剑桥雅思阅读模拟题test4passage2原文-智课教育出国考试

智课网雅思备考资料剑桥雅思阅读模拟题test4passage2原文-智课教育出国考试本文为大家带来剑桥雅思阅读模拟题test4passage2原文供大家参考，希望大家能够关注。雅思阅读是雅思考试的重要部分，有人说得阅读者得雅思，确是如此，而掌握一些雅思阅读真题无疑是很重要的。READINGPASSAGE2Youshouldspendabout20minutesonQuestions15-28,whicharebasedonReadingPassage2below.RISINGSEAParagraph1.INCREASEDTEMPERATURESTheaverageairtemperatureatthesurfaceoftheearthhasrisenthiscentury,ashasthetemperatureofoceansurfacewaters.Becausewaterexpandsasitheats,awarmeroceanmeanshighersealevels.Wecannotsaydefinitelythatthetemperaturerisesareduetothegreenhouseeffect;theheatingmaybepartofa“natural，，variabilityoveralongtime-scalethatwehavenotyetrecognizedIourshort100yearsofrecording.However,assumingthebuildupofgreenhousegasesisresponsible,andthatthewarmingwillcontinue.Scientistsandinhabitantsoflow-lyingcoastalareaswouldliketoknowtheextentoffuturesealevelrises.Paragraph2.Calculatingthisisnoteasy.Modelsusedforthepurposehavetreatedtheoceansaspassive,stationaryandone-dimensional.Scientistshaveassumedthatheatsimplydiffusedintotheseafromtheatmosphere.Usingbasicphysicallaws,theythenpredicthowmuchaknownvolumeofwaterwouldexpandforagivenincreaseintemperature.Buttheoceansarenotone-dimensional,andrecentworkbyoceanographers,usinganewmodelwhichtakesintoaccountanumberofsubtlefacetsofthesea-includingvastandcomplexoceancurrents-suggeststhattheriseinsealevelmaybelessthansomeearlierestimateshadpredicted.Paragraph3Aninternationalforumonclimatechange,in1986,producedfiguresforlikelysea-levelrisesof20cmand1.4m,correspondingtoatmospherictemperatureincreasesof1.5and4.5Crespectively.Somescientistsestimatethattheoceanwarmingresultingfromthosetemperatureincreasesbytheyear2050wouldraisethesealevelbybetween10cmand40cm.Thismodelonlytakesintoaccountthetemperatureeffectontheoceans;itdoesnotconsiderchangesinsealevelbroughtaboutbythemeltingoficesheetsandglaciers,andchangesingroundwaterstorage.Whenweaddonestimatesofthese,wearriveatfiguresfortotalsea-levelrisesof15cmand70cmrespectively.Paragraph4It’snoteasytryingtomodelaccuratelytheenormouscomplexitiesoftheever-changingoceans,withtheirgreatvolume,massivecurrentsandsensitivelytotheinfluenceoflandmassesandtheatmosphere.Forexample,considerhowheatenterstheocean.Doesitjust“diffuse”fromthewarmerairverticallyintothewater,andheatonlythesurfacelayerofthesea?(Warmwaterislessdensethancold,soitwouldnotspreaddownwards).Conventionalmodelsofsea-levelrisehaveconsideredthatthistheonlymethod,butmeasurementshaveshownthattherateofheattransferintotheoceanbyverticaldiffusionisfarlowerinpracticethanthefiguresthatmanymodelshaveadopted.Paragraph5Muchoftheearlywork,forsimplicity,ignoredthefactthatwaterintheoceansmovesinthreedimensions.Bymovement,ofcourse,scientistsdon’tmeanwaves,whicharetoosmallindividuallytoconsider,butrathermovementofvastvolumesofwaterinhugecurrents.Tounderstandtheimportanceofthis,wenowneedtoconsideranotherprocess-advection.Imaginesmokerisingfromachimney.Onastilldayitwillslowlyspreadoutinalldirectionsbymeansofdiffusion.Withastrongdirectionalwind,however,itwillallshiftdownwind,thisprocessisadvection-thetransportofproperties(notablyheatandsalinityinocean)bythemovementofbodiesofairorwater,ratherthanbyconductionordiffusion.Paragraph6Massiveoceanscurrentcalledgyresdothemoving.Thesecurrentshavefarmorecapacitytostoreheatthandoestheatmosphere.Indeed,justthetopBmoftheoceancontainsmoreheatthanthewholeoftheatmosphere.TheoriginofthegyresliesinthefactthatmoreheatfromtheSunreachestheEquatorthanthePoles,andnaturallyheattrendstomovefromtheformertothelatter.WarmairrisesattheEquator,anddrawsmoreairbeneathitintheformofwinds(the“TradeWinds”)that,togetherwithotherairmovements,providethemainforcedrivingtheoceancurrents.Paragraph7WateritselfisheatedattheEquatorandmovespoleward,twistedbytheEarth’srotationandaffectedbythepositionsofthecontinents.Theresultantbroadlycircularmovementsbetweenabout10and40#NorthandSouthareclockwiseintheSouthernHemisphere.Theyflowtowardstheeastatmindlatitudesintheequatorialregion.TheythenflowtowardsthePoles,alongtheeasternsidesofcontinents,aswarmcurrents.Whentwodifferentmassesofwatermeet,oncewillmouebeneaththeother,dependingontheirrelativedensitiesinthesubductionprocess.Thedensitiesaredeterminedbytemperatureandsalinity.TheconvergenceofwaterofdifferentdensitiesfromtheEquatorandthePolesdeepintheoceanscausescontinuoussubduction.Thismeansthatwatermovesverticallyaswellashorizontally.ColdwaterfromthePolestravelsasdepth-itisdenserthanwarmwater-untilitemergesatthesurfaceinanotherpartoftheworldintheformofacoldcurrent.Paragraph8.HOWTHEGREENHOUSEEFFECTSWILLCHANGEOCEANTEMPERATURESOceancurrents,inthreedimensions,fromagiant“conveyorbelt”，distributingheatfromthethinsurfacelayerintotheinterioroftheoceansandaroundtheglobe.Watermaytakedecadestocirculateinthese3-Dgyresinthelopkilometeroftheocean,andcenturiesinthedeepwater.Withtheincreasedatmospherictemperaturesduetothegreenhouseeffect,theoceansconveyorbeltwillcarrymoreheatintotheinterior.Thissubductionmovesheataroundfarmoreeffectivelythansimplediffusion.Becausewarmwaterexpandsmorethancoldwhenitisheated,scientistshadpresumedth