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Implications of measurement metrics on soil freezing curves: A simulation of freeze-thaw hysteresis
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  • Renato Pardo Lara,
  • Aaron Berg,
  • Jon Warland,
  • Gary Parkin
Renato Pardo Lara
University of Guelph
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Aaron Berg
University of Guelph
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Jon Warland
University of Guelph
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Gary Parkin
University of Guelph
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Abstract

Soil freeze-thaw events have important implications for water resources, flood risk, land productivity, and climate change. A property of these phenomena is the relationship between unfrozen water content and sub-freezing temperature, known as the soil freezing characteristic curve (SFC). It is documented that this relationship exhibits hysteretic behaviour when frozen soil thaws, leading to the definition of the soil thawing characteristic curve (STC). Although explanations have been given for SFC/STC hysteresis, the effect that “scale”—particularly “measurement scale”—may have on these curves has received little attention. The most commonly used measurement scale metric is the “grain” or “support,” which is the spatial (or temporal) unit within which the measured variable is integrated—in this case, the soil volume sampled. We show (1) measurement support can influence the range and shape of the SFC and (2) hysteresis can be, at least partially, attributed to the support and location of the measurements comprising the SFC/STC. We simulated lab measured temperature, volumetric water content (VWC), and permittivity from soil samples undergoing freeze-thaw transitions using Hydrus-1D and a modified Dobson permittivity model. To assess the effect of measurement support and location on SFC/STC, we masked the simulated temperature and VWC/permittivity extent to match the instrument’s grain and location. By creating a detailed simulation of the intra- and inter-grain variability associated with the penetration of a freezing front, we demonstrate how measurement support and location can influence the temperature range over which water freezing events are captured. We show it is possible to simulate hysteresis in homogenous media with purely geometric considerations, suggesting that SFC/STC hysteresis may be more of an apparent phenomenon than mechanistically real. Lastly, we develop an understanding of how the location and support of soil temperature and VWC/permittivity measurements influence the temperature range over which water freezing events are captured.

Peer review status:IN REVISION

04 Nov 2020Submitted to Hydrological Processes
06 Nov 2020Submission Checks Completed
06 Nov 2020Assigned to Editor
06 Nov 2020Reviewer(s) Assigned
11 Feb 2021Review(s) Completed, Editorial Evaluation Pending
13 Feb 2021Editorial Decision: Revise Major
13 Apr 20211st Revision Received
13 Apr 2021Submission Checks Completed
13 Apr 2021Assigned to Editor
13 Apr 2021Reviewer(s) Assigned
16 May 2021Review(s) Completed, Editorial Evaluation Pending
27 May 2021Editorial Decision: Revise Minor
02 Jun 20212nd Revision Received
02 Jun 2021Reviewer(s) Assigned
02 Jun 2021Submission Checks Completed
02 Jun 2021Assigned to Editor