Ninth International Conference on Permafrost ... - IARC Research

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Hydrogen and Oxygen Isotope Studies from an Ice Wedge in SvalbardHelle VittinghusInstitute of Geography, University of Copenhagen, Denmark andDepartment of Geology, The University Centre in Svalbard, UNIS, NorwayHanne H. ChristiansenDepartment of Geology, The University Centre in Svalbard, UNISHanno MeyerThe Alfred Wegener Institute, Potsdam, GermanyBo ElberlingInstitute of Geography, University of CopenhagenIntroductionSvalbard is located in an area of great sensitivity to climatechange. Palaeo-climate archives from glaciers have beeninvestigated; however, the longest record analysed datesback 800 years. Ice wedges in Adventdalen are believedto be up to 3500 years old (Jeppesen 2001) and, therefore,possibly contain mid to late Holocene palaeo-environmentalinformation.Field SiteThe Adventdalen Valley is located in central Svalbard.The valley trends east–west and is 3.5 km wide and 27 kmlong. The permafrost in Adventdalen is continuous, withwidespread ice wedges. Polygonal networks are found onthe flat terraces along the riverbed and on the gentle valleyslopes up to 25° and up to 500 m a.s.l. (Sørbel & Tolgensbakk2002). They are of variable sizes reaching 10–20 m indiameter. Distinct troughs range from 0.5–5 m across withadjacent ramparts, clearly delimiting the ice wedges below.The oldest age of an ice wedge in Adventdalen is 3685–3640cal. yr BP (Jeppesen 2001). At the northernmost edge of theterrace at the south side of Adventdalen, thermal erosion ofgullies into ice wedges have developed in the river bank cliff.In other places ice wedges are exposed due to river erosion.MethodsAn ice wedge was first exposed in the terrace river cliffin 2003 during stratigraphical studies in outer Adventdalen.This ice wedge was 1.6 m wide, with the top 145 cm exposed.It is a syngenetic ice wedge, reflected by an elevated upperpart of the top 10 cm of the ice wedge being only 60 cmwide. Leaves of Salix twigs found in the outer part of thisice wedge were 14 C AMS dated to 1980–2150 cal. yr BP(Christiansen et al. in prep).The ice wedge was sampled, cutting horizontally acrossby chainsaw in winter, to avoid any thawing during cuttingand transportation. Ice wedge sampling was designed tocapture the isotopic chronology of the vein accumulationand to study vein orientation and/or reactivation event. Sincethe ice wedge exposure was assumed syngenetic, two setsof samples were taken: one across the widest part of the icewedge, sampling 107 cm, and one 60 cm above, across thesmaller top of the ice wedge, sampling 12 cm.To capture the horizontal variation in as much detail aspossible preferably representing each vein, only a few mmwide samples were necessary. This was achieved by verticalsampling with a microtome from the ice wedge sample blocsin the freezing laboratory at UNIS. Several microtome slicesrepresenting 2–3 mm of ice wedge were collected in onesample. The wide ice wedge sample was sampled only in1–1.5 cm slices, using a standing band saw for ice in thefreezing laboratory. This method offered a good opportunityto cut along the vein orientation, since skew cutting wasmanageable.The water stable isotopic compositions of δ 18 O andδD from the ice wedge samples were determined using aFinnigan MAT Delta-S mass spectrometer by the equilibriumtechnique at the AWI laboratory. δD and δO 18 values werecalculated by the commercial software ISODAT (version5.2) and displayed as per mille differences relative to ViennaStandard Mean Ocean Water (V-SMOW) with an internal1 σ error of better than 0.8‰ and 0.1‰ for δD and δO 18 ,respectively (Meyer et al. 2000).ResultsResults from the ice wedge studies are shown in Figure1a–d. The grey line in Figure 1b–d represents results fromhigh-resolution sampling from the upper, smaller ice- wedgepart. The black line represents the samples from the widerpart of the ice wedge. Figure1a shows the general verticalveins, with some veins displaced and some crossings. Thisshows that, to some extent, a complete horizontal vein patterncould not be assumed to reflect a perfect chronologicalevolution across the ice wedge, but we believe the overallpattern reflects a symmetrical growth.DiscussionThe horizontal distribution of δ 18 O (Fig. 1b) and δD(Fig. 1c) values from the wider part shows, respectively,a peak and a low towards the middle, with descendingand ascending values going towards the sides. An overallsymmetrical pattern is thus visible, but the values from thesmaller part show a more detailed picture, with significantlydifferent values to the samples from the wider part. Thus,333
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 td-excessdD vs. SMOWdO 18 (o/oo) vs. SMOW1086420-80-90-100-110-11-12-13-14-150 20 40 60 80 100Cm from left contact zoneConclusionWhile an overall symmetrical pattern could be interpretedfrom the horizontal δ 18 O and δD variations, a climatic trendduring the period of activity was considered detectable.Since a more detailed isotopic pattern was revealed from thehigher resolution samples, the lower resolution samples arebelieved to reflect a mean value of the veins represented inthe respective samples. No vertical climatic trend could beseen between the two cores. The veins of the investigated icewedge are seen to crossing, which most likely complicatespalaeo-environmental reconstructions.ReferencesChristiansen, H.H., Hormes, A. & Snowball, I. (in prep).High Resolution Late Holocene Loess Record withSyngenetic Ice-Wedges in Adventdalen, Svalbard.Jeppesen 2001. Palæoklimatiske Indicatorer for CentralSpitsbergen, Svalbard. Eksemplicificeret ved Studieraf Iskiler og Deres Værtssedimenter. M.Sc. Thesis.Svalbard: The University Centre in Svalbard.Meyer, H., Schönicke, L., Wand, U., Hubberten, H.W. &Frederichsen, H. 2000. Isotopes studies of hydrogenand oxygen in ground ice. Experiences with theequilibration technique. Isotopes in Environmental andHealth Studies 36: 133-149.Sørbel, L. & Tolgensbakk, J. 2002. Ice wedge polygons andsolifluction in the Adventdalen area, Spitsbergen,Svalbard. Norsk Geografisk Tidskrift 56: 62-66.Figure 1. 1a represents the ice wedge part from 28–43 cm fromthe left contact zone and shows the general vertical vein structure.1b–d shows the horizontal distribution of δ 18 O, δD and d-excesswith the black line representing the wider ice wedge part and thegrey line representing the upper, smaller ice wedge part.the higher resolution samples reveal a more detailed isotopicpattern, and the lower resolution samples from the wider partreflect a mean value of the veins represented in the respectivesamples. The small vertical distance of 60 cm between thetwo set of samples is not enough, in this case, to detect avertical climatic trend, and could account for the similarity(from a climatic point of view) in the isotopic values.The horizontal d-excess signal (Fig. 1d) shows that valuesfrom the side sections are too low for a genetic relation withan oceanic moisture source. D-excess values in the smallerpart range from -0.7‰ to 10‰, with decreasing valuestowards the sides. The mean value of winter precipitationcollected in 2006 in Adventdalen was 7.5‰. Since meanvalues of winter precipitation should be found in the veins,another moisture source or an altered signal from potentialfractionation processes since deposition must be assumedtowards the ice wedge sides.334
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NICOP 2008 Ninth <
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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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Ninth International Conference on Permafrost ... - IARC Research

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