Abstract Volume7th Swiss Geoscience MeetingNeuchâtel, 20th – 21st November 2009

4. Open Cryosphere session

164Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion 4. Open Cryosphere session

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

M. Schwikowski

Swiss Snow, Ice and Permafrost Society

4.1 DalbanCanassyP.,FunkM.:FlowdynamicsofthesteeppartofTriftgletscher(Switzerland)

4.2 DelaloyeR.,HauckC.,HilbichC.,LambielC.,MorardS.,ScapozzaC.:ElectricalResistivityTomographyMonitoringofpermafrostwithinthePERMOSnetwork

4.3 FaillettazJ.,FunkM.,SornetteD.:Icequakesasprecursorsoficeavalanches

4.4 FarinottiD.,HussM.,BauderA.,FunkM.:HowmuchiceisstoredbytheSwissglaciers?

4.5 Groot Zwaaftink C., Cagnati A., Crepaz A., Fierz C., Lehning M., Valt M.: Surface snow modeling at Dome C,Antarctica

4.6 HauckC.,HoelzleM.,HussM.,SalzmannN.,ScherlerM.,SchneiderS.:Integrativecryosphericresearch-anexampleintheSwissAlps

4.7 HussM.,BauderA.,FunkM.:Largescatterandmultidecadalfluctuationsinthe20thcenturymasslossof30Swissglaciers

4.8 HussM.:MassbalancemonitoringonPizolgletscher

4.9 LeBrisR.,BerthierE.,MabileauL.,TestutL.,RémyF.:IcewastageontheKerguelenIslands(49°S,69°E)between1963and2006.

4.10 MittererC.,MottR.,SchirmerM.,SchweizerJ.:Observationandanalysisoftwowet-snowavalanchecycles

4.11 ReiwgerI.,ErnstR.,SchweizerJ.,DualJ.:Shearexperimentswithsnowsamples

4.12 RiesenP.,HutterK.,FunkM.:Aviscoelasticconstitutiverelationdescribingprimaryandsecondarycreepandsolidelasticbehaviourofice

4.13 RingsJ.,HauckC.,HilbichC.:CouplingofERTandthermalmodellingtomonitorpermafrostwithoutboreholes

4.14 RyserC.,LüthiM.,BlindowN.,SuckroS.:ThepolythermalstructureofGrenzgletscher(SwissAlps)

4.15 SchaefliB.,HussM.:Simulationofhighmountainousdischarge:howmuchinformationdoweneed?

4.16 SchneiderS.,ScherlerM.:Impactofsnowmeltonzerocurtainandthawlayerdepthfordifferentsubsurfacetextures.Fieldandmodeling-basedstudiesattheMurtél-Chasteletsarea.

4.17 SchneiderT.,Katona-SerneelsI.:UsingXPDfordeterminingphysicalrockparametersofpermafrostmaterials

4.18 SteinkoglerW.,FierzC.,LehningM.,ObleitnerF.:AsystematicapproachtoquantifytheperformanceofSNOWPACK

4.19 StummD.,FitzsimonsS.J.,CullenN.J.,HoelzleM.,MachguthH.,AndersonB.MackintoshA.:MassbalanceofBrewsterGlacier,NewZealand,modelledoverthreedecades

4.20 ThevenonF.,AnselmettiF.S.,BernasconiS.M.,SchwikowskiM.:NaturalandanthropogenicprimaryaerosolsrecordfromanAlpineicecore(ColleGnifetti,SwissAlps).

4.21 UsselmannS.,HussM.,BauderA:Impactsofclimatechangeon22south-easternSwissglaciersfrom1900until2100

4.22 VieliA., FaezehM.N.:Understanding rapiddynamic changesofmarineGreenlandoutletglaciers fromnumericalmodeling

4.23 WerderM.,BauderA.,KeusenH.-R.,FunkM.:HazardassessmentinvestigationsinconnectionwiththeformationofalakeonthetongueoftheUntererGrindelwaldgletscher,BerneseAlps,Switzerland

4.24 WirzV.,SchirmerM.,LehningM.:Analysisoftemporalandspatialsnowdepthchangesinasteeprock

165

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n4.1

Flow dynamics of the steep part of Triftgletscher (Switzerland)

DalbanCanassyPierre1,FunkMartin1

1 Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, CH-8092 Zurich, Switzerland (dalban@vaw.baug.ethz.ch)

Severalstudiesonhangingglaciershavebeentriedtohighlihtpossibleprecursorsbeforebreakoffs.Ifsatisfactoryresultshavebeenobtainedoncoldglaciers,itseemsthatbreakoffmechanismsaredifferentforthosewhicharetemperate,suchastheTriftgletscher,Switzerland(Gadmertal,BerneseAlps).

Duetothedisapearanceofahugeamountoficeinitslowerpartduringthelastdecades,thesteeppartofTriftgletscherwasdestabilized,andapro-glaciallakeappeared.Studiesshowedthatareleaseofanicemasswithmorethanonemillionm3couldcreateawavetriggeringafloodinthedownglaciervalley(Gadmertal).

To improve our understanding about ice break offs of temperate hanging glaciers, we have monitored the ice fall ofTriftgletscherusingdifferentways:Twoautomaticcameraswithatriggertimeeverythreehours,permittoperformthecomputationofthesurfacemotions,andthreeseismicsensors,whichpermittodetectandlocateseismiceventsassociatedwithiceqakes.

Theaimistocombineseismicandphotogrammetricresultsandcorrelatetheseismicactivitywithchangesintheobservedicesurfacemotions,inordertoforeseepossiblebreakoffs.

Firstresultsshowedthattimeperiodscharacterizedbythehighestsurfacevelocitiesalsohavethebiggestamountofseis-micevents.Thusthereseemstobearelationshipbetweendisplacementsinthesteeppartandseismicactivity,andthatseismicitycanbeusedasaforecasttool.Wealsonoticedthatthereweremoreeventsduringnightthanduringdaytime.Thisindicatesthatbasaldrainageactivityplaysanimportantroleintheicemotions.Welocatedeventsindifferentpartsoftheseracfall:cracksduetocrevassesopeningnearthesurface,andyetunknowneventsinthelowerpartbecauseoffallingoficeblocks.Thenextstepistodetectandlocateeventsfromstickandslipmotion,whichcouldcharacterizeprecursormotionstobreakoffs,andtodoavalidationbyusingtheterrestrialphotogrammetry.

Newsresultsaboutstickandslipmotioncharacterizationandphotogrammetricresultswillbepresented.

4.2

Electrical Resistivity Tomography Monitoring of permafrost within the PERMOS network

DelaloyeReynald1,HauckChristian1,HilbichChristin2,LambielChristophe3,MorardSebastien1,ScapozzaCristian3

1Department of Geosciences, Geography Unit, University of Fribourg, Chemin du Musée 4, 1700 Fribourg 2Glaciology, Geomorphodynamics & Geochronology, Physical Geography Division, Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, and Department of Geography, University of Jena, Germany (chilbich@geo.uzh.ch)3Faculté des géosciences et de l'environnement, Institut de Géographie, IGUL Quartier UNIL-Dorigny, Bâtiment Anthropole, 1015 Lausanne

ThePERMOSnetwork(PermafrostMonitoringSwitzerland)startedin2000andaimsatalong-termobservationofmountainpermafrost.Itcurrentlycomprisesmorethan20siteswherethethermalevolutionofthegroundand/orthegroundsurfaceismonitored.Besidesthesurfaceandsubsurfacetemperaturestheicecontentofthefrozengroundisnotonlyakeyparam-etercontrollingslopestabilityinperiglacialenvironmentsbutalsoanimportantinputparameterforpermafrostmodels.

Addressingthenecessityforamethodtomonitorthelong-termevolutionofthegroundicecontentinmountainpermafrostin the context of globalwarming, an Electrical Resistivity TomographyMonitoring (ERTM)networkwas initiated in theframeworkofPERMOSin2005.Incontrasttosinglegeophysicalsurveystheso-calledtime-lapseapproachofrepeatedmeas-urementsservestoovercomethecommonproblemoftheoftenambiguousinterpretationofabsoluteresistivityvalues.TheERTMapproachisbasedontheassumption,thattemporalchangesinthemeasuredelectricalresistivityprovideinformationonchangesinthesubsurfaceiceandwatercontent.

166Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion

FollowingapilotstudyontheSchilthorncrest,runningsince1999,anetworkoffourpermanentgeoelectricprofileswasestablishedin2005/2006atthreefurthersites(Murtèlrockglacier,Stockhornrockplateau,Lapirestalusslope)toevaluatethepotentialofpermafrostmonitoringbyrepeatedgeoelectricalmeasurements.BasedonthegoodresultsERTMisnowanoperationalelementofthePERMOSprogrammeandanumberofnewpermanentprofileswasinstalledduringthelastyears.Thenetworknowcomprises14permanentERTMprofilesat10 sites inSwitzerland, includingbedrock sites (Schilthorn,Stockhorn), rock glaciers (Murtèl, Gianda Grischa, Rechy), talus slopes (Lapires, Les Attelas, Dreveneuse, Creux du Van,Arolla),andanice-coredmoraine(Gentianes).

FirstresultsofthisuniquenetworkindicateahugepotentialoftheERTMapproachtodetectandcharacteriseclimatein-ducedgroundicedegradation.Theobserved2-dimensionalresistivitychangesrevealspatiallymoredetailedinformationthan1Dboreholetemperaturesandcontributetoanincreasedunderstandingoftheresponseofdifferentpermafrostland-formstoclimatechange.

4.3

Icequakes as precursors of ice avalanches

JéromeFaillettaz1,MartinFunk1&DidierSornette2,3

1 VAW, ETH Zürich, Laboratory of Hydraulics, Hydrology and Glaciology, Switzerland (faillettaz@vaw.baug.ethz.ch)2Department of Management, Technology and Economics, ETH Zürich3Department of Earth Sciences, ETH Zürich

AhangingglacierattheeastfaceofWeisshornbrokeoffin2005.Wewereabletomonitorandmeasuresurfacemotionandicequakeactivityfor21daysuptothreedayspriortothebreak-off.

Resultsarepresentedfromtheanalysisofseismicwavesgeneratedbytheglacierduringtherupturematurationprocess.Threetypesofprecursorysignalsoftheimminentcatastrophicrupturewereidentified:

anincreasingseismicactivitywithintheglacierachangeinthesize-frequencydistributionoficequakeenergy,andalog-periodicoscillatingbehavioursuperimposedonpowerlawaccelerationoftheinverseofwaitingtimebetweentwoicequakes.

Theanalysisoftheseismicactivitygaveindicationsoftheruptureprocessandledtotheidentificationoftworegimes:astableonewhereeventsareisolatedandnoncorrelatedwhichischaracteristicofdiffusedamage,andanunstableanddan-gerousoneinwhicheventsbecomesynchronizedandlargeicequakesaretriggered.

4.4

How much ice is stored by the Swiss glaciers?

DanielFarinotti1,MatthiasHuss1,2,AndreasBauder1&MartinFunk1

1Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH-Zurich, CH-8092 Zurich (farinotti@vaw.baug.ethz.ch)2 Department of Geosciences, University of Fribourg, CH-1700 Fribourg

Glaciersarecharacteristicfeaturesofmountainenvironmentsandplayanimportantroleinvariousaspects.Theyareakeyelementofthewatercycle,beingthusimportantforhydropowerproductionoragriculturalexploitation,andepitomizethe”untouchedenvironment”,beingpreciousfortourismindustry.Withtheongoingclimatewarming,theretreatofmountainglaciersisofmajorconcernandstudiesassessingfutureglacierchangesandrelatedimpactsrecentlyreceivedincreasinginterest.Suchpredictionsnecessarilyneedthepresenticevolumeasinitialconditionandfortransientmodelling,theicethicknessdistributionhastobeknown.

i)ii)iii)

167

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

nRecently,Farinottietal.(2009a)developedamethodbasedonmassconservationandprinciplesoftheiceflowdynamicsforinferringtheicethicknessdistributionofaglacierfromtheinversionofthesurfacetopography.Weappliedthemethodto62glaciersintheSwissAlps,includingallicemasseslargerthan3km2insurfacearea,usingdirecticethicknessmeasure-mentstoconstrainthemodelparameters.Theresultingsetoficevolumeswerereferencedtotheyear1999bymeansofatimeseriesofglaciermassbalance(Farinottietal.,2009b,Hussetal.,2008)andusedtocalibrateavolume-areascalingrela-tion(Bahretal.,1997).TheobtainedrelationwasthenappliedtotheglacierscontainedintheSwissGlacierInventory2000(Paul,2007)inordertoestimatethetotalglaciericevolumeintheSwissAlps.

In1999,theglacierizedareaintheSwissAlpswas1063±10km2,with67%coveredbyglacierslargerthan3km2.FortheSwissAlps,weinferatotalglaciericevolumeof74±9km3(Farinottietal.,2009b).Nearlyonequarterofthisvolumeisstoredinthe hydrological basin of the Massa river, which comprises the three large glaciers Grosser Aletschgletscher,MittelaletschgletscherandOberaletschgletscher(Fig.1).Accordingtothetimeseriesofglaciermassbalance,theicevolumeintheSwissAlpsdecreasedby12%between1999and2008.Theextraordinarilywarmsummerof2003causedaicevolumelossofabout3.5%.

Figure1.InferredicethicknessdistributioninthehydrologicalbasinoftheMassariver.Availableradio-echosoundingprofilesareshown.

Hatchedareasareanalysedusingascalingrelation(FiguretakenfromFarinottietal.,2009b).

REFERENCESBahr,D.B.,Meier,M.F.andPeckham,S.D.,1997.Thephysicalbasisofglaciervolume–areascaling. JournalofGeophysical

Research102(B9),20355-20362.Farinotti,D.,Huss,M.,Bauder,A.,Funk,M.andTruffer,M.,2009a,Amethodtoestimatetheicevolumeandice-thickness

distributionofalpineglaciers.JournalofGlaciology,55(191),422-430.Farinotti,D.,Huss,M.,Bauder,A.andFunk,M.,2009b.AnestimateoftheglaciericevolumeintheSwissAlps.Globaland

PlanetaryChange,68,225-231.Huss,M.,Bauder,A.,Funk,M.andHock,R.,2008.DeterminationoftheseasonalmassbalanceoffourAlpineglacierssince

1865.JournalofGeophysicalResearch,113,F01015.Paul, F., 2007.ThenewSwissGlacier Inventory2000 -ApplicationofRemoteSensingandGIS. SchriftenreihePhysische

Geographie,Vol.52,UniversityofZurich.210pp.

168Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion 4.5

Surface snow modeling at Dome C, Antarctica

GrootZwaaftinkChristine1,CagnatiAnselmo2,CrepazAndrea2,FierzCharles1,LehningMichael1,ValtMauro2

1WSLInstituteforSnowandAvalancheResearchSLF,Davos,Switzerland2ARPAV CVA, Arabba di Livinallongo, Italy

ModelingeffectivelysurfacesnowcompactioninAntarcticaisofgreatinterestforabetterunderstandingofexchangeproc-essesbetweenthesnowsurfaceandtheatmosphereaswellastheirrelevancetosurfacemassbalance.AtDomeC,wemeas-uredwaterequivalentofsolidprecipitationcollectedabout0.8mabovethesnowsurface.Thedensityofthiscollectedsnowvariesroughlyfrom50to300kgm-3withameanaround80kgm-3.Ontheotherhand,themeasureddensityoverthetop10cmofthesnowcoverbeingabout300kgm-3,thislayerroughlyrepresentsthemeanyearlyaccumulationatDomeC,forwhichdetailedsnowprofiles,continuousrecordsofsnowtemperatures,andatwoyearmeteorologicaldatasetareavailable.Therearesomeobservationsofdriftingsnoweffectsandweexpectwindtoplayamajorroleinthisdensificationprocess.

Extensive qualitative descriptions of the snow deposition process exist in literature but no detailed quantitative study.AdjustingitssettingstotheextremeAntarcticclimate,weuseSNOWPACK,aflexible,modularsnowcovermodeltosimulatesnowcoverevolution.Theinfluenceofthewindonrapiddensificationisparameterizedbymeansofaneventdrivensnowdeposition.Thisresultsinamorerealisticsnowcoverwithapronouncedstratigraphy,evidentinsnowdensityandgrainsizes.

Othermechanismswhichwetrytoincludearetheinfluenceofwatervapordepositionandsublimationatthesurface,forexample.

Wewilldiscussimplicationsfromourresultsforfuturestudieswithrespecttobothmodelingandinsitumeasurementsrelatingtothisveryimportantprocess.

4.6

Integrative cryospheric research - an example in the Swiss Alps

HauckChristian,HoelzleMartin,HussMatthias,SalzmannNadine,ScherlerMartin,SchneiderSina

Alpine Cryosphere and Geomorphology (ACAG), Department of Geosciences, University of Fribourg, Chemin du Musée 4, CH-1700 Fribourg

Asclimateischangingandthediscussiononimpactsandadaptationareemergingrapidlyinthescientificandpoliticaldialogue,itbecomesevenmorecriticaltoobserve,analyseandunderstandimportantcomponentsoftheclimatesysteminanintegratedmanner.Observationsaretheindispensablepreconditiontoimproveprocessunderstanding.Moreover,onlywithareliableandconsistentdatabaseline,modelscanbeverifiedandtheuncertaintyinprojectionsoffuturechangescanbeassessed.

Thehigh-mountaincryosphereisparticularlysensitivetochangesintheatmosphericconditionswithseveralfeedbackme-chanismsonvariousspatialandtemporalscales.Atthesametime,alsothecryosphericcomponents,snow,iceandperma-frost,interrelatewhichleadstonon-linearresponsestoclimatechange.Atypicalexampleisthedifferingeffectofthesnowcoverforglaciermassbalancevariabilityandgroundisolationoverpermafrostoccurrences.Itisthereforecriticaltoadvan-ceintegratedmeasurementandanalysisconceptsforallcryosphericcomponentsofhigh-mountainenvironments.

Therecentlyformednewresearchgroup ‘AlpineCryosphereandGeomorphology (ACAG)’attheUniversityofFribourgisaimingatactivelyadvancingintegratedinvestigationinhigh-mountainenvironments.Thearea‘Stockhorn-Findelgletscher’nearZermatt,Valais,hasbeenchosentobecomea‘posterchild’ofintegratedcryosphericresearchwherevariousmeasure-mentandmodellingapproachesareapplied.Measurementsincludeallcomponentsoftheenergybalance,spatialdistribu-tionofsnowaccumulation,glaciermassbalance,permafrostgroundtemperaturesdownto100m,geophysicalmonitoringoficeandwatercontentandgroundsurfacetemperatures(e.g.Gruberetal.2004,Machguthetal.2006,Hilbichetal.2008).Inaddition,newmodelapproachestodeterminetheresponseofglaciermassbalance(Findelgletscher),activelayerdepth(permafrostStockhorn)andevolutionofgroundicecontentareusedtoanalysetheimpactofclimatechangeonglaciersandpermafrostandtheirrespectivedifferences(e.g.Haucketal.2008).

169

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

nOurpresentationwillfocusonsomeofthemainresearchactivitiesintheStockhorn-Findelgletscherareaandgiveexamplesforintegratingthescientificactivities.

Figure1.FindelgletscherandStockhornpermafrostmonitoringsite.Firstresultsofthedistributedsnowaccumulationmeasurementsin

April2009areshown.Crossesindicatesnowprobings,theinferreddistributionofthesnowwaterequivalentisshowningreyscales.

REFERENCESGruber, S., L.King,T.Kohl, T.Herz,W.Haeberli,&M.Hoelzle. 2004. Interpretationofgeothermalprofilesperturbedby

topography:TheAlpinepermafrostboreholes at StockhornPlateau, Switzerland. PermafrostPeriglacial Processes, 15,349-357.

Hauck,C.,Bach,M.&Hilbich,C.2008.A4-phasemodeltoquantifysubsurfaceiceandwatercontentinpermafrostregionsbasedongeophysicaldatasets.Proceedingsofthe9thInternationalConferenceonPermafrost,Fairbanks,Alaska,1,675-680.

Hilbich,C.,Hauck,C.,Delaloye, R.&Hoelzle,M. 2008.A geoelectricmonitoringnetwork and resistivity-temperaturerelationshipsofdifferentmountainpermafrostsitesintheSwissAlps.ProceedingsNinthInternationalConferenceonPermafrost,Fairbanks,Vol.1,KaneD.L.andHinkelK.M. (eds), InstituteofNorthernEngineering,UniversityofAlaskaFairbanks,699-704.

Machguth,H., Eisen,O., Paul, F.&Hoelzle,M., 2006. Strong spatial variability of snow accumulation observedwithhelicopter-borne GPR on two adjacent Alpine glaciers. Geophysical Research Letters, 33 (L13503): doi:10.1029/2006GL026576

4.7

Large scatter and multidecadal fluctuations in the 20th century mass loss of 30 Swiss glaciers

HussMatthias1,2,BauderAndreas2&FunkMartin2

1 Department of Geosciences, University of Fribourg, 1700 Fribourg, Switzerland (matthias.huss@unifr.ch)2 Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, 8092 Zürich, Switzerland

Theongoingretreatofmountainglaciersstronglyimpactsonthehydrologicalcycle,mightcauseeconomiclossesinalpineregionsandisexpectedtodominateeustaticsealevelriseoverthenextcentury.Long-termtimeseriesofglaciermassba-lancerepresentakey toprojecting futureglacierchangesandunderstandingtheglacier-climate linkage.However,massbalanceismeasuredononlyafewglaciers,andtherecordstypicallyareonlysomedecadeslong.

170Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion Here,wepresentthirtynewtimeseriesofglaciersurfacemassbalance,accumulationandmeltoverthepast100yearsin

theSwissAlps.Thedatasetincludesdifferentglaciersizes,exposuresandregions,andthusconstitutesthefirstlong-termmassbalancetimeseriesbeingrepresentativeonamountainrangescale.Ourresultsarebasedonacomprehensivesetoffielddataandmodelling.Foreachglacier,upto10high-accuracydigitalelevationmodels(DEMs)wereestablishedprovidingicevolumechangesinsubdecadaltosemicentennialperiods.Inaddition,morethan8000directobservationsofannualmassbalanceandwinteraccumulationareavailable.Thisdatabasewasusedtoconstrainadistributedtemperature-indexmodel(Hock,1999;Hussetal.,2008)drivenbydailyairtemperatureandprecipitationfortheperiod1908-2008.

Allglaciersshowconsiderablemassloss,butratesdifferstronglybetweenindividualglaciers(Fig.1).100-yearcumulativemassbalancevariesbetween–11mwaterequivalent(Allalingletscher)and–65mw.e.(Griesgletscher).Thesestrongdiffe-rencesintheresponseofglaciermassbalancetochangesinclimateforcingareattributedtoaninteractionofseveralcom-plexprocesses.Largeandflatglacierstendtohavemorenegativemassbalanceduetotheirlongreactiontime.Positiveandnegativealbedofeed-backmechanisms,aswellaschangingwinterprecipitation,variableonsmallerspatialscalesthanairtemperatures,mightalsoexplainsomeofthedifferences.

Masslossisparticularlyrapidinthe1940sandlate1980stopresent,whileshortperiodsofmassgainoccurredinthe1910sandlate1970s(Fig.1).Thisindicatesthatglaciermasslossoverthe20thcenturywasnotlinear,butexhibitsimportantlong-termvariations.WefindoscillationsintherateofglaciermasslossintheSwissAlpswithaperiodof65years.GlaciermassbalanceissignificantlyanticorrelatedtotheAtlanticMultidecadalOscillation(AMO)indexwhichreferstoanomaliesintheseasurfacetemperatureintheNorthAtlantic.WethusproposealinkbetweenAtlanticOceancirculationandAlpineglaciermassloss.

Figure1.Timeseriesofcumulativemeanspecificannualmassbalanceof30Swissglaciersinthe20thcentury.Blackdotsindicatethe

datesofDEMs.Thesolidlinerepresentsthearithmetic30-glacieraverage.Glaciernamesandnumbersarearrangedaccordingtodescen-

dingglaciersize.Thedash-dottedlineshowsthecumulativetotalvolumechangeofthe30glaciers(right-handsideaxis).Twoshortperi-

odswithmassgainandtwoperiodswithfastmasslossaremarked.

REFERENCESHock,R.,1999.Adistributedtemperature-indexice-andsnowmeltmodelincludingpotentialdirectsolarradiation.Journal

ofGlaciology,45,101–111.Huss,M.,Bauder,A.,Funk,M.&Hock,R.,2008.DeterminationoftheseasonalmassbalanceoffourAlpineglacierssince

1865.JournalofGeophysicalResearch,113,F01015.

171

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n4.8

Mass balance monitoring on Pizolgletscher

HussMatthias1,2

1 Department of Geosciences, University of Fribourg, 1700 Fribourg, Switzerland (matthias.huss@unifr.ch)2 Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, 8092 Zürich, Switzerland

Verysmallglaciersarerarelysubjectofglaciologicalstudies.AlthoughtheseglaciersonlycoveralimitedfractionoftheglacierizedareaintheAlps,theirnumberisconsiderable.Accordingtoglacierinventorydata,82%oftheSwissglaciersaresmaller than 0.5 km2. So far, the mass balance of glaciers in this important size class was never investigated inSwitzerland.

In2006anewmassbalancemonitoringprogramontheverysmallPizolgletscher,north-easternSwissAlps,wasstarted.Pizolgletscherhasanareaofcurrently0.08km2andisarelativelysteep,north-exposedcirqueglacier(Fig.1).Themonitoringprogramconsistsoftwofieldsurveys,oneinAprilandoneinSeptember,andwillbecontinuedoverthenextyears.Duringthewintersurveythespatialdistributionofsnowaccumulationisdeterminedbyupto100snowprobingsonadensenet-workandsnowdensitymeasurementsinasnowpit.Threestakesdrilledintotheiceprovideinformationabouttheannualmassbalance(Fig1a).Inaddition,thechangesinglacierareaandicevolumeareknowninsubdecadalintervalsfromsevenphotogrammetricsurveyssince1968providinghigh-accuracydigitalelevationmodels.

Basedontheseasonalin-situmeasurementsglacier-widemassbalanceisdeterminedusinganovelmethod.Adistributedmassbalancemodelwithdailytimestepsistunedtomatchboththemeasuredsnowwaterequivalentinspringandtheannualmassbalanceatthestakes(Huss,2009).Theobservedaccumulationdistributionisusedtoconstrainthemodelinspace.Thismethodallowsanoptimalexploitationofthefielddata,thedeterminationofmassbalanceoverfixedtimepe-riodsand,thus,thecomparisonofdifferentyears.

InthetwofirstyearsofthesurveyPizolgletscherwassubjectedtostrongmassloss.Theannualmassbalancein2006/2007was–1.60mwaterequivalent(w.e.)andin2007/2008–0.83mw.e.Thewinteraccumulationwaslowin2007withanearlyonsetofthemeltingseason.InApril2008and2009,however,averagesnowdepthsofalmost5metresweremeasured,coun-teractingthehighairtemperaturesofthefollowingsummer.ThespatialpatternofsnowdepositiononPizolgletscherishighlyvariableandimportantlydeterminedbywind(Fig.1b).Consequently,glacieradvanceisduetoanappositionoffirninfrontoftheglaciertongue,andisnotrelatedtoadynamicreactionoficeflow.Pizolgletschercan,thus,changeitsareaandlengthrapidly,whichisillustratedbythelengthchangemeasurementscarriedoutsincethelate19thcentury.

Figure1.(a)FrontviewandmapofPizolgletscher.Thepositionofthemassbalancestakesisshown.(b)OrthophotographofPizolgletschertakeninSeptember1973.Linesindicateglacierextentin1968,1973,1997and2006.Theinhomogeneousdis-tributionofsnowiswellvisible.Theinsetshowsthechangeinglacierarea(dA)andvolume(dV)relativetotheyear1968.

172Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion Between1968and2006Pizolgletscherhaslostmorethan60%ofitsareaandvolume,mostofthedecreasetakingplaceover

thelasttwodecades(insetinFig.1b).Extrapolatingthislossintothefutureis,however,unreliable,astheglacierwillretre-atbydegreesintoamoreprotectedcirquewithhighaccumulationrates,seekingforanewequilibrium.Basedontheobser-vedicevolumechanges,theseasonalmassbalanceoverthelast40yearswasreconstructedaccordingtoHussetal.(2008).The cumulativemass balance is –17mw.e.,which is consistentwith othermass balance records in the SwissAlps (e.g.Silvrettagletscher).Ashortperiodofmoderatemassgains inthe late1970s is followedbystrongmass loss, inparticularsince2003.

ThefirstresultsofthenewmassbalancemonitoringprogramonPizolgletscherarepromisingandhaverevealedinterestinginsightsintotheresponseofsmallglacierstoclimatewarming,inparticulartheirhighsensitivitytoaccumulationchangesandtheimportanceofthespatialdistributionofsnowdeposition.

REFERENCESHuss,M.,Bauder,A.,Funk,M.&Hock,R.,2008.DeterminationoftheseasonalmassbalanceoffourAlpineglacierssince

1865.JournalofGeophysicalResearch,113,F01015.Huss,M,2009.PastandFutureChangesinGlacierMassBalance,Chap.A.1.DissertationNo.18230,ETHZürich,218pp.

4.9

Ice wastage on the Kerguelen Islands (49°S, 69°E) between 1963 and 2006

RaymondLeBris2,EtienneBerthier1,LaureMabileau1,LaurentTestut3,andFrédériqueRémy1

1LEGOS, CNRS, Toulouse, France.2Department of Geography, University of Zurich, Zurich, Switzerland. (rlebris@geo.uzh.ch)3LEGOS, Université de Toulouse, Toulouse, France.

TheglaciersandicecapslocatedaroundtheAntarcticandGreenlandicesheetscontainasignificantfractionofthelandiceonEarth(Dyurgerov&Meier.2005).Difficulttoaccess,theirresponsetoclimaticfluctuationsandtheirrecentevolutionarepoorlyknown(Gordonetal.2008).Becausethebehavioroftheseicemassesalsoconstitutesagenuineclimaticindicator,theobjectiveofthisstudyistoassessthechangesoftheextentandvolumeofglaciersandicecapsonKerguelenIslanddur-ingthelastfortyyears(Berthieretal.2009).ThisstudyisalsoacontributiontotheGLIMSinitiative(Raupetal.2007)

Basedonarchiveddata (e.g. IGNmappublishedin1967,glaciologicalcampaignscarriedout inthe1970s)andonrecentsatellitedata(Landsat,SPOT,SRTM,ICESat),wedefinesuccessiveoutlinesoftheprincipaloutletglacierstomeasurethepaceoftheretreatoftheCookIceCap.InordertounderstandtheresponseoftheIceCaptoclimaticforcing,wealsoanalyzedtheclimaticdatarecordedbytheMétéoFrancestationinPortauxFrançais.

Theresultsrevealthatallglaciershaveretreatedsince1965althoughastrongvariabilityexistsfromoneoutletglaciertoanother.OnestrikingresultistheEast/Westasymmetryoftheglacierretreat:west-flowingglaciershavelost11.4%oftheirareawhileeast-flowingglacierlost28.2%.ThedramaticretreatontheeasternsideisillustratedbytheretreatofExplorer’sGlacierfrontby3150m+/-162msince1965oranaverageof75m/yr.Furthermore,theAmpèreGlacierthinnedonaverageby125m+/-16minthefrontalarea,about-4.8m/yr.(cf.alsoVallon1977).Locally,themeanthinningrateduringthelast40yearsreachedasmuchas10m/yr.

Intotal,theicecaplost20%ofitssurfaceareaoveraperiodofthirty-eightyears(1965-2003).TheCookIceCapisinrecessionsincenearlyonecenturyandthistrendacceleratedsincetheyears1960-70(Frenotetal.1993).Theanalysisofmostrecentsatelliteimages(fromtheyears2003to2007)showsthattheretreatcontinuestodaywiththesamespeedorevenslightlyfaster.

Theicecapisthusfarfromitsstateofbalance. If thecurrentclimaticconditionsprevail (hightemperaturesandarela-tivelylowlevelofprecipitation)oriftheyareevenamplifiedinthefuture,itmightbepossiblethattheicecapwilltotallydisappear.

173

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n

Figure1.TopographyoftheKerguelenIslands.Thefourmainglacierizedregionsandthebasestation(Portaux-Français)arealsoindicated.

ThesmallglobeidentifiesthelocationoftheislandintheSouthIndianOcean.

Figure2.East-westasymmetryoftheCookIceCapshrinkage.

Thedarkgrayrepresentsice-coveredareasthatdisappearedbetween1963and2001.

REFERENCESBerthier, E., Y. Arnaud,C. Vincent, and F. Remy (2006), Biases of SRTM inhigh-mountain areas: Implications for the

monitoringofglaciervolumechanges,Geophys.Res.Lett.,33,L08502,doi:10.1029/2006GL025862.Dyurgerov,M.B.,andM.F.Meier(2005),GlaciersandtheChangingEarthSystem:A2004Snapshot,117pp.,Inst.ofArctic

andAlp.Res.,Univ.ofColo.,Boulder.Frenot, Y., J.-C.Gloaguen,G. Picot, J. Bougère, andD. Benjamin (1993),Azorella selagoHook.used to estimate glacier

fluctuationsandclimatichistoryintheKerguelenIslandsoverthelasttwocenturies,Oecologia,95,140–144.Gordon, J. E.,V.M.Haynes, andA.Hubbard (2008),Recentglacier changesandclimate trendsonSouthGeorgia,Global

Planet.Change,60(1–2),72–84,doi:10.1016/j.gloplacha.2006.07.037.Raup,B.,etal.(2007),RemotesensingandGIStechnologyintheGlobalLandIceMeasurementsfromSpace(GLIMS)project,

Comput.Geosci.,33(1),104–125,doi:10.1016/j.cageo.2006.05.015.Vallon,M. (1977a), Bilandemasse et fluctuations récentes du glacierAmpère (Iles Kerguelen, TAAF), Z.Gletscherkd.

Glazialgeol.,13,55–85.

174Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion 4.10

Observation and analysis of two wet-snow avalanche cycles

ChristophMitterer,RebeccaMott,MichaelSchirmer,JürgSchweizer

WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, CH-7260 Davos Dorf (mitterer@slf.ch)

Theformationofwet-snowavalanchesaswellasthesnowpackprocessesleadingtowet-snowinstabilitiesarepoorlyunder-stood.Forecastingwet-snowavalanchesisagreatchallengeandposesgreatdifficultiesforlocalauthorities.Betterknowl-edgeabouttheprocessesleadingtowet-snowinstabilitiesisthereforeveryimportant.Duringthewintersof2007-2008and2008-2009twodistinctwet-snowavalanchecyclesoccurredinthesurroundingsofDavos,Switzerland.Weanalyzedmete-orologicaldata,in-situsnowpackinformationandmappedavalancheextent.Inaddition,thesnowcovermodelSNOWPACKwasusedtofillthegapwheresnowpackdata,suchasvolumetricwaterorsnowtemperature,werenotavailable.Snowpackinformationfordifferentelevationbandsweremodelledbyusingaconstantlapse-rateforairtemperatureandincominglongwaveradiation.Theanalysisfocusedonthecausesofinstability:loadingand/orweakeningduetowaterinfiltration.The full energy balance was calculated usingmeteorological data and extrapolated to the investigation area using themodelALPINE3D.Bothavalanchecyclesoccurredinashortperiodoftime.The2007-2008avalanchecyclewascharacterizedbyshortperiodsofwarmingandadditionalloadingbysnowfallandinputofmeltwaterduetorain.Forthe2008-2009wet-snowavalanchecycle,ontheotherhand,distinctwarmingandsolarradiationwereprobablyresponsibleforahigherpro-ductionofmeltwater.Terrainparameterssuchasaspectandslopeanglecombinedwithliquidwaterinfiltrationpatternswerecrucialduringthesecondwet-snowavalanchecycle.Snowpackdatasuggestthatinthefirstyearsnowstratigraphyfavouredtheformationofweaklayers,whereasforthesecondyearsnowstratigraphymayhavefavouredagradualripeningofsnowpackleadingtoaweakeningofthebasallayers.

4.11

Shear experiments with snow samples

IngridReiweger1,RobertErnst1,JürgSchweizer1,JürgDual2

1 WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland (reiweger@slf.ch)2 Institute of Mechanical Systems, ETH Zürich, Switzerland

Naturaldry-snowslabavalanchesstartwithafailurewithinaweaksnowlayer.Inordertounderstandthemechanicalbe-haviourandthefailuremechanism,weperformedloadingexperimentswithhomogeneousandlayeredsnowsamplesundercontrolledconditionsinacoldlaboratory.Forsimulatingloadingconditionssimilartothenaturalsnowpack,wedesignedandbuiltanapparatuswhereasnowsamplecanbetiltedbya‘slopeangle’andisloadedviathegravitationalforce.Thedeformationwithin the snow samplewasmeasuredopticallywith a pattern recognition algorithm (PIV). Shortly beforemacroscopicfailure(breakingofthewholesample)weobservedaconcentrationofdeformation(softening)withintheweaklayer.Additionally,wemeasureacousticemissionsduringtheshearexperimentstoquantifythemicroscopicfailure(brea-kingofbonds) inthesnowsamplebeforethecompletefailure.Ourresultssupporttheassumptionthatthedominatingmechanismsforsnowdeformationarethecompetingprocessesofbreakingandsinteringofbondsbetweengrains.ResultsfromPIVclearlyshowedthatwhenalayeredsnowsamplewassubjectedtoaconstantslowloadingrate,thedeformationwasconcentratedwithintheweaklayer.Thishasoftenbeenassumedbuthasnotbeendocumentedsofar.Preliminaryre-sultsoftheacousticemissionmeasurementsofthehomogeneoussamplesindicatedthattheAEmayhintonthemicrome-chanicsduringdeformation.

175

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n4.12

A viscoelastic constitutive relation describing primary and secondary creep and solid elastic behaviour of ice

RiesenPatrick1,HutterKolumban1,FunkMartin1

1Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie (VAW), ETH Zürich, CH-8092 Zürich

Theflowofglaciericeiswidelytreatedbyastress-strainrelationcommonlyreferredtoasGlen'sflowlaw.TheGlenflowlawisapureviscousrelation,henceacertainamountofstressimmediatelycorrespondstodeformation(i.e.strainrate),inde-pendentoftimeandpossiblerelaxation.Thisbehaviourisappropriateforstationary(secondary)creepofice.However,re-centdetailediceflowmeasurementsonGornergletscher,Switzerland,performedduringthedrainageofaglacierdammedlake,haveidentifiedparticularunexplainedflowchangeswheresignificantvariationsoccurwithinafewhourstoseveraldays.Itwassuggestedthatelasticeffectsmayplayaroleinsucharapidresponseofglacierice.Fromanengineeringpointofview,theloadsrequiredtoproducedisplacementsoftheicesimilartothoseobserved,isontheorderofseveral105Pa.Inthisrange,linearviscoelasticbehaviouroficemaybeinappropriateandonemustconsidernon-linearviscoelasticresponseoftheice.However,manyexperimentsandcreeptestsconductedinthepasthaveshownnon-stationary(primary)creeptobeeffectiveforapproximatedurationsofafewhourstoafewdays.Wethereforeconjecturethatprimarycreepplaysaroleinshort-timeglacierflowvariations.Totestourhypothesisandelucidatetheinfluenceofpossibleviscoelasticeffects,weconstructedaconstitutiverelationwhichisabletoreproduceprimaryandsecondarycreepaswellaselasticeffects.Amo-difiedRivlin-Eriksenfluidmodel,wherethestressisrelatedtobothstrainrateandstrainaccelerationsisusedtodescribeprimaryandsecondarycreepoftheice.Wecoupletheviscousfluidmodelwithanon-linearelasticKelvin-typestress-strainrelationtoenablethematerialtoexhibitelasticbehaviourofasolid.Theconstitutiverelationobeysthermodynamicrequire-ments.Thetransientresponseiniceflowisthusassignedtotheeffectsofviscoelasticrelaxationandprimarycreep.Thedecoupledformulationallowstostudythoseeffectsseparatelyorincombination.Somefirstnumericalresultsusingthefiniteelementmethodhavebeenobtainedfortwoglaciologicalbenchmarkproblemsof(i)flowinachanneland(ii)flowoveraninclinedslab.

4.13

Coupling of ERT and thermal modelling to monitor permafrost without boreholes

RingsJörg1,HauckChristian2,HilbichChristin3

1 ICG 4 Agrosphere, Forschungszentrum Jülich, Germany2 Alpine Cryosphere and Geomorphology (ACAG), Department of Geosciences, University of Fribourg, Chemin du Musée 4, CH-1700 Fribourg3 Glaciology, Geomorphodynamics & Geochronology, Department of Geography, University of Zurich, Winterthurerstr. 190, CH-8057 Zurich

Geophysicalmethods,andespeciallytheElectricalResistivityTomography(ERT)method,arebeingrecognisedasstandardtoolsforthedetectionandmonitoringofpermafrost,sincerecentadvancesindataacquisitionandprocessinghavemadetheirapplicationworthwhileeventhoughsomeefforthastobemadetoensuregooddataqualityandreliableinversionresults(Hilbichetal.2009).Inmanyscientificstudiesboreholetemperaturedataserveasgroundtruthforthegeophysicalresults,enablingathoroughandrigorousassessmentofthequalityoftheapproach.Furthermore,ERTyields2-and3-di-mensionaldataofthesubsurfaceandissensitivetotheunfrozenwaterandicecontent,whichiscomplementarytothe1-dimensionaltemperaturemeasurementsinboreholes.

Ontheotherhand,thenon-invasivenessofthegeophysicalsurveysandthecorrespondinglowcostsandminimaldistur-banceofthesystemtobemonitoredisusuallyseenasthemajoradvantageofgeophysicsasopposedtoboreholes.Forfutu-reautonomousandwidespreadmonitoringsystemsforpermafrost(similartothesnowandmeteostationnetworks),apu-relygeophysicalapproachisenvisaged.However,ERTmeasurestheelectricalresistivityofthesubsurface,whichhastoberelatedtoicecontentortemperature.Commonapproachesusepetrophysicalrelationships(suchasthewell-knownArchie'sLaw)torelatethemeasuredresistivitychangestosaturationandicecontentchangesortemperature(Haucketal.2008).Butwithoutgroundtruthdatafromboreholesorextensivelaboratorycalibrationusingsubsurfacematerial,theexactnatureofthesite-specificpetrophysicalrelationshipcannotbedetermined.

176Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion Inthiscontribution,weintroduceafilteringapproachcombinedwithcoupledmodellingofthermalconductionandERT

topredictsubsurfacetemperaturesbasedonERTmonitoringdatawithouttheneedforboreholeorlaboratorydata.WeusesequentialBayesianfilteringorparticlefiltering(seee.g.Arulampalametal.2002),whichhastheadvantageofcontinuous-lyprovidingprobabilitydistributionsofstate(temperature)andparameters(e.g.thermalconductivity)whenevermeasure-mentsbecomeavailable.Aparticlefilterapproximatesthesedistributionsbyasetofdiscrete,weightedparticles.Initialstateandparameteraredrawnfrompriordistributionsandthermalconductionismodelledindependentlyforeachparticle.Themodelledchangeintemperatureistransferredtochangeinresistivitybyalinearrelation,andanERTforwardmodelisusedtosimulatethesystemresponse.Then,theparticlesareweightedaccordingtotheagreementbetweenmeasuredandmo-delledERTresponse.Are-samplingroutineisusedtoensurethat,overtime,theparticlesgravitatetowardstheposteriordistributionsofstateandparameter.

Totesttheapproach,modelledandobservedgroundtemperatureswerecomparedatthehigh-altitudepermafroststationonSchilthorn,BernerOberland/SwissAlps.FirstresultsusingautomatedERTmonitoringdatafromthePERMOS(PermafrostMonitoring Switzerland) network show a good performance during a 3-month period in spring and summer 2009.Improvementscanbeachievedbyusingmoresophisticatedthermalmodelsandbyiterativeprocedurestodeterminethe(verticallyvariable)materialpropertiesofthesubsurface,suchasporosityandthermalconductivity.

REFERENCESArulampalam,M.S.,Maskell,S.,Gordon,N.&Clappt,T.2002.Atutorialonparticlefiltersforonlinenonlinear/non-Gaussian

Bayesiantracking,IEEETransactionsonSignalProcessing,50,174-188.Hilbich,C.,Marescot,L.,Hauck,C.,Loke,M.H.&Mäusbacher,R.2009.ApplicabilityofERTmonitoringtocoarseblockyand

ice-richpermafrostlandforms.PermafrostandPeriglacialProcesses20(3),269-284.Hauck,C.,Bach,M.&Hilbich,C.2008.A4-phasemodeltoquantifysubsurfaceiceandwatercontentinpermafrostregionsbased

ongeophysicaldatasets.Proceedingsofthe9thInternationalConferenceonPermafrost,Fairbanks,Alaska,1,675-680.

4.14

The polythermal structure of Grenzgletscher (Swiss Alps)

ClaudiaRyser1,MartinLüthi1,NorbertBlindow2,SonjaSuckro2

1 Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie (VAW), ETH-Zürich, 8092 Zürich, Switzerland (ryser@vaw.baug.ethz.ch)2 Institut für Geophysik der Westfälischen Wilhelms- Universität Münster, 48149 Münster, Germany

Withacombinationofboreholemeasurementsandhelicopter-borneiceradar,thetemperaturedistributioninthelowerpartofthepolythermalGrenzgletscher(SwissAlps)wasinvestigated.Verticaltemperatureprofilesweremeasuredin12deepboreholes.ColdicewasfoundinacentralflowbandintheGrenzgletscherbranch,wherethecoldestice(-2.6°C)wasfoundin60-75mdepth.Thecoldiceoccupies80-90%oftheicethicknessof200-320m,andislaterallyconnedtoabandof+/-200mfromthecentralflowline.Theiceistemperateclosetothebedandtowardsthemargins.ComparisonoficeradarsoundingsacquiredwiththeUMAIRgeoradarwithboreholetemperaturesshowsthatlow-backscatterzonescoincidewithiceattem-peraturesmore than0.5Kbelow thepressuremelting temperature. The low-backscatter zonesare thusused tomap thedistributionofcoldiceonthewholelowerglacier.Thecoldiceadvectedfromtheaccumulationcausesazoneofpersistentsuperficialmeltwaterstreamsandlakes.

177

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n4.15

Simulation of high mountainous discharge: how much information do we need?

Schaefli,Bettina1andHuss,Matthias2

1 Water Resources Section, Faculty of Civil Engineering and Geosciences, Delft University of Technology, 2600GA Delft, The Netherlands (b.schaefli@tudelft.nl)2 Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, 8092 Zurich. Now at: Alpine Cryosphere and Geomorphology, Department of Geosciences, University of Fribourg, 1700 Fribourg, Switzerland

Forthemanagementofwaterresources,thehydrologiccycleofhighmountainouscatchmentsisfrequentlysimulatedwithverysimpleprecipitation-dischargemodelsrepresentingthesnowaccumulationandablationbehaviorofaverycomplexenvironmentwith a set of lumped equations accounting only for altitudinal temperature andprecipitationdifferences.Thesemodelsaregenerallycalibratedsothatthemodelreproducesascloselyaspossibleaseriesofobserveddischargemea-surements.Thequestioninevitablyariseswhetherlongtermpredictionsofsuchacalibratedmodelareactuallyreliable,sinceknowingthatamodelperformswellforhistoricsituationsdoesbynomeansimplythatitwillperformwellforfuture,considerablymodifiedcatchmentconditions.Afirst,althoughnotsufficientsteptoanswerthisquestion,isinvestigatingwhetherwithsuchamodel,weare“gettingtherightanswersfortherightreasons”.Inglacierizedcatchments,thiswouldforexampleimplythataprecipitation-runoffmodelshouldnotjustmimicobserveddischargebutalsoreproducetheglaciermassbalance.

Inthisstudy,weshowhowmuchobservedinformationweneedtoreliablycalibrateahydrologicalmodelforahighmoun-tainous catchment. Based on glacio-hydrological data from theRhone glacier catchment,we analyzehowwell a simpleconceptualprecipitation-runoffmodel(GSM-SOCONT,Schaeflietal.,2005)canreproduceseasonalglaciermassbalancedataandinasecondstep,howmuchinformationisrequiredtoachieveareliablemodelcalibration.Here,wefocusontheques-tionwhetherobserveddischargeissufficientorwhetherweneedannualorevenseasonalglaciermassbalancedata.

Forthisparticularcatchment,adetailedreproductionofobservedseasonalbalancesrequiresamodificationoftheaccumu-lation and ablationmodule of GSM-SOCONT. Themodel only accounts for altitudinal differences of themeteorologicalconditionsande.g.notforwinddriftorexposition.Asourresultsshow,introducingseasonalaccumulationandablationparametersissufficienttoenablethissimplemodeltoreproduceobservedseasonalbalances (Fig.1)andannualnetbal-ances(Fig.2).Furthermore,ourresultssuggestthatcalibratingthehydrologicalmodelexclusivelyondischargecanleadtowrongrepresentationsof the intra-annualaccumulationandablationprocessesand, thus, toabias in longtermglaciermass balance simulations (Fig. 2). Adding only a few annual net balance observations considerably reduces this bias.Calibrating exclusively on annual net balance data can, in turn, lead towrong seasonalmass balance simulations (notshown).

Eveniftheseresultsarecasestudyspecific,ourconclusionsgivevaluablenewinsightsintothebenefitofdifferenttypesofobservationsforcalibratinghydrologicalmodelsinhighalpinecatchments.

Figure1:Wintermassbalancefor5elevationbands(winter1979/1980);greybars:10%and90%percentilesofallobservedpointmassba-

lances(Funk,1985),redbars:simulatedmeanmassbalance(modifiedGSM-SOCONTwithseasonalaccumulationandablationparame-

ters).

178Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion

Figure2.Comparisonofannualnetbalancesimulationsobtainedwiththedetailedglaciologicalmodelpresentedin(Hussetal.,2008)

andwiththesimplehydrologicalmodelGSM-SOCONT(withseasonalaccumulationandablationparameters),calibratedonseasonaldata,

onnetbalancedata(Funk,1985)orondischarge.

REFERENCESFunk,M.: RäumlicheVerteilungderMassenbilanz auf demRhonegletscherund ihre Beziehung zuKlimaelementen,

EidgenössischeTechnischeHochschuleZürich,Zürich,183pp.,1985.Huss,M.,Bauder,A.,Funk,M.,andHock,R.:DeterminationoftheseasonalmassbalanceoffourAlpineglacierssince1865,

JournalofGeophysicalResearch,113,F01015,10.1029/2007JF000803,2008.Schaefli,B.,Hingray,B.,Niggli,M.,andMusy,A.:Aconceptualglacio-hydrologicalmodelforhighmountainouscatchments,

HydrologyandEarthSystemSciences,9,95-109,2005.

4.16

Impact of snowmelt on zero curtain and thaw layer depth for different subsurface textures. Field and modeling- based studies at the Murtél- Chastelets area.

SchneiderSina,ScherlerMartin

Alpine Cryosphere and Geomorphology (ACAG), Department of Geosciences, University of Fribourg, Chemin du Musée 4, CH-1700 Fribourg

Thesummerzerocurtainphase,atimeperiodcharacterizedbyconsumptionoflatentheatinanisothermalsoilregionattemperaturesnearthemeltingpoint,isofhighimportanceforthethermalregimeofpermafrost.Itisassumedthatthemaincausefortheinitialisationofthesummerzerocurtainisthethawingofthesnowpackandthustheinfiltrationofmeltwaterintothefrozenactivelayer.Furthermoreweassumethattheevolutionofthezerocurtaindependsonthetextureofsubsurface.

BoreholetemperaturemeasurementsfromourfieldsiteMurtél-Chasteletsshowthatonfinegrainedmaterialtheisother-malregionismuchthickerthanincoarseblockymaterial.Inadditionweuseanumericalheatandmasstransfermodeltofurtherinvestigatetheinfiltrationprocessesonthesedifferentsubstrates.

179

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n

B33 (28.04.2008 - 30.06.2008)

-10

-5

0

5

10

15

20

25

30

35

28.04.

08

05.05.

08

12.05.

08

19.05.

08

26.05.

08

02.06.

08

09.06.

08

16.06.

08

23.06.

08

30.06.

08

Date

Tem

per

atu

re (

°C)

0_m

0.1_m

0.2_m

0.3_m

0.4_m

0.5_m

0.6_m

0.8_m

1.0_m

1.5_m

2.0_m

2.5_m

3.0_m

3.5_m

4.0_m

4.5_m

5.0_m

5.95_m

Figure1.:ZerocurtainofboreholeB33(coarseblockymaterial)duringspring2008

B34 (28.04.2008 - 30.06.2008)

-10

-5

0

5

10

15

20

25

30

35

28.04.

08

05.05.

08

12.05.

08

19.05.

08

26.05.

08

02.06.

08

09.06.

08

16.06.

08

23.06.

08

30.06.

08

Date

Tem

per

atu

re (

°C)

0.0_m

0.1_m

0.2_m

0.3_m

0.4_m

0.5_m

0.6_m

0.8_m

1.0_m

1.5_m

2.0_m

2.5_m

3.0_m

3.5_m

4.0_m

4.5_m

5.0_m

6.0_m

Figure2.:ZerocurtainofboreholeB34(finegrainedmaterial)duringspring2008

REFERENCES:Outcalt, S., F. E.Nelson, andK.M.Hinkel (1990). TheZero-CurtainEffect:Heat andMassTransferAcross an Isothermal

RegioninFreezingSoil.WaterResourcesResearch26(7),1509-1516.Kane,D.L.andJ.Stein(1983).WaterMovementIntoSeasonallyFrozenSoils.WaterResourcesResearch19(6),1547-1557.

180Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion 4.17

Using XPD for determining physical rock parameters of permafrost materials

TiloSchneider1,IldikoKatona-Serneels2

1 Institut für Geowissenschaften, Burgweg 11, 07749 Jena, Germany2 Department of Geoscience, Chemin du Musée 6, CH - 1700 Fribourg, Switzerland

Permafrostoccursindifferentsubstrates.Variabilityinrocktype,porosity,blocksizedistributionandweatheringattitudedeterminesmorphology,dynamicandicecontentofrockglaciersandtalusslopes.Toanalyzetheseconditionsgeophysicaltechniquessuchasgeoelectricsandseismicsareadequatemethodstodeterminepropertiesoftheshallowsurfaceinpermafrostregions.Eventhoughvaluesforthephysicalcharacteristicsoftheprevailingrockscanusuallybefoundinliterature,theymayvaryoverawiderange.Inordertocalculatemoredetailedmodelsofthesubsurface the physical rock parameters like electrical resistivity and acoustic impedance have to be known very well.Determiningthephysicalcharacteristicsofsinglemineralsmaythereforelimittheuncertaintiesofthewholegeophysicalrockanalysis.

Attypicalpermafrostmonitoringsites,suchastheMurtèl/ChasteletsareaintheEasternSwissAlps,severaldrillcoresandrocksampleswerecollectedandanalyzedusingX-RayPowderDiffractometry.Bythis,itispossibletodeterminethemineralcompositionoftherocksintheinvestigationarea.Inaddition,aReed-Fieldanalysiswasusedtocalculatethequantityoftherespectivemineralcontent.Thisenablestodeterminemeanphysicalrockpropertiesinthesubsurfacewhichthencanbeusedtoimprovegeophysicalmodeling.TheXPDanalysisisafastandexactmethodtodeterminethemineralcontentinrocksamplesqualitativelyandquantitatively.InthisstudyrocksamplesfromthreedifferentpermafrostareasintheSwissAlpshavebeenanalyzed.Allthreesites(Murtèl/Chastelets(GR),Schilthorn(BE),Stockhorn(VS))areincludedintheSwisspermafrostmonitoringnetworkPERMOS,whereboreholetemperatures,meteorologicaldataandgeophysicaldataarebeingcollectedextensively.Inourcontributionwewillpresentresultsfromthemineralanalysisandcomparethemtogeophysicalparametersobservedatthethreesites.

4.18

A systematic approach to quantify the performance of SNOWPACK

SteinkoglerWalter1,2,FierzCharles1,LehningMichael1,ObleitnerFriedrich2

1WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, CH-7260 Davos Dorf (Steinkogler@slf.ch)2Institute of Meteorology and Geophysics, Innsbruck University, Innrain 52, A-6020 Innsbruck

Newsnowsettlementintheveryfirsthoursanddaysafterasnowfallhasnotyetbeenfullyunderstood.Modellingerrorsatthisinitialstagepropagatethroughawholewinterseason,thusaffectingacorrectmodellingofcrucialsnowcoverproper-tiessuchasdensity,temperaturedistributionandsnowdepth.

Uptonow,parametertuningforsettlinginSNOWPACK(Lehning&Fierz,2008)hasmainlybeendonebyvisualcomparisonofmodelledwithmeasuredsettlingcurves.Thiscanbeaccomplishedbytrackingmodellayersthatcorrespondtopositionsofcombinedsettlementandtemperaturesensors(snowharps).Asaresult,verificationofmodelperformancewithinsitumeasurementsispossible.Herecomprehensivedatasetsobtainedduringanumberofsnowfallperiodsareused.Basedontheseobservationswepresentasystematicapproachtoassesstheperformanceofthemodel.Sensitivitystudiesallowtolocatethemostimportantmodelparameterswhichinfluencethesettlementofdepositedsnow.Ourapproachoffersthepossibilitytovisualiseandquantifytheperformanceofdifferentmodelruns.Inparticular,wewillpresentsuchananalysisbothduringandafewdaysaftersnowfalls.

REFERENCESLehning,M.,&FierzC.,2008:Assessmentofsnowtransportinavalancheterrain.ColdReg.Sci.Technol.,51(2-3),240–252.

181

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n4.19

Mass balance of Brewster Glacier, New Zealand, modelled over three decades

DorotheaStumm1,FitzsimonsSeanJ1,CullenNicolasJ1,HoelzleMartin2,MachguthHorst3,AndersonBrian4&MackintoshAndrew5

1Department of Geography University of Otago, PO Box 56, Dunedin, New Zealand (dorothea.stumm@geography.otago.ac.nz)2Department of Geosciences, University of Fribourg, Chemin de musée 4, 1700 Fribourg3Department of Geography, University of Zurich, Winterthurerstr. 190, 8057 Zurich4 Antarctic Research Centre, Victoria University of Wellington, PO Box 600 Wellington, New Zealand 5 School of Geography, Environment and Earth Science, Victoria University of Wellington, PO Box 600 Wellington, New Zealand

TheaimofthisstudywastomodelthemassbalanceandsnowlinesonBrewsterGlacierforthepastthreedecades,byusingadistributedmassbalancemodel(Oerlemans,2001;Machguthetal.,2006).

Themassbalancemodelisbasedontheenergybalance,andrunswithmeteorologicalinputdata.Inputdataareaninter-polatedclimatedatasetfromtheNationalInstituteofWaterandAtmosphericResearch(NIWA),andtheERA-40re-analysisdataset from the European Centre for Medium-RangeWeather Forecasts (ECMWF). Directmass balancemeasurements,whichwereinitiatedin2004,provideddatatocalibratethemodel.Thesemeasurementswerecollectedwiththeglaciologi-calmethodthatincludesstakeandsnowpitmeasurements.Formodelvalidation,weusedtheannualend-of-summersnow-line(EOSS)recordsfromtheGlacierSnowlineSurvey(Chinn,1995;Willsmanetal.,2008),whichdocumenttheevolutionoftheBrewsterGlacierexcellentlysince1978.Aftercalibratingthemassbalancemodel,themassbalanceandsnowlinesweresimulatedforthepastthreedecades.ThemodellingresultswerethencomparedtotheyearlyEOSSrecords.

ThemassbalancemodelperformedwellwiththeinterpolatedNIWAdatasetforthecalibrationperiod.Butfortheprevious30years,themodelcalculationsdidnotcorrespondwelltotheEOSSrecords.Therefore,themodelinputdatasetwasex-changedwiththeERA-40re-analysisdata.TheresultscomparedmuchbettertotheEOSSrecords,andfitbetterwithmassbalanceestimatesfromaparameterisationscheme(Haeberli&Hoelzle1995)andaGPSmassbalancesurvey(Willisetal.,2008).Furthermore,massbalancetrendsweremodelledwell.However,spatialresolutionoftheERA-40datasetisverycoar-se,andwesuggesttestinginfuturestudieswhethertheperformanceofmassbalancemodellingcanbeimprovedbyapply-ingfinerresolutionRegionalClimateModeldatadrivenfromre-analysis.

REFERENCESChinn,T. J.1995:GlacierFluctuationsintheSouthernAlpsofNewZealanddeterminedfromSnowlineElevations.Arctic

andAlpineResearch,27(2),187-198.Haeberli,W.&Hoelzle,M.1995:Applicationofinventorydataforestimatingcharacteristicsofandregionalclimatechange

effectsonmountainglaciers-apilotstudywiththeEuropeanAlps.AnnalsofGlaciology,21,206-212.Machguth,H., Paul, F.,Hoelzle,M.&Haeberli,W. 2006:Distributed glaciermass balancemodelling as an important

componentofmodernmulti-levelglaciermonitoring.AnnalsofGlaciology,335-343.Oerlemans,J.2001:GlaciersandClimateChange.A.A.BalkemaPublishers,Lisse/Abingdon/Exton(PA)/Tokyo.Willis, I., Lawson,W.,Owens, I., Jacobel,B.&Autridge, J. 2008: Subglacialdrainage systemstructureandmorphologyof

BrewsterGlacier,NewZealand.HydrologicalProcesses,DOI:10.1002/hyp.7146.Willsman,A.,Salinger,M.J.&Chinn,T.J.2008:GlacierSnowlineSurvey2008.Technicalreport,NationalInstituteofWater

andAtmosphericResearchLtd.

182Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion 4.20

Natural and anthropogenic primary aerosols record from an Alpine ice core (Colle Gnifetti, Swiss Alps).

FlorianThevenon1,FlavioS.Anselmetti2,StefanoM.Bernasconi3&MargitSchwikowski4

1Institut F.-A. Forel, Université de Genève, CH-1290 Versoix (Florian.Thevenon@unige.ch)2 Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf3 Geological Institute, ETH Zurich, CH-8092 Zurich4 Paul Scherrer Institut, CH-5232 Villigen

TheColleGnifettiglacier,locatedintheMonteRosamassif (Swiss-Italianborder,4455ma.s.l.),satisfactoryconservestheaccumulationhistoryofsummerprecipitationchemistryandclimaticconditionsoverrelativelylongtime-period(i.e.afewhundredyears).Infact,theColleGnifettiglacierischaracterizedbyahighice-thickness(about60to130m)andalownetsnowaccumulationofabout30cmwaterequivalentperyear (weq.), resultingfromthepreferentialwinderosionofdrywintersnow.

Consideringthat1)theanthropogenicaerosolsaremostlydepositedinsummer,whenpollutedairistransporteduptohighaltitudesbyconvection,andthat2)duetoitsorographicalpositionintheSouthernAlpinechain,theColleGnifettiglacierisstronglyinfluencedbyairmassesadvectedfromsoutherlydirections,theColleGnifettisummerarchivesthereforeofferauniquepossibility for reconstructing i) regional (pre-)industrial carbonaceousaerosolemissions,and ii) changes in thedynamicofthesouthwesterlydust-ladenwindsfromtheSahara.

TheColleGnifettiicecoreanalysisdemonstratesthattheelementalblackcarbon(BC)aerosolrecordisindependentofthelarge-scaleclimaticcontrolaffectingthetransportofmineraldusttotheSouthernAlps,butprimarilyreflectsregional-scaleanthropogenicactivity(Thevenonetal.,2009).Moreprecisely,theδ13CcompositionofBCsuggeststhatwoodcombustionwasthemainsourceofpreindustrialatmosphericBCemissions.Moreover,biomassburningactivityandespeciallyC

4grassland

burningabruptlydroppedbetween1560and1750 (Figure1), suggestingthatagriculturalpracticesstronglydecreased inEuropeduringthiscoldperiodofthe‘LittleIceAge’.UnliketheBCdeposition,themineraldusttransporttothesummitsoftheSouthernAlpsisprimarilycontrolledbylarge-scaleclimaticpatterns(i.e.drierwinterinNorthAfricaandstrongerNorthAtlanticsouthwesterlies),leadingtotransportofmassivedustplumesfromtheSaharaaround1560-1685,1775-1785,andafter1860.Incontrast,theperiodsoflowSaharandustdepositionaround1515-1560,1690-1770and1790-1850mayindi-cateweakermeridionalatmosphericcirculationatthattimes,leadingtocolderanddrierspring/summerconditionsoverWesternandCentralEurope.

REFERENCEThevenon, F., F. S.Anselmetti, S.M. Bernasconi, andM. Schwikowski (2009).Mineral dust and elemental black carbon

records from anAlpine ice core (ColleGnifetti glacier) over the lastmillennium. J. Geophys. Res., 114,D17102,doi:10.1029/2008JD011490.

183

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n

Figure1.Thelastmillenniumrecordofblackcarbon(BC)concentrationandtheassociated δ13CBCcomposition,asafunctionofage(year

A.D.;leftaxis)anddepth(meterwaterequivalent,mweq;rightaxis).Thedigitalimagesofthefilters,thetotalandmineralaerosolre-

cords,andthemeandiameterofthemineralfraction.Thethreelastmajorsolaranomalousperiods,theSpörer,the(Late)Maunder,and

theDaltonMinima,arereportedforcomparison(Thevenonetal.,2009).(NextPage)

4.21

Impacts of climate change on 22 south-eastern Swiss glaciers from 1900 until 2100

UsselmannStephanie1,HussMatthias1,2&BauderAndreas1

1 Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, CH-8092 Zürich (usselmas@vaw.baug.ethz.ch)2 Department of Geosciences, University of Fribourg, CH-1700 Fribourg

Sincethe1850s,theendoftheLittleIceAge,Alpineglaciershavesufferedmajorlossesoficevolume.Theimpactofclimatechangeonglaciersisreflectedmostclearlyintheirsurfacemassbalance.Therefore,areconstructionofmassbalancetimeseriesofdifferentglaciersduringthelastcenturyisimportantforabetterunderstandingoftheresponseofAlpineglacierstocurrentglobalwarming.

Inthisstudy,thetemporalandspatialchangesof22glaciersinthesouth-easternSwissAlpsareanalyzedbetween1900and2008usingdifferenttypesoffielddataanddistributedmodelling.Theinvestigatedglacierscoverawiderangeofglacierareaandicevolume,aswellasexposureandslope.Thisallowsinvestigationofdifferencesintheresponseofindividualglacierstoclimatechangeinarelativelysmallregion.

Seasonalmassbalancetimeseriesofglaciershavebeencalculatedfortheperiod1900–2008usingadistributedaccumula-tionandtemperature-indexmeltmodel(Hussetal.,2008).Themodeliscalibratedusingobservedicevolumechangesinmultidecadalperiods.Inordertocalculatethevolumechange,twosuccessivedigitalelevationmodels(DEMs)arecompared

184Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion toeachother.ThebasisfortheseDEMsare(i)terrestrialtopographicsurveys,(ii)photogrammetricanalysisofaerialphoto-

graphs,and (iii)alreadyexistingdatasets,asDHM25(swisstopo)andSRTM(NASA). In-situpointmeasurementsofannualmassbalanceandwinteraccumulation,available for someglaciers, aswell as long-termdischarge records for the threemajorcatchmentsinthestudyregionareusedformodelvalidation.

Since1900thechangesinglacierareaandvolumeareconsistentlynegative.Betweenthe1930sandtheendofthelastcen-turytheareaofthe22investigatedglaciersdecreasedbyabout24%.Overthelastcentury(1900–1999)theregionalicevo-lumehasdecreasedby30%,withstrongdifferencesbetweenindividualglaciers(20–60%).Therateof100-yearmasslossstronglydiffersbetweenadjacentglaciers.Whereaslargevalleyglaciers(e.g.VadrecdelForno)showcumulativemassbalan-cesofupto-70mw.e.,smallerandsteeperglaciers(e.g.VadretdaPalü)exhibitlessnegativemassbalancesofaround-15mw.e.(Fig.1).Usingregionalclimatescenarios(Frei,2007),futureglacierretreatissimulatedtransientlyforallglaciersoverthe21stcen-tury.Weprojectglacierareachangesbetween-80%and-100%andvolumechangesbetween-70%and-100%withstrongim-pactsonthewatercycle(Fig.2).

Figure1.Cumulativeseriesofmeanspecificmassbalanceofthe22investigatedglaciersfrom1900to2008.Timeseriesfortheindividual

glaciersaredisplayedingrey;trianglesindicatethedatesofDEMs.Thesolidvioletlinerepresentsthearithmeticaveragefortheinvesti-

gatedglaciers.Glaciernamesaregivenattheright-handsideandcoloursindicateglaciersize(Usselmann,2009).

Figure2.SimulatedfutureevolutionofVadretdaMorteratschuntil2100.Glacierextentisshownfortheyears2020,2060and2100forthe

mostlikelyclimatescenario.Glacierextentintheyear2008isshown(Usselmann,2009).

REFERENCESFrei,C.,2008.DieKlimazukunftderSchweiz.In:KlimaänderungunddieSchweiz2050–ErwarteteAuswirkungenaufUmwelt,

GesellschaftundWirtschaft.BeratendesOrganfürFragenderKlimaänderung(OcCC):12–16,http://www.occc.ch.Huss,M.,Bauder,A.,Funk,M.&Hock,R.,2008.DeterminationoftheseasonalmassbalanceoffourAlpineglacierssince

1865.JournalofGeophysicalResearch,113,F01015.Usselmann, S., 2009. SchweizerGletscher imWandel vonKlimaundZeit.Diplomarbeit, Friedrich-Alexander-Universität

Erlangen-Nürnberg,pp.179.

185

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n4.22

Understanding rapid dynamic changes of marine Greenland outlet gla-ciers from numerical modeling

AndreasVieli12,FaezehM.Nick3

1 VAW, Glaziologie, ETH Zuerich, Gloriastr 37/39, CH-8092 Zuerich 2 Department of Geography, Durham University, South Road, Durham DH1 3LE, UK (andreas.vieli@Durham.ac.uk.ch)3GEUS, Ostervolgade 10, DK-1350, Copenhagen, DK

RecentrapiddynamicchangesofGreenland'soutletglaciersraisedconcernsoverthecontributiontofuturesealevelrise.ThesedynamicchangesseemtobelinkedtothewarmingtrendinGreenland,butthemechanismsthatlinkclimateandicedynamicsarepoorlyunderstood,andcurrentnumericalmodelsoficesheetsarenotabletosimulatethesechangesrealis-tically.ThesedynamicchangesthereforeprovidemajoruncertaintiesinthepredictionsofmasslossfromtheGreenlandicesheet. Wedevelopedanumerical ice-flowmodelthatreproducestheobservedrapidchanges inHelheimGlacier,oneofGreenland'slargestoutletglaciers.Oursimulationsshowthattheiceacceleration,thinningandretreatbeginattheoceanterminatingcalvingfrontandthenpropagaterapidlyupstreamthroughdynamiccouplingalongtheglacier.Wefindthatthesechangesareunlikelytobecausedbybasallubricationthroughenhancedsurfacemeltfromtherecentatmosphericwarmingandthatmasslossisamplifiedbyadeepbasaloverdeepeningatthebed.Importantly,themodellingfurthershowsthatsuchtidewateroutletglaciersareextremelysensitivetochangingboundaryconditionsatthecalvingterminusanddynamicallyadjustextremelyrapidly.ThisimpliesthattherecentrapidmasslossofGreenland'soutletglaciersmayreflectshort-termvariationsinclimateoroceanconditionsandshouldnotbeextrapolatedintothefuture.

4.23

Hazard assessment investigations in connection with the formation of a lake on the tongue of the Unterer Grindelwaldgletscher, Bernese Alps, Switzerland

MauroA.Werder1,AndreasBauder1,Hans-RudolfKeusen2,MartinFunk1

1VAW, ETH Zurich, CH-8092 Zurich, Switzerland (werder@vaw.baug.ethz.ch)2GEOTEST AG, Birkenstrasse 15, CH-3052 Zollikofen, Switzerland

ThesurfaceleveloftheUntererGrindelwaldgletscherglaciertonguehassubsidedbymorethan200\,moverthelast150years.Thesurfaceloweringisnotuniformovertheglaciertonguebutdependsonthethicknessoftheunevendebriscover,whichledtotheformationofadepressiononthetongue.Alakehasformedinthisbasin,forthefirsttimein2005,whichcandrainrapidlyleadingtoaso-calledglacierlakeoutburstflood.Thelakebasinhasbeenincreasinginsizeatanalarmingrateand,in2008itreachedavolumewhichposesasignificantfloodingthreattothecommunitiesdownstream,aswasexemplifiedbyanoutburstofthelakeinMay2008.Weextrapolatedthefutureevolutionofthelakebasinbasedonsurfaceloweringratesin2004--2008.Wetunedamodelwiththemeasuredhydrographfrom2008andranitwiththeextrapolatedlakevolumestosimulatesuchalakeoutburstandestimatedpossiblefuturefloodhydrographs.Wediscusstherapidlyin-creasingriskforGrindelwaldandothercommunities,thereasonswhyin2009norapidlakedrainageoccurred,aswellastheinstallationofanearlywarningsystemandtheconstructionofa2.1kmlongdrainagetunnel.

186Sy

mp

osi

um

4:

Op

en

Cry

osp

he

re s

ess

ion 4.24

Analysis of temporal and spatial snow depth changes in a steep rock face

VanessaWirz,MichaelSchirmer,MichaelLehning

WSL-Institut für Schnee- und Lawinenforschung SLF, Flüelastrasse 11, CH-7260 Davos Dorf (wirz@slf.ch)

Thepresenceofsnowinsteepalpineterrainaffectsmanyphenomena,e.g.watermanagement,snowavalanchesorperma-frostdistribution.Hencegoodknowledgeonspatialandtemporaldistributionof snowinsteepalpine terrain isofhighimportance.Inaccessibilityandalpinedangersinverysteepterrainarethemainreasonsforlackofstudiesonsnowdepthinthoseareas.Themaingoalofthisstudyistogetmoredetailedinformationabouttheamountanddistributionofsnowinverysteepterrainandtobetterunderstandtherelevantprocessesandfactors,whichaffectsnowaccumulation,redistri-bution,erosionandablationinsteeprockfaces.Forthispurpose,ahighresolutionterrestrialLaserScanner(TLS)wasusedproducingprecisesnowheightdigitalsurfacemodels.Wecollectedsurfacedatawithoutsnow,beforeandaftersignificantsnowfallorwinddrifteventsandduringtheablationperiod.Wethengenerateddigitalsurfacemodels(DSM)foreachob-servationperiod.Thesummerscanunderthetotalabsenceofsnowallowedustoprovideadigitalelevationmodel(DEM)andtocalculateabsolutesnowdepth.Relativesnowdepthchangescanbeextractedbythecomparisonofdifferentwinterscans.Inadditiontothelaserscans,orthophotosweretakenwithadigitalcamera.

InafirststepwecouldshowthatwithTLSreliableinformationonsurfacedataofasteeprockysurfacecanbeachieved.Incomparisontoaflatfieldpointmeasurementthemeansnowdepthintherockfacewassmallerduringtheentirewinter,buttrendsofsnowdepthchangesweresimilar.Weobservedrepeatingaccumulationandablationpatternsintherockface,whilemaximumsnowdepthlossoccurredalwaysatthoseplaceswithmaximumsnowdepthgain.Furthermore,increasingsnowdepthresultedinadecreaseofhighslopeangles.Furtheranalysesshouldinvolvethestatisticalrelationofspatialandtemporaldistributionofsnowdepthto(i)terrainfeaturese.g.slopeangle,aspectorcurvatureand(ii)resultingsurfacepro-cessesderivedfromspatialdistributedmodeloutputse.g.radiation,windfieldsorblowinganddriftingsnow.

187

Sym

po

siu

m 4

: O

pe

n C

ryo

sph

ere

se

ssio

n

4. Open Cryosphere session4.1 Dalban4.2 Delaloye4.3 Failletaz4.4 Farinotti4.5 Zwaaftink4.6 Hauck4.7 Huss, Bauder4.8 Huss4.9 Le Bris4.10 Mitterer4.11 Reiweger4.12 Riesen4.13 Rings4.14 Ryser4.15 Schaefli4.16 Schneider, S.4.17 Schneider, T.4.18 Steinkogler4.19 Stumm4.20 Thevenon4.21 Usselmann4.22 Vieli4.23 Werder4.24 Wirz