To better understand the changes in the hydrologic cycle caused by global warming in Antarctica, it is crucial to improve our understanding of the groundwater flow system, which has received less attention despite its significance. Both hydraulic and thermal properties of the active layer, through which groundwater can flow during thawing seasons, are essential to quantify the groundwater flow system. However, there has been insufficient information on the Antarctic active layer. The goal of this study was to estimate the hydraulic and thermal properties of Antarctic soils through laboratory column experiments and inverse modeling. The column experiments were conducted with sediments collected from two lakes in the Barton Peninsula, Antarctica. A sand column was also operated for comparison. Inverse modeling using HydroGeoSphere (HGS) combined with Parameter ESTimation (PEST) was performed with data collected from the column experiments, including permeameter tests, saturation -drain tests, and freeze -thaw tests. Hydraulic parameters (i.e., K s , theta s , S wr , alpha , beta, and S s ) and thermal diffusivity ( D ) of the soils were derived from water retention curves and temperature curves with depth, respectively. The hydraulic properties of the Antarctic soil samples, estimated through inverse modeling, were 1.6 x 10 - 5 -3.4 x 10 -4 cm s -1 for K s , 0.37 -0.42 for theta s , 6.62 x 10 - 3 -1.05 x 10 -2 for S wr , 0.53 -0.58 cm - 1 for alpha, 5.75 -7.96 for beta, and 5.11 x 10 - 5 -9.02 x 10 -5 cm - 1 for S s . The thermal diffusivities for the soils were estimated to be 0.65-4.64 cm 2 min -1 . The soil hydraulic and thermal properties reflected the physical and ecological characteristics of their lake environments. The results of this study can provide a basis for groundwater -surface water interaction in polar regions, which is governed by variably -saturated flow and freezethaw processes.

By altering the physical properties of soil through root activity, plants can act as important agents in affecting soil hydrothermal properties. However, we still know little about how plant roots regulate these properties in certain ecosystems, such as alpine meadows. Thus, we studied the influence of roots on soil hydrothermal properties in the Qinghai-Tibet Plateau (QTP). Root biomass as well as soil physicochemical and hydrothermal properties were examined at a depth of 0-30 cm at three study sites in the QTP. The relationship between root biomass and saturated soil hydraulic conductivity (K-s) was examined, as was the applicability of common soil hydrothermal properties models to the alpine meadow system. Results revealed that approximately 91.10%, 72.52%, and 76.84% of root biomass was located in the top 0-10 cm of soil at Maqu, Arou, and Naqu, respectively. Compared with the bulk soil, the water-holding capacity of rhizosphere soil was enhanced by 20%-50%, while K-s was decreased by at least 2- to 3-fold. The thermal conductivity (lambda) of rhizosphere soils was lower than that of the bulk soil by 0.23-0.82 W m(-1).K-1 on average. Lastly, soil hydrothermal properties models that do not explicitly consider root effects overestimated the Ks and lambda in the rhizosphere soil of these systems. Overall, our results revealed distinctive differences in soil hydrothermal properties between the rhizosphere soil and the bulk soil in the QTP. This research has important implications for future modeling of soil hydrothermal processes of alpine meadow soils.

Recently, there has been a revival in the development of models simulating coupled heat and water transport in cold regions. These models represent significant advances in our ability to simulate the sensitivity of permafrost environments to future climate change. However, there are considerable differences in model formulations arising from the diverse backgrounds of researchers and practitioners in this field. The variability in existing model formulations warrants a review and synthesis of the underlying theory to demonstrate the implicit assumptions and limitations of a particular approach. This contribution examines various forms of the Clapeyron equation, the relationship between the soil moisture curve and soil freezing curve, and processes for developing soil freezing curves and hydraulic conductivity models for partially frozen soils. Where applicable, results from recent laboratory tests are presented to demonstrate the validity of existing theoretical formulations. Identified variations in model formulations form the basis for briefly comparing and contrasting existing models. Several unresolved questions are addressed to highlight the need for further research in this rapidly expanding field. (C) 2013 Elsevier Ltd. All rights reserved.