Ninth International Conference on Permafrost ... - IARC Research

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The Omnsbreen Glacier:Possible Aggrading Permafrost, Southern Central NorwayIntroductionKarianne Staalesen LilleørenDepartment of Geosciences, University of Oslo, NorwayOle HumlumDepartment of Geosciences, University of Oslo, NorwayThe Omnsbreen Glacier is a small (< 0.5 km 2 ) mountainglacier situated in southern central Norway about 1500m a.s.l. Presently, the glacier exists approximately 100 mbelow the regional equilibrium line altitude (ELA), due tolocal accumulation of wind-redistributed snow.During the “Little Ice Age” (LIA), the glacier was of aconsiderable size and extent (approximately 6 km 2 ) andoccupied the whole valley, where today it occupies onlyparts of the western slope. The maximum size was reachedaround 1750, as for most of the glaciers in southern Norway(Andreassen et al. 2005). At that time, the effect of snowaccumulating by wind on the glacier was significantlyreduced because of the glacier’s different geometry, fillingup the valley.From the LIA maximum and until around 1930, the glacierremained relatively stable in shape and size. Between 1930and 1985, however, the bulk of the glacier disappeared.Since then, the glacier has lost mass at a much lower ratecompared to the years before, until recent years when theglacier apparently has stagnated with a fairly constant size.An ongoing study aims at explaining the rapiddisappearance of Omnsbreen since 1930 by using local andregional climate data (temperature, precipitation, and wind)and also tries to explain the apparent recent stagnation ofthe glacier. Couplings between the glacier, the climate, andmountain permafrost is investigated (Lilleøren 2007).Climatology and Area DescriptionLocationThe Omnsbreen Glacier is located close to Finse (1220 ma.s.l.) at the northwestern margin of the flat Hardangerviddaarea (Fig. 1). Finse is situated in a transition zone betweenthe marine western coast and the more continental easternparts of Norway, and has a high mountain climate. The meanannual air temperature (MAAT) was -2.1°C (1970–2000),and the mean annual precipitation in the same period was1030 mm, according to measurements by the NorwegianInstitute of Meteorology at Finse (DNMI 2007).TemperatureIn the before-mentioned ongoing study of the Omnsbreenarea, Tinytag-Loggers measuring air temperature, bottomtemperature of winter snow cover (BTS), and groundtemperature were placed in the area close to the glacier, andthe mean difference in air temperature measured betweenFinse and Omnsbreen was found to be 2.1°C, with the lowestNOmnsbreenFinseFigure 1. Location of Finse and Omnsbreen, southern centralNorway.temperatures at Omnsbreen for the period 06/08/22 through07/08/19. The picture is complicated by large temperatureinversions in the area, especially during the winter. Finse issituated in a valley bottom that efficiently traps heavy coldair cooled in higher elevations.WindMapping of snow cover surface forms demonstrated thatthe mean winter wind direction is from the west or slightlysouthwest. Omnsbreen’s valley has a north –south extension,and snow transported by westerly winds can efficientlyaccumulate in the valley’s east-facing slopes. When studyingthe wind directions measured by the meteorological stationat Finse, it seems like there has been a shift in the winddirections since the 1970s, from a wide directional spreadduring the winter to a more consistent wind direction fromwest in the 1980s. This shift also coincides with the reductionin the mass loss from the Omnsbreen glacier.Permafrost?Of the loggers measuring the BTS today (four places) inthe area earlier covered by ice, one had a stable temperatureclose to -4°C, which can be interpreted as an indicationof permafrost in the area (Fig. 2). The MAAT in the areapresumably is too high to allow widespread permafrost,but some sporadic permafrost may exist at this altitude atwind-exposed sites. Situated in a transition area betweenmaritime and continental climate types, the area experienceslarge differences in snow cover from one year to the next,185
Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tATemperature (C)20.0015.0010.005.000.00-5.00-10.00-15.00-20.00-25.0022.8.2006Time13.8.2007object to erosion by the wind. As the glacier became smaller,it also became possible for wind-redistributed snow toaccumulate in the western parts of the valley. Today’s glacieris probably depending on this amount of wind transportedsnow to exist.One cannot ignore the possibility that similar wind andtopography-induced changes between two stable situationshave occurred several times in the history of the OmnsbreenGlacier.BTemperature (C)CTemperature (C)40.0030.0020.0010.000.00-10.0030.0025.0020.0015.0010.005.000.00-5.0022.8.200622.8.2006TimeTimeFigure 2. A: Air temperature at Omnsbreen for the period 06/08/22–07/08/13. B: Ground surface temperature (GST) in the Omnsbreenarea (1559 m a.s.l.). Snow from mid-October, temperature at ca.-4°C from mid-February to May. C: GST in the Omnsbreen area(1431 m a.s.l.).including wind-redistributed snow. This situation alsochanges the permafrost conditions from year to year. In thisarea, differences in snow cover might be more importantfor the permafrost distribution than temperature changes,compared to areas further northeast where permafrost isknown to exist (Etzelmüller et al. 2003).The zone covered by ice during the LIA is todaycharacterized by landforms created beneath a warm-basedglacier such as flutings, eskers, striae, and crag-and-tails,which indicates non-permafrost conditions at that time.Based on the findings of sporadic permafrost in this areatoday, the paraglacial zone might be subject to aggradingpermafrost (Etzelmüller & Hagen 2005).13.8.200713.8.2007PermafrostIn the following years, time series will be established onBTS, air temperature, and snow cover distribution, consideringespecially the conditions for permafrost to exist.ReferencesAndreassen, L.M., Elvehøy, H., Kjøllmoen B., Engeset, R.V. & Haakensen, N. 2005. Glacier mass-balance andlength variations in Norway. Annals of Glaciology42: 317-325.DNMI. 2007. eKlima. Oslo: The Norwegian MeteorologicalInstitute.Etzelmüller, B., Berthling, I. & Sollid, J.L. 2003. Aspectsand concepts on the geomorphological significanceof Holocene permafrost in southern Norway.Geomorphology 52: 87-104.Etzelmüller, B. & Hagen, J.-O. 2005. Glacier-permafrostinteraction in Arctic and alpine mountain environmentswith examples from southern Norway and Svalbard.In: C. Harris & J.B. Murton (eds.), CryosphericSystems: Glaciers and Permafrost. London:Geological Society, London, Special Publications,242: 11-27.Lilleøren, K.S. 2007. Omnsbreen. Utbredelse og dynamikkunder “Den lille istid” og gjennom det 20. århundre.(English: The Omnsbreen glacier. Extent and dynamicsduring the “Little Ice Age” and the 20th century.).M.Sc. Thesis. Oslo: Department of Geosciences,University of Oslo.DiscussionDuring the LIA, the Omnsbreen Glacier filled the wholevalley. The geometry of the glacier itself probably madeaccumulation of wind-redistributed snow hard at that time,and it is more likely that the summit areas of the glacier were186
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ContentsPreface ...................
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Mapping and Modeling the Distributi
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Satellite Observations of Frozen Gr
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xiiIce Wedge Thermal Regime in Nort
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xivPermafrost Response to Dynamics
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NICOP SponsorsUniversitiesUniversit
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Deep Permafrost Studies at the Lupi
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Effect of Fire on Pond Dynamics in
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Cryological Status of Russian Soils
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Acoustical Surveys of Methane Plume
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Permafrost Delineation Near Fairban
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Preparatory Work for a Permanent Ge
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A Provisional Soil Map of the Trans
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Martian Permafrost Depths from Orbi
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Time Series Analyses of Active Micr
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Impact of Permafrost Degradation on
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DC Resistivity Soundings Across a P
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Modeling Thermal and Moisture Regim
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A Provisional Permafrost Map of the
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Alpine Permafrost Distribution at M
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Cryogenic Formations of the Caucasu
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Modeling Potential Climatic Change
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A Hypothesis: A Condition of Growth
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Modeled Continual Surface Water Sto
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Freeze/Thaw Properties of Tundra So
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Discontinuous Permafrost Distributi
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Thermal Regime Within an Arctic Was
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Seasonal and Interannual Variabilit
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Twelve-Year Thaw Progression Data f
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Continued Permafrost Warming in Nor
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Landsliding Following Forest Fire o
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A Permafrost Model Incorporating Dy
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Seasonal Sources of Soil Respiratio
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Greenland Permafrost Temperature Si
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The Importance of Snow Cover Evolut
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The Account of Long-Term Air Temper
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The Combined Isotopic Analysis of L
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Adaptating and Managing Nunavik’s
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Human Experience of Cryospheric Cha
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HiRISE Observations of Fractured Mo
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A Soil Freeze-Thaw Model Through th
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Mapping and Modeling the Distributi
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First Results of Ground Surface Tem
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Historical Changes in the Seasonall
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Rock Glaciers in the Kåfjord Area,
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Snowpack Evolution on Permafrost, N
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Climate Change in Permafrost Region
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Maximizing Construction Season in a
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Pleistocene Sand-Wedge, Composite-W
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