Groundwater controls on post-fire permafrost thaw: Water and energy balance effects

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1029/2018JF004611.

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Authors

Samuel C Zipper , Pierrick Lamontagne-Halle, Jeffrey M. McKenzie, Adrian Rocha

Abstract

Fire frequency and severity are increasing in high latitude regions, but the degree to which groundwater flow impacts the response of permafrost to fire remains poorly understood. Here, we use the Anaktuvuk River Fire (Alaska, USA) as an example for simulating groundwater-permafrost interactions following fire. We identify key thermal and hydrologic parameters controlling permafrost response to fire both with and without groundwater flow, and separate the relative influence of changes to the water and energy balances on active layer thickness. Our results show that mineral soil porosity, which influences the bulk subsurface thermal conductivity, is a key parameter controlling active layer response to fire in both the absence and presence of groundwater flow. However, neglecting groundwater flow increases the perceived importance of subsurface thermal properties, such as the thermal conductivity of soil solids, and decreases the perceived importance of hydrologic properties, such as the soil permeability. Furthermore, we demonstrate that changes to the energy balance (increased soil temperature) drive increased active layer thickness following fire, while changes to the water balance (decreased groundwater recharge) lead to reduced landscape-scale variability in active layer thickness and groundwater discharge to surface water features such as streams. These results indicate that explicit consideration of groundwater flow is critical to understanding how permafrost environments respond to fire.

DOI

https://doi.org/10.31223/osf.io/27s3z

Subjects

Earth Sciences, Environmental Sciences, Hydrology, Physical Sciences and Mathematics

Keywords

hydrogeology, groundwater, groundwater recharge, Cryosphere, Permafrost, fire, active layer, disturbance hydrology

Dates

Published: 2018-02-22 02:14

Last Updated: 2018-09-13 02:01

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License

CC BY Attribution 4.0 International

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