmanconvergenceinthemixedlayer(d) IntheGulfStreamisassociatedwithlowsurfaceheightinthecenterofthegyre(near

Bermuda)andhighsurfaceheightalongtheU.S.coastline5) Whichofthefollowingwatermass/straitcirculationsisNOTassociatedwithdensewater

formationinasemi-enclosedsea?a) IndonesianThroughflowWaterb) MediterraneanOverflowWaterc) NordicSeasOverflowWaterd) RedSeaWater

6) TheNyquistfrequency

a) Iscalculatedfromthetotallengthoftimeofatimeseriesb) Isthetypicalfrequencyofsurfacewavesc) Iscalculatedfromthetimeseparationbetweensamplesinatimeseriesd) Isthetypicalfrequencyofinternalwaves

7) UpwellingintheCaliforniaCurrentsystem

a) Occursonlywithinaverynarrowzonealongthecoastb) Isduetonorthwardalongshorewinds

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c) Isoftenassociatedwithlargeeddies/filamentsofupwelledwaterthatspreadwestwardoffshore

d) Bringswaterfromtheabyssalocean(>1000m)totheseasurface8) SubtropicalgyressuchastheGulfStreamgyre

(a) Extenddowntothebottomoftheoceanwithoutchangeofhorizontalextent(b) AredrivenbyEkmanconvergenceanddownwelling(pumping)(c) Usuallyhaveveryfreshwaterinthecenterattheseasurface(d) Aredrivenbycoolingoftheseparatedwesternboundarycurrent(GulfStream)

9) Potentialtemperature

a) Doesnotchangeasaparcelofwaterismovedadiabaticallyfromtheseasurfacetothedeepocean

b) Changesasaparcelofwaterismovedadiabaticallyfromthesurfacetothedeepoceanc) Cannothaveaverticalinversion(coldabovewarm)d) Ismeasureddirectlywithathermistororthermometer

10) TheLeeuwinCurrentis

a) ThewesternboundarycurrentoftheIndianOceanb) TheeasternboundarycurrentoftheSouthAtlanticOceanc) Anequatorwardflowingeasternboundarycurrentd) Apolewardflowingeasternboundarycurrent

Problems11)14(2,3,2,3,2,2)Atthesurfaceoftheocean,thetropicaloceanisheatedandthehighlatitudeoceaniscooled,intheannualmean(averageovermanyyears).Themapshowstheannualmeansurfaceheatflux.Positive:oceanisheated.Negative:oceaniscooled.

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a)Circlethetworegionsofmaximumoceanheatlossinthemid-latitudeNorthernHemisphere.Namethemajorsurfacecurrentsassociatedwiththeseheatlossareas.

_Kuroshio_________________(NorthPacific)

_GulfStream_________________(NorthAtlantic).

Circletheoneareaofmajorheatlossinthehigh-latitudeNorthernHemisphere.CircleregionoffNorway(alittlehardtofindinthismapprojection–youcanseeitbestintheupperleftcorner)

b)Circlethethreeregionsofmaximumoceanheatlossinthemid-latitudeSouthernHemisphere.Namethemajorsurfacecurrentsassociatedwiththeseheatlossareas.

_EastAustralianCurrent___________________(SouthPacific)

_BrazilCurrent___________________(SouthAtlantic)

_Agulhas___________________(Indian)

c)Explainingeneraltermshowthesecurrentsin(a)and(b)contributetolargeheatlossintheseregions.

Allofthesecurrentsarepoleward.Thebackgroundoceantemperaturegradient(upperocean)ishighinthetropicstolowinthesubpolar/polarregions.Polewardcurrentscarrywarmwater.Theatmospherecirculationismuchmorezonal,andsothewarmcurrentsencountercoolerairinregionswhereinsolationislowerthaninthetropics.Thiscausesoceancooling.

e) IntheequatorialPacificOcean,thereisheatgain.Whereistheheatgainlargest?(circleit)Circlethehighheatfluxregionalongtheeasternequator.

Explainwhytheequatorialheatgainislargerinthisregionthanatotherlocationsalongtheequator.Describetheoceancirculationthatresultsinthislargeheatgain.

Surfacewateriscoolerhere,sothewaterheatsmorethaninotherpartsofthetropics,giventheapproximatelysameinsolationandairtemperature.Surfacewateriscoolerhereduetoupwellingofcoolerwaterfrombelow.Upwellinghereisduetotheeasterlytradewinds(Walkercirculation),whichmovessurfacewaterfromeasternequatortopoolinthewest.ThedeeperwarmpoolinthewestmeansthatlocalupwellingthereduetoEkmandivergenceonlyupwellswarmwater,sodoesnotcreatecoolsurfacetemepratures.BecausethethermoclineismuchshallowerintheeasternPacificduetothewestwardflowofsurfacewater,localupwellingaccessescoolerwaterandcreatestheequatorialcoldtongue.

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f) Inthemid-latitudeNorthPacific(around30°N),theocean’smeridionalheattransportispoleward(andlarge).Describethecirculationandheatloss/gainthatcreatesthispolewardheattransport.(AssumethatthedeepNorthPacificdoesnotcontributemuchtooceanheattransport.)

Poleward(northward)Kuroshiomoveswarmwaternorthacross30N.Thereislargeheatlosstothenorth.Waterreturningsouthwardinthesubtropicalgyreiscooler.Thenetbalanceofnorthwardwarmandsouthwardcoolflowinthegyretransportsheatpoleward(intotheheatlossregion).12)(6points)Thehorizontalmomentumequationsinafluidinarotatingreferenceframeincludeacceleration,advection,Coriolis,pressuregradient,andviscousterms.x:¶u/¶t+u¶u/¶x+v¶u/¶y+w¶u/¶z-fv=-(1/r)¶p/¶x+¶/¶x(AH¶u/¶x)+¶/¶y(AH¶u/¶y)+

¶/¶z(AV¶u/¶z)y:¶v/¶t+u¶v/¶x+v¶v/¶y+w¶v/¶z+fu=-(1/r)¶p/¶y+¶/¶x(AH¶v/¶x)+¶/¶y(AH¶v/¶y)+

¶/¶z(AV¶v/¶z

(a) Whichpairsoftermsyieldgeostrophicbalance?(circleandnametheterms)Coriolisandpressuregradienttermsinbothequations.

(b) WhichpairsoftermsyieldEkmanbalance?(circleandnametheterms)Coriolisandverticalviscousterms

(c) Whichpairsoftermsyieldinertialbalance?(circleandnametheterms)Coriolisandaccelerationterms

13)22(2,2,4,4,4,2,4)ThemapshowstheannualmeanwindvectorsforthePacificOcean.

(a) MarkthelocationofthewesterlywindsintheNorthPacificandSouthPacific.Generalregionsurrounding40°Nand50°S.

(b) MarkthetradewindsintheNorthandSouthPacific.Generalregionaround20Nto10N

andlikewiseinsouthernhemisphere.

(c) IntheeasternNorthandSouthPacific,circletheregionswherethereisupwellingalongtheboundary.Whatisthenameofthecurrentsystemineachoftheseupwellingregions?

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___CaliforniaCurrentSystem________________________(NorthPacific)___Peru-ChileCurrentSystem(Ialsoaccept‘HumboldtCurrent”)_____(SouthPacific)

(d) ExplaintheupwellinginthesetworegionsintermsofEkmantransport.Youmaydrawrelevantarrowsonthemap,anddescribehereinwords.

Equatorwardwindsthatarepartofthesubtropicalhighpressuresystems(westerlywindsstrikingthecoastlines/mountains)driveoffshoreEkmantransport.Thisrequirescoastalupwellingforcontinuity.

(e) DescribethehorizontalvelocitieswithinanEkmanlayer,startingattheseasurface.Use

youranswertoProblem12baspartofyourexplanation.Windcreatesfrictionalstressattheseasurface.BecauseofCoriolisforce,thesurfacecurrentsareatanangletothewind(totherightinthenorthernhemisphereandleftinsouthernhemisphere).Thea

(f) HowdeepisatypicalEkmanlayerinmeters?____50meters_________

(g) InthecentralNorthPacific(180°to160°W,and10°Nto40°N),indicatethegeneraldirectionofEkmantransportrelativetothewesterlyandtradewinds.Usearrowsonthemap.IsthisaregionofEkmanconvergence(pumping)ordivergence(suction)?Underthewesterlies,Ekmantransportisequatorward(usearrows).Underthetrades,Ekmantransportispoleward(usearrows).BetweentheequatorwardandpolewardEkmantransportsthereisconvergence(pumping),i.e.downwardverticalvelocity

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14)12(2,2,2,2,4)Thefigureshowsthecartoonofthenormalwinds,precipitation,currents,surfacetemperatureandthermoclineintheequatorialPacific.

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(a) Onthefigure,circlethepartthatisthetradewindsandtheWalkercirculation.Explainhowthiscirculationisdrivenbytheocean.Circlethelittleblackarrowinthemiddle,pointingwestward–thisisthetradewinds.Thewholedashed‘convectiveloop’istheWalkercirculation.ThisisdrivenbytheSSTdistributionillustratedincolor,withwarmSSTtothewestandcooltotheeast,resultinginrisingairoverthewarmandsinkingoverthecool.(b) SupposethetradewindsintheequatorialPacificweaken.Explainhowthesurfaceoceancirculationchangesinresponsetothewindchange.IsthisanElNinooraLaNinastate?TheSSTdistributionisaresultofthewinds.Ifthewindsweaken,thereislesswestwardfrictionalflow(intheSouthEquatorialCurrent)atthesurface,andthereislessupwellingofcoolwaterintheeast,andlesspileupofwarmwaterinthewest.ThisistheElNinostate.

(c) Explainhowtheseoceancirculationandwindchangesaffecttheoceansurfacetemperaturedistribution.

Alreadyimplicitin(b)answer:changeincirculationcreateswarmanomalyineasternPacificsincethereisnolongerupwelledcoolwater.(Itdoesn’tactuallychangetheSSTmuchinthewest,becausethewarmpoolissodeep,butthisisadetailthatwasnotexpectedinthisanswer.)(d)ThefigureisthetimeseriesoftemperatureanomalyforthetropicalPacific(alsocalledtheNino3.4index).Positivemeanswarmtemperatureanomaly. MarkatleastonemajorElNinoepisodeonthefigure.Anyofthelargepositiveevents. MarkatleastonemajorLaNinaepisodeonthefigure.Anyofthelargenegativeevents.

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(e)TheequatorialthermoclineintheeasternPacific,asmarkedbythe20°Cisotherm,iscenteredat70metersdepth.Theverticaltemperaturegradientthroughthethermoclineis0.1°C/meter.Howfarupordownmustthe20°Cisothermmoveinordertoproduceapositive(warm)5°Ctemperatureanomalyat70metersdepth?Straightforwardcalculation:dT/dz=0.1°C/meterTohaveawarmanomalyat70mdepth,isothermmustmovedown.A5°Canomalyinagradientof0.1°C/meterrequiresdownwardmotionof50m.15)10(3,2,3,2)SEECOLORFIGUREONLASTPAGE(SEPARATEPAGE)NADW(greenpathways)formsintheNorthAtlanticanditsmarginalseas.

(a) Onthemap,markthelocationofthethreedeepconvectionsitesthatcreatethenew(northern)componentsofNADW.

Lookingfor:GreenlandSea,LabradorSeaandwesternMediterraneanSea.Iacceptedabroaderrange,includingIrmingerSea.

(b) WhatistheapproximatenetformationrateofNADW(overturningrateinunitsofSverdrups)asawhole?(Youcangivearangeofvaluesoranorderofmagnitude.)

Rateis15to20Sv.Iaccepted10Svalsoasanorderofmagnitude.

(c) IfthetemperatureofthesurfacewaterfeedingtheAtlanticoverturnaverages17°Candthedeepwaterformedintheoverturnaverages2°C,usetheoverturningvolumetransportfromyouranswer(a),andexpressionsgivenatthetopoftheexam,andcalculatethenetmeridionalheattransportassociatedwiththeoverturn.Thisisasimplecalculation:heatisgivenintheequationsattopofexam.

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Multiplythetransport,whichgoesnorthwardat17Candsouthwardat2C,bythetemperature,densityandspecificheat.Thetransportbalancesbydefinition.Heattransport=(VnorthTnorth)rcp+(VsouthTsouth)rcpVsouth=-VnorthAssumercpisthesameforboth,forsimplicityHeattransport=Vnorth(Tnorth–Tsouth)rcpEvaluatethiswithyouranswerfortransportin(b).Iwilluse15Sv,where1Sv=1x106m3/sec.Heattransport=(15x106m3/sec)(15°C)(1025kg/m3)(4000J/kg°C)=0.92x1015J/sec

(d) Inorderfortheretobeupwellingfromthedeepoceantotheupperocean,theremustbea

processthatconvertsdeepwatertoupperoceanwater.Listatleastoneprocessandcircleitontheschematiccirculationmap___Twoprocessescouldbelisted:diapycnaldiffusivity,andSouthernOceanupwellingfromdeeptosurface______________________

16)16(10,2,2,2)Thecolorfigurewith4panelsshowsPacificOceanpropertiesalongameridionalsectionat150°W.

(a) Labelthefollowingwatermasses,anddescribebrieflyhowyouidentifythem(salinityminimum,etc):

SubantarcticModeWater(SAMW)___Thicklayer(relativelyunstratified),northoftheACC_______AntarcticIntermediateWater(AAIW)___SalinityminimumnorthoftheACC__________________PacificDeepWater(PDW)____DeepoxygenminimumthroughoutPacific_________________LowerCircumpolarDeepWater(NorthAtlanticDeepWater)(LCDW)__Deepsalinitymaximum,especiallyintheACCbutalsonorthoftheACCwheremaximumisatbottom___________________AntarcticBottomWater(AABW)__Verycold,densewateratbottom,alsosameasLCDWnorthoftheACC___________________

(b) Onthepotentialtemperaturesection(topleft),indicatethelocationoftheAntarcticCircumpolarCurrent(ACC).Useournotationforcurrents(circlewithinacircleorx-within-a-circle,orarrow),toshowthedirectionoftheACC.

Drawbiggestcirclewitharrowhead(pointingouttowardsreader)atsurface,ATlocationofthesteepisothermslope(notatthebottomofthecurvewheretheisothermsflatten!)Thisisaround50to55°S.Thendrawdirectlyunderneaththat,circleswithdecreasingdiameterwithdepth

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(c) Acrossthetopofthepotentialtemperaturesection,sketch(draw)theseasurfaceheight(SSH)thatyouinferfromyouranswerto(b),andthencontinuetheseasurfaceheightforthewholesection.MakesurethatyourlowSSHandhighSSHareinapproximatelytherightlocations.Easiestwaytodothisisdrawthemirrorimageofthedensitycontours,whicharesimilartothetemperaturecontours,intheupper500morso.IntheACCyouwillmirrortheflatisopycnalsatsouthernend,steepslopewithintheACC.Inthesubtropicalgyres,youwillmirrorthecurvingisotherms/isopycnalsthatrepresentthesubtropicalgyres.Atthefarnorthernend(Alaska)youwillmirrorthediveoftheisothermsintothecoastline.

(d) Whatdynamicalbalance(fromproblem12)didyouuseinanswering(c)?Geostrophicbalance.Ifyouanswered‘hydrostatic’Igaveyoupartialcredit,sinceweassumeitisbothgeostrophicandhydrostaticbalance.

----FORPROBLEM15---

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