DOCSLIB.ORG

Predictive Modeling of Freezing and Thawing of Frost-Susceptible Soils

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Predictive Modeling of Freezing and Thawing of Frost-Susceptible Soils PREDICTIVE MODELING OF FREEZING AND THAWING OF FROST-SUSCEPTIBLE SOILS Final Report Report Number: RC-1619 Michigan Department of Transportation Office of Research Administration 8885 Ricks Road Lansing, MI 48909 By Gilbert Baladi and Pegah Rajaei Michigan State University Department of Civil & Environmental Engineering 3546 Engineering Building East Lansing, MI 48824 September 2015 Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. MDOT Project Manager RC-1619 N/A Richard Endres 4. Title and Subtitle 5. Report Date Predictive Modeling of Freezing and Thawing of Frost- September 2015 Susceptible Soils 6. Performing Organization Code N/A 7. Author(s) 8. Performing Org. Report No. Gilbert Baladi and Pegah Rajaei N/A Michigan State University Department of Civil and Environmental Engineering 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Michigan State University N/A Department of Civil and Environmental Engineering 3546 Engineering 11. Contract No. East Lansing, Michigan 48824 2010-0294 11(a). Authorization No. Z9 12. Sponsoring Agency Name and Address 13. Type of Report & Period Covered Michigan Department of Transportation Final Report Research Administration 10/01/12 to 9/30/15 8885 Ricks Rd. P.O. Box 30049 14. Sponsoring Agency Code Lansing MI 48909 N/A 15. Supplementary Notes 16. Abstract Frost depth is an essential factor in design of various transportation infrastructures. In frost susceptible soils, as soils freezes, water migrates through the soil voids below the freezing line towards the freezing front and causes excessive heave. The excessive heave can cause instability issues in the structure, therefore predicting the frost depth and resulting frost heave accurately can play a major role in the design. The objectives of this study are to develop accurate and reliable models for predicting frost depths and frost heave and to estimate the resulting heave pressure. The frost depth model was developed and verified using data from MDOT and Minnesota DOT. The frost heave model was also developed and verified using the available MDOT data. 17. Key Words 18. Distribution Statement Heat Transfer, Thermal Conductivity, Cumulative No restrictions. This document is available Freezing Index, Frost Depth, Analytical Models, to the public through the Michigan Empirical Models, Frost Heave, , Heave Pressure, Frost Department of Transportation. Heave and Frost Depth Field Data 19. Security Classification - report 20. Security Classification - page 21. No. of Pages 22. Price Unclassified Unclassified N/A ii Acknowledgement The authors like to thank the Michigan Department of Transportation (MDOT) for the financial support and the MDOT staff for their cooperation and for providing soil samples and the soil temperature data. In addition the authors gratefully acknowledge the Minnesota Department of Transportation (MNDOT) for providing the soil temperature data and for its assistance. Research Report Disclaimer “This publication is disseminated in the interest of information exchange. The Michigan Department of Transportation (hereinafter referred to as MDOT) expressly disclaims any liability, of any kind, or for any reason, that might otherwise arise out of any use of this publication or the information or data provided in the publication. MDOT further disclaims any responsibility for typographical errors or accuracy of the information provided or contained within this information. MDOT makes no warranties or representations whatsoever regarding the quality, content, completeness, suitability, adequacy, sequence, accuracy or timeliness of the information and data provided, or that the contents represent standards, specifications, or regulations.” iii Table of Contents Chapter 1 - Introduction .................................................................................................................. 1 1.1 Problem Statement ........................................................................................................... 1 1.2 Study Objectives .............................................................................................................. 1 1.3 Research Plan ................................................................................................................... 2 1.4 Organization of this Report .............................................................................................. 3 Chapter 2 - Literature Review ......................................................................................................... 4 2.1 Frost Depth ....................................................................................................................... 4 2.1.1 Numerical Models .............................................................................................................. 4 2.1.2 Mechanistic Empirical Models ......................................................................................... 6 2.1.3 Empirical Models ............................................................................................................. 11 2.2 Frost Heave .................................................................................................................... 12 2.2.1 Capillary Theory ............................................................................................................... 13 2.2.2 Frozen Fringe Theory ...................................................................................................... 17 2.2.3 Frost Pressure .................................................................................................................... 32 2.3 Thaw Depth and Seasonal Load Restrictions ................................................................. 34 2.3.1 Thaw Depth ....................................................................................................................... 34 2.3.2 Seasonal Load Restriction ............................................................................................... 36 Chapter 3 - Data Mining ............................................................................................................... 40 3.1 Data Base........................................................................................................................ 40 3.2 Frost Depth Data ............................................................................................................ 40 3.2.1 The State of Michigan...................................................................................................... 40 3.2.2 The State of Minnesota .................................................................................................... 46 3.3 Soil Properties Data ........................................................................................................ 46 3.4 Frost Heave Data ............................................................................................................ 48 Chapter 4 - Analysis and Discussion of Frost Depth and Frost Heave ......................................... 51 4.1 Introduction .................................................................................................................... 51 4.2 UNSAT-H Model........................................................................................................... 51 4.3 Freezing Index and Freezing Degree Day Calculation .................................................. 53 4.3.1 Minnesota Cumulative Freezing Degree Day ......................................................... 53 4.3.2 Boyd Cumulative Freezing Degree Day .................................................................. 54 iv 4.4 Existing Frost Depth Prediction Models ........................................................................ 56 4.4.1 Stefan Equation..................................................................................................... 56 4.4.2 Modified Berggren Equation ................................................................................. 57 4.4.3 Chisholm and Phang Equation .............................................................................. 63 4.5 Empirical Models ........................................................................................................... 65 4.6 Thaw Depth .................................................................................................................... 79 4.6.1 Calculation of Cumulative Thawing Degree day (CTDD) .................................... 79 4.6.2 Nixon and McRoberts Equation ............................................................................ 79 4.7 Frost Heave .................................................................................................................... 79 4.7.1 Frost Heave Mitigation .......................................................................................... 86 4.7.2 Gilpin Frost Heave Model ..................................................................................... 92 4.7.3 Revised Frost Heave Model .................................................................................. 96 4.7.4 Discussion of the Results of the Revised Frost Heave Model ............................... 97 4.7.5 Heave Pressure .................................................................................................... 104 Chapter 5 - Conclusions .............................................................................................................. 108 5.1 Summary .....................................................................................................................
Load more

Recommended publications
  • Controls of Soil Organic Matter on Soil Thermal Dynamics in the Northern High Latitudes
    ARTICLE https://doi.org/10.1038/s41467-019-11103-1 OPEN Controls of soil organic matter on soil thermal dynamics in the northern high latitudes Dan Zhu 1, Philippe Ciais 1, Gerhard Krinner 2, Fabienne Maignan 1, Albert Jornet Puig1 & Gustaf Hugelius3,4 Permafrost warming and potential soil carbon (SOC) release after thawing may amplify climate change, yet model estimates of present-day and future permafrost extent vary widely, 1234567890():,; partly due to uncertainties in simulated soil temperature. Here, we derive thermal diffusivity, a key parameter in the soil thermal regime, from depth-specific measurements of monthly soil temperature at about 200 sites in the high latitude regions. We find that, among the tested soil properties including SOC, soil texture, bulk density, and soil moisture, SOC is the dominant factor controlling the variability of diffusivity among sites. Analysis of the CMIP5 model outputs reveals that the parameterization of thermal diffusivity drives the differences in simulated present-day permafrost extent among these models. The strong SOC-thermics coupling is crucial for projecting future permafrost dynamics, since the response of soil temperature and permafrost area to a rising air temperature would be impacted by potential changes in SOC. 1 Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Gif Sur Yvette 91191, France. 2 CNRS, Univ. Grenoble Alpes, Institut de Géosciences de l’Environnement (IGE), Grenoble 38000, France. 3 Department of Physical Geography, Stockholm University, Stockholm 10691, Sweden. 4 Bolin Centre for Climate Research, Stockholm University, Stockholm 10691, Sweden. Correspondence and requests for materials should be addressed to D.Z.
    [Show full text]
  • Edaphic and Microclimatic Controls Over Permafrost Response to Fire in Interior Alaska
    Home Search Collections Journals About Contact us My IOPscience Edaphic and microclimatic controls over permafrost response to fire in interior Alaska This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2013 Environ. Res. Lett. 8 035013 (http://iopscience.iop.org/1748-9326/8/3/035013) View the table of contents for this issue, or go to the journal homepage for more Download details: IP Address: 137.229.80.42 The article was downloaded on 22/07/2013 at 18:39 Please note that terms and conditions apply. IOP PUBLISHING ENVIRONMENTAL RESEARCH LETTERS Environ. Res. Lett. 8 (2013) 035013 (12pp) doi:10.1088/1748-9326/8/3/035013 Edaphic and microclimatic controls over permafrost response to fire in interior Alaska Dana R Nossov1,2, M Torre Jorgenson3, Knut Kielland1,2 and Mikhail Z Kanevskiy4 1 Department of Biology and Wildlife, University of Alaska Fairbanks, PO Box 756100, Fairbanks, AK 99775, USA 2 Institute of Arctic Biology, University of Alaska Fairbanks, PO Box 757000, Fairbanks, AK 99775, USA 3 Alaska Ecoscience, 2332 Cordes Drive, Fairbanks, AK 99709, USA 4 Institute of Northern Engineering, University of Alaska Fairbanks, PO Box 755910, Fairbanks, AK 99775, USA E-mail: [email protected] Received 20 April 2013 Accepted for publication 21 June 2013 Published 10 July 2013 Online at stacks.iop.org/ERL/8/035013 Abstract Discontinuous permafrost in the North American boreal forest is strongly influenced by the effects of ecological succession on the accumulation of surface organic matter, making permafrost vulnerable to degradation resulting from fire disturbance.
    [Show full text]
  • The Influence of Shallow Taliks on Permafrost Thaw and Active Layer
    PUBLICATIONS Journal of Geophysical Research: Earth Surface RESEARCH ARTICLE The Influence of Shallow Taliks on Permafrost Thaw 10.1002/2017JF004469 and Active Layer Dynamics in Subarctic Canada Key Points: Ryan Connon1 , Élise Devoie2 , Masaki Hayashi3, Tyler Veness1, and William Quinton1 • Shallow, near-surface taliks in subarctic permafrost environments 1Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, Ontario, Canada, 2Department of Civil and fl in uence active layer thickness by 3 limiting the depth of freeze Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada, Department of Geoscience, University of • Areas with taliks experience more Calgary, Calgary, Alberta, Canada rapid thaw of underlying permafrost than areas without taliks • Proportion of areas with taliks can Abstract Measurements of active layer thickness (ALT) are typically taken at the end of summer, a time increase in years with high ground synonymous with maximum thaw depth. By definition, the active layer is the layer above permafrost that heat flux, potentially creating tipping point for permafrost thaw freezes and thaws annually. This study, conducted in peatlands of subarctic Canada, in the zone of thawing discontinuous permafrost, demonstrates that the entire thickness of ground atop permafrost does not always refreeze over winter. In these instances, a talik exists between the permafrost and active layer, and ALT Correspondence to: must therefore be measured by the depth of refreeze at the end of winter. As talik thickness increases at R. Connon, the expense of the underlying permafrost, ALT is shown to simultaneously decrease. This suggests that the [email protected] active layer has a maximum thickness that is controlled by the amount of energy lost from the ground to the atmosphere during winter.
    [Show full text]
  • Effect of Soil Property Uncertainties on Permafrost Thaw Projections: a Calibration-Constrained Analysis
    The Cryosphere, 10, 341–358, 2016 www.the-cryosphere.net/10/341/2016/ doi:10.5194/tc-10-341-2016 © Author(s) 2016. CC Attribution 3.0 License. Effect of soil property uncertainties on permafrost thaw projections: a calibration-constrained analysis D. R. Harp1, A. L. Atchley1, S. L. Painter2, E. T. Coon1, C. J. Wilson1, V. E. Romanovsky3, and J. C. Rowland1 1Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA 2Climate Change Science Institute, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA 3Geophysical Institute, University of Alaska Fairbanks, USA Correspondence to: D. R. Harp ([email protected]) Received: 5 May 2015 – Published in The Cryosphere Discuss.: 29 June 2015 Revised: 15 January 2016 – Accepted: 19 January 2016 – Published: 11 February 2016 Abstract. The effects of soil property uncertainties on per- peat residual saturation. By comparing the ensemble statis- mafrost thaw projections are studied using a three-phase sub- tics to the spread of projected permafrost metrics using dif- surface thermal hydrology model and calibration-constrained ferent climate models, we quantify the relative magnitude uncertainty analysis. The null-space Monte Carlo method of soil property uncertainty to another source of permafrost is used to identify soil hydrothermal parameter combina- uncertainty, structural climate model uncertainty. We show tions that are consistent with borehole temperature measure- that the effect of calibration-constrained uncertainty in soil ments at the study site, the Barrow Environmental Obser- properties, although significant, is less than that produced by vatory. Each parameter combination is then used in a for- structural climate model uncertainty for this location.
    [Show full text]
  • Monitoring of Active Layer Dynamics at a Permafrost Site on Svalbard Using Multi-Channel Ground-Penetrating Radar
    The Cryosphere, 4, 475–487, 2010 www.the-cryosphere.net/4/475/2010/ The Cryosphere doi:10.5194/tc-4-475-2010 © Author(s) 2010. CC Attribution 3.0 License. Monitoring of active layer dynamics at a permafrost site on Svalbard using multi-channel ground-penetrating radar S. Westermann1, U. Wollschlager¨ 2,*, and J. Boike1 1Alfred-Wegener-Institute for Polar and Marine Research, Telegrafenberg A43, 14473 Potsdam, Germany 2Institute of Environmental Physics, Ruprecht-Karls-University Heidelberg, 69120 Heidelberg, Germany *now at: UFZ – Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany Received: 11 March 2010 – Published in The Cryosphere Discuss.: 22 March 2010 Revised: 28 October 2010 – Accepted: 29 October 2010 – Published: 8 November 2010 Abstract. Multi-channel ground-penetrating radar is used to mafrost areas. The novel non-invasive technique is partic- investigate the late-summer evolution of the thaw depth and ularly useful when the thaw depth exceeds 1.5 m, so that it the average soil water content of the thawed active layer at a is hardly accessible by manual probing. In addition, multi- high-arctic continuous permafrost site on Svalbard, Norway. channel ground-penetrating radar holds potential for map- Between mid of August and mid of September 2008, five ping the latent heat content of the active layer and for esti- surveys have been conducted in gravelly soil over transect mating weekly to monthly averages of the ground heat flux lengths of 130 and 175 m each. The maximum thaw depths during the thaw period. range from 1.6 m to 2.0 m, so that they are among the deepest thaw depths recorded in sediments on Svalbard so far.
    [Show full text]
  • Geomorphology of the Northeast Planning Area, National Petroleum Reserve-Alaska
    GEOMORPHOLOGY OF THE NORTHEAST PLANNING AREA, NATIONAL PETROLEUM RESERVE-ALASKA. 2002 FINAL REPORT Prepared for ConocoPhillips Alaska, Inc. P.O. Box 100360 Anchorage, AK 995 10 And Anadarko Petroleum Corporation 3201 C Street, Suite 603 Anchorage, AK 99503 Prepared by M. Torre Jorgenson, Erik. R. Pullman, ABR, 1nc.-Environmental Research & Services PO Box 80410 Fairbanks, AK 99708 and Yuri L. Shu~ Dept. of Civil Engineering University of Alaska PO Box 755900 Fairbanks, AK 99775 April 2003 8 Printed on recycledpape,: EXECUTIVE SUMMARY When comparing relationships among- ice Permafrost development on the Arctic Coastal structures, lithofacies,-and terrain &its using data Plain in northern Alaska greatly affects the kom 31 cores (2-3 m), there were strong distribution of ground ice, engineering propetties relationships that can be used to partition the of the soil, ecological conditions at the ground variability in distribution of ice across the surface, lake-basin development, and response of landscape. Large differences were found in the the terrain to human activities. Of particular frequency of occurrence of the various ice interest for assessing potential impacts from oil structures among lithofacies: pore ice was nearly always associated with massive, inched, and development in the National Petroleum layered sands; lenticular and ataxitic ice were most ReserveAlaska (NPRA) are the identification of terrain relationships for predicting the nature and frequently associated with massive and layered distribution of ground ice across the landscape and fines, organic matrix ice was usually found in the evaluation of disturbance effects on permafrost. massive and layered organics and licfines. Accordingly, this study was designed to determine Reticulate ice was broadly distributed among fine the nature and abundance of ground ice at multiple and organic lithofacies.
    [Show full text]
  • Surface Permafrost Degradation to Soil Column Depth and Representation of Soil Organic Matter
    JOURNAL oF GEOPHYSICAL RESEARCH, VOL. 113, F02011, doi: 10.1029/2007JF000883, 2008 Sensitivity of a model projection of near-surface permafrost degradation to soil column depth and representation of soil organic matter David M. Lawrence,1 Andrew G. Slater,2 Vladimir E. Romanovsky,3 and Dmitry 1. Nicolsky3 Received 31 July 2007; revised 16 January 2008; accepted 21 February 2008; published 6 May 2008. [I] The sensitivity of a global land-surface model projection of near-surface permafrost degradation is assessed with respect to explicit accounting of the thermal and hydrologic properties of soil organic matter and to a deepening of the soil column from 3.5 to 50 or more m. Together these modifications result in substantial improvements in the simulation of near-surface soil temperature in the Community Land Model (CLM). When forced off-line with archived data from a fully coupled Community Climate System Model (CCSM3) simulation of 20th century climate, the revised version of CLM produces a 6 2 near-surface permafrost extent of 10.7 X 10 km (north of 45°N). This extent represents an improvement over the 8.5 x 106 km2 simulated in the standard model and compares reasonably with observed estimates for continuous and discontinuous permafrost area (11 .2 - 13.5 x 106 km2), The total extent in the new model remains lower than observed because of biases in CCSM3 air temperature and/or snow depth. The rate of near-surface permafrost degradation, in response to strong simulated Arctic warming (~ +7.5oC over Arctic land from 1900 to 2100, A IB greenhouse gas emissions scenario), is slower in the improved version of CLM, particularly during the early 21 st century (81,000 2 versus 111,000 km a-1, where a is years).
    [Show full text]
  • Reproducing Field-Scale Active Layer Thaw in the Laboratory Aaron A
    Technical Note Reproducing Field-Scale Active Layer Thaw in the Laboratory Aaron A. Mohammed,* Robert A. Schincariol, Ranjeet M. Nagare, and William L. Quinton A method to simulate freeze–thaw and permafrost conditions on a large peat-soil column, housed in a biome, was developed. The design limits ambient temperature interference and maintains one-dimensional freezing and thawing. An air circulation system, in a cavity surrounding the active layer, allows manipulation of the lateral temperature boundary by actively maintaining an air temperature matching the average temperature of the A method is presented to maintain soil column. Replicating realistic thermal boundary conditions enabled field-scale rates of active-layer thaw. Radial temperature gradients were one-dimensional heat transport in small and temperature profiles mimicked those for similar field conditions. variably saturated soil cells over The design allows complete control of key hydrologic processes related to freezing and thawing tempera- heat and water movement in permafrost terrains without scaling require- tures. It applies transient thermal ment; and presents a path forward for the large-scale experimental study boundary conditions and repli- of frozen ground processes. Because subarctic ecosystems are very vulner- able to climate and anthropogenic disturbances, the ability to simulate cates field-scale ground thaw. The perturbations to natural systems in the laboratory is particularly important. method allows the isolated study of coupled heat and transport in Abbreviations: ATI, ambient temperature interference. permafrost environments. Permafrost and active-layer processes occur over approximately 25% of the Earth’s surface (Williams and Smith, 1989) and play a vital role in the hydrologic func- tioning of northern watersheds (Woo and Winter, 1993).
    [Show full text]
  • Simulation of Soil Freezing and Thawing for Different Groundwater
    Published March 14, 2019 Original Research Core Ideas Simulation of Soil Freezing and Thawing • The SHAW model was used to simu- for Different Groundwater Table Depths late the freeze–thaw process during freeze–thaw periods. Junfeng Chen,* Xuguang Gao, Xiuqing Zheng, • It revealed the effects of soil texture Chunyan Miao, Yongbo Zhang, Qi Du, and Yongxin Xu and groundwater table depth on soil freezing and thawing. During freeze–thaw periods, the transformation between phreatic water and • The frost depth and accumulated soil water will change the soil hydrothermal properties and affect the soil freez- negative soil surface temperature ing and thawing in shallow groundwater areas. The purpose of this study was to relationship was determined. determine the effect of four different groundwater table depths (GTDs) and two soil textures on the process of soil freezing and thawing during two successive freeze–thaw periods using the Simultaneous Heat and Water (SHAW) model. The results show that the frost depth was the maximum when the GTD was 1.0 m, and the maximum frost depths of sandy loam and fine sand were 97.6 and 98.9 cm, respectively. When the GTD was larger than 1.5 m, the maximum frost depth decreased with an increase in GTD, and the maximum frost depth of the soil pro- file was more sensitive to changes in the air temperature. The frost depth of the soil profile was linear with the square root of the accumulated negative soil sur- face temperature (ANST) under different GTDs. The ANST was influenced by the phreatic evaporation, and the soil freezing rate increased with an increase in GTD under the same ANST.
    [Show full text]
  • Experimentally Increased Nutrient Availability at the Permafrost Thaw Front Selectively Enhances Biomass Production of Deep-Rooting Subarctic Peatland Species
    Received: 19 December 2016 | Accepted: 31 May 2017 DOI: 10.1111/gcb.13804 PRIMARY RESEARCH ARTICLE Experimentally increased nutrient availability at the permafrost thaw front selectively enhances biomass production of deep-rooting subarctic peatland species Frida Keuper1,2,3 | Ellen Dorrepaal1,2 | Peter M. van Bodegom1,4 | Richard van Logtestijn1 | Gemma Venhuizen1 | Jurgen van Hal1 | Rien Aerts1 1Systems Ecology, Department of Ecological Science, VU University Amsterdam, Abstract Amsterdam, The Netherlands Climate warming increases nitrogen (N) mineralization in superficial soil layers (the 2Department of Ecology and Environmental dominant rooting zone) of subarctic peatlands. Thawing and subsequent mineraliza- Science, Climate Impacts Research Centre, Umea University, Abisko, Sweden tion of permafrost increases plant-available N around the thaw-front. Because plant 3UR1158 AgroImpact, INRA, Barenton- production in these peatlands is N-limited, such changes may substantially affect net Bugny, France primary production and species composition. We aimed to identify the potential 4Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands impact of increased N-availability due to permafrost thawing on subarctic peatland plant production and species performance, relative to the impact of increased N-avail- Correspondence Frida Keuper, UR1158 AgroImpact, INRA, ability in superficial organic layers. Therefore, we investigated whether plant roots are Barenton-Bugny, France. present at the thaw-front (45 cm depth) and whether N-uptake (15N-tracer) at the Email: [email protected] thaw-front occurs during maximum thaw-depth, coinciding with the end of the grow- Funding information ing season. Moreover, we performed a unique 3-year belowground fertilization experi- Darwin Centre for Biogeosciences, Grant/ Award Number: grant 142.161.042, grant ment with fully factorial combinations of deep- (thaw-front) and shallow-fertilization FP6 506004; EU-ATANS, Grant/Award (10 cm depth) and controls.
    [Show full text]
  • Ecological Response to Permafrost Thaw and Consequences for Local and Global Ecosystem Services
    ES49CH13_Schuur ARI 26 September 2018 13:58 Annual Review of Ecology, Evolution, and Systematics Ecological Response to Permafrost Thaw and Consequences for Local and Global Ecosystem Services Edward A.G. Schuur and Michelle C. Mack Center for Ecosystem Science and Society, and Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona 86011, USA; email: [email protected] Annu. Rev. Ecol. Evol. Syst. 2018. 49:279–301 Keywords The Annual Review of Ecology, Evolution, and carbon, nutrient, climate, vegetation change, disturbance, Arctic Systematics is online at ecolsys.annualreviews.org ecosystem, boreal ecosystem https://doi.org/10.1146/annurev-ecolsys-121415- 032349 Abstract Copyright c 2018 by Annual Reviews. The Arctic may seem remote, but the unprecedented environmental changes All rights reserved occurring there have important consequences for global society. Of all Arc- tic system components, changes in permafrost (perennially frozen ground) are one of the least documented. Permafrost is degrading as a result of cli- Access provided by University of Alaska - Fairbanks on 02/04/19. For personal use only. Annu. Rev. Ecol. Evol. Syst. 2018.49:279-301. Downloaded from www.annualreviews.org mate warming, and evidence is mounting that changing permafrost will have significant impacts within and outside the region. This review asks: What are key structural and functional properties of ecosystems that interact with changing permafrost, and how do these ecosystem changes affect local and global society? Here, we look beyond the classic definition of permafrost to include a broadened focus on the composition of frozen ground, including the ice and the soil organic carbon content, and how it is changing.
    [Show full text]
  • Effects of Soil Freezing and Thawing on Vegetation Carbon Density in Siberia
    GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 21, GB1012, doi:10.1029/2006GB002760, 2007 Click Here for Full Article Effects of soil freezing and thawing on vegetation carbon density in Siberia: A modeling analysis with the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM) C. Beer,1,2 W. Lucht,3 D. Gerten,3 K. Thonicke,4 and C. Schmullius1 Received 18 May 2006; revised 8 November 2006; accepted 16 November 2006; published 20 February 2007. [1] The current latitudinal gradient in biomass suggests a climate-driven limitation of biomass in high latitudes. Understanding of the underlying processes, and quantification of their relative importance, is required to assess the potential carbon uptake of the biosphere in response to anticipated warming and related changes in tree growth and forest extent in these regions. We analyze the hydrological effects of thawing and freezing of soil on vegetation carbon density (VCD) in permafrost-dominated regions of Siberia using a process-based biogeochemistry-biogeography model, the Lund- Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM). The analysis is based on spatially explicit simulations of coupled daily thaw depth, site hydrology, vegetation distribution, and carbon fluxes influencing VCD subject to climate, soil texture, and atmospheric CO2 concentration. LPJ represents the observed high spring peak of runoff of large Arctic rivers, and simulates a realistic fire return interval of 100 to 200 years in Siberia. The simulated VCD changeover from taiga to tundra is comparable to inventory-based information. Without the consideration of freeze-thaw processes VCD would be overestimated by a factor of 2 in southern taiga to a factor of 5 in northern forest tundra, mainly because available soil water would be overestimated with major effects on fire occurrence and net primary productivity.
    [Show full text]