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permafrost
Focus Topic: Permafrost and Cold Vadose Zone

Soil freeze–thaw affects physical and biological processes at scales ranging from the individual soil profile to vast regions. Interacting hydrological and mechanical processes alter the soil structure and control snowmelt infiltration and runoff. Soil microbial activity, nutrient cycling, and greenhouse gas emissions in permafrost regions are sensitive to soil temperature and moisture dynamics. Nutrients leached from rapidly thawed soil may affect surface and groundwater quality, especially in combination with enhanced erosion and sediment load. This focus topic will provide a platform for consideration of key aspects of soil freeze–thaw processes and related research challenges and opportunities in seasonally or permanently frozen environments.
Invited Review: Hydrologic Impacts of Thawing Permafrost—A Review
    by Michelle A. Walvoord and Barret L. Kurylyk
 
Jong-Sub Lee, Yong-Hoon Byun and Hyung-Koo Yoon
The elastic wave velocity and electrical resistivity of a medium are affected by changes in temperature, which can cause phase changes. The objective of this study was to predict the activation energy...more
 
Michelle A. Walvoord and Barret L. Kurylyk
Where present, permafrost exerts a primary control on water fluxes, flowpaths, and distribution. Climate warming and related drivers of soil thermal change are expected to modify the distribution of p...more
 
Yuki Kojima, Joshua L. Heitman, Gerald N. Flerchinger, Tusheng Ren and Robert Horton
Soil ice content is an important component for winter soil hydrology. The sensible heat balance (SHB) method using measurements from heat pulse probes (HPPs) is a possible way to determine transient s...more
 
Kunio Watanabe and Yurie Osada
Understanding the hydraulic conductivity of frozen soils near melting temperature is important in agricultural management and water balance calculation in cold regions and in the use of artificial gro...more
 
Yaning Liu, Gautam Bisht, Zachary M. Subin, William J. Riley and George Shu Heng Pau
We propose a hybrid reduced-order model that efficiently predicts fine-resolution responses to forcings by first training the model with solutions from a computationally intensive model. The method wa...more
 
Zhengchao Tian, Joshua Heitman, Robert Horton and Tusheng Ren
Determining soil ice content during freezing and thawing is important and challenging for both engineering and environmental issues. The thermo-time domain reflectometry (T-TDR) probe, which can monit...more
 
Yuki Kojima, Joshua L. Heitman, Gerald N. Flerchinger, Tusheng Ren, Robert P. Ewing and Robert Horton
Feasibility of the sensible heat balance (SHB) method for determining in situ soil ice content with heat pulse (HP) sensors was evaluated using field measurements. The required accuracy of HP sensor m...more
 
Aaron A. Mohammed, Robert A. Schincariol, Ranjeet M. Nagare and William L. Quinton
A method is presented to maintain one-dimensional heat transport in variably saturated soil cells over freezing and thawing temperatures. It applies transient thermal boundary conditions and replicate...more
 
Scott L. Painter and Satish Karra
A constitutive relation for phase partitioning of water in unsaturated frozen soils is proposed. This relation compares well with existing experimental data on unfrozen water content as a function of...more
 
Baptiste Dafflon, Susan S. Hubbard, Craig Ulrich and John E. Peterson
A novel approach has been developed to estimate the subsurface electrical conductivity distribution from electromagnetic induction data and evaluate influence of prior constraints, data information co...more