B120-01
Empirical model for estimating hydraulic properties of the organic-rich arctic permafrost soils

Wednesday, 16 December 2020: 08:30
Virtual
Kazem Bakian Dogaheh1, Yonghong Yi2, Richard H Chen3, Yuhuan Zhao1, Mahta Moghaddam1 and Alireza Tabatabaeenejad1, (1)University of Southern California, Ming Hsieh Department of Electrical and Computer Engineering, Los Angeles, CA, United States, (2)University of California Los Angeles, Joint Institue for Regional Earth System Science and Engineering, Los Angeles, CA, United States, (3)Jet Propulsion Laboratory, Pasadena, CA, United States
Abstract:
Recent evidence shows that the warming trend in the northern circumpolar region, which is underlain in many places by permafrost, is unfolding twice as fast as in the temperate zone. This could potentially release the sequestered carbon in the perennially frozen soil layers and expose it to microbial activity, which will result in increased emission of greenhouse gases and, in turn, of positive feedback to the global climate system. The current predictions of the carbon feedback, however, show a large uncertainty due to poorly constrained ecosystem models and observational data gaps related to permafrost soil properties and their dynamics.

Understanding the hydrologic processes in the arctic permafrost active layer, which has high organic matter content, is crucial to studying the carbon losses due to permafrost thawing. However, the arctic soil hydraulic characteristics are generally not sufficiently represented in Earth system models. The existence of organic matter content and its decomposition rate can substantially impact the hydraulic and thermal properties of the soil.

In this work, we will present a newly developed pedo-transfer function (PTF) to find the van Genuchten model parameters based on soil physical properties. We will also show the behavior of the SWRC parameters along the active layer profile. This new parameterization has been developed based on a set of experiments performed on a large number of samples we have collected along Alaska’s Dalton Highway in the foothills of the Brooks Range. A detailed soil textural and decomposition rate analysis has been performed on the samples in support of this parameterization. The performance of the reconstructed SWRC based on the new PTF is evaluated against the water matric potential measurement for a full range of soil moisture content for corresponding soil samples, and the results show good agreement between model and measurement. Our finding shows SWRC’s parameters are highly correlated to the soil sample's porosity and SWRC behavior for highly organic samples is governed by the organic matter decomposition stage and its fiber content.

The results of this work provide an experimental model for estimating active layer soil hydraulic properties that can be broadly applicable to Arctic permafrost soils.

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