Seite 70 Stichwörter: Lawinen, Klimawandel, Norwegen zum Untersuchungen von und Expertinnen Thema Klimawandel Experten undLawinen. lawinengefährdete Gebietezukünftig zumeiden, wissenschaftliche brauchtessorgfältige habendieseEffektewenigerEinflussauf Lawinen.und indennördlichenBergregionen Um kürzerer Winter mitwenigerSchnee, wahrscheinlich abnehmen. Imküstennahen Hochgebirge in Küstenregionen aufgrund eines Anstiegs der Schneefallgrenze und der Waldgrenze und einen Anstieg der Häufigkeit bedeuten. von Naturgefahren Lawinengefährdungen werden indennächsten50–100Jahren,Stärke durchdieKlimaerwärmung bedingt kannauch gegenüber Naturgefahren. DieZunahmevon extremen Wetterereignissen inFrequenz und zueinerhöheren imländlichenRaumführen Die Siedlungsentwicklungen Vulnerabilität mehrals1500Lawinentote wurdeninNorwegen verzeichnet. 150Jahren In denletzten Zusammenfassung: Keywords: of avalanche expertstoavoid theuseofavalanche-endangered areas. northern Norway, these effects have less importance. This will demand careful investigations the snow seasonwithlesssnow. Inthecoastalhighmountainrange andinthemountainsof near coastalregionsduetoincreasedelevation ofthesnow andtreelineashorteningof increase inthefrequency ofgeohazardevents. The snow avalanche hazardmay decreasein quency andstrengthofextremeweatherevents inthenext50to100years may leadtoan in rural areasmakeusmorevulnerable togeohazards.Climaticwarming withincreasedfre- Avalanches have causedmorethan1500deathsthepast 150years inNorway. Development Abstract: Lawinen undKlimawandelinNorwegen of climatechangeinthenorthernregions Avalanches inthecontext ULRIK DOMAAS,KJERSTIGISNÅS Avalanche, climaticchange, Norway Schwerpunktthema: Visionen imLawinenschutz that wemustfaceintheyears tocome. of theconsequencesrelatedtoavalanche activity matic scenarios;itwillrather trytoindicatesome picture shows. This articlewillnotdisputethecli- may resultinmorevariation thanwhat thegeneral changes inthecomplex topography inNorway lesser degree.However, theprojectedclimate range, theavalanche activity may declinetoa and lower regions.Inthecoastalhighmountain lanche situations, in particular along the coast climatic changes toreduce thenumberofava- see ageneral riseofthetreeline. We expectthe warmer wintertemperatures. As aresult,wealso amounts andintensity, shorterwinterseasonsand We observe ageneral increaseinprecipitation the century. The weatherisgettingmoreunstable. present andarelikelytoincreaseby theendof all show thatchanges intheclimatearealready dicke etal.,2008)andInfraRisk (NGI2009). These 2015) andtheresearch projectsGeoextreme (Jae- Meteoro as the"Klima2100"reportfromNorwegian are describedby several research projects,such current andfutureclimatechanges inNorway living inthemountainousdistrictsofNorway. The lanche activity isofgreatimportancetopeople Climatic changes andrelatedeffectsonava- Introduction logical Institute (Hanssen-Bauer et al. Arctic. significantly high temperature anomaliesin the warmest year ontheNASA GISTEMPrecord,with NASA 2017).Bythis,2016turnedouttobethe an anomalyof22 was highesttowards thenorthernregions,with 1 mean temperature in2016was approximately erally warmer winters. The average globalannual (Figure 1)show a positive trend indicating gen- 1971–2000 in Norway from 1900 until 2014 Temperature deviations from thereference period Changes intemperature the northofNorway. the windtobemostimportantsinglefactorin important singlefactorinthesouthofNorway and findings indicatedtheprecipitationtobemost the picturevaried throughNorway. The major trols ofavalanche activity. For snow avalanches, Norway. The projectaimedtofindthekeycon- showed varying importanceindifferentpartsof bination ofdifferentclimaticparameters, which discussed avalanche activity relatedtoacom- The Avalanches inNorway °C above the1951–80average. The increase Geoextreme project(Jaedicke etal.,2008) °C innorthernNorway (NOAA/ 1971 –2000. Mittelwert derReferenzperiode Abweichungen (in°C) zum Diagramm zeigtdiejährlichen Das (1900 –2014). Norwegen Jährliche Temperaturen für Abb. 1: 2/2015). (Klima 2100,NCCS–reportno reference period1971–2000 from theaverageover deviations intemperature(°C) (1900 Annual temperatureforNorway Fig. 1: – 2014). Thefigureshows
Seite 71 Seite 72 increase inCO the atmosphere. RCP 8.5 is closest to the observed radiative forcing duetogreenhousegasrelease in theyear 2100depending ontheincreasein (RCPs) describe different possibleclimatefutures The four Representative Concentration Pathways areas along thecoastof Norway. still causeclassic avalanche situations forregional ations withheavy snow precipitation. This may cold winterperiodsmay stilloccurpriortositu- implies thateven iftheclimategetswarmer, long periods withcoldormild weather. This also latitudes (Francis and Vavrus, 2012). winds in the upper atmosphere at northern pressure over the Arctic leadstostrongerwesterly progression. A pattern withlower atmospheric the Rossby wave patternwithaslower eastward weakening ofthepolarvortex andanincreasein ture increaseby theendofcentury(Figure 2). Abb. 2:ZunahmederTemperaturen imWinterfürdas SzenarioRCP8.5. Fig. 2:IncreaseinwintertemperaturefortheRCP8.5scenario. For Norway, thismay resultinlonger Increases intemperature leadtoa 2 , andindicatesa4 – 6 °Ctempera- lanche situations. event mildweather, leaddirectlytotheava- Heavy snowfall, strongwindsand, fortheOdda with depthhoardeveloped neartheground. tains duringthecoldearlywinter aweaklayer occurred. Duetoathinsnow cover inthemoun- early winterfromOctoberuntil theavalanche mon forallthesethreesituationswas acold and thethirdin1993Odda(Jan 17 (Feb 19 in thisperiod(Figure 3). The firstin1968Sæbø years betweenevery "cold"winter. for thewhole periodtherewas onaverage 3–5 0 °Cfor4 ters having average monthlytemperatures below the last15years therewere onlytwo "cold" win- Norway clearly show a warming climate. During period 1951 The monthly temperatures during winterinthe Schwerpunktthema: Visionen imLawinenschutz th ), thesecondin1979Ørsta(Feb 11 Three majoravalanche events occurred – 5 consecutive months.Incomparison, – 2015 forthewesternpartofsouth th ). Com- th ) precipitation» isdefinedasdailyprecipitation tation events inallofNorway (Figure 4).«Heavy in bothintensityandfrequency ofheavy precipi- from 3 %to26 % over Norway. to increaseby onaverage 17 The winter precipitationforNorway isexpected of thecenturywilloccurinautumnandwinter. The largest changes inprecipitationby theend Changes inprecipitation and c)Odda(1993,FotoEirikBrekke). Abb. 3:FotographiengroßerLawinenereignisseinNorwegen.a)Sæbø(1968,FotoAftenposten),b)Ørsta(1979,KarsteinLied) Lied) andc)Odda(1993,photoEirikBrekke). Fig. 3:PhotosfromthreemajoravalanchesituationsinNorway. a)Sæbø(1968,photoAftenposten),b)Ørsta(1979,Karstein den Zeiträumen1971 –2000und20712100fürdieSzenarien RCP4.5undRCP8.5.DieschwarzenBalken stellendenMediandar. Abb. 4:RelativeÄnderungen (in%)derTagesanzahl mit Starkniederschlägen(links)undderNiederschlagsintensität (rechts)zwischen 2071–2100 periodforthescenariosRCP4.5 andRCP8.5.Medianvalue(blackline).Seasonalannualvalues. Fig. 4:Relativechange(%)inthenumber ofdayswithheavyprecipitation(left)andintensity(right)fromthe1971–2000period tothe The climate projections show increases % (RCP8.5),varying values duringthesummerseason. for theentireyear inallregions, butwithhighest narios (Figure 4,right). The increaseispredicted country isbetween12 in precipitationintensityaveraged forthewhole increase innorthernNorway. The relative change the century(RCP8.5;Figure 4,left),withlargest winter ispredictedtobe143 frequency of heavy precipitationevents during the period1971 exceeded approximately every second year in – 2000. The overall increasein % and19 % by theendof % forthe2sce-
Seite 73 Seite 74 upper elevation limitforpotentialforestgrowth annual temperatures (+4 been triggered(AndersonandMcClung,2012). edge ontheeffectofforestafteravalanche has grown forest.However, thereislimitedknowl- they have clearedseveral hundredmetersoffully- may stopsmalltomediumsizeavalanches after of previousavalanche incidents(Figure 5).Forests forests. This isdemonstrated by several examples the avalanches may clear away even fully-grown the forestbelow willhave littleornoeffect,and reach terminal velocity, experienceshows that forest may have some effect. When avalanches ity when itpassesthrough theforest,and yet reached ahighvelocity oraterminalveloc- release area.Inthesecases,theavalanche hasnot mountainside alltheway uptotheavalanche ley below, primarily when the forest covers the ing thevelocity andrunoutlengthsintheval- (Gubler andRychetnik, 1991). of weak layers that may cause slab avalanches porting thesnow pack andreducingtheformation al., 2001). This iscauseddirectlyby thetreessup- lanche release (Olschewski et al., 2012; Bebi et Dense forest has a protective effect against ava- Forest growthandtheeffectonavalancheactivity Abb. 5:BilderderDrevja Lavine1995mitZerstörungenderWaldflächen bishinabauf den flachen Talboden. Fig. 5:Picturesshow the1995Drevjaavalanchethattookout theforestalsoalongflatvalleybottom. Increases in growth season and higher Forest canaffectavalanches by reduc- – 6 °C)willraise the alter thesituationrapidly. In addition,forestdiseases,cuttingandfiresmay are sufficient: est growth, even thoughtheclimaticconditions some partsofthemountainswedonotexpectfor release areasforsnow avalanches. However, in coastal areaswillreducethenumberofpotential the Rondanemountainmassif. the exception ofisolated mountain areas, such as Norway willhave potentialforforestgrowth, with (Figure 7).Mostoftheeastern partsofsouthern range willstillbe above thetreelineinfuture ure 6). The higherpartsofthecoastalmountain to thecoastmay becomecovered by forest(Fig- m). As aresult,alsomany ofthelower areasclose (assuming alapserate ofapproximately1 by approximately400 Schwerpunktthema: Visionen imLawinenschutz • • • strong winds. increase inintensityandfrequency of est away, amplified by theprojected Wind exposedareaswill keepthefor than 30–50year returnperiod. unless thefrequency decreasestoless lanches occurwillkeepthe forestaway Avalanche tracks where frequentava- faces. In steepreleaseareaswithbarerock The increased forestgrowth inthe – 500 mcomparedtotoday °C/100 - - snow cover during thewinter months. entirely snow free,orhave only discontinuous line. Inthecoastal areas,wintersmay become shortened winterseasonsand ariseofthesnow peratures willresultinreducedsnow amounts, over Norway. Inmany areastheincreasingtem- affect thesnow cover, butwithlargevariations bined withchanges inprecipitationwillhighly The projectedriseinannualtemperatures com- fewer avalanchesituations? Shorter wintersandlesssnow– ist fürdensteilen,kahlenGebirgsteilaufderrechtenBildseitenichtmöglich. Abb. 7:Küstengebirgsregion.DerWald könntebiszudenLawinenanbruchgebieten inderlinkenSeitedesBildeshinaufreichen.Dies the rightwheremountainsaresteepwithbarerockfaces. Fig. 7:Thecoastalmountainrange.forestmayreachtheavalanchereleaseareas seenontheleftpartofphoto,butnotto Linie dieheutigeBaumgrenzeunddickeblaugestricheltemöglichein100Jahren. Abb. 6:ProfillinieSüdnorwegen(nördlichvonBergen) West nachOst.DieschwarzeLinestelltdasGelände dar, diegestrichelte today's treeline,andbluedottedlinerepresentsthepossiblein100years.Source:NorwegianMappingAuthority. Fig. 6:West toEastcrosssectioninsouthernNorway(northofBergen).Blacklinerepresentstopography, reddottedlinerepresents may remain snow free all year inthe future.Other RCP 8.5scenario, largeareasalongthewestcoast a reductionsof between 50to100days. With the less than100days ofsnow cover today may see Bauer etal.2015)shows thatcoastalareaswith sea currents. The report„Klima2100“(Hanssen- temperature increase,butis also related to warmer coast (Figure 8). This ismainlyduetothegeneral be reduceddramatically, particularlyalongthe June. The lengthofthesnow-covered periodwill 1971 ered by snow halfoftheyear over theperiod On average, large partsofNorway werecov- – 2000, typicallyfromNovember toMay/
Seite 75 Seite 76 to ahighdegreeinpopulatedareas. shorten thesnow seasoninlargepartsofNorway, the reducedamountsofsnow willsignificantly number ofsnow covered days astoday. Ingeneral, east andaway fromthecoastmay stillhave similar weeks ofsnow. The highmountainareasfurther areas onthewestcoastwillhave lessthanthree the numberofdays comparedtotoday, andlarge areas willhave asnow seasonlastingonlyhalf 1971 –2000sowiedieSchätzungfürJahre20712100. Abb. 8:ProfilliniedurchSüdnorwegenvon West nachOst.AnzahlderSchneetagemitSchneebedeckungfürdieReferenzperiode and estimatedforthe2071 Fig. 8:West toEastcrosssectioninsouthernNorway. Numberofsnowdayswithcoverinthereferenceperiod1971 – 2100 period. depths. vations show a23 the high mountains in southern Norway, obser 50-year period(Figure 9,Dyrrdaletal.,2012).For line alongthecoastandlowland duringthelast tern partsofsouthernNorway, alongwithadec- mum snow depthsinthehighmountainandeas- There hasbeenanincreaseintheannualmaxi- Schwerpunktthema: Visionen imLawinenschutz % increaseinmaximumsnow relativer Trend (rechts). 1958 –2010(links)und in NorwegenimZeitraum Maximale Schneehöhen Abb. 9: 2012). trends (right)(Dyrrdaletal, with (left) 1958 –2010 Norway overtheperiod Maximum snowdepthsin Fig. 9: – 2000 - and more intensesnow fall events. activity inthe future,duetolargersnow depths may experi high mountainareasabove the0°C-isothermwe and thusnotbeatriskforsnow avalanches. In some areaswillnotreceive snow inthefuture, high mountainsfurthereast. On thewestcoast and thecoastalmountainrange, andlessinthe The effectismostpronouncedalongthecoast reduction ofavalanche situationsduringwinter. similar snow amountsastoday. east andaway fromthecoastmay stillreceive mountain range. The highmountainareasfurther predicted for the west coast and in the western Norway, where themostsignificantreduction is Figure 10 shows across section in southern even outtheeffectoftemperature increase. areas theincreasedprecipitationamountswill amount along the coast of Norway, while in other increase may give alargereductioninsnow The climatic change withahightemperature normal period1971 Fig. 10:West toeastcross-sectioninsouthernNorway(blackline).Annualmaximumsnowamount(SWE,mm)duringwinterthe 1971 –2000(blau)undfürdasSzenariodieJahre20712100(orange). Abb. 10:ProfillinieSüdnorwegenvon West nachOst(schwarzeLinie).JährlichemaximaleSchneehöhenimWinterfürdenZeitraum The reducedsnow amountsindicatea ence ahigherpossibility foravalanche – 2000 andscenarioforthe2071 – 2100 period. snow amounts may experience increased rather tain areas where there is a projected increase in lanche situations. Additionally, thehighmoun- cipitation intensitymay stillcreatemajorava- strong wind intensity along with increase in pre- snow heightsandawarmer snowpack. mid winter(December–February) duetolower lanches may occurmoreseldomandprimarilyin out ofriskduetoabsencesnow. Drysnow ava - lanches inmany areas,withsomeareasbeing often duringthewinter. intensity. Mildweatherwithrain willoccurmore winds may occurmoreoftenandincreasein peratures towards theendofcentury. Strong shorter winterswithlesssnow andhighertem- ios RCP4.5and8.5forNorway, weexpect Based ontheclimateprojectionsforscenar Consequences However, theprojectedincrease in This may reducethepotentialforava- - Seite 77 Seite 78 conducted avalanche hazard warning foran An exampleofthiswas seen in2015,when NGI weather types: shut down more frequent due to two different gered terrain (withhazardwarning) willhave to Work onmountainfacilitiesinavalanche-endan- exposed duetoincreaseinthesenatural hazards. sides andhydroelectric power linesmay bemore and slushflow activity. Roadsclosetomountain- experience anincreaseinwetsnow avalanches than reducedavalanche danger. We may also Abb. 11:Nassschneelawine inSprongdalen,Styggevassdammen am16.Juni2015. Fig. 11:Wet avalancheinSprongdalen, Styggevassdammen16thJune 2015. • • avalanche situations winter withstrongwindscausingdry More frequentsituationsduringmid- winter monthscausingwetavalanches More often mild weather situations in [email protected] N-0855 Oslo,Norway Sognsveien 72 Norwegian Geotechnical Institute (NGI) Ulrik Domaas Anschrift derVerfasser /Authors’addresses: work. area, and caused challenges for the entrepreneur activity was much higherthanexpectedforthis summer (Figure 11). The amountofwet avalanche ing thewinterandcontinueddoingsountilearly numerous wetsnow avalanche situationsdur facility. A north-facingmountainsideproduced entrepreneur working on the Styggevassdammen Schwerpunktthema: Visionen imLawinenschutz - Forest policy andEconomics,17,19-24. Avalanche protection by forests—A choice experiment in the Swiss Alps. (2012) OLSCHEWSKI, R.,P. BEBI,M. TEICH, U. W. HAYEK & A. GRÊT-REGAMEY Annual Global Analysis for2016. NOAA/NASA January 2017. Norwegian Geotechnical Institute. 94. A. AAHEIM, LUDVIGSEN, N.K.MEYER,R.RAUKEN, K.SVERDRUP-THYGESON & Klæboe, J. J. E. Haugen, H. O. Hygen, H. Haakenstad, C. Jaedicke, Á. Jónsson, R. Isaksen, B. Romstad, A. V. Dyrrdal, R. Gangstø, A. Harbitz, C. B. Harbitz, - Final reportNFR-project200689.,eds.R.Frauenfelder, A. Solheim,K. Impacts ofextremeweatherevents oninfrastructure inNorway (InfraRisk) NGI. 2009. climate, theGeoExtremeProject.Nat.HazardsEarthSyst.Sci.,8,893-904. Spatial andtemporal variations ofNorwegiangeohazardsinachanging & H.MESTL(2008) SLETTEN, K.KRISTENSEN,I.BARSTAD, C.MELCHIORRE, Ø. A. HØYDAL A. AAHEIM, K.KRONHOLM,D. VIKHAMAR-SCHULER, K.ISAKSEN, JAEDICKE, C., A. SOLHEIM,L.H.BLIKRA,K.STALSBERG, A. SORTEBERG, 2015. Klima iNorge2100.Kunnskapsgrunnlag forklimatilpasningoppdaterti & B. ÅDLANDSVIK. 2015. MAYER, A. NESJE,J.NILSEN,S.SANDVEN, A. SANDØ, A. SORTEBERG HANSSEN-BAUER, I.,E.J.FØRLAND, I.HADDELAND, H.HISDAL, S. 19-37. at Vienna, Effects offorests near thetimberline on avalanche formation.In Symposium GUBLER, H.&J.RYCHETNIK. 1991. Geophysical Research Letters,39. Evidence linking Arctic amplificationtoextremeweatherinmidlatitudes. FRANCIS, J. A. &S.J. VAVRUS (2012) Norway. ClimateResearch, 55,153-165. Changes inmeteorologicalvariables thatcantriggernatural hazardsin DYRRDAL, A. V., K.ISAKSEN,H.O. HYGEN&N.K.MEYER(2012) 145, 3-14. ests’ dynamics and protective function. Forest Ecology and Management, Assessing structuresinmountainforestsasabasisforinvestigating thefor BEBI, P., F. KIENAST & W. SCHÖNENBERGER(2001) rain. CanadianGeotechnical Journal, 49,477-484. Snow avalanche penetration intomatureforestfromtimber-harvested ter ANDERSON, G.&D. MCCLUNG(2012) References /Literatur: [email protected] N-0855 Oslo,Norway Sognsveien 72 Norwegian Geotechnical Institute(NGI) Kjersti Gisnås - -
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