5-5 From Freeze to Flow: Soil Moisture and Thermal Dynamics in Thawing Permafrost Regimes

Session: Advances in Mountain Hydrology: Connecting Cryosphere, Surface, and Subsurface Processes

Presenting Author:

Ruben Keane

Authors:

Keane, Ruben¹, Baxter, Brad², Barbato, Robyn³, Brehm, Elise⁴, Douglas, Thomas⁵, Maakestad, Jon⁶, Sullivan, Taylor⁷, Vas, Dragos⁸, Barker, Amanda⁹

Abstract:

Across Arctic and sub-Arctic regions, permafrost degradation and active layer thickening continue to reshape terrestrial and aquatic ecosystems by altering soil water content and biogeochemical processes. Understanding the mechanisms behind these effects requires constraining thermal and moisture regimes with respect to the full soil profile. While significant research has targeted soil moisture dynamics and permafrost degradation using remote-sensing data and spot observations, many studies overlook spatial heterogeneity and seasonal variability throughout the entire subsurface. As a result, findings are often limited in their applicability at broader, map-based scales. Model input parameters representing permafrost degradation typically rely on surface or shallow subsurface observations that may not reflect the complexity of deeper soil conditions. Additionally, uncertainties linked to sample heterogeneity, field collection, and laboratory processing remain understudied, despite their importance in assessing biogeochemical shifts caused by permafrost thaw. To address these limitations, we integrate spot observations, soil texture classification, and continuous in-situ soil moisture data collected throughout the active layer thickness from seven field sites previously examined in similar studies. Our approach aims to better constrain temporal moisture dependencies on soil type, thermal regime, and depth within thawing permafrost environments, and to identify which soil properties are most affected. Preliminary results show that soil moisture content is strongly influenced by soil composition and seasonal freeze–thaw dynamics. Moss and peat soils exhibit high variability near the surface, while mineral and disturbed soils retain greater moisture at depth. As active layers deepen, water infiltration patterns shift into newly thawed zones. These transitions carry important implications for subsurface biogeochemistry, including metal transport and rare-earth element mobilization into groundwater. Future work will focus on quantifying the influence of predictor variables such as soil permeability, hydraulic conductivity, bulk electrical conductivity, pH, texture, and respiration. These data will improve modeling frameworks for evaluating soil moisture and thermal processes across Arctic soils. Our goal is not to dismiss shallow or remote-sensing studies but to contribute to a more robust, subsurface-informed framework for understanding evolving Arctic soil environments in an altered thermal regime.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9328

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