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Sensitivity

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SensitivitySensit

    Sensitivity

    J.Geogr.Sci.(2008)18:190200

    Doh10.1007/s11442-008.0190.6

    Sensitivityanalysisofglaciersystemstoclima

    warminginChina

    WANGXin',

    XIEZichu.,

    LIQiaoyuan.,

    WANGShuhong.,

    CHENGLei.

    1.StateKeyLaboratoryofCryosphericSciences,ColdandAridRegionsEnvironmentalandEngineering

    ResearchInstitute,CAS,Lanzhou730000,China;

    2.ResearchInstituteofGeo

    spatialInformationScience,HunanUniversityofScience&Technology,Xiangtan 411201,China;

    3.CollegeofResourcesandEnvironment,HunanNormalUniversity,Changsha410081,China

    Abstract:Dataof44glaciersystemsinChinausedinthispaperwereobtainedfrOmChinese GlacierlnventoriesandthemeteOrOlOaicaldataweregotfrOmMeteorologicalAtlasofPlateau

    ofwestChina.Basedonthestatisticalanalysisandfunctionalmodelsimulationresultsofthe 44glaciersystemsinChina.theglaciersystemsweredividedintoextremely

    sensitiveglacier

    system,semisensitiveglaciersystem,extremelysteadyglaciersystemandsemi

    steady

    Qlaciersystemintermsofglaciersystem'slevelofwater

energyexchange.risinggradientof

    theequilibriumlinealtitudesandretreatingrateofareatoclimatewarming.theirmediansize andverticalspandistribution.andtheirrunoffcharacteristicstoclimatewarming.Furthermore

    thefunctionalmodelofglaciersystemtoclimatewarmingwasappliedinthispapertopredict theaveragevariationtrendsofthe4typesofglaciersystems,whichindicatethatdifferent sensitivitytypesofglaciersysternsrespondtotheclimatewarmingdifferently. Keywords:glaciersystem;functionalmodel;responsetoclimatewarming;typeofsensitivity

    1Introduction

    Glaciersystemisregardedasmulti.glacierssharingthesameregion.influencedbythe similarclimateandorganizedbycertaininsidelaws.Itcanbedividedandsub.dividedbased oncertainphysicalcharacteristics.mountainranges,watershedboundariesandetc.(Kot- lyakoveta1..1990).GlaciersinChinahavebeendominantlyretreatingduetoclimate warming(Liueta1.,2002).Asflresult,manystudieswerecarriedoutontheglaciersvaria

    tionresponsetoglobalwarming(Shieta1.,2000;Yeeta1.,2003;Xieeta1.,2006;Wanget a1..2005).Themodelsthatcanbeusedforglaciersrespondingtoclimatewarmingcouldbe eitherusedforflsingleglacierorforflglaciersystem.Modelsfortheindividualglaciers Received:20071206Accepted:2oo80218

    Foundation:KnowledgeInnovationProjectoftheCAS.No.KzCx2Yw

    301:NationalBasics&TProjectoftheMinistry

    ofScienceandTechnologyofthePeopie'sRepublicofChina.No.2oo6FYl10200;NationalNaturalScience

    FoundationofChina.No.4084002

    Auther:WangXin(1973

    ),Ph.DCandidate,specializedinenvhonmentalvariationandnaturalhazards. E-mail:Xinwanghn@163.corn

    WWW.scichina.cornWWW.springerlink.corn

    WANGXineta1.:SensitivityanalysisofglaciersystemstoclimatewarminginChina191

    mainlyinvolvetheglaciermeltingcalculationassociatedtotemperature.indexmodels (Hock,2003;Braiteta1.,2000;Ohmura,2001),dynamicalmodels(Oerlemanseta1.,1998; Yeetal.,2003),energy

    balancemodels(Kangeta1.,1994;Oerlemans,1993),glacier-runoff

    modelsandsoon.Thetemperatureindexmodelsareestablishedusingpositiveaccumula

    

    tivetemperaturetocalculatemeltingwaterofaglacieronthebasisofmeteorologicaldata. Thedynamicalmodelsandenergybalancemodelsarebothphysicallybasedprocessones.

    Glacier-runoffmodelsweresetupbasedontherelationshipsbetweenclimatefluctuation andglacierrunoffvariation,suchasSRMmodel(Martineceta1.,1986),HYMETmode (Tangborn,19841andSHEmodel(Boggildeta1.,19991andsoon.

    withtheincreasingdemandsofunderstandingaglaciersystemvariationtrend.some modelsweredevelopedforsimulatingtheglaciersystemsrespondingtoclimatewarming, suchassensitivityofthemeanspecificbalancemodels(Gregoryeta1.,1998;Zuoeta1., 1997;Vanderala1.,20011,girdingthemassbalanceattheELAmodel(Rapereta1., 2006).functionalmodelforglaciersystemsfXieeta1.,20021andsoon.Itisnoteasyforto obtaintheparametersthatrunthemeanspecificbalancemodelsandgirdingthemassbal

    anceatELAmodel.Uptonowtheabovetwotypesofmodelshavenotbeenappliedin China.Thefunctionalmodelofglaciersystemisestablishedonthebasisofthestructureof glaciersystemandthenatureoftheequilibriumlinealtitudesatthesteadystate.Themodel wasappliedtosimulatetheglaciersystemsrespondingtoclimatewarminginsouthernTibet fXiePfa1.,2002),aswellasthesourceregionsofthe11arim(Wangeta1.,2006)andthe Yangtzerivers(Wanga1.,2005).Itwasfurthergeneralizedtopredictthevariationtrends ofglaciersystemstoclimatewarminginChinaandevaluatetheglacialrunoffinthecoming 50yearsaftersomenecessaryverificationworkwascarriedout(Xieeta1.,2006a,b). Inthispaper,weanalyzethecharacteristicsof44glaciersystemsinChineseGlacierIn

    ventorywhichweredividedbywatershedboundaries.applyfunctionalmodeltosimulate theglaciersystemstoclimatewarming,summaryandclassifythe44glaciersystemsac

    cordingtotheirsensitivitiestoclimatewarming.andpredictdifferentsensitivitytypesof glaciersystems'variationtrendsunderdifferentclimatewarmingevents.

2Dataandmethod

    Theoriginaldataforthe44glaciersystemswereobtainedfromtheChineseGlacierInven

    tories,supportedbyaerosurveyphotosandthetopographicmapsatascaleof1:50,000or 1:100,000duringthe1960s1970s(someaero

    surveyphotosoftheYarlungZangboRiver

    weretakenintheearly1980s),andtheoriginalmeteorologicaldatacamefromtheMete

    orologicalAtlasofPlateauofwestChina(LanzhouInstituteofPlateauAtmosphericPhysics, unpublisheddata),whichwerecompiledfromthehighaltitudemeteorologicalsurveydata duringthe1960s-1970s.Sothetwokindsofdatacanapproximatelyreflectthephysical stateofglaciersandtheirmeteorologicalconditionsinthesameperiod. ThetemperatureinwestofChinawillriseatarangeof2.3-4.3?higherin2050than

    theaveragetemperatureof1960-1990(Zhaoeta1.,2002;Lieta1.,1999).Accordingtothis predictionresult,wemakesomeassumptionsaboutclimaticscenarioswithpossibletem

    peraturerisingratesof0.01K/a.0.03K/aand0.05K/auntilthemid21stcentury.Weob

192JournalofGeographicalSciences

    tainedtheprecipitationincreasingratealsoguidedbyZhaogta1.(2002)predictionresultsof about19%——43%moreprecipitationinthenext50yearsthantheaverageprecipitationin 19601990.Atthesametime,wenoticedthatOerlemans(1998)committedthesimilarre

    searchesemployingthewayofevery1?higheraccompaniedby10%precipitationincre

    ment.Furthermore,herewesupposetheincreasingprecipitationisvalidtoglaciers,i.e.,it takessolidformandsuppliesforglaciereffectivelyboth.Wetaketheyear1980asthe originalyearandcalculatethevariationscharacteristicsofglaciersystemsrespondingto possibleclimaticscenariosinthiscentury.

    Thefunctionalmodelofglaciersystemtoclimatewarmingisemployedtoanalyzethe sensitivitiesofglaciersysteminChinainthispapersinceitwasverifiedtobereliableand waswidelyappliedinglaciatedregionsofChina(Wanggta1.,2005,2006;Xiegta1.,2006a, b1.

    3Anintroductiontothefunctionalmodel

    3.1Calculationofmassbalance

    Theelevationofaglacierwherethespecificnetmassbalanceisequaltomeannetmass balanceoftheglacierisregardedasELA0.Wesupposethattheglaciersystemsremain steadystateintheoriginalyearwhenELA0coincideswithEfJAh(Hess,1904);whileclimate varies,theELA0undoubtedlychangesintoELAoiinagivenyeari,andthespecificnetmass balancenearELAoi,bn(ELAoi)isapproximatelyequaltomeannetmassbalanceofglacier, (Xiegta1.,1996):

    (E):f(1)

    Whensummertemperaturerisesandprecipitationincreasessimultaneously,employing theablationformulabyKotlyakoveta1.(1982),thenetbalanceofaglacier,bni,inagiven yearicanbeexpressedas(Wanggta1.,2005):

    =

    1.33[(9.66+tso)(9.66+tso+At")+Ap

    wherets0isthemeansummertemperatureattheELA0intheoriginalyear;At,iistheincre

    mentofmeansummertemperatureand?Piistheincrementofsolidprecipitationwhichcan

    effectivelysupplyfortheglacierinthegivenyeari.

    ThentheratiobetweenIbanda0ofaglacierinthegivenyearis:

    :

    (3)

    ?O

    wherea0istheablationoftheglaciersystemintheoriginalyear.

    3.2Calculationofglacierrunoffandareachangeforclimatewarming

    Whentemperaturerisesaccompaniedwithprecipitationincreasing,glaciermeltingwillac

    celerate,negativemassbalancewilloccur(Oerlemans,1998;Wanggta1.,2005)andthere

    forethedepthofglacierrunoffwillincrease.Ontheotherhand,theglacierareawillde

    creaseforglacierretreating,thenthetotalglacierrunoff,wi,inagivenyeariwillbe: wi=(ro+Fdi)(SoS)(4)

    WANGXineta1.:SensitivityanalysisofglaciersystemstoclimatewarminginChinal93 wherer0andsoaretherunoffdepthandareaoftheglacierintheoriginalyearrespectively;

    rdiandSdiaretheincrementofrunoffdepthandthedecrementofglacierareaduetoclimate warrmnginagivenyearirespectively.Withtemperaturecontinuouslyrising,glacierrunoff firstlyincreasesfortheincreaseofablation.whenitreachesthemaximumamount.itwill fallbackbecauseofthereducingtoomuchglacierarea;whenitreturnstotheoriginal amountoftheglacialrunoffagain,wenameditrestoringoriginalglacierrunoffstate(Xieet a1.,1996);atthattime,ifevaporationisneglected,wecangetr0=a0,t'di=fbnthenthedec

    rementofglacierareasis:

    (5)

    Theempiricalformataboutrelationshipbetweentheglacierareaandthickness(Liueta1., 1986)waswidelyusedinChineseglacierinventories:

    =53.21s~___11.

    32

    Weemployed(6)toworkoutthetimewhenglacierreaches

    stateundercontinuouslywarming,(Xieeta1.,1996):

    {53.2]Thentheglacierareasiinagivenyeariis:

    小一]

    3.3Calculatingrunoffofglaciersystem

    restoringoriginalglacierrunoff

    11.32aI

    f+lI

    (8)

    WhathasbeendiscussedabovelSaboutthevariationlawsofan1ndividualglacierrunoff. Forthesakeofcalculatingtherunoffvariationofaglaciersystem,theglaciersystem'sme

    diansize(Smgd)wasutilized,whichrepresentstheglaciersizewhenthepercentageofcumu

    lativeglacierareareaching50%intheglaciersystem.Inagivenyeari,whentheSmediofthe glaciersystemreachesTe,50%oftheglacierssmallerthanSmediinthewholesystemwill reachoroverpasssuccessively,i.e.,theirtotalrunoffislessthantheiroriginalrunoff. Whiletheother50%oftheglacierslargerthanSmediintheglaciersystemhasnotreached

i.e.,theirtotalrunoffisstillmorethantheiroriginalrunoff;thereforewhenaglaciersys

    tem'sSmedireachesTe,therunoffofthewholesystemisaveragelytorestoretothelevelof theoriginalrunoffofthewholesystem.Thus,whenitcomestopredictthevariationofa glaciersystem,wecanuseStnedtorepresentthetotalareaofthewholeglaciersystem,and applythelawsmentionedabovetoreachthegoals.Ifignoringevaporation,thetotalrunoff ofaglaciersystem,W,inagivenyeariis:

    :

    I.000.000

    whereSiisthetotalareaoftheglaciersysteminagiven

    1,000,000isinvolvedtoconvertthecriterionof1TlIntokm.

    3.4CalculationofAELAoofglaciersystem

    year;andtheconstantof

    InordertocomputetherisingvalueofE0ofaglaciersystemundertheconditionofcli

194JournalofGeographicalSciences

    matewarming,AELA0,wemakeuseofthealtitudestructureoftheglaciersystem(Wanget a1.,2004)tocomputetheaccumulativearearate(AAR).AARistheindicatorofclimateand immediatesurroundingsinacertainglaciatedregion;itisrelativelybyfarlessaffectedby climaticfluctuation.Sowhenglacierretreatingbeginswiththeterminus,ELA0willrisesi

    multaneously.Thestatisticresultsshowthatthereexistpolynomialrelationshipsbetween AELA0iandAS/S:

    ELAof=C1(As/)+c2(As/)+c3(/)(10)

    whereAS/Sistheretreatingrateoftheglaciersystem'Sarea;C1,C2andC3areempirical coefficients.

    4SensitivityanalysisofglaciersysteminChina

    4.1Sensitivitytypesofglaciersystem

    Combiningthefunctionalmodelresultswiththestatisticcharacteristicsofthe44glacier systemsinChina.theindexesweresummarizedtorankthesensitivityoftheglaciersystems toclimatewarmingwhichincludethelevelofwater-heatexchange(a0),altituderangeof

    glaciation(?H,thedifferenceofelevationbetweenthemeanhighestaltitudeandthemean lowestaltitudewheretheglaciersaredistributedinaglaciersystem),theglacierareaofme

    diansize(),therisingrateofELA0ofaglaciersystem(AELA0),therunoffincreasing rateofaglaciersystem(Wm",W0,theratiobetweenthemaximumrunoffandoriginalrunoff ofaglaciersystem).tl1earearetreatingrateofaglaciersystem(S/So,theratioofglacier areaintheyearofandintheoriginalyear),thesignalrunoffyearsofaglaciersystem(T1is theyearwhentherunoffofaglaciersystemreachingitsmaximumrunoffmagnitudefor climatewanning;T2istheyearwhentherunoffofaglaciersystemrestoringitsoriginal runoffleve1).Alltheindexesindicatingthesensitivitiesofglaciersystemtoclimatewarl'n

    ingareshowninTable1.Accordingtocriteriondescriptionoftheindexes,wedividedthe 44glaciersystemsinChinainto4typesofglaciersystems,extremely(sensitiveglaciersys

    

    tem,semisensitiveglaciersystem,semisteadyglaciersystemandextremely

    steadyglacier

    system.Thedistributionandtheiramountofthe4sensitivitytypesofglaciersystemsin ChinaareshowninTable2andFigure1.

    WANGXineta1.:SensitivityanalysisofglaciersystemstoclimatewarminginChina195 Table2DistributionofdifferentsensitivitytypesofglaciersystemsinChina Typeofgla

    Clersystem

    Area

    (km)

    v0lume

    (km)Regionofdistribution

    Ex..011559

    .321o66.9579

    sensltire

    Semi-9363

    .37622.7831

sensltire

    Semi

    stead'/

    Extremely

    stead,/

    Commonlydistributinginlow,marginalmountainousareawithabundantpre cipitation,suchastheeastcrnpartofQilianMountainssouthernAltayMOLIn

    tains,KaidouKongqiRiverBasininsouthwestofTainshanMountains.inte

    riordrainageareaofscatteredflowineastandsoutheastofTibet.etc. Commonlydistributinginmarginalmountainousareawithrelativelyabundant precipitationbutrelativelyhigheraltitudethanthatoftheextremelysensitive

    glaciersystems',suchasthemiddleofQilianMountains,OinghaiLake,the middlepartofnorthernslopeofTianshan,AltayMountainsYiliRiverBasin. middleandeasternpartsofnorthernslopeofHimalayas,etc. Mainlydistributingininteriorhighmountainswithrelativelyscarceprecipita 19307.311846.7450

    Q

    tio

    

    n,s

    m

    uc

    B

    haso

    B

    fQil

    ian:'

    KarakorumMountains,Pamirs,upriverregionsofYarlungZangbo,etc MainlydistributinginthehugeandaridmountainsofQinghaiXizangPlateau

    19170.O62056.4085andTianshan.suchasthewestKunlunMountains.interiorregionsofTi

bet.

    centralmountainsofTianshaneastPamirs,westernpartofHimalayas.etc 30.

    70.80.90.

    80.

    Figure1SensitivitytypesofglaciersystemsandtheirdistributioninChina

    (ThealtitudebasedontheSRTMdata)

    l00.

    4.2VariationtrendsofglaciersystemsinChinatoclimatewarming 50.

    30.

    Usingfunctionalmodelofglaciersystemandthedatadescribedabove,thevariationtrends

    ofdifferentsensitivitytypesofglaciersystemswereshowninFigure2whichrevealsthat,

    underthreekindsofpossibleclimatewarmingscenarios,differentsensitivitytypesofgla

    ciersystemsrespondtoclimatechangingindifferentways.

JournalofGeographicalSciences

    

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    04

    105

    095

    075

    12

    1

    08

    06

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