Ninth International Conference on Permafrost ... - IARC Research

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Occurrence of Permafrost and Ground Frost Phenomena in MongoliaCh. OppPhilipps-University Marburg, GermanyIntroductionBecause of the climatic peculiarities and of the extremecontinental location, the formation of permafrost andground frost phenomena in Mongolia are widespread(Opp & Barsch 1993). Most of them belong to differentforms of discontinuous and periodic permafrost. Types ofground frost occur in dependence from the zonal climatic,soil, and vegetation conditions. Zones of ground frost aredistinguishable by their location above the sea level, by theirarea, by their spatial share, by their distribution within thezone, and by the thickness of the permafrost (cf. Table 1).On the basis of observations, measurements, andinterpretations during five field trips between 1989 (Barschet al. 1993) and 1998 (Opp 1998, 2005), selected results areimparted.ResultsSeasonal average periods of freezing of discontinuouspermafrost were established between October and May. Thecorresponding periods of thawing were established from lateApril until late September (cf. Fig. 1). The processes andperiods of freezing and thawing can differ in dependencefrom the site conditions. Such examples were proved independence from the exposition (northern and southernslopes), or in river valleys (cf. Fig. 2) Characteristicdifferences of temperatures and pH values between the topand the bottom position of thufurs (earth hummocks) wereanalysed.The degradation of many thufur fields in Mongolia iscaused by climate (warmer winters) and land use changes(higher share of grazing animals) during the last decade.Thermokarst bank erosion is caused by deep thawingduring the summertime and lateral erosion by river water.The erosion rate of bank caving processes is much higherat the natural levee side in southern exposition than at otherriver bank positions. Within the river valley of the OrkhonRiver, south of the city of Darkhan, a maximum value of 1.5m per year of backward erosion of the river bank, causedby permafrost degradation, were measured (Opp 1998,2006). This “fluvio-cryo-thermo-erosion” of the river banksis a characteristic phenomenon of many rivers in northernMongolia.Figure 1. Average seasonal freezing and thawing periods ofdiscontinuous permafrost within the Orchon catchment (northernMongolia).Figure 2. Sequence of seasonal freezing and thawing of a permafrostinfluencedsite near Erdenet (northern Mongolia).Table 1. Selected features of the belts of frozen ground in Mongolia (Source: National Atlas of Mongolia, Ulan Bator, 1990).belts offrozen grounddiscontinuouspermafrostdiscontinuouspermafrostsporadicpermafrostseasonal groundfreezingaltitude a.s.l area portion withinthe permafrostdominant maximum thicknessof permafrosttemperature in 20 mdepthportion within the areacountryin valleys on slopesand onwatersheds(m) (km²) (%) (%) (m) (m) (°C)1200–2800 175,280 11.2 40–80 20–500 (bis 1000) -5 bis +1700–2600 350,560 22.4 1–40 5–50 (bis 100) 5-20 -5 bis +5600–1900 460,110 29.4
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 3. Pore size distribution of a Gelic Fluvisol (Turbel) withinthe Orkhon floodplain (northern Mongolia).ReferencesBarsch, H., Opp, Ch. & Steinhardt, U. 1993. GeoökologischeProbleme in der Waldsteppe der nördlichen Mongolei.Potsdamer Geographische Forschungen 3: 1-89.Opp, Ch. & Barsch, H. 1993. Geomorphological processesin the Mountain Forest Steppe of Northern Mongolia.Z. Geomorph. N.F., Suppl.-Bd. 92: 145-157.Opp, Ch. 1998. Bodenökologische Aspektedauerfrostbeeinflusster Standorte in der Mongolei.Mitteilungen Deutsche Bodenkundliche Gesellschaft88: 121-124.Opp, Ch. 2005. Natürliche und nutzungsbedingte Land- undBodendegradationsprozesse, untersucht am unterenOrchon (Nord-Mongolei). Erforschung BiologischerRessourcen der Mongolei 9: 475-494.Opp, Ch. 2006. Natural and land use caused land and soildegradation processes, a case study from the lowerOrkhon region (northern Mongolia). Proceedings ofthe <strong>Conference</strong> “Soil as a connecting link – function ofnatural and anthropogenic ecosystems in transition.”Irkutsk September 4–7, 2006: 480.A warmer climate and an intensive use of pastures ofthe river valleys are the main reasons for permafrost andground frost degradation in Mongolia. Effects on soils wereproved with the help of cylinders measuring specific soilphysicparameters (pore volume, pore-size distribution, soildensity, saturated vertical water conductivity) which, forexample, allow statements about natural and man-made soildegradation and ground frost degradation processes. Thoughthe pore volume in the upper soils of these sites is on averagebigger than 50%, it is striking that their macro pore volumecontent is very small. The percentage of quickly-drainingcoarse pores is zero (cf. Fig. 3).One reason for this seems to lie in the permafrost ofthe subsoil. The permafrost table during the summermeasurement was at a depth of 90 cm.Systems of polygonal ice wedges were observed on wetmeadows near the river. A different distribution of the soilmoisture of the ice wedges—wetter margin of the polygon,drier core of the polygon—was established by the differentcolouring of the grass. Besides that, ice wedge gaps of awidth of 10 up to 40 cm are typical for a soil surface whichwas deformed by ice push and shrinking. The biggest icewedge gaps (depth and width) were found in direct proximityof the Orkhon River.AcknowledgmentsThe author is especially grateful to Prof. Dr. Barsch(Potsdam), Dr. Böttcher (Magdeburg), Dr. Tulgaa (UlanBator) and Mr. Enktuvshin (Ulan Bator), who were includedin the field research.238
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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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370Huang, B. 339Hugelius, G. 105, 1
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