Active layer thickness as a function of soil water content

Abstract Active layer thickness (ALT) is a critical metric for monitoring permafrost. How soil moisture influences ALT depends on two competing hypotheses: (a) increased increases the latent heat of fusion thaw, resulting in shallower active layers, and (b) thermal conductivity, deeper layers. To investigate their relative influence thaw depth, we analyzed Field Measurements Soil Moisture Layer Thickness (SMALT) Alaska Canada dataset, consisting thousands measurements depth collected at dozens sites across as part NASA’s Arctic Boreal Vulnerability Experiment (ABoVE). As bulk volumetric water content (VWC) integrated over entire increases, decreases, supporting hypothesis. However, VWC top 12 cm conductivity Regional temperature variations determine baseline while precipitation may sensitivity to changes VWC. dominates determining ALT, effect appears consistent sites.