Abstract Volume Swiss Geoscience Meetinggeoscience-meeting.scnatweb.ch/...Symposium10.pdf · 10.5...

Abstract Volume8th Swiss Geoscience MeetingFribourg, 19th – 20th November 2010

Department ofGeosciences

10. Open Cryosphere Session

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Platform Geosciences, Swiss Academy of Science, SCNATSwiss Geoscience Meeting 2010

10. Open Cryosphere Session

A. Bauder, M. Hoelzle, B. Krummenacher, J. Nötzli, C. Lambiel, M. Lüthi, J. Schweizer, M. Schwikowski

Swiss Snow, Ice and Permafrost Society

10.1 BoeckliL.,BrenningA.,NoetzliJ.,GruberS.:Anempirically-basedpermafrostdistributionmodelfortheentireAlps

10.2 EtzelmüllerB.,FarbrotH.,GuomundssonÁ.:SevenyearsofpermafrostmonitoringinIceland-updatedresultsandgeomorphologicalimplications

10.3 Eugster M.: Snow, ice and permafrost study in Swiss schools: From local student observations to globalunderstanding

10.4 GabbiJ.,FarinottiD.,Bauder.,A.:PastandfuturechangesandimpactsonrunoffconditionsintheMauvoisinregion

10.5 HussM.:PresentandfuturecontributionofglacierstoragechangetorunofffrommacroscaledrainagebasinsinEurope

10.6 HussM.,MachguthH., JörgP.,ZempM.,SalzmannN.,Linsbauer A.,HoelzleM.: Re-analysisofmassbalancemeasurementsonFindelengletscher2005-2009

10.7 HussM.,StokvisM.,SalzmannN.,HoelzleM.:Towardsshort-termmonitoringofglaciermassbalanceandsnowaccumulationdistribution

10.8 KellerA.,FunkM.:Icedeformationmeasurementinboreholes onRhonegletscher

10.9 Lambiel C., Baron L.: Mapping ground ice distribution in an ice-cored moraine with electrical resistivitytomography,ColdesGentianes,SwissAlps

10.10 LinsbauerA.,PaulF.,KünzlerM.,FreyH.,HaeberliW.:FormationofnewlakesindeglaciatingregionsoftheSwissAlps

10.11 LüthiM.P.,BauderA.,FunkM.:VolumechangereconstructionofSwissglaciersfromlengthchangedata

10.12 MatzlM., Steiner S., SchneebeliM., SteinfeldD., Köchle B., Singer J.: 3-D-reconstruction and visualization ofmicroscalesnowstratigraphyandweaklayers

10.13 MorardS.,BochudM.,DelaloyeR.:RapidchangesoftheicemassconfigurationinthedynamicDiablotinsicecave–FribourgPrealps,Switzerland

10.14 NathS.K.,HussM.:GlaciologicalinvestigationsonthreeglaciersatLesDiablerets,AlpesVaudoises

10.15 SalzmannN.,MachguthH.:TheSwissAlpineGlacier’sResponsetothe“2°CTarget”

10.16 ScapozzaC.,BaronL.,LambielC.:Boreholelogginginalpineperiglacialtalusslopes,ValaisAlps,Switzerland

10.17 ScherlerM.,HauckC.:Modellingofpermafrostevolutionunderclimatechangescenarios

10.18 SchneiderS.,HoelzleM.:Investigationofthehighvariabilityofmountainpermafrost

10.19 Walthard P., Gulley J., BennD.,Martin J.: Using speleologicalmethods to test dye tracing interpretations inglaciology

10.20 ZechR.,HuangY.,ZechM.,TarozoR.,ZechW.: PermafrostcarbondynamicscontrolledatmosphericCO2andPleistoceneclimate

10.21 ZenklusenMutterE.,PhillipsM.:ActiveLayerdevelopmentinAlpinepermafrost

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10.1

An empirically-based permafrost distribution model for the entire Alps

LorenzBoeckli1,AlexanderBrenning2,JeanneteNoetzli1&StephanGruber1

1 Department of Geography, University of Zurich, Switzerland([email protected])2 Department of Geography, University of Waterloo, Ontario, Canada

Permafrostdistributionmodellinginhighlypopulatedmountainregionsisanimportanttaskandseveraldifferingmo-dellingapproachesexist.MostpermafrostmodelsintheAlpsarecalibratedforalocalregionandonlyapplicableforaspecificarea.Foranalyzingthepermafrostdistributionandevolutiononanalpine-widescale,oneconsistentmodelforthewholedomainisneeded,insteadofdifferingandincomparablemodels.WepresentastatisticalpermafrostmodelfortheentireAlpsbasedonpermafrostevidences.TheevidenceswerecollectedintheframeworkofthePermaNETprojectandcontaindifferentdata(e.g.rockglacierinventories,boreholetemperatures,groundsurfacetemperatures).Twomodelsweredeveloped,oneforthedebriscoveredarea(debrismodel)andoneforsteeprockfaces(rockmodel).Inbothcasesthepredictorvariablesaremeanannualairtemperature(MAAT)andpotentialdirectsolarradiation.Forthedebrismodelweusea logisticregressiontopredicttheprobabilityofactiveagainst inactiverockglacier.Fortherockmodelalinearregressionwasusedtomodelrocktemperaturesbasedontemperatureloggerslocatedinsteeprockwalls.Todistinguishbetweenthosetwosurfacecharacteristicsathirdmodel (surfacetypemodel) isused,whichisbasedonslopeonly.Thefinaloutputproductcombinesthesethreemodelsandprovidesalpine-widepermafrostprobabilities.

10.2

Seven years of permafrost monitoring in Iceland - updated results and geomorphological implications

BerndEtzelmüller1,HermanFarbrot1,ÁgustGuðmundsson2

1 Department of Geosciences, University of Oslo Department of Geosciences, University of Oslo ([email protected])2 Jarðfræðistofan Geological Services, Iceland

Thedistributionofmountainpermafrosthasbeenmappedandmonitoredmainlyinlocationswithrelativelycontinentalclimatescharacterizedbyastablesnowcoverandlowwintertemperatures.Incontrast,thereisapaucityofsystematicground temperature investigations frommaritimemountainareas suchas Icelandand transitionalareasbetween theScandinavianmountainpermafrostzoneandthecontinuouspermafrostinSvalbard.Knowledgeofthepresentdistribu-tionandthermalcharacteristicsiscrucialforassessingtheresponseofpermafrosttoclimatechangeanditsgeomorpho-logicalandgeotechnicalimpact.

Intensivefield-basedstudiesonthedistributionofpermafrostandthedynamicsofselectedperiglaciallandformswerecarriedoutinnorthern(Tröllaskagipeninsula)andeasternIcelandsince2003.Sincethengroundthermalmonitoringhascontinuedatfoursites.Thispresentationreviewsandsynthesisesthemainresultsofthe7yearsofmonitoring,anddrawslinestoformerandfuturegeomorphicprocessdynamicsandlandscapedevelopment.

Thepresentationdemonstratesthatpermafrostiswidespreadatelevationsabovec.900ma.s.l.inIceland,mainlydepen-dingonthesnowcoverregime.Atthiselevation,permafrosttemperaturesarecloseto0°C,andthushighlyvulnerablefor climate variability.Modelling exercises showquite rapid responses of ground temperatures fromchanges in snowconditionsandairtemperatures.Climatevariabilityhasbeenlargeduringtheperiodofinstrumentalmeasurementofmeteorologicalvariables(startlate18.Century).Thisisduetothelargeinfluenceofseaice,occasionallyoccurringclosetonorthernIceland,resultinginlowerwintertemperatures.DuringtheLIAandpartsofthelastcentury(e.g.the1970ies)permafrost must have been much more widespread than today, mainly because of the lower winter temperatures.Furthermore,themodellingindicatesthatunderfutureclimatescenariosthepermafrostwilldegradeatthesesitesontheorderofdecadesdependingonclimatescenarioschosenandsubsurfaceicecontent

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10.3

Snow, ice and permafrost study in Swiss schools: From local student observations to global understanding

EugsterMarkus

Sekundarschule, Schöntalstrasse 2, 9244 Niederuzwil

Introduction:IwillpresenttoyouawaytoimplementpolarscienceinSwissclassrooms.Withlocalmeasurements,fundamentalexpe-rimentsandworldwideexchangewithintheGLOBEnetworkstudentscometoabetterunderstandingoftheEarthasasystemandespeciallyofthechangingcryosphere.Method:Learningbydoing.

GLOBESwitzerland is amember (http://www.globe-swiss.ch/de/) of GLOBE (= Global Learning andObservations to Benefit theEnvironment;http://globe.gov),andourschooljoinedGLOBEin2003.

SeasonsandbiomesGLOBEstartedseveralEarthSystemScienceProjects(ESSP)in2007,amongthem“SeasonsandBiomes”waspartoftheIPY.IwasinvitedtoattendtwoworkshopsinFairbanks,Alaska,withteachersfromallovertheworld.

SpaceshipEarthIncollaborationwithNicolasGessner,thedirectorof52shortfilmsaboutourplanet,Idesigned52worksheetstohelpmystudentsunderstandtheoutsideinfluencesthatdeterminetheEarth’ssystems.

IceseasonalityMystudentsobservethecoveringofsnowandtheiceonourschoolpond,fillinprotocolsandtakepicturestodocumentfreeze-upandbreak-up.Thishelpsthemtobecomeawareofseasonalcycles.

Figure1:SchoolpondSekUzwil Figure2:Iceprotocol

FrosttubesWemanufactureandtestdifferenttypesoffrosttubes.Inadditionwemeasuresoiltemperatureswithburiedsensors.Takingmeasurementshelpsmystudentsunderstandthedifferentbehaviourofairandsoil.ThisleadstoquestionsaboutpermafrostandtheactivelayerandtheconsequencesofthawingpermafrostinPolarRegionsaswellasinourAlps.

LearningActivitiesI’mdevelopinglowcostexperimentstoequipmystudentswithbasicknowledgeaboutsnow,ice,freshandseawaterice,oceancurrentsandglaciers.

WorkshopsIwasinvitedtotheOsloIPYconference(http://ipy-osc.no/)inJune2010.IattendedthePolarTeacher’sconferencewithallitsworkshopsandpresentationsandestablishnewcontactswithteachersandscientistsfromaroundtheworld.InAugust2010IgavemyfirstSwissteacher’scourse(“EwigerSchnee”)inthePizolregion.Iwouldbegladtofindagla-ciologistfornextyear’scourse.

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Figure3:Studentscontrollingfrosttubes Figure4:ExperimentMeltingice

Figure5:Pizolglacier(allpicturesbyM.Eugster)

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10.4

Past and future changes and impacts on runoff conditions in the Mauvoisin region

GabbiJeannette1,FarinottiDaniel1&BauderAndreas1,

*VersuchsanstaltfürWasserbau,HydrologieundGlaziologie(VAW),ETHZürich,CH-8092Zürich([email protected])

TheprogressiveicemasslossinAlpineregionsisaresponsetotheongoingglobalclimatechange.Inthenearfutureanevenpronouncedglacierretreatisexpectedduetoafurthertemperatureriseconfirmedbyseveralclimatestudies(e.g.Frei,2007;vanderLindenandMitchell,2009).Hence,therunoffconditionsinhighmountainvalleyswillsignificantlychange.

TherunoffconditionsandtheevolutionoftheglaciersintheMauvoisinareaaredetermineduntiltheendofthe21stcenturyusing theGlacierEvolutionandRunoffModel (GERM,Huss et al., 2008). TheGERM is basedonadistributedtemperature-indexmeltmodelcombinedwithanaccumulationmodel.Further,arunoffrouting,anevaporationandaglacierevolutionmodelisimplemented.Theglaciersurfaceisupdatedinannualtimesteps.Inordertocomputethefu-tureglacierextensiontheknowledgeabouttheinitialicethicknessdistributionisfundamental.ThecurrenticevolumeisderivedusingtheicethicknessestimationapproachbyFarinottietal.(2009)whichisbasedonprinciplesoftheice-f lowmechanics.Ifradar-echosoundingsareavailabletheradarprofilesareincludedintheicethicknessanalysis.Theincor-poratedclimatescenariosareadoptedfromastudyofFrei(2007)whichprovidestemperatureandprecipitationprojec-tionsfortheNorthandtheSouthofSwitzerlandinseasonalresolutionfortheyears2030,2050and2070andthecorres-ponding95%confidenceinterval.Threedifferentclimateregimesarededuced:abest-case(coldandwet),amedianandaworst-case(warmanddry)scenario.Theparametersofthemodelarecalibratedonthebasisofpasticethicknesschangesderivedfromtopographicmapsandarealphotographs,dischargedataanddirectmassbalancemeasurements.

AsaconsequenceoftheenhancedmeltingtherunoffoftheMauvoisinareaincreasesinthenearfuture.Thedurationoftheperiodwithpronounceddischargedependsmainlyontheclimatescenario.Inthecoldandwetclimateregimethemaximalannualrunoffisevensuspectedtoariseaftertheendofthe21stcentury.Incaseofthemedianandworst-casescenariothemaximalrunoffisachievedin2060.Afterreachingthepeakrunoffthedischargediminishessignificantlyduetothestrongreductionoftheglacierizedarea.Theamountofreductiondependsonthecharacteristicsofthecatch-mentandthechosenclimatescenario.Duetotheglacierlosstherunoffregimeismainlyinfluencedbysnow-meltinsteadofice-melt.Thepeakrunoffisshiftedtoearliertimesintheseasonwhereasthesummerrunoffisstronglyreduced.AllglaciersintheMauvoisinareashowaconsiderableicevolumelossuntiltheendofthe21stcentury(Fig.1).Butthepro-ceedingoftheglacierretreatisdifferentfortheindividualglaciersdependingonthecurrenticevolumeanditsdistribu-tioninrelationtothealtitude.

Figure1.TheglaciergeometryoftheGlacierdeCorbassièreandtheGlacierduPetitCombinfortheyears2020,2060and2100inthe

medianclimatescenario.Theblueareaindicatespostivemassbalancesandthegreyareanegativemassbalances.

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REFERENCESFarinotti,D.,Huss,M.,Bauder,A.,Funk,M.&Truffer,M.2009:Amethodtoestimatetheicevolumeandice-thickness

distributionofalpineglaciers,JournalofGlaciology,55(191),422–430.Frei,C.2007:DieKlimazukunftderSchweiz. In:KlimaänderungunddieSchweiz2050–ErwarteteAuswirkungenauf

Umwelt,GesellschaftundWirtschaft. BeratendesOrgan für FragenderKlimaänderung (OcCC): 12-16,http://www.occc.ch.

Huss,M.,Farinotti,D.,Bauder,A.&Funk,M.2008:Modellingrunofffromhighlyglacierizedalpinedrainagebasinsinachangingclimate,HydrologicalProcesses,22,3888–3902.

vander Linden, P.&Mitchell, J. (2009): ENSEMBLES:Climate change and its impacts: Summery and results from theENSEMBLEsproject,MetOfficeHadleyCentre,ExeterEX13PB,UK,160pp.

10.5

Present and future contribution of glacier storage change to runoff from macroscale drainage basins in Europe

HussMatthias1

1 Department of Geosciences, University of Fribourg, Fribourg, Switzerland

Glaciersare important seasonal storagecomponents in thehydrological cycle. In this study, the importanceofglacierstoragechangeinthesummermonthsforrunofffromlarge-scaledrainagebasinsinEuropeisanalyzed.AlongthemajorstreamsdrainingtheAlps–Rhine,Rhone,PoandDanube–thecontributionofsnow-andicemeltfromglacierizedcatch-mentstodischargeisevaluatedforthreetosevenmeasurementstations.Theanalyzeddrainagebasinsvaryinsizefrom200to800’000km2,andhaveaglacierizationofbetween60%and0.06%.

Detailedinformationonglacierstoragechangeisavailablefrommonthlymassbalancedatafor50glaciersintheSwissAlps.Massbalancetimeserieswerederivedbasedonacomprehensivesetoffielddatacoveringtheentire20thcenturycombinedwithdistributedmodelling(Hussetal.,2010a,b).Usingclimatescenariosthetransientfutureglacierretreatandconsequentchanges inmonthlyrunoffcontributionwerecalculated foreachglacier individuallyuntil2100.Basedonglacierinventorydata,storagechangesareextrapolatedtoallglaciersintheEuropeanAlps.

Bycomparisonofthemonthlyrunoffyieldsfromglacierizedsurfacesinthesummermonthsandthemeasureddischargefromlarge-scalecatchmentstherelativeportionofglaciermeltwateriscalculated.

Foratypicalmacroscalecatchmentwithasizeof96’000km2,andaglacierizationof1%(RhoneatBeaucaire,France),glacierstoragechangepotentiallycontributedtoAugustrunoffby19%overthelastcentury(Fig.1).EvenonthelowerDanubewithanice-coveredfractionofonly0.06%glaciersmakeacontributionof2.2%toobservedrunoffvolumeinAugust.Intheextremeyearof2003glaciercontributionwashigherbyafactorof2to3.It isshownthattherelativeimportanceofglaciercontributiontorunoffdoesnotscalelinearlywiththepercentageofglacierization.Astherunoffregimechangesfromnivo-glacialtopluvial(withaminimuminsummer)movingawayfromtheAlps,therelativeimpor-tanceofglaciermeltwaterincreasesdownstream.

Overthe21stcenturymostAlpineglacierswillshrinktolessthan10%oftheircurrentsizeaccordingtothemodelresults.Thus,glacierstoragechangewillbestronglyreducedduetoalackofbothsnow-andicemelt.Inconsequence,adecreaseinrunoffcontributionfrompreviouslyglacierizedcatchmentstosummerdischargebyabouttwothirdsisexpecteduntil2100.Thiswillintensifyissueswithwatershortageinthesummermonths,notonlymountainousdrainagebasins,butaswellinpoorlyglacierizedmacroscalecatchments.

REFERENCESHuss,M.,Hock,R.,Bauder,A.&Funk,M.(2010a).100-yearglaciermasschangesintheSwissAlpslinkedtotheAtlantic

MultidecadalOscillation.GeophyiscalResearchLetters,37,L10501.Huss,M.,Usselmann,S.,Farinotti,D.&R.,Bauder,A.(2010b).Glaciermassbalanceinthesouth-easternSwissAlpssince

1900andperspectivesforthefuture.Erdkunde,64(2),119-140.

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Figure1.RelativecontributionofglacierstoragechangeinAugusttorunofffromseveraldrainagebasinsalongthefourstreamslea-

vingtheAlps.Thenameofthegaugingstationandcatchmentglacierizationisgiven.Dataareevaluatedfortheperiod1908-2008,

1961-1990,andtheextremeyearsof1977and2003.Notethatthebarfor2003iscutoffinsomecases,andthecontributionisstated

usingnumbers.

10.6

Re-analysis of mass balance measurements on Findelengletscher 2005-2009

HussMatthias1,MachguthHorst2,JörgPhilipClaudio2,ZempMichael2,SalzmannNadine1,2,LinsbauerAndreas2&HoelzleMartin1

1 Department of Geosciences, University of Fribourg, Fribourg, Switzerland2 Department of Geography, University of Zurich, Zurich, Switzerland

IntheSwissAlps,long-termglaciermassbalanceseriesarecurrentlyonlymaintainedonthreeglaciersusingthedirectglaciologicalmethod.Moreover, theseglaciersarerathersmallandmaydisappearwithinthecomingdecades.There-presentativenessofmassbalanceseriesinSwitzerlandthusneedstobeenhancedbyincludinglargerglaciersinthemo-nitoringnetwork.

Since2004directmassbalancemeasurementshavebeenperformedonFindelengletscher,Valais,butnoglacier-widemassbalanceshavebeencalculatedsofar.Since2009,themassbalancemeasurementsarejointlyperformedbytheUniversitiesofZurichandFribourg,andtheprogramwasextended.Recently,high-accuracyDigitalElevationModels(DEMs)fortheyears2005and2009(LiDAR),and2007(photogrammetry)becameavailable.TheseDEMsallowthecalculationoficevolu-mechangesforFindelen-andAdlergletscher.

Theaimofthisstudyisthere-analysisofthemassbalancemeasurementsperformedbetween2005and2009resultinginhomogenizedglacier-wideseasonalmassbalancesforbothglaciers.Wefocusonthecomparisonoftheresultstothein-dependentlydeterminedgeodeticmasschanges(DEMcomparison)allowingthequantificationofsystematicuncertaintiesinbothdatasources.

Annualpointmeasurementsofmassbalanceareevaluatedusingadistributeddailyaccumulationandmeltmodelthatiscalibratedtothefielddataineachyearindividually(Hussetal.,2009).Inthismethod,winteraccumulationdataavailab-

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lefor2005,2009and2010arecrucialfordeterminingthespatialmassbalancevariability.Inaddition,firstresultsofthehelicopter-borneGroundPenetratingRadar(GPR)surveyofApril2010areincludedintheanalysis.Electromagneticwavesarereflectedatthesnow-iceinterfaceprovidingcontinuousrecordsofsnowlayers(Machguthetal.,2006).Inthefirnareauptofourannualfirnlayersaredetectableintheradarsoundings.Thus,accumulationratesoverthelastyearsathighelevationmaybereconstructed(Fig.1).AlthoughtheinterpretationandtemporalallocationofthefirnlayersobtainedfromGPRisnottrivial,thisdatasourceisvaluableinregionsabove3300ma.s.l.–representinghalfoftheglaciersurface–astherearenodirectfielddataavailable.

The re-analysis of themass balance data yields a cumulative thickness change of –1.40mwater equivalent (w.e.) forFindelengletscher,and–0.87mw.e.forAdlergletscherbetweenOctober2005and2009.Whereasmasslosseswereaboveaveragein2005/2006,themassbudgetofFindelengletscherwasnearlybalancedin2008/2009duetohighwinteraccumu-lation.Comparisonwiththegeodeticicevolumechangebetween2005and2009basedonLiDARDEMs(Jörgetal.,2010),however,indicatesthatmasslosseswerehigherbyabout50%.

Thesignificantdisagreementbetweentheglaciologicalandgeodeticmethodneedstobereduced,andtheuncertaintiesinbothmethodshavetobeunderstoodbeforetheFindelengletschermassbalanceseriescanbeusedforclimaticinter-pretation.Severalreasonscouldpotentiallycontributetothismisfit:(1)Accumulationmightbeoverestimatedinthere-analysisduetoverysparsedirectobservationsathighaltitude.However,high-resolutionsnowprobingsupto3800ma.s.l.,andthefirnlayerthicknessinferredfromGPR(Fig.1)indicatethataccumulationratesarewellreproducedbythemodel.(2)ConvertingicevolumechangeobtainedbyDEMcomparisonintomasschangeisdifficultasthedensityofthevolume change isunknown leading to a considerableuncertainty in the geodeticmass changeover short periods. (3)Severaladditionaluncertaintieshaveyettobeexplored,andmightbeimportant.

Figure1.Thicknessoffirnlayersbetweenthemassbalanceyears2005/2006and2008/2009inferredwithhelicopter-borneGPR.The

uppermostlayerrepresentsthewintersnow2009/2010.Thesurfacetopography(rightaxis)isverticallyexaggerated.Twoprofiles

throughtheaccumulationlayersareshown.Thicknessisconvertedintowaterequivalentusingestimatedfirndensities.

REFERENCESHuss,M,Bauder,A.andFunk,M.(2009).Homogenizationoflong-termmassbalancetimeseries,AnnalsofGlaciology,

50(50),198–206.Jörg, P.C.,Morsdorf, F. and Zemp,M (2010). Operational use of airborne laserscanning for glaciermonitoring in

Switzerland.GeophysicalResearchAbstracts,EGU2010-750.Machguth,H., Eisen,O., Paul, F.&Hoelzle,M. (2006): Strong spatial variability of snowaccumulationobservedwith

helicopter-borneGPRontwoadjacentAlpineglaciers.GeophysicalResearchLetters,33,L13503.

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10.7

Towards short-term monitoring of glacier mass balance and snow accu-mulation distribution

HussMatthias1,StokvisMazzal1,SalzmannNadine1&HoelzleMartin1

1 Department of Geosciences, University of Fribourg, Fribourg, Switzerland

Glaciermassbalanceisanimportantindicatorofclimatechange.Massbalancemonitoringprogramsmostlyreportannu-alvaluesbecausefieldmeasurementsarelaborious.Forclimaticinterpretation,theseparationofthecomponentsofmassbalance – accumulation andmelt – is important. This canbe achievedbyperforming seasonalmass balance surveys.However,themonthlyorevendailyglaciermasschangeoveroneyear,whichiscrucialforanalyzinge.g.theimportanceofglaciermeltcontributiontothehydrologicalcycle,wasonlymodelledsofar,andnotobserveddirectlyinthefield.Asecondgapincurrentmassbalancemonitoringprogramsisthespatialdistributionofsnowaccumulationshowingahighvariabilityinspacethatisdifficulttocapturewithdirectmeasurements.

Here,weoutlineanewmethodthatallowsatemporallycontinuousmonitoringofglaciermassbalance,aswellasthespatial snowaccumulation variability over glacierized surfaces. Themethod is basedon twodata sources that canbeacquiredremotely,i.e.withoutdirectfieldsitecontact.Thus,alsoinaccessibleregionsoftheglaciersurfacecanbeinclu-ded.Weuserepeateddigitalphotographyoftheglacier,andsnowdistributionmeasurementsattheendofwinterusinghelicopter-borneGroundPenetratingRadar(GPR).

In April 2010, an automatic digital camera was installed on Unterrothorn overlooking the entire catchment ofFindelengletscher,Valais,Switzerland.Photosaretakenathourlyintervalsanddirectlytransmittedtoaserver.Thesnow-lineinselectedpicturesisdelineated,andthephotosaredeskewed,orthorectifiedandgeoreferenced(Corripio,2004).Ithasbeenshownthatsnowaccumulationdistributioninthelowerreachesofaglaciercanbederivedusingrepeatedpho-tographycombinedwithsimplemodelling(Farinottietal.,2010).

First results of the helicopter-borne Ground Penetrating Radar (GPR) survey of April 2010 are used in this study.Electromagneticwavesarereflectedatthesnow-iceinterfaceprovidingcontinuousrecordsofsnowlayers(Machguthetal.,2006).Intotal,about13kmofsnowprofilesonFindelengletscherareavailableforApril2010.

ThemethodtocontinuouslydeterminetotalmassbalancereliesontheAccumulationAreaRatio(AAR)thatcanbedeter-mined for eachday from the repeatedglacierphotography.Here, theAAR isdefinedas thepercentageof theglaciersurfacecoveredwithwintersnow.Therelationbetweenglacier-widemassbalanceandtheAARmainlydependson(1)thequantityandthespatialdistributionofsnow(givenbytheGPRsurveys),and(2)thecharacteristicsofglaciergeometry,e.g.hypsometry,exposure(obtainedfromadigitalelevationmodel).

WepresentthesnowaccumulationdistributiononFindelengletscherinApril2010andthedepletionpatternofwintersnowthroughoutthemeltingseasonoftheyear2010asdepictedbyrepeatedgeoreferencedphotography.RatingcurvesforAARversusglacier-widemassbalancearederivedbasedonasimplemodel.Themethodtocontinuouslydetermineglaciermassbalanceusingremotelysenseddataisillustratedwithfirstresultsfortheyear2010.

REFERENCESCorripio, J.G. (2004). Snow surface albedo estimationusing terrestrial photography. International Journal ofRemote

Sensing,25(24),5705–5729.Farinotti,D.,Magnusson, J.,Huss,M.&Bauder,A. (2010). Snowaccumulationdistribution inferred from time-lapse

photographyandsimplemodelling.HydrologicalProcesses,24,2087-2097.Machguth,H., Eisen,O., Paul, F.&Hoelzle,M. (2006): Strong spatial variability of snowaccumulationobservedwith

helicopter-borneGPRontwoadjacentAlpineglaciers.GeophysicalResearchLetters,33,L13503.

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Figure1.FindelengletscherasseenbytheAutomaticCamerainstalledonUnterrothorn.ThepictureistakenonJuly6,2010.Thecur-

rentsnowlineisindicated.

10.8

Ice deformation measurement in boreholes on Rhonegletscher

KellerArne,FunkMartin

Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, Gloriastr. 37-39, CH-8092 Zürich

Inorder toprovideboundaryconditions fornumerical f lowmodeling, informationon thebasalmotionof temperateglaciersarenecessary.Whereasbasalprocessesareusuallynotdirectlyaccessibleandcannoteasilybeinferredfromsur-facemeasurements,boreholedeformationmeasurementsallowviadeterminationofvelocityprofilestoinvestigatethecontributionsofbothslidingandinternalicedeformationtosurfacemotion.

Insummer2009boreholedeformationmeasurementscoveringbothverticalandshearstrainhavebeencarriedoutonthetongueofRhonegletscher(Valais,Switzerland).Unlikeearlierstudiesusinguniquelygravitationsensorsforinclino-metry,ourexperimentalsetupincludesbothgravimetersandmagnetometers.Thisallowstodeterminetheboreholede-formationwithrespecttoafixedcoordinatesystemgivenbygravitationalandgeomagneticalfields.

Theinclinationangleoftheboreholesshowscharacteristicdiurnalvariations.Thosearecorrelatedwiththevariationsofenglacialwaterpressuremeasuredinanearbyborehole.Themechanismgoverningthiseffectisnotentirelyclearyet.

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10.9

Mapping ground ice distribution in an ice-cored moraine with electrical resistivity tomography, Col des Gentianes, Swiss Alps

LambielChristophe1,BaronLudovic2

1 Institut de Géographie, Université de Lausanne ([email protected])2 Institut de Géophysique, Université de Lausanne

Themappingofgroundiceinsedimentarydepositsotherthanrockglaciersnecessitatesinmostcasestheuseofgeophy-sicalmethods.Thatisparticularlythecaseforglacierforefields.Forthis,severalERTprofileswerecarriedoutintheColdesGentianesmoraine,ontheorographicleftsideoftheTortinglacier(Verbierarea).Thesiteislocatedat2900ma.s.l.,thatiswithinthealpinepermafrostbelt.Groundtemperaturesrecordedina20mdeepboreholesince2002attestthepresenceofpermafrostconditionsinthemoraine(Lambiel2006).Acablecarstationwasbuiltonthenorthernpartofthemoraineattheendofthe1970’s(Figure1).Massivegroundicewasencounteredatthisoccasion.InOctober2006,exca-vationsforski-runlandscapingpurposesrevealedoutcropsofcongelationandsedimentaryiceatdepthsof50cmto2m(Lambiel&Schuetz2008).Sedimentaryiceisalsoregularlyobservedintheinternalf lankofthemoraine,justbelowthebuilding,aftertheslideofsurfacedebrisonburiediceduetotheglacierretreatatthefootoftheslope.

Themainresultsshowthatabandupto40meterswidewithgroundresistivities(ataround10mdepth)between100kWmandmorethan2000kWmoccupiestheinnerpartofthemoraineontheedgeoftheglacier(Figure1).Thiscorrespondstosedimentaryiceburiedundersuperficialdebris.Attheplaceoftheexcavationsof2006,valuesupto200kWmhavebeenmeasured.Betweenthose2sectors,resistivitiesaround10-20kWmarepresent.Thisprobablyindicatesalowicecontent(onlycongelationice?).Finally,atthebaseofthebuildingtheresistivitiesarelowerthan4kWm,showingthaticeobservedduringtheconstructionhascompletelymelted.Thishasbeenresultinginthesubsidenceofthemoraine.

Thelargerangeofresistivitiesmeasured,interpretedasdifferenttypesoficethatdonotsystematicallycoincidewithtopo-geomorphologicalevidences,probablyresultsfromacomplexhistoryofglacier-permafrostinteractionsduringtheLittleIceAge.Today,theevolutionofthisice-coredmoraineisbothcontrolledbyglacierretreatandpermafrostcreep.

Figure1.Distributionoftheresistivitiesataround10mdepthintheColdesGentianesmoraine.

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REFERENCESLambiel, C. 2006: Le pergélisol dans les terrains sédimentaires à forte déclivité: distribution, régime thermique et

instabilités.Thèse,UniversitédeLausanne,InstitutdeGéographie,coll.“TravauxetRecherches”n°33,260p.Lambiel, C., & Schuetz, P. 2008: Ground characteristics and deformation of a frozenmoraine affected by tourist

infrastructures(ColdesGentianes,Valais).Klima-veränderungen auf der Spur. Studien des Europäischen Tourismus Instituts an der Academia Engiadina, Samedan,5, 110-122.

10.10

Formation of new lakes in deglaciating regions of the Swiss Alps

LinsbauerAndreas1,PaulFrank1,KünzlerMatthias1,FreyHolger1&HaeberliWilfried1

1 Glaciology, Geomorphodynamics and Geochronology Group, Department of Geography, University of Zurich, Switzerland ([email protected])

Thealpineenvironmentisstronglyaffectedbyclimatechangeandtheongoingincreaseinmeantemperaturehasaseve-reimpactonglaciersintheAlps.Withtheongoingrapidglaciershrinkingorevenvanishing,characteristicsofthesurfacetopographyoverwideregionswillnowandinthefutureundergostrongchangeswithconsiderableimpactsontheenvi-ronmentatallscales.

Forfutureassessmentsandmodelingofglacierretreatscenariosandtheirimpacts,itiscrucialtohaveabetterknowledgeonbothglacierbedtopographyandicevolumesforalargenumberofglaciers(e.g.Linsbaueretal.2009,Farinottietal.2009).Thereby,glacierbed topography iscalculatedbysubtractingmodeled ice thicknessdistributions fromasurfaceDEM.Thesebedscanthenbeusedamongothersforthemodelingoffutureglacierevolution,glacierf low,detectionofoverdeepeningswithpotentialfuturelakeformationandhazardassessment.

InthisstudywehavemodeledbedtopographiesandicethicknessdistributionsofallSwissglaciers>0.1km2withasim-plebutrobustGIS-tool(Paul&Linsbauersubm.).Subsequently,weanalyzedthegeomorphometriccharacteristicsoftheglacierbedsandthedetectedoverdeepenings,whichcanbeseenaspotentialsitesforfuturelakeformation(Freyetal.2010).Suchnewlakescanbeattractivefortourismandhydropowerproduction,butalsoconstituteserioushazardpoten-tialsastheycomeintoexistenceinanincreasinglydestabilizedenvironment(e.g.steeprockwalls,warmingpermafrost,de-buttressingofover-steepenedslopesfromglaciervanishing).

Theanalysisofthehypsographicdistributionoftheicethicknesswithreferencetotheglacierbedsrevealsthathugeicemassesarebasedonbedrockwithlowaltitude(below2400ma.s.l).Thishaswideimplicationsforfutureglacierdevelop-mentasitsupportstheself-accelerationofmassloss,i.e.glaciertonguescannotretreattohigherelevations.Somelargervalleyglacierswithaprominenttonguereachingdowntoelevationsbelow2500ma.s.l.areselectedtomapelevationprofilesoftheglaciersurfaceandbedalongtheircentralf lowline.Theseprofilesrevealthemoderateslopeofthelowglacierbedsandthelargenumberofoverdeepenings.Summingupthetotalareaofalldetectedoverdeepenings,exposeapotentialof50-60km2ofnewlakeareaundercurrentlystillexistingglaciers.ByapplyingtheGIS-basedmodelingoftheglacialsedimentbalance(Zempetal.2005),astatementonthesedimentary/rockynatureoftheglacierbedcanbemadeandhelpstoindicatewhetheradepressionsmayfillwithwaterorwithsedimentaftertheglacierhasdisappeared.Byusingasimplifiedmodeloffutureglacierretreat(Pauletal.2007),thepotentiallakeformationsitesarefurtherroughlyclassifiedfortheirdateofappearance(nextdecade,firsthalfofthecenturyorlater).

REFERENCESFrey,H.,Haeberli,W.,Linsbauer,A.,Huggel,C.&Paul,F.2010:Amulti-levelstrategyforanticipatingfutureglacierlake

formationandassociatedhazardpotentials.NaturalHazardsandEarthSystemSciences,10,339–352.Farinotti,D.,Huss,M.,Bauder,A.&Funk,M.2009:AnestimateoftheglaciericevolumeintheSwissAlps.Globaland

PlanetaryChange,68,225–231.Linsbauer,A.,Paul,F.,Hoelzle,M.,Frey,H.,&Haeberli,W.2009:TheSwissAlpswithoutglaciers–aGIS-basedmodelling

approachforreconstructionofglacierbeds.ProceedingsofGeomorphometry2009,Zurich,Switzerland,243–247.Paul,F.,Maisch,M.,Rothenbuehler,C.,Hoelzle,M.&Haeberli,W.2007:Calculationandvisualisationoffutureglacier

extentintheSwissAlpsbymeansofhypsographicmodelling.GlobalandPlanetaryChange55(4),343–357.Paul,F.&Linsbauer,A.subm:Modelingofglacierbedtopographyfromglacieroutlines,centralbranchlinesandaDEM.

InternationalJournalofGeographicalInformationScience.Zemp,M.,Kääb,A.,Hoelzle,M.&Haeberli,W. 2005:GIS-basedmodellingof glacial sedimentbalance. Zeitschrift für

Geomorphologie,138,113–129.

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Figure1.GlaciersubsetaroundGreatAletschglacierintheBerneseOberlandandValais:Thedetectedoverdeepeningsinthemodeled

glacierbedtopographiesareclassifiedbytheirmeandepth.Theplotsshowthelongitudinalprofilelines(distanceinkm)ofglacier

surfaceandbed(elevationinma.s.l.)ofsomemajorglaciersoftheregion.

10.11

Volume change reconstruction of Swiss glaciers from length change data

MartinP.Lüthi,AndreasBauderandMartinFunk

Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, ETH Zürich, CH-8092 Zürich ([email protected])

Anovelmethod toreconstructglaciervolumechanges fromameasured lengthrecord ispresented,and tested for13glaciers intheSwissAlps.Theresponseofaglaciertochanges inclimateismodeledwithatwo-parameterdynamicalsysteminthevariables``length’’and``volume’’.Drivenbyahistoryofequilibriumlinealtitude(ELA),themodelyieldsvariationsofglacierlengthandvolume.Adynamicallyequivalentsimplemodel(DESM)isdeterminedforeachglacierbymatchingmodeledandmeasuredlengthchanges.ThevolumechangespredictedwiththeDESMagreewellwithmeasu-rementsfortwelveglaciers,whereasagreementispoorforoneglacierwithtopographicbreaksintheterminusarea.Forallglaciers,whicharelocatedindifferentclimateregions,thelengthandvolumechangesarereproducedwiththesameELAhistory.Thisagreementshowsthatthemacroscopicglacierresponsetotheclimatehistoryiswellcorrelatedoverawholemountainrange.Modelingthefutureevolutionoftheglaciersunderaconstantpresent-dayclimaterevealsthatfast-reactingglaciersareclosetoequilibrium,whereaslengthandvolumeofthelargevalleyglacierswouldbereducedduringthenextcenturybyanamountsimilartothevolumelostduringthelast150years.

REFERENCESLüthi,M.P., Bauder,A.& Funk,M., 2010.Volume change reconstruction of Swiss glaciers from length change data.

JournalofGeophysicalResearch;EarthSurfaceProcesses,(inpress).Lüthi,M.P.&Bauder,A., 2010.Analysis ofAlpine glacier length change recordswith amacroscopic glaciermodel.

GeographicaHelvetica,(inpress).Lüthi,M.P.,2009.Transientresponseofidealizedglacierstoclimatevariations.JournalofGlaciology,55(193):918—930.

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Figure1.Modelledglaciervolumechangesfor13glaciersareshownwithlines.Measuredvolumechangesforglaciersareindicated

withsymbolsforcomparison.Theglaciernamesaregivennexttocurves.

Figure2.Phasespacediagramsofmodeledlengthandvolumechangesfor13glaciersintheSwissAlps(solidlines).Measuredvolume

andlengthchangesareshownwithsymbols.Dottedlinesindicatethelocusofthesteadystates.Clearly,smallandsteepglaciersare

closetoasteadystateatpresent,whereaslargeandf latglaciers(Aletsch,Morteratsch,Unteraar)arefaroutofequilibrium.

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10.12

3-D-reconstruction and visualization of microscale snow stratigraphy and weak layers

MatzlMargret1,SteinerStephen1,SchneebeliMartin1,SteinfeldDaniel1,KöchleBernadette1&SingerJulia1

1 WSL Institute for Snow and Avalanche Research SLF, Flüelastr. 11, CH-7260 Davos Dorf ([email protected])

Duringthelast10yearsX-raymicrotomography(micro-CT)hasprovedtobethefirstsuccessfulmethodtomeasurethetruethree-dimensional(3-D)structureofsnowontheground.However,duetoitsconstrictiontosmallsamples(withatypicallyevaluatedsizeof5x5x5mm3)onlymoreorlesshomogeneoussampleshavebeenanalyzed.Anewreplicame-thodintroducedbyHegglietal.(2009)for3-Dmicro-CTsamplesnowallowsthevisualizationofsnowsamplesupto70mmheight,andabout10mmdiameter,witharesolutionof10μm.Basedonthismethod,wecastedhighlyfragilesnowsamples,likenewsnow,buriedsurfacehoarandotherweaklayersduringwinter2009-2010.Thesamplesshowafascina-tingnewimageofhowcomplexsnowlayersare.Manysamplesshowstrongdensitygradientswithinastructurallysimi-lar layer.Fromsome3D-reconstructionswecreatedanaglyph imagesallowing tosee the intricatestructures in3D. Inaddition, several snowpackswere characterized by stability tests,Near Infrared Photography and SnowMicroPen.Wethinkthatthistechniquewillimproveourunderstandingofsnowmetamorphismandsnowpropertiesandthatsuchvi-sualizationsofthesnowmicrostructurecouldbeausefultoolbothforpractitionersandresearcherstoimprovetheun-derstandingoffractureprocessesduringavalancheformation.

REFERENCESHeggli,M.;Frei,E.;Schneebeli,M., 2009:InstrumentsandMethods.SnowReplicamethodforthree-dimensionalX-ray

microtomographicimaging.J.Glaciol.55,192:631-639.

10.13

Rapid changes of the ice mass configuration in the dynamic Diablotins ice cave– Fribourg Prealps, Switzerland

MorardSébastien1,BochudMartin2,3&DelaloyeReynald1

1 Geography Unit, Department of Geosciences, Chemin du Musée 4, CH-1700 Fribourg ([email protected])2 Geology Unit, Department of Geosciences, Chemin du Musée 6, CH-1700 Fribourg3 Spéléo-Club des Préalpes Fribourgeoises (SCPF), Rue François Guillimann 7, CH-1700 Fribourg

Locatedat2’000m.a.s.l.intheentrancezonesoftheGouffredesDiablotins(-652m),theDiablotinsicecaveisthemostimportantmassiveicevolumeknownintheFribourgPrealps(Switzerland).Mostpartoftheiceisencountered10minsi-dethelowerentranceofthecaveandextendsdiscontinuouslyinalowerhorizontalgalleryforabout40metersuntiltheintersectionwithaverticalshaftleadingtotheupperentrance100mabove.

TheparticularityofthisicecaveisfoundedintherapidchangesoftheicemassconfigurationobservedduringthelasttwodecadesandrelayedinthearchiveoftheSCPF.In1983,thelowergallerywaspluggedbyice.Howeverinsummers1991and1992,theicecontentwasverylow,allowingintenseexplorationsofthekarsticnetworkduringtheseyears.Since1994theicemasshassharplyincreasedmakingdifficultthespeleologicalexplorations,andpluggingcompletelythelowergalleryin1995.Sincethemithasbeenimpossibletoreachagaintheintersectionwiththeverticalshaftfromthelowerentrance. Infall2009itwasstillpossibletopenetratetheicecavebeyondabout20mtoanintermediateroomwithaparticularf laticeceiling.

Inordertobetterunderstandtheprocessesoccurringinthisicecave,thelowerentrancewasequippedin2009withse-veraldevices tomeasureairf lowcharacteristics (temperature,humidity, velocityanddirection), rock temperatureandexternalairtemperature.Firstresultshaveshownthatachimney-effectventilationsystemoccurredcurrentlyintheicecave:airf lowdirectionreversesinthelowerentrancewhentheexternalairtemperaturecrossesathresholdofabout+2°C.

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Thecontinuouscaveclimatemeasurementshavealsoshowedthepredominantroleofwinteratmosphericairconditionstodriveboththeefficiencyofchimney-effectcirculationandtheseasonalmodificationsoftheicemass.Importantcoolinganddryingphaseswerethusrecordedinwinter2009-2010andmainpartoftheicelossiscurrentlyduetosublimationinwintertime.Incontrast,formationofnewicewasobservedinspringduringsnowmeltperiod.

Wintermeteorological conditionswerealso reconstructedbetween1980and2009 to estimate the causesof the rapidchangesobservedinthe1990s.Theresultsshowedthatwinters1989,1990,1992and1993weremild,lesssnow-coveredandwithdryairconditions.Theseyearscorrespondwiththelowicecontentperiodoftheicecave.Incontrastoppositemeteorologicalconditionswereencounteredduringwinters1994and1995,whenthestrongincreaseoftheicemasswasobserved.

10.14

Glaciological investigations on three glaciers at Les Diablerets, Alpes Vaudoises

NathSovikKumar1,HussMatthias1

1 Department of Geosciences, University of Fribourg, Chemin du Musée 4, 1700, Fribourg, Switzerland ([email protected])

GlaciersintheSwissAlpsrespondedtoclimatechangeoverthelastcenturywithstronglydifferingratesofmassloss.Inordertocorrectlyextrapolateglaciermassbalanceobservedatindividualglacierstounmeasuredicemassesthedifferen-cesinglacierresponsedrivenbythesameclimaticchangesneedtobeunderstood.

ForthisreasonwefocusonthreeglaciersaroundLesDiablerets,AlpesVaudoises,withstronglydifferentcharacteristicsdescendingfromthesamemountain.Areachangesoverthe20thcenturyappeartobestronglydifferentaccordingtoglacierinventorydata(Mülleretal.,1976):GlacierdeTsanfleuron,aneast-exposedandrelativelyf latglacier,haslostal-mosthalfofitsareabetweenthemaximumoftheLittleIceAge(around1850)and1973.Incontrast,GlacierdePrapio,asmallandsteepcirqueglacier,hasonlydecreasedinareaby12%overthesameperiod.GlacierduSexRougeisasmallnorth-exposedglacierwithaf lataccumulationareaandasteepablationzone(formerlycalledGlacierduDar)thathasrecentlyseparatedfromthemainicebodyandisabouttodisappear(Fig.1).GlacierduSexRougeshowedanareachangeof–26%between1850and1973.WhereasGlacierdeTsanfleuronstillhasasizeofmorethan3km2,thetwootherglaciersarearound0.3km2.Duetotheimportantdifferencesinareathatareobservedinthepast,weexpectthattherateofmassloss–whichismoredirectlyrelatedtoclimatechange–showsasimilarbehavior.

TheUniversityofFribourgplanstosetupanintegrativecryosphericmonitoringsiteatLesDiablerets.Here,firstresultsofglaciologicalinvestigationsonthethreeglaciersaroundLesDiableretsarepresented.Sincewinter2009/2010severaltypesoffieldobservationshavebeenperformed.Stakeswereplacedontheglaciersurfacetomeasuresnowaccumulationandiceablation(Fig.1).ManualprobingsofthesnowdepthincludingsnowdensitysurveyshavebeencarriedoutinApril2010todeterminethewinterbalanceofGlacierdeTsanfleuron.WepresentafirstevaluationoftheseasonalglaciermassbalanceofTsanfleuronfortheyear2009/2010.Inaddition,GroundPenetratingRadar(GPR)wasusedtomeasuretheicethickness(Fig.1).OnGlacierdeTsanfleuronicethicknessesofupto180mweremeasured.OnGlacierduSexRougeicethicknessisstillhigherthan60moverconsiderableparts,whichissurprisingforitslimitedsize.

Thelong-termevolutionoftheglaciersisinvestigatedbasedonoldtopographicmapsthatareavailableforallglaciersfortheyears1880,1950,1961,1986,1992and2006.Bydigitizingcontourlines,DigitalElevationModels(DEMs)oftheglacierswereestablishedallowingthecalculationoficevolumechangesindecadalperiods(Bauderetal.,2007).TheuncertaintyintheDEMswasassessedbycomparingsurfaceelevationinglacierizedareasyieldinganerrorofabout2m.Between1950and2006wefindmeanchangesinglaciersurfaceelevationof–31mforGlacierdeTsanfleuron,–21mforGlacierduSexRouge,andof–14mforGlacierdePrapio.Icevolumechangeswerefurtherevaluatedusingadistributedaccumulationandtemperature-indexmeltmodel(Hussetal.,2009).Basedonthismethodmassbalanceseriescoveringthe20thcentu-rywerederivedforallglaciers.

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Figure1:OverviewmapthethreeglaciersaroundLesDiablerets.Thecontourlineintervalis100m.Diamondsindicatethepositionof

stakestomeasureannualmassbalance.LinesshowtheGPRprofilesrealizedinApril2010,andsmallcrossesmeasurementsofthe

wintersnowdepth.

REFERENCESBauder,A.,Funk,M.&Huss,M.(2007):Ice-volumechangesofselectedglaciersintheSwissAlpssincetheendofthe19th

century.AnnalsofGlaciology,46,145–149.Huss,M,Bauder,A.& Funk,M. (2009).Homogenizationof long-termmassbalance time series.Annals ofGlaciology,

50(50),198–206.Müller,F.,Caflisch,T.&Müller,G.(1976).FirnundEisderSchweizerAlpen:Gletscherinventar,No.57,Geographisches

InstitutderETHZürich,Zürich.

10.15

The Swiss Alpine Glacier’s Response to the “2°C Target”

NadineSalzmann1,2HorstMachguth2,3

1 (1) Alpine Cryosphere and Geomorphology, Department of Geosciences, University of Fribourg, Switzerland([email protected])2 Glaciology and Geomorphodynamics Group, Department of Geography, University of Zurich, Switzerland3 Marine Geology and Glaciology, Geological Survey of Denmark andGreenland - GEUS, Copenhagen, Denmark

The“2°Ctarget”forglobalwarming(relativetopre-industriallevel)becameamainfocusintheclimatechangedebatesincetheUNClimateChangeConferenceinCopenhagen(COP15)inDecember2009atthelatest.Whilethistargetimpliestobea‘clear’goalforpoliticiansanddecisionmakers,theeffectiveimpactsthataglobalmeanairtemperatureincreaseof2°Chasonnaturalandhumansystemsonregionaltolocalscalesremaincomplex.Her,wepresentanapproachtoassessthepotentialimpactofa2°CwarmingontheSwissAlpineglaciers.

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Inglacierizedmountainregions,whereglaciersrepresentanimportantsourceforfreshwaterandcontrolagreatpartofthehydrologicalcycle,theretreatordisappearanceofglaciersasaconsequenceofclimaticchangeswillhavemajorsocio-economicalconsequencesonthepeoplelivingthereandtheadjacentlowland.Atrendtonegativeglaciermassbalancesisobservedandwelldocumentedformanymountainrangesallovertheworld(WGMS,2009).

Globalclimatechange,however,isnotequallydistributedaroundtheglobe.Observationsshowthatthelastcentury’sairtemperaturetrendssignificantlydifferbetweenregions,andthisistrueevenwithinSwitzerland.The12homogenizedairtemperature series available for Switzerland for example, show a range of trends between 0.82°C/100y for Lugano, to1.63°C/100yforChateau-d’Oex.(Meteoschweiz,2009).Ourstudyis(i)basedonthe12homogenizedairtemperatureseriestodefinethewarmingthathasalreadytakenplaceinthepast,and(ii)onresultsfromaselectionofRegionalClimateModel(RCM)simulationsthathavebeencompletedintheframeoftherecentlyfinishedEU-fundedENSEMBLESprogram,forthetransientsimulationandtodefinethe‘remai-ning’temperatureincreaseuptothelevelof2°C.TheRCMresultsarebias-correctedandthentakenasinputforadistri-butedmassbalancemodel(Machguthetal.2009)inordertoassesstimeandmassbalancetrendsfortheSwissAlpineglacierswithregardtoa2°Cincrease.Thedifferentrunsoftheglaciermassbalancemodelshowarangeoffuturescena-rios,mainlyasaresultofthedifferentdrivingRCMs.Allscenarioshaveincommonthatnumerousglacierswilllosetheiraccumulationareabeforeorwhenthe2°Ctargetisreached.Becauseaglobal2°Ctemperatureriseislikelytoimpactwithawarmingofmore than2°Con theSwissAlps,our scenarios representa lower limit for thechanges tobeexpected.Therefore,weadditionallyconsidereda4°Cincreaseinourstudy.

REFERENCESWGMS2009:GlacierMassBalanceBulletin,No.10,96ppMeteoschweiz2009:OriginaleundhomogeneReihenimVergleich.Dezember2009.Machguth,H.,Paul,F.,Kotlarski,S.,Hoelzle,M. 2009:Calculatingdistributedglaciermassbalance for theSwissAlps

from regional climatemodel output: Amethodical description and interpretation of the results. Journal ofGeophysicalResearch,114,D19106,doi:10.1029/2009JD011775

10.16

Borehole logging in alpine periglacial talus slopes, Valais Alps, Switzerland

ScapozzaCristian1,BaronLudovic2,LambielChristophe1

1 Institut de Géographie, Université de Lausanne, Anthropole-Dorigny, CH-1015 Lausanne ([email protected] ; [email protected])2 Institut de Géophysique, Université de Lausanne, Amphipôle-Sorge, CH-1015 Lausanne ([email protected])

RecentdrillingprojectsinthreeperiglacialtalusslopesoftheValaisAlps,Switzerland(seeScapozzaetal.2010a,b),open-edup thepossibilityof carryingoutboreholegeophysicalmeasurement to study the stratigraphyand thepermafroststructureoftheprospectedtalus.Boreholeloggingisanimportanttoolforinvestigatingtheverticaldistributionofsomephysicalparameters,suchasdensity(gamma-gamma),naturalradioactivity(gamma-ray)andhydrogencontent(neutron-neutron)(VonderMühll&Holub1992).

InLesAttelassite,threeboreholesweredrilleddestructivelyalonganupslope-downslopetransect.Frozensedimentsarepresentonlyinthetwolowestboreholes,whereastheupperboreholedoesnotpresentgroundice.Theinternalstructureofsomeoftheboreholescouldbeobservedwithahand-madeboreholecamera.Otherinformationabouttheboreholestructurecomesfromthefieldexperienceofthedrillingteamandfromobservationsofthecharacteristicsoftheexpulsedmaterials.Astheboreholesweredrilleddestructivelyandnotcored, itwasnotpossibletoquantifythevolumetric icecontentoftheground.Onlyaqualitativeestimation(loworhighcontentofice)wasestablishedonthebasisofthenatu-reoftheexpulsedmaterials.Logginghadtobedoneindryholes,whathaslimitedthechoiceoftheloggingmethods.

Boreholegeophysics at the studied talus slope confirms theborehole stratigraphy. InLesAttelas site, for example, animportant shift in the logs separate the surface layer ofunfrozen sediments (high activity in the gamma-gammaand

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neutron-neutronlogs)andthelayercharacterisedbyice-rockmixture(lowactivityinthegamma-gammaandneutron-neutronlogs).Theicecontentinthefrozenlayerisnothomogeneous,aspointedoutbytheimportantvariationsinthethreelogs.Wherelayersrelativelyrichinicearepresent(icecontentestimatedbetween10and50%),adecreasingactivi-ty in thegamma-gamma logandan increasingactivity in theneutron-neutron logcanbeobserved.Thisbehaviour isparticularlyevidentfortheboreholeB01/08(fig.1).

Asdrillinginmountainpermafrost(andinparticularintalusslope)isoftenexpensiveandcomplicated,itisnecessarytoderiveasmuchinformationfromaboreholeaspossible.Forthisreason,boreholeloggingisaverypowerfulmethodforstudyingthestratigraphyofaboreholewhenitisnotcored.Inthisframework,theboreholegeophysicsperformedinthestudiedtalusslopeallows:(1)toconfirmthepermafroststratigraphyderivedfromdirectobservationsandthermalmea-surementsand;(2)toperformthecalibrationsofthewidthandthenatureofthestructuresdetectedbysurfacegeophy-sicalprospecting.

Figure1.ResultsofboreholegeophysicsinboreholeB01/08(lowerpartoftheslope)inLesAttelastalusslope.i-vi:layersrelativelyrich

inice.

REFERENCESVonderMühll,D.&Holub,P.1992:Borehole logging inalpinepermafrost,UpperEngadin,SwissAlps.Permafrostand

PeriglacialProcesses,3,125-132.DOI:10.1002/ppp.3430030209.Scapozza,C.,Lambiel,C.,Baron,L.,Marescot,L.&Reynard,E.2010a:Internalstructureandpermafrostdistributionin

twoalpineperiglacialtalusslopes,Valais,SwissAlps.Geomorphology,submitted.Scapozza,C.,Lambiel,C.,Abbet,D.,Delaloye,R.&Hilbich,C.2010b:Internalstructureandpermafrostcharacteristicsof

theLapirestalusslopes(Nendaz,Valais).8thSwissGeoscienceMeeting,Fribourg,thisvolume.

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10.17

Modelling of permafrost evolution under climate change scenarios

ScherlerMartin1,HauckChristian2

1 Alpine Cryosphere and Geomorphology (ACAG), Department of Geosciences, University of Fribourg, Fribourg, Switzerland ([email protected]) 2 Alpine Cryosphere and Geomorphology (ACAG), Department of Geosciences, University of Fribourg, Fribourg, Switzerland ([email protected])

Themodelusedinthisstudyisaone-dimensionalcoupledsoilwaterandheattransfermodelofthesoil-snow-atmosphe-reboundarylayer(Jansson&Karlberg2001).Itaccountsfortheaccumulationandmeltofaseasonalsnowcover,aswellasforthefreezingandthawingofthesoil.Themodelisdrivenbythefollowingmeteorologicalparameters:airtempera-ture,relativehumidity,globalradiation,incominglong-waveradiation,windspeed,andprecipitation.Acompleteenergybalanceiscalculatedforthesnoworsoilsurface,yieldingasurfacetemperaturerepresentingtheupperthermalbound-aryconditionofthesoilprofile.Aconstantgeothermalheatf luxdeterminesthelowerthermalboundary.

Themodelhasbeenappliedtosimulategroundtemperaturestogetherwithwaterandicecontentevolutionoftwohigh-altitude alpine permafrost sites in Switzerland. The sites are Schilthorn in the Bernese Oberland and Murtèl in theEngadin.Thesiteswerechosenbecauseoftheirdifferentmorphologiesandsubstrates,i.e.arockslopewithasubstantialfine-grainedsurficialcoveratSchilthornandaboulderysurfacewithlargeblocksatrockglacierMurtèl.Theaimofthesimulationswasthelongtermmodelling(9yearsforSchilthornand6yearsforMurtèl)andthecalibrationofthemodelforthetwostudysites.Themodelisvalidatedwithboreholetemperaturedata.

Inanextstepthemodelwasdrivenbydailymeanvaluesofmeteorologicalparameterswhichweretakenfromregionalclimatemodel(RCM)output(ENSEMBLESProject)forthetimeperiodof1991to2101.Thebiasinrelationtothemeasuredclimatedatahasbeendeterminedonthebasisofanobservationperiodfrom1999to2008forSchilthornandfrom1997to2008forMurtèl.Thesedeviationshavebeencorrectedinthemodelinputbyadditionorsubtractionofthesodetermi-nedbias.OneofthegivenscenariosshowsthattheactivelayerattheSchilthornsitevariesbetween5mand10mforthenext30years.Afterthatperiod,thethawlayerdoesnotfreezeupanymoreandatalikdevelops.Inthesubsequentyearsthepermafrostdegradesasthepermafrosttablegraduallydeclines.

Figure1.ThawlayerdepthprojectionforSchilthornbasedonamodelrundrivenwithregionalclimatemodel(RCM)data

REFERENCESENSEMBLESProject.http://ensemblesrt3.dmi.dk/JanssonP-E.&KarlbergL.2001:Coupledheatandmasstransfermodelforsoil-plant-atmospheresystems.RoyalInstitute

ofTechnology,DeptofCivilandEnvironmentalEngineering,Stockholm.

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10.18

Investigation of the high variability of mountain permafrost

S.Schneider&M.Hoelzle

Alpine Cryosphere and Geomorphology (ACAG), Department of Geosciences, University of Fribourg, Switzerland

Comparedtopolarregionspermafrostinhighmountainareasoccursinagreatvariationofsurfaceandsubsurfacemate-rialandtexturewithinshortdistances.Therefore,thethermalregimeoftheactivelayerstronglydependsonsite-specificfactorslikethegrainsize,theporevolumeandtypeofmaterialbesideclimaticfactorssuchasairtemperature,incomingradiation,precipitationandinfiltration.

Thebackgroundofthisworkistheanalysisoftheseasonalandlong-termtemperaturechangesinapermafrostregionwithdifferentmaterials,whereasthemicroclimaticfactors(likeairtemperature,windspeedanddirection,relativehu-midityandincomingsolarradiation)aswellasthetopographicsituation(exposition,inclination)arethesame.Therefore,observedchangesinsubsurfacetemperaturesareduetothedifferentsubsurfacematerialsandtheircorresponding,ma-terialdependingprocesses.Theaimofthisworkistounderstandthesedifferentprocessesandtocalculatethedifferentsensitivitiesofthegroundthermalregimetochangesinthemicroclimate.

Boreholetemperaturedatafrom2002–2009downto6mdepthwillbepresentedforfivedifferentsites.AllsitesarelocatedattheMurtèl-Corvatscharea(HansonandHoelzle2004)andsomeofthemarenotmorethan25mawayfromeachother.Thematerialinwhichtheboreholesweredrilledvariesfrombedrocktocoarseblockyandfine-grainedsubs-tratewithcorrespondingchangesinicecontent.Someofthemhaveonlyseasonalfrostwhereasothersaredrilledwithinarockglacierwithapproximately10mofice.

Figure1showsthemeanannualtemperatureforthreeoftheseboreholes.Thethermalregimeofthebedrocksite(a)ismainlydrivenbyheatconductionwithintherock.Duringsummerthetemperaturedecreasesalmostlinearwithdepth(respectively increases inwinter).At the talus slope (b) thepermafrost table is recognizableat3.5mdepthwhere thetemperatureisaround0°Cthroughoutthewholeyear.Hence,thisdepthisthelowerboundarywherethecolderaircancirculate.Thisprocessiscalledbalch-effect,i.e.warmairofthesubsurfacewillbereplacedbysubsidingcoldair.Thetemperatureattherockglaciersite(c)at2.5–6mdepthisstronglyinfluencedbytheicecontentoftherockglacier.Duetothehighairtemperatureandthecoolingbytheice,ahightemperaturegradientispresentduringsummer.

Toestimatethesensitivityofpermafrosttoclimaticchangesthethermaldiffusivityandthesoilheatf luxwascalculatedforallsites(fortheperiod2003–2009).Thethermaldiffusivitydescribesthedegreeofhowfastamaterialmaychangeitstemperature.Whereashighvaluesofapparentdiffusivityindicatetheoccurrenceofnon-conductiveprocesses,whilelowdiffusivityvaluesindicatethedominanceofconductiveheattransfer.Atallsitesthediffusivityisquitelowatthesurface (10-5–10-6m2s-1).Thatmeansthatthethermalregimenearthesurface ismainlyconductive.Asexpectedthediffusivityvalueswithinthesubsurfacevarystrongly,dependingonthesubsurfacematerial.Thebedrocksitesshowlowvaluesdownto6mdepth,duetoconductiveprocesses.Thevaluesattherockglaciersiteincreaseatthepermafrosttableat2.5masaconsequenceofatemperaturecloseto0°Candthereforethemeltingoftheice.

a) b) c)

Figure1:meansummer(black)andwinter(white)temperaturedatafrom2003-2008fora)bedrock,b)talusslopeandc)rockglacier

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Theanalysisofthistemperaturedataandtheirdevelopmentoverthelastyearsshowstrongdifferencesdependingonthematerial.Understandingthedifferentprocessesandcalculatingthetimewhichisneededfortheenergytransportinthesubsurfaceisthefirststeptoestimatethesensitivityofmountainpermafrosttoclimaticchanges.Inaddition,thecalcu-latedthermaldiffusivitiesandthesoilheatf luxford-ifferentmaterialsmightbeimportantinputparametersformode-lingthedevelopmentofmountainpermafrost.

REFERENCESHanson,S.andHoelzle,M.,2004.ThethermalregimeoftheactivelayerattheMurtèlrockglacier-basedondatafrom

2002.PermafrostandPeriglacialProcesses,15(3):273-282.

10.19

Using speleological methods to test interpretations of dye tracing results in glaciology

WalthardPeter1,2GulleyJason3,BennDouglas1,MartinJon3

1 University Centre in Svalbard, Pb 156, NO-9171 Longyearbyen2 Geographisches Institut, Klingelbergstrasse 27, CH-4056 Basel3 Department of Geological Sciences, 241 Williamson Hall, US-32611 Gainesville, FL

Hydrologicalpropertiesofglacialdrainagesystemsareanimportantcontrolonglacierdynamicsandarethoughttoin-f luenceshorttermvariationsinslidingspeed.Sincemostdrainagesystemsremaininaccessibletodirectexploration,thedevelopmentofdrainagesystemsduringmeltseasonisusuallyinvestigatedbyquantitativedyetracing.

Previousstudiesshowedthatthedyebreakthroughcurve(BTC)usuallyshowslowtransitvelocities(TV)andpeakconcen-trations(PC)atthebeginningofthemeltseasonandhighTV,PClaterintheseason,andthatthistransitiontakesplaceoncethesnowlineisretreatingbeyondtheinjectionmoulin.

Thisbehaviourisinterpretedasachangeintheconfigurationofthesubglacialdrainagesystem:DispersedBTCwithlowTV,PCareseenasanindicatorofadistributeddrainagesystem,wherewaterf lowsthroughlinkedcavitiesandwaterfilmsattheglacierbed,whereashighTV,PCareseenasanindicatorofanefficientdrainagesystemthroughasubglacialcon-duit.ThetransitionbetweenthetwoBTCpatternsisthenexplainedasacollapseofadistributedsystemandit’sreplace-mentbyanefficientchannelizedsystem.

Duetothephysicalinaccessibilityofmostsubglacialdrainagesystems,thishypothesishasnotyetbeentestedbydirectexploration.

In2009/10,both speleologicalmappinganddye tracing investigationshavebeen conducted ina subglacial conduit inRieperbreen,acold-basedglacierincentralSpitzbergen,Svalbard,Norway.Theconduit,whichhadbeenmappedbeforein2007wasremappedafterthemeltseason2009andexploredagainbeforeandafterthemeltseason2010.Duringmeltseason2010,numerousdyetraceinvestigationswereconductedbyinjectionofRhodamineW/Tviaasupraglacialstreamthatdischarges into theexploredsubglacialconduit.Dyereturnwasmeasured in theproglacial rivernear theglaciersnout.BTC-Patternscouldthenbecomparedtotheobservedchangesinthemorphologyofthesubglacialchannel.

Speleologicalexplorationshowsthatthesubglacialconduitislocatedatthebedoftheglacierwhereitispartlyincisedinfrozentill.Theicethicknessabovetheconduitislessthan30m.Theconduithasthemorphologicaltraitsofaclassiccutandclosureconduitthatdevelopedbyincisionofasupraglacialchannelandmusthavedevelopedafter1996,whenthedrainageofRieperbreenwasmainlysupraglacial.

Repeatedmappingandexploringusingspeleologicalmethodsindicatesthatthegeometryoftheconduitshowsnosigni-ficantchangesbetweentheinvestigatedseasons,and,accordingtothemappingof2007,alsodoesn’tchangesignificantlybetweenyears.

Dyetracingresultsshowedthepatternmentionedabove,withlowTV,PCintheearly,andhighTV,PCinthepeakmeltseason.

Theconduitisnotsubjecttochangesinmorphology,sothisfactorcanbeeliminatedasacauseoftheobservedhydrolo-gicalchanges.Instead,weinferthattheBTCcharacteristicsreflectchangesinrecharge,andthevaryingeffectsofchannelroughnessatdifferentdischargerates.Theseresultsimplythatrechargeratesmustbetakenintoaccountwheninterpre-tingtheresultsoftracerstudiesinglacialdrainagesystems.

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10.20

Permafrost carbon dynamics controlled atmospheric CO2 and Pleistocene climate

ZechRoland1,HuangYongsong1,ZechMichael2,TarozoRafael1&ZechWolfgang2

1 Geological Sciences, Brown University, Providence, USA ([email protected])2 Institute of Soil Science, University of Bayreuth, Germany

Theprevailing‘oceanhypothesis’explainslowerlevelsofatmosphericCO2duringglacials(~180ppm)comparedtointer-glacials(~280ppm,pre-industrial)withreduceddeepoceanventilationandresultanttrappingofCO2.Theblindspotofthishypothesis,however,isthattheassumedlargepoolofoldradiocarboninthedeepoceanhasnotbeenfoundsofar(BroeckerandBarker2007),andthatcurrentclimateandcarbonmodelscannotadequatelysimulatetheCO2trapping(Tagliabueetal.2009).Oneshouldthereforebeopen-mindedtoalternativehypothesis,namelythatcarbonsequestrationandstorageinterrestrialecosystemsincreasedduringglacials.

Revisedcarbonstorageestimateshighlightthatthesoilorganiccarbonpoolsinnorthernpermafrostregionshavebeenextremelyunderestimatedsofar(>1670PgC,Tarnocaietal.2009).Goodpreservationofsoilorganicmattermorethancompensatesforlowbiomassproductivity.AlthoughreportsofincreasingpermafrostdegradationandrelatedCO2andmethaneemissionshavefueledconcernsaboutastrongpositiveclimatefeedbacktoanthropogenicwarming,thepoten-tialroleofpermafrostcarbondynamicsonlonger,glacial-interglacialtimescaleshaslargelyescapedscientificinterests.

Weinvestigateda15high,240kaoldpermafrostloessprofileinNE-Siberiausingstandardgeochemicaltechniques,aswellascompound-specificdeuteriummeasurements (dD)onplant-derived long-chainn-alkanes.Ourresults showthatorganic-richhorizonsaccumulatedduringcold(glacial)periodsasindicatedbymorenegativedDvalues,whereassoilor-ganicmaterialdegradedandmineralizedmoreintensivelyduringwarm(interglacial)periods(morepositivedDvalues,Fig.1).Thesefindingsreflectandillustratethelong-termcarbondynamicsofpermafrostsoils,andspatialextrapolationofthesedynamicstothevast,non-glaciatedSiberianplainsindicatesthatmorethan1000Pgsoilorganiccarbonmighthaveaccumulatedslowlyduringeachglacial(Zimovetal.2009).Similaramountsofcarbonwouldhavebeenreleasedrapidlyduringterminations,anequivalentto~500ppmCO2intheatmosphere.Thisimpliesthattheoceanswouldhaveactedassinksduringterminationsratherthansources,assuggestedbythe‘oceanhypothesis’.

Onlong,glacial-interglacialtimescales,permafrostcarbondynamicsarecontrolledbymeanannualtemperatures,whichareexternallyforcedbyintegratedannualinsolation.The~40kaperiodicityoficeagesduringtheearlyPleistocenecanthus readily be linked to the orbital parameter obliquity, which controls high-latitude integrated annual insolation(Huybers2006).Ourproposed‘permafrostglacialhypothesis’canalsoreadilyexplaintheMid-PleistoceneTransitionafter~1Ma,whentheperiodicityoficeageschangedto~100ka:TheoverallPleistocenecoolingtrendcausedpermafrosttoreachmid-latitudes(~45°N),whereintegratedannualinsolationisnolongercontrolledbyobliquity,buteccentricity.Asaconsequence,obliquitycycles(glacialterminations)wereskipped,unlesstheycoincidedwithincreasingeccentricity,re-sultingin80or120kaglacialcycles.

REFERENCESBroecker,W.&Barker, S. 2007:A190‰drop in atmosphere’sΔ14Cduring the “Mystery Interval” (17.5 to 14.5kyr).

EarthPlanet.Sci.Lett.256:90-99.Huybers,P.2006:EarlyPleistoceneGlacialCyclesandtheIntegratedSummerInsolationForcing.Science313:508-511.Tagliabue,A., Bopp, L.&Roche,D.M. et al. 2009:Quantifying the roles of ocean circulation andbiogeochemistry in

governingoceancarbon-13andatmosphericcarbondioxideatthelastglacialmaximum.Clim.Past5:695--706.Tarnocai, C., Canadell, J. G.& Schuur, E. A. G. et al. 2009: Soil organic carbon pools in the northern circumpolar

permafrostregion.GlobalBiogeochem.Cycles23:GB2023.Zimov,N.S.,Zimov,S.A.&Zimova,A.E.etal.2009:Carbonstorageinpermafrostandsoilsofthemammothtundra-

steppebiome:Roleintheglobalcarbonbudget.Geophys.Res.Lett.36:L02502.

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Figure1.Sketchofthepermafrostglacialhypothesis.Moretotalorganiccarbon(TOC)issequesteredinourSiberianloessprofiledu-

ringcoldperiodsasindicatedbymorenegativedD,andincreasedglobalicevolumeasindicatedbymorepositived18O(marinestack).

Terminationscoincidewithobliquitymaxima,andaftertheMPTalsowithincreasingeccentricity(notebreakintimescale).

10.21

Active Layer development in Alpine permafrost

ZenklusenMutterEvelyn1&PhillipsMarcia1

1 WSL Institute for Snow and Avalanche Research SLF, CH-7260 Davos Dorf, Switzerland

Theactivelayeristhegroundlayerabovepermafrostthatthawsinsummerandrefreezesinwinter.Itsthicknessisdefi-nedthermallyasthemaximumseasonaldepthofpenetrationofthe0°Cisothermintotheground(Burn1998).Mainlycontrolledbyairtemperature,groundsurfacecharacteristics,moisturecontentandsnowcover,theactivelayerthicknesscanvarybothspatiallyandtemporally.Warmingairtemperaturesmayleadtoincreasingactivelayerthicknessandindu-ceslopeorinfrastructureinstabilityinmountainpermafrost.

InthisstudyactivelayerpropertiesintenpermafrostboreholesintheSwissAlpshavebeenstudiedandcomparedusingboreholetemperatures.Alltensitesshowdifferentactivelayerdepthsrangingfrom0.5mto5mdepth.Acharacteristicdepthatwhichgroundtemperatureinsidetheactivelayerisanalysedhadtobedeterminedtoallowreasonablecompari-sonsbetweenthesites.Weusedthegroundtemperatureseriesmeasured(ifavailable)orinterpolatedinthemiddleoftheactivelayerforeachlocation(seelegendofFigures1and2inbrackets).Tokeepthingssimpletheinterpolationofthesethermaldatawaseffectedlinearly,yettakingintoconsiderationthephaseshiftwithincreasingdepth.

Theactivelayerdepthsandthedifferentstagesintheseasonalcourseofthecharacteristicactivelayertemperatureseries(autumn and spring zero curtains, winter cooling andwarming rates and active layer duration) have been analysed.Furthermoretherelationbetweenthawingdegreedaysandactivelayerthickness(Harlan&Nixon1978,Smithetal.2009)hasbeencomparedwiththeresultsfoundinstudiesoncircumpolarpermafrostlocations.

Theresultsshowthatmaximumactivelayerdepthsarerelativelystableatthedifferentsites(Fig.1).Theimpactoftheexceptionallyhotsummer2003is,however,clearlyvisibleattwosites,buttherewasalmostcompleterecoveryfromthisstrikingactivelayerdeepeninginthecourseofthefollowingtwoyears.Incontrasttothethickness,thedurationoftheactivelayershowsanincreasingtendencyforallsites(Fig.2).

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Autumnandspringzerocurtaindurationsarehighlyvariablerangingfrom0to90days.Ratesofcoolingandthawingduringthefrozenstageoftheyeararesimilarforthedifferentsitesandrangefrom-0.006to-0.001°C/dayforcoolingandfrom0.001to0.01°C/dayforwarming.Therelationbetweenthawingdegreedaysandactivelayerdepthonlyshowssigni-ficantpositivecorrelationsfortheearlyactivelayerseason(MaytoJuly).Atmanysiteswithcoarsegrainedsurfacemate-rialintheAlpstheactivelayerisunderlainbyarelativelyice-richpermafrosttablewhichpreventsafurtheractivelayerdeepeninglaterinthesummer(Phillipsetal.2009).

REFERENCESBurn,C.R.1998:Theactivelayer:twocontrastingdefinitions.PermafrostandPeriglacialProcesses,9,411-416.Harlan,R.L&J.F.Nixon1978:Groundthermalregime.MacGraw-Hill,NewYork.Phillips,M.,E.ZenklusenMutter,M.Kern-Luetschg&M.Lehning2009:RapidDegradationofGroundIceinaVentilated

TalusSlope:FlüelaPass,SwissAlps.PermafrostandPeriglacialProcesses,20,1-14.Smith,S.L.,S.A.WolfeD.W.Riseborough&F.M.Nixon2009:ActiveLayerCharacteristicsandSummerClimaticIndices,

MackenzieValley,NorthwestTerritories,Canada.PermafrostandPeriglacialProcesses,20,201-220.

Fig.1:Activelayerthicknessatthetenboreholesites.Inbrackets:characteristicdepthinthemiddleoftheactivelayerforthecorres-

pondingsite.

Fig.2:Activelayerdurationatthetenboreholesites.Inbrackets:characteristicdepthinthemiddleoftheactivelayerforthecorres-

pondingsite.

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