Active layer thickness as a function of soil water content

Active layer thickness (ALT) is a critical metric for monitoring permafrost. How soil moisture influences ALT depends on two competing hypotheses: (a) increased soil moisture increases the latent heat of fusion for thaw, resulting in shallower active layers, and (b) increased soil moisture increases...

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Published in:Environmental research letters Vol. 16; no. 5; pp. 55028 - 55036
Main Authors: Clayton, Leah K, Schaefer, Kevin, Battaglia, Michael J, Bourgeau-Chavez, Laura, Chen, Jingyi, Chen, Richard H, Chen, Albert, Bakian-Dogaheh, Kazem, Grelik, Sarah, Jafarov, Elchin, Liu, Lin, Michaelides, Roger John, Moghaddam, Mahta, Parsekian, Andrew D, Rocha, Adrian V, Schaefer, Sean R, Sullivan, Taylor, Tabatabaeenejad, Alireza, Wang, Kang, Wilson, Cathy J, Zebker, Howard A, Zhang, Tingjun, Zhao, Yuhuan
Format: Journal Article
Language:English
Published: Bristol IOP Publishing 01.05.2021
Subjects:
active layer thickness
Alaska
Environmental monitoring
ENVIRONMENTAL SCIENCES
Heat
Heat conductivity
Heat of fusion
Heat transfer
Hypotheses
Latent heat
Moisture content
Permafrost
Soil conductivity
Soil investigations
Soil layers
Soil moisture
Soil temperature
Soil water
thaw depth
Thermal conductivity
Thickness
Water content
Canada
United States > US
Alaska
ISSN:1748-9326, 1748-9326
Online Access:Get full text
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Summary:Active layer thickness (ALT) is a critical metric for monitoring permafrost. How soil moisture influences ALT depends on two competing hypotheses: (a) increased soil moisture increases the latent heat of fusion for thaw, resulting in shallower active layers, and (b) increased soil moisture increases soil thermal conductivity, resulting in deeper active layers. To investigate their relative influence on thaw depth, we analyzed the Field Measurements of Soil Moisture and Active Layer Thickness (SMALT) in Alaska and Canada dataset, consisting of thousands of measurements of thaw depth and soil moisture collected at dozens of sites across Alaska and Canada as part of NASA’s Arctic Boreal Vulnerability Experiment (ABoVE). As bulk volumetric water content (VWC) integrated over the entire active layer increases, ALT decreases, supporting the latent heat hypothesis. However, as VWC in the top 12 cm of soil increases, ALT increases, supporting the thermal conductivity hypothesis. Regional temperature variations determine the baseline thaw depth while precipitation may influence the sensitivity of ALT to changes in VWC. Soil latent heat dominates over thermal conductivity in determining ALT, and the effect of bulk VWC on ALT appears consistent across sites.
Bibliography:ERL-109655.R2
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National Aeronautics and Space Administration (NASA)
89233218CNA000001; NNX10AR63G; NNX06AE65G; NNX13AM25G; NNX17AC59A; NA09OAR4310063; ARC 1204167; 80NSSC18K0983
National Science Foundation (NSF)
LA-UR-21-22253
USDOE Office of Science (SC). Biological and Environmental Research (BER)
National Oceanic and Atmospheric Administration (NOAA)
ISSN:1748-9326
1748-9326
DOI:10.1088/1748-9326/abfa4c