Ninth International Conference on Permafrost ... - IARC Research

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Seasonal and Interannual Variability of Active Layer Development in PermafrostWetland SystemsC.M. ChiuDepartment of Agronomy, Purdue University, West Lafayette, IN, USAL.C. BowlingDepartment of Agronomy, Purdue University, West Lafayette, IN, USAIntroductionOver the last decades, the arctic region has been warmingat an accelerated rate with sometimes puzzling effectson lakes and wetlands. Wetlands are common landscapecharacteristics in the northern high latitudes. Permafrost andseasonal frost can be a powerful factor affecting wetlandhydrology. The interaction of soil thermal and moistureregimes controls the structure of the seasonally thawedactive layer and hydrological response in permafrost regions.Soil thermal and moisture properties regulate the transfer ofheat though the active layer, thus affecting the annual thawand frost depth. The maximum active layer thickness canvary substantially with annual soil temperature change,given similar moisture conditions (Brown & Hinkel 2000).Spatially, the active layer thickness can vary over shortlateral distances due to differences in heat transfer underdifferent soil moisture conditions subject to freezing andthawing (Outcalt et al. 1990). For example, Woo and Xia(1996) found that a wetland site had shallower maximumthaw depth than a drier site due to the buffering effect ofthe large ice content. The spatial variation may also reflectthe interaction of a large number of highly localized factors,including vegetation type, snow cover, organic layerthickness, soil thermal properties, microtopography, and theoperation of nonconductive heat transfer processes (Outcaltet al. 1990). This study will examine the spatial and temporalvariation of soil temperature and soil moisture content in acontinuous permafrost environment and how they relate tothe duration and thickness of seasonal active layer in uplandand wetland systems. In particular, the ability of the VariableInfiltration Capacity (VIC) land surface model to reproducethe observed relationship between moisture condition andmaximum annual thaw depth will be evaluatedStudy AreaThe study area is the 471 km 2 Putuligayuk River watershedlocated on the coastal plain south of Prudhoe Bay on theAlaskan North Slope. Observations of soil temperaturesand weather are taken from the Betty Pingo weather station(70°16′46.3ʺN, 148°53′44.5ʺW) operated by the Universityof Alaska Fairbanks. The watershed is dominated by drainedlakes and numerous permafrost features such as high- andlow-centered polygons, pingos, hummocky terrain, frostboils, and strangemoor ridges (Kane et al. 2000). The poordrainage results in extensive wetlands, ponds, and lakes. Themaximum thickness of the permafrost along the arctic coastis about 600 m, whereas the maximum depth of thaw of theactive layer was about 53 cm between 1993 to 2002 (Brown& Hinkel 2000). The vegetation in this area is dominated bysedge tundra, with shrubs in wetter areas and tussock tundrain higher and drier areas. Observed meteorological and soiltemperature data for the period 1994–2004 was obtainedthrough the National Snow and Ice Data Center (Kane &Hinzman 1997).Model DescriptionThe Variable Infiltration Capacity (VIC) model is amacroscale hydrologic model which has been applied tomany environmental studies associated with global climateand land use change prediction (Liang et al., 1994). VICmodel features relevant to this application include (1) a finitedifference soil thermal solution (Cherkauer & Lettenmaier1999, Cherkauer & Lettenmaier 2003) and (2) representationof the surface storage and energy dynamic of sub-grid lakesand wetlands (Bowling 2003, Cherkauer & Lettenmaier2003). In this study, we will examine the ability of the VICmodel to simulate upland and wetland soil temperature, soilmoisture, and active layer depth. The VIC model is run as asingle point centered on the two sites. A constant temperaturebottom boundary condition is used with a fixed temperatureof -10°C at 4 m damping depth. Two scenarios are run withcontrasting initial moisture conditions, bulk density andbase flow parameters to simulate the contrasting moistureconditions of the site.Preliminary ResultAdjacent upland and wetland sites were instrumented byUAF beginning in 1994. The upland site was instrumentedwith 12 temperature probes vertically arranged at depths of0, 1, 2, 3, 4, 5, 6, 7, 8, 15, 35, and 60 cm. The adjacentwetland site was also instrumented with 12 temperatureprobes vertically arranged at depths of 0, 0.5, 1, 2, 3, 4, 5, 6,15, 30, 50, and 75 cm. Mean annual soil temperatures for theupland and wetland sites derived from hourly observationsbetween 1996–2001 are shown in Figure 1. The patterns atboth sites are very similar, although observed annual averagetemperatures are 0.27 to 0.74°C warmer for the wetter soils.The simulated temperatures are 0.35 to 0.6°C warmer forthe wetter soil. In the wetter soil, water or ice displaces airin soil pores, increasing the bulk conductivity as well as thesoil heat capacity. Thus, more energy may be required tochange the temperature within the same depth resulting in ashallower active layer depth and shorter thawed period in thewetter soil (Figs. 2, 3).43
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 tAs shown in Figure 2, simulated annual average activelayer depth is slightly underestimated for the wetland site(58.78 cm). Since the 60 cm temperature sensor at theupland site exceeds 0°C in most years, the annual activelayer depth is unknown, but still deeper than wetland. Figure3 illustrates that both the observed and simulated frost-freeperiod is longer in the upland than in the wetland site.Depth (cm)Depth (cm)0204060UplandWetlandupland-simwetland-sim80-7.5 -7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0Soil Temperature ( o C)Figure 1. Mean annual soil temperature at 12 probe levels from1996 to 2001 at upland and wetland site at Betty Pingo, Alaska.806040200UplandWetlandObsSimFigure 2. Observed and simulated maximum active layer depths(depth to the 0° isotherm) from 1996 to 2001 at upland and wetlandsite at Betty Pingo, Alaska. (The maximum temperature sensor inupland site is located at 60 cm.)Julian Day350300250200150100500Upland-Thaw Wetland-Thaw Upland-Frost Wetland-FrostObsX DataSimFigure 3. Observed and simulated mean Julian day that soil thawreaches 50 cm (Thaw) and Julian day that soil freezes to within 1cm (Frost) from 1996 to 2001 at upland and wetland site at BettyPingo, Alaska.SummaryThe wetter wetland site is observed to have higher averagesoil temperature than the dryer upland site. The higher wateror ice content in the soil retards the development of the activelayer and results in a shallower active layer and shorterthawed period than the upland site. The VIC soil temperaturepredictions appear to be less sensitive to the soil moisturedifferences due to heat capacity and bulk conductivity,although the actual difference in moisture content betweenthe sites is unknown. Future work will focus on the activelayer seasonal dynamic and hydrology response abovecontinuous permafrost at the watershed scale.AcknowledgmentsThis research has been supported and funded by NASAthrough the Northern Eurasia Earth Science PartnershipInitiative (NEESPI). The observed data was collected byWater and Environmental Research Center, University ofAlaska Fairbanks.ReferenceBrown, J. & Hinkel, K. 2000. Circumpolar Active LayerMonitoring (CALM) Network. Available online: http://www.geography.uc.edu/~kenhinke/CALM/sites.html.Bowling, L.C. 2002. Estimating the freshwater budget ofhigh-latitude land areas. Ph.D. dissertation. Univ. ofWashington, Seattle.Cherkauer, K.A. & Lettenmaier, D.P. 1999. Hydrologicaleffects of frozen soils in the upper Mississippi Riverbasin. J. of Geophysical Research 104: 19559-19610.Cherkauer, K.A., Bowling, L.C. & Lettenmaier, D.P. 2003.Variable infiltration capacity cold land process modelupdates. Global and Planetary Changes 38: 151-159.Kane, D.L. & Hinzman, L.D. 1997. updated 2003. Meteorologicaland hydrographic data, Kuparuk River Watershed.Boulder, CO: National Snow and Ice Data Center,World Data Center for Glaciology. Digital media.Kane, D.L., Hinzman, L.D., McNamara, J.P., Zhang, Z.& Benson, C.S. 2000. An overview of a nestedwatershed study in Arctic Alaska. Nordic Hydrology31(4/5): 245-266.Liang, X., Lettenmaier, D.P., Wood, E.F. & Burges, S.J. 1994.A simple hydrogically based model of land surfacewater and energy fluxes for GSMs. J. Geophys. Res.99(D7): 14415-14428.Nixon, J.F. 1975. The role of convective heat transport in thethawing of frozen soil. Canadian Geotechnic Journal.12: 425-429.Outcalt, S.I., Nelson, F.E. & Hinkel, K.M. 1990. The zerocurtain effect: heat and mass transfer across andisothermal region in freezing soil. Water Resour. Res.26: 1509-1516.Woo, M.K. & Xia, Z.J. 1996. Effects of hydrology onthe thermal conditions of the active layer. NordicHydrology. 27: 129-142.44
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NICOP 2008 Ninth <
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ContentsPreface ...................
Page 8 and 9:
Mapping and Modeling the Distributi
Page 10 and 11:
Satellite Observations of Frozen Gr
Page 13 and 14: xiiIce Wedge Thermal Regime in Nort
Page 15 and 16: xivPermafrost Response to Dynamics
Page 17 and 18: xvi
Page 19 and 20: NICOP SponsorsUniversitiesUniversit
Page 22 and 23: Deep Permafrost Studies at the Lupi
Page 24 and 25: Effect of Fire on Pond Dynamics in
Page 26 and 27: Cryological Status of Russian Soils
Page 28 and 29: Acoustical Surveys of Methane Plume
Page 30 and 31: Permafrost Delineation Near Fairban
Page 32 and 33: Preparatory Work for a Permanent Ge
Page 34 and 35: A Provisional Soil Map of the Trans
Page 36 and 37: Martian Permafrost Depths from Orbi
Page 38 and 39: Time Series Analyses of Active Micr
Page 40 and 41: Impact of Permafrost Degradation on
Page 42 and 43: DC Resistivity Soundings Across a P
Page 44 and 45: Modeling Thermal and Moisture Regim
Page 46 and 47: A Provisional Permafrost Map of the
Page 48 and 49: Alpine Permafrost Distribution at M
Page 50 and 51: Cryogenic Formations of the Caucasu
Page 52 and 53: Modeling Potential Climatic Change
Page 54 and 55: A Hypothesis: A Condition of Growth
Page 56 and 57: Modeled Continual Surface Water Sto
Page 58 and 59: Freeze/Thaw Properties of Tundra So
Page 60 and 61: Discontinuous Permafrost Distributi
Page 62 and 63: Thermal Regime Within an Arctic Was
Page 66 and 67: Twelve-Year Thaw Progression Data f
Page 68 and 69: Continued Permafrost Warming in Nor
Page 70 and 71: Landsliding Following Forest Fire o
Page 72 and 73: A Permafrost Model Incorporating Dy
Page 74 and 75: Seasonal Sources of Soil Respiratio
Page 76 and 77: Greenland Permafrost Temperature Si
Page 78 and 79: The Importance of Snow Cover Evolut
Page 80 and 81: The Account of Long-Term Air Temper
Page 82 and 83: The Combined Isotopic Analysis of L
Page 84 and 85: Adaptating and Managing Nunavik’s
Page 86 and 87: Human Experience of Cryospheric Cha
Page 88 and 89: HiRISE Observations of Fractured Mo
Page 90 and 91: A Soil Freeze-Thaw Model Through th
Page 92 and 93: Mapping and Modeling the Distributi
Page 94 and 95: First Results of Ground Surface Tem
Page 96 and 97: Historical Changes in the Seasonall
Page 98 and 99: Rock Glaciers in the Kåfjord Area,
Page 100 and 101: Snowpack Evolution on Permafrost, N
Page 102 and 103: Climate Change in Permafrost Region
Page 104 and 105: Maximizing Construction Season in a
Page 106 and 107: Pleistocene Sand-Wedge, Composite-W
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