Staff Research Highlight - Assessment of hydraulic and thermal properties of the Antarctic active layer: Insights from laboratory column experiments and inverse modelling
Kim, J., Hwang, H.-T., Lee, J., Illman, W. A., & Jeen, S.-W. (2024). Assessment of hydraulic and thermal properties of the Antarctic active layer: Insights from laboratory column experiments and inverse modeling. In Science of The Total Environment (Vol. 937, p. 173474). Elsevier BV. https://doi.org/10.1016/j.scitotenv.2024.173474
“To simulate the freezing and thawing processes specifically, we utilized the one-dimensional analytical solution implemented in HGS.”
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We’re pleased to highlight this publication, co-authored by Aquanty’s senior scientist, Hyoun-Tae Hwang, which investigates the hydraulic and thermal properties of the Antarctic active layer using laboratory column experiments and HydroGeoSphere (HGS) for inverse modelling. This work provides crucial insights into the dynamics of groundwater flow and freeze-thaw processes in Antarctica's Barton Peninsula, a region significantly impacted by climate change.
By leveraging HGS combined with the popular model-independent Parameter ESTimation and uncertainty analysis tool (PEST), the researchers accurately determined key hydraulic and thermal parameters of soils collected from two lakes in the Barton Peninsula. These include saturated hydraulic conductivity, van Genuchten parameters, specific storage, and thermal diffusivity. Laboratory freeze-thaw and saturation-drain experiments were conducted under controlled conditions, simulating the unique environmental conditions of Antarctica.
Findings highlighted that the soils’ hydraulic and thermal properties varied significantly, influenced by factors such as porosity, organic matter, and particle size distribution. For example, thermal diffusivity was higher in sandy soils than in organic-rich samples. Additionally, freeze-thaw cycles were found to significantly alter the water flow and temperature profiles in the active layer, emphasizing the necessity of accurately modelling these interactions for understanding groundwater dynamics in polar regions.
This research emphasizes the importance of integrating laboratory experimentation with advanced numerical modelling to characterize the active layer's hydrological behavior, which is essential for predicting the impacts of climate change on polar water systems. The insights gained have profound implications for understanding groundwater-surface water interactions and managing polar hydrological systems effectively in a changing climate.
“Inverse modelling by coupling HGS with Parameter ESTimation (PEST) (Doherty, 2004) was performed to estimate optimum parameters. PEST has been used to estimate parameters or calibrate various numerical models (Lawrence et al., 2009).”
Abstract:
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 modelling. 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 modelling 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., Ks, θs, Swr, α, β, and Ss) 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 modelling, were 1.6 × 10−5–3.4 × 10−4 cm s−1 for Ks, 0.37–0.42 for θs, 6.62 × 10−3–1.05 × 10−2 for Swr, 0.53–0.58 cm−1 for α, 5.75–7.96 for β, and 5.11 × 10−5–9.02 × 10−5 cm−1 for Ss. The thermal diffusivities for the soils were estimated to be 0.65–4.64 cm2 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 freeze-thaw processes.