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