https://hdl.handle.net/10214/29060

We advance methodologies for monitoring ground surface freeze/thaw (F/T) detection, integrating laboratory pedology, field observations, and satellite remote sensing (RS) to enhance terrestrial cryosphere monitoring. The thesis addresses critical gaps stemming from reliance on static, intrinsic thresholds for F/T classification, advocating for and developing more accurate, scalable, and context-adaptive methods through a multiscale approach. Beginning with detailed characterization of soil moisture sensors in frozen, thawed, and transitional states in the laboratory, Chapter 2 introduces permittivity-based soil freezing characteristic curves (SFCCs) in agricultural fields. This approach improves the accuracy of F/T detection and deepens our understanding of the dynamics involved, serving as a tool for monitoring water resources in cold climate agriculture. The analysis in Chapter 3 reveals that the scale and location of soil moisture measurements can significantly influence the shape of SFCCs and their thawing branches known as soil thawing characteristic curves (STCCs). Through simulations and empirical data, we demonstrate that measurement support—the size of the spatial or temporal dimensions over which the sensor integrated the measured variable–affects the hysteresis captured in SFCCs and STCCs. These insights meaningfully enhance the robustness and applicability of models used in environmental and climate monitoring, emphasizing the need to understand measurement nuances to scale techniques effectively for field applications and beyond. Building on these ground-based methodologies, Chapter 4 explores the innovative integration of RS data with in situ temperature measurements and forecasts to monitor surface F/T state. By incorporating RS data into the SFCC paradigm, we introduce surface freezing characteristic curves (SurFCCs) and validate Soil Moisture Active Passive (SMAP) F/T products against in situ data, providing robust new tools for climate change monitoring. Overall, this thesis establishes new foundations in cryospheric monitoring, seasonally frozen soil physics, and environmental monitoring by integrating detailed pedological insights with advanced satellite remote sensing. These methodologies not only advance our understanding of the cryosphere’s response to climate changes but also refine techniques for practical applications in climate adaptation and resource management, marking significant progress in terrestrial cryosphere monitoring capabilities.

https://hdl.handle.net/10214/29060