Ninth International Conference on Permafrost ... - IARC Research

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Permafrost, Parameters, Climate Change, and UncertaintyAndrew G. SlaterNSIDC, University of Colorado, Boulder, CO, USADavid M. LawrenceNational Center for Atmospheric Research, Boulder, CO, USAIntroductionRecently observed changes in the state of permafrostare many and varied. Appearance and disappearance oflakes, degradation of ice wedges, and changes in riverchannel morphology are several of the processes that havebeen linked to thawing of permafrost and warming of soiltemperatures. Osterkamp (2007) suggests that permafrost atWest Dock, Alaska, has warmed about 3.7°C since 1976 andmay have warmed greater than 6°C since 1900. While mostmodeling efforts to assess the effects of future climate changeon permafrost and frozen ground indicate that there will besubstantial change, the magnitude and extent of the changeis still uncertain (e.g., Lawrence & Slater 2005; Zhang etal. 2008). Part of the uncertainty in permafrost simulationscan be associated with somewhat external factors such assimulation of snow or specification of soil and vegetationparameters. Here we present a sensitivity study of suchinputs and parameters.MethodsModelA simple analytic model following the method ofKudryavtsev (Sazonova & Romanovsky 2003) was appliedto estimate the current and future state of permafrost. Themodel produces a steady-state solution under the assumptionof constant sinusoidal temperature forcing. The model alsoaccounts for the presence of snow, vegetation, and theorganic matter above the mineral soil. The primary inputsto the model are the mean annual air temperature, annualamplitude of air temperature, and the mean snow depth overthe winter period. Parameters required by the model includesoil texture, so as to compute thermal conductivity and heatcapacity as well as estimates of snow thermal conductivity.The model is applied on a 100 x 100 km EASE equal-areagrid for the region covered by the pan-arctic drainage basins;this region extends down to 45°N in places.DataTemperature data was derived from the ECMWF 40-yearreanalysis project. This data has been shown to produce.Average snow depth and density was obtained as theensemble average from five land surface models (CHASM,CLM, ECMWF, NOAH, and VIC) that had performed 23-year simulations over the region (Slater et al. 2007). Theestimates from the models are more consistent with stationbasedmeasurements than the available passive microwavesatellite data; this is particularly so in the eastern Siberianuplands, where satellite products have known biases.Parameter data for soil texture properties is based on themap of Zobler (1986) and has been used extensively inlarge-scale modeling experiments. To simplify matters andmaintain a conservative estimate of change, soil moisturewas prescribed at 99% of saturation.Figure 1. Analytic model simulation of present-day permafrost. Temperature is in degrees Celsius. Disregard results for Greenland.293
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 tFigure 2. Analytic model simulation of permafrost with a simple climate change scenario of 7°C increase in annual mean temperature.Results and SummaryFigure 1 shows the results from the analytic model for thelate 20 th century. Estimates of the active layer depth as wellas the mean annual temperature at the top of the permafrostare shown. These results compare favorably to the estimateddistribution of permafrost as given by the <strong>International</strong>Permafrost Association map. Temperature at the top ofthe permafrost is shown in four ranges that are roughlyconsidered to compare to permafrost zones of continuous,discontinuous, sporadic, and isolated.Some initial simple experiments were performed in whichmean annual temperature was raised by 7°C, which is withinthe range of changes expected to be seen over the Arctic inthe coming century according to IPCC estimates (Fig. 2).Snow depth and cover for these preliminary simulations waskept the same as present day. Estimates of changes in snowdepth and cover vary widely, but Räisänen (2008) suggeststhat there is a likelihood of deeper snow over mid-winterin the high latitudes, as the increased precipitation will stillfall in solid phase. This will no doubt have an impact onthe future state of permafrost. Further simulations assessingsensitivity to snow and soil will be carried out and presentedat the NICOP meeting.ReferencesOsterkamp, T.E. 2007. Characteristics of the recent warmingof permafrost in Alaska, J. Geophys. Res. 112:F02S02, doi:10.1029/2006JF000578.Räisänen, J. 2008. Warmer climate: Less or more snow?Clim. Dynamics 30(2–3): 307-319.Sazonova, T.S. & Romanovsky, V.E. 2003, A model forregional-scale estimation of temporal and spatialvariability of active layer thickness and mean annualground temperatures. Permafrost Periglac. Process.14: 125-139.Slater, A.G., Bohn, T.J., McCreight, J.L., Serreze, M.C. &Lettenmaier, D.P. 2007. A multimodel simulation ofpan-Arctic hydrology, J. Geophys. Res. 112: G04S45,doi:10.1029/2006JG000303.Zhang, Y., Chen, W. & Riseborough, D.W. 2008.Disequilibrium response of permafrost thaw to climatewarming in Canada over 1850–2100. Geophys. Res.Lett. 35: L02502, doi:10.1029/ 2007GL032117.Zobler, L. 1986. A World Soil File for Global ClimateModeling. NASA Tech. Memo 87802, Natl. Aeronaut.and Space Admin., Goddard Inst. for Space Stud.,New York.AcknowledgmentsThis work was partially funded by NSF grants ARC-0229769 and ARC-0531040.294
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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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