Characterizing The Complex Dielectric Properties Of Permafrost Across Freeze-Thaw Cycles
Research Poster Engineering 2025 Graduate ExhibitionPresentation by MD Mashfiqur Rahman
Exhibition Number 38
Abstract
Remote sensing in the Arctic regions is an essential tool for tracking the changing landscapes due to climate change, employing a wide range of frequencies in the electromagnetic spectrum to assess the condition of permafrost. Permafrost is a complex material of solid, liquid, gas, organic, and inorganic phases with each constituent contributing to the broadband dielectric response. In this study, permafrost was synthesized from sand, silt, and clay mixed with various amounts of water. Various weight fractions of permafrost/water mixtures were prepared by mixing sand, silt, and clay with different amounts of water. Microwave characterization and IR spectroscopy were subsequently performed on these mixtures to analyze their properties. The dielectric permittivity and loss of individual permafrost constituents in the dry and wet states were measured from radio frequency to infrared, using various reflection and transmission techniques. A coax reflection method was developed to provide complex dielectric data between 200 MHz and 26 GHz over a temperature range from 25 to -15 C. Dry constituents had low permittivity (r< 5) and low dielectric loss (tan < 0.02). Wet constituents had high permittivity (10<r< 40) and there was a significant dielectric relaxation in the GHz frequency due to the dipolar state of water. Linking broadband dielectric and thermodynamic responses of water-organic and water-inorganic interfaces in permafrost will provide critical insight into the dipolar mechanisms governing permittivity and loss during the freeze-thaw cycle.
Importance
This study focuses on understanding the unique properties of permafrost, a frozen soil mixture found in Arctic regions, which is increasingly affected by climate change. By creating artificial permafrost and studying its behavior, researchers can better mimic natural Arctic conditions. The findings will improve remote sensing techniques, which use electromagnetic waves to monitor the Arctic landscape. This is crucial for tracking environmental changes, predicting the effects of thawing permafrost, and safeguarding ecosystems. The study also bridges laboratory experiments and real-world Arctic conditions, offering data that help scientists refine models for more accurate predictions. Ultimately, this research aids in developing tools to monitor and manage the effects of climate change on fragile Arctic environments