• Title, Summary, Keyword: Permafrost

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Projection of Circum-Arctic Features Under Climate Change (미래 기후 변화 시나리오에 따른 환북극의 변화)

  • Lee, Ji Yeon;Cho, Mee-Hyun;Koh, Youngdae;Kim, Baek-Min;Jeong, Jee-Hoon
    • Atmosphere
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    • v.28 no.4
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    • pp.393-402
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    • 2018
  • This study investigated future changes in the Arctic permafrost features and related biogeochemical alterations under global warming. The Community Land Model (CLM) with biogeochemistry (BGC) was run for the period 2005 to 2099 with projected future climate based on the Special Report on Emissions Scenarios (SRES) A2 scenario. Under global warming, over the Arctic land except for the permafrost region, the rise in soil temperature led to an increase in soil liquid and decrease in soil ice. Also, the Arctic ground obtained carbon dioxide from the atmosphere due to the increase in photosynthesis of vegetation. On the other hand, over the permafrost region, the microbial respiration was increased due to thawing permafrost, resulting in increased carbon dioxide emissions. Methane emissions associated with total water storage have increased over most of Arctic land, especially in the permafrost region. Methane releases were predicted to be greatly increased especially near the rivers and lakes associated with an increased chance of flooding. In conclusion, at the end of $21^{st}$ century, except for permafrost region, the Arctic ground is projected to be the sink of carbon dioxide, and only permafrost region the source of carbon dioxide. This study suggests that thawing permafrost can further to accelerate global warming significantly.

On the Spatial and Temporal Variability of L-band Polarimetric SAR Observations of Permafrost Environment in Central Yakutia

  • Park, Sang-Eun
    • Korean Journal of Remote Sensing
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    • v.33 no.1
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    • pp.47-60
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    • 2017
  • The permafrost active layer plays an important role in permafrost dynamics. Ecological patterns, processes, and water and ice contents in the active layer are spatially and temporally complex depending on landscape heterogeneity and local-scale variations in hydrological processes. Although there has been emerging interest in the application of optical remote sensing techniques to permafrost environments, optical sensors are significantly limited in accessing information on near surface geo-cryological conditions. The primary objective of this study was to investigate capability of L-band SAR data for monitoring spatio-temporal variability of permafrost ecosystems and underlying soil conditions. This study exploits information from different polarimetric SAR observables in relation to permafrost environmental conditions. Experimental results show that each polarimetric radar observable conveys different information on permafrost environments. In the case of the dual-pol mode, the radar observables consist of two backscattering powers and one correlation coefficient between polarimetric channels. Among them, the dual-pol scattering powers are highly sensitive to freeze/thaw transition and can discriminate grasslands or ponds in thermokarst area from other permafrost ecosystems. However, it is difficult to identify the ground conditions with dual-pol observables. Additional backscattering powers and correlation coefficients obtained from quad-pol mode help understanding seasonal variations ofradar scattering and assessing geo-cryological information on soil layers. In particular, co-pol coherences atHV-basis and circular-basis were found to be very usefultools for mapping and monitoring near surface soil properties.

THE CHANCES OF PERMAFROST INDUCED BY GREENHOUSE WARMING: A SIMULATION STUDY APPLYING MULTIPLE-LAYER GROUND MODEL

  • Yamaguchi, Kazuki;Noda, Akira;Kitoh, Akio
    • Proceedings of the Korea Society for Simulation Conference
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    • pp.329-334
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    • 2001
  • Many of past studies using physically based numerical climate models indicate that increases in atmospheric $CO_2$could enhance summer dryness over continental region in middle-high latitudes. However the models used in those studies do not take account of permafrost in high latitudes. We have carried out a set of experiments applying a version of global climate model that can reproduce realistic distribution of the permafrost. From the results, it is indicated that permafrost functions as a large reservoir in hydrologic cycle maintaining dry, hot summer over continents in northern middle-high latitudes, and that the $CO_2$warming would reduce this function by causing climatological thawing of permafrost, which would result in moister and cooler summer, and warmer winter in the same region. The present study indicates that an inclusion of very simple description of soil freezing process can make a large difference in a model simulation.

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Study on failure and subsidence law of frozen soil layer in coal mine influenced by physical conditions

  • Zhang, Yaning;Cheng, Zhanbo;Lv, Huayong
    • Geomechanics and Engineering
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    • v.18 no.1
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    • pp.97-109
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    • 2019
  • Physical conditions play vital role on the mechanical properties of frozen soil, especially for the temperature and moisture content of frozen soil. Subsequently, they influence the subsidence and stress law of permafrost layer. Taking Jiangcang No. 1 Coal Mine as engineering background, combined with laboratory experiment, field measurements and empirical formula to obtain the mechanical parameters of frozen soil, the thick plate mechanical model of permafrost was established to evaluate the safety of permafrost roof. At the same time, $FLAC^{3D}$ was used to study the influence of temperature and moisture content on the deformation and stress law of frozen soil layer. The results show that the failure tensile stress of frozen soil is larger than the maximum tensile stress of permafrost roof occurring in the process of mining. It indicates that the permafrost roof cannot collapse under the conditions of moisture content in the range from 20% to 27% as well as temperature in the range from $-35^{\circ}C$ to $-15^{\circ}C$. Moreover, the maximum subsidence of the upper and lower boundary of the overlying permafrost layer decreases with the increase of moisture content in the range of 15% to 27% or the decrease of temperature in the range of $-35^{\circ}C$ to $-15^{\circ}C$ if the temperature or moisture content keeps consistent with $-25^{\circ}C$ or 20%, respectively.

An Study on Efficiency and Application of Thermal Siphon in the Permafrost (영구동토 지대에서 Thermal Siphon의 효율성 연구)

  • Kang, Jae-Mo;Kim, Hak-Seung
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.963-966
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    • 2009
  • A Construction of pipe line foundation and railroad, buildings in a permafrost area requires engineering technology of ground stabilization. In the permafrost area, thermal siphons have been used to stabilize foundation by eliminating the heat of ground to the air. the thermal siphon is a passive heat transfer device that operates by convection through vaporization and condensation. The heat transfer from ground to the air is driven by a temperature difference across the unit. A buried part in ground working as vaporizing function and upper part work as condensing. In this study, buried thermal siphon around the pipe lines laid in the Vladivostok site and measuring temperature variation. It is found that the thermal siphons freezing ground faster and decrease temperature variation in winter season.

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Numerical Study about Influence Variables of Permafrost Pipeline by using Thermal Flow Analysis (극한지 온도조건에 파이프라인 내부 열유동 영향변수 평가)

  • Jo, Chul H.;Hwang, Su-Jin;Jang, Choon-Man;Lee, Jun-Ho
    • Transactions of the Korean hydrogen and new energy society
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    • v.25 no.4
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    • pp.443-448
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    • 2014
  • This paper describes thermal flow characteristics in various pipelines: straight pipeline and curved pipeline. In the permafrost area, pipelines are exposed to an extremely low temperature ($-40^{\circ}C$). In this situation, three-dimensional flow analysis should be analyzed to investigate thermal effects such as pressure drop, temperature change, velocity deficit and distribution change of liquid droplet of internal fluid. In this paper, multi-phase and multi-species analysis was introduced to analyze the flow characteristics of permafrost pipelines on the vertical support members above ground.

Stochastic analysis for uncertain deformation of foundations in permafrost regions

  • Wang, Tao;Zhou, Guoqing;Wang, Jianzhou;Zhao, Xiaodong;Yin, Leijian
    • Geomechanics and Engineering
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    • v.14 no.6
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    • pp.589-600
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    • 2018
  • For foundations in permafrost regions, the displacement characteristics are uncertain because of the randomness of temperature characteristics and mechanical parameters, which make the structural system have an unexpected deviation and unpredictability. It will affect the safety of design and construction. In this paper, we consider the randomness of temperature characteristics and mechanical parameters. A stochastic analysis model for the uncertain displacement characteristic of foundations is presented, and the stochastic coupling program is compiled by Matrix Laboratory (MATLAB) software. The stochastic displacement fields of an embankment in a permafrost region are obtained and analyzed by Neumann stochastic finite element method (NSFEM). The results provide a new way to predict the deformation characteristics of foundations in permafrost regions, and it shows that the stochastic temperature has a different influence on the stochastic lateral displacement and vertical displacement. Construction disturbance and climate warming lead to three different stages for the mean settlement of characteristic points. For the stochastic settlement characteristic, the standard deviation increases with time, which imply that the results of conventional deterministic analysis may be far from the true value. These results can improve our understanding of the stochastic deformation fields of embankments and provide a theoretical basis for engineering reliability analysis and design in permafrost regions.

Effect of thermal regime on the seismic response of a dry bridge in a permafrost region along the Qinghai-Tibet Railway

  • Zhang, Xiyin;Zhang, Mingyi;Chen, Xingchong;Li, Shuangyang;Niu, Fujun
    • Earthquakes and Structures
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    • v.13 no.5
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    • pp.429-442
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    • 2017
  • Dry bridges have been widely applied in the Qinghai-Tibet Railway (QTR) to minimize the thermal disturbance of engineering to the permafrost. However, because the Qinghai-Tibet Plateau is an area with a high potential occurrence of earthquakes, seismic action can easily destroy the dry bridges. Therefore, a three-dimensional numerical model, with consideration of the soil-pile interactions, is established to investigate the thermal characteristics and their impact on the seismic response of the dry bridge in permafrost region along the QTR. The numerical results indicate that there exist significant differences in the lateral displacement, shear force, and bending moment of the piles in different thermal conditions under seismic action. When the active layer become from unfrozen to frozen state, the maximum displacement of the bridge pile reduces, and the locations of the zero and peak values of the shear force and bending moment also change. It is found that although the higher stiffness of frozen soil confines the lateral displacement of the pile, compared with unfrozen soil, it has an adverse effect on the earthquake energy dissipation capacity.

Development and Verification of High Efficiency Experimental Apparatus to Evaluate Freezing Phenomenon of Soils (고효율 실내 동결실험장비의 개발 및 성능검증)

  • Choi, Chang-Ho
    • Journal of the Korean Geosynthetics Society
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    • v.10 no.4
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    • pp.93-103
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    • 2011
  • In order to design suitable geo-structures in cold region, it is generally required to consider the mechanical properties of permafrost soils. 'Frost heave' as one of the primary phenomenon is considered to be an important factor together with 'adfreeze bond-strength' and 'creep deformation' for structural design process in permafrost area. Therefore, the fundamental study for frost heave has to be preceded for design of geo-structures in cold region. While various experimental apparatuses have been developed, there still exist a certain level of limitation to evaluate the frost-heave characteristics as design parameters. In this paper, a new type of experimental apparatus is proposed to evaluate the engineering characteristics of frost heave in permafrost soils and a set of verification test results is presented. Based on the verification tests, the proposed apparatus is a suitable to obtain frost characteristics of soils.