DOI : https://doi.org/10.1016/j.jhydrol.2024.132285
- Neelarun Mukherjee1*
- Jingyi Chen1,2
- Bethany T. Neilson3
- George W. Kling4
- M. Bayani Cardenas1
- Department of Earth and Planetary Sciences, The University of Texas at Austin
- Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin
- Civil and Environmental Engineering and Utah Water Research Laboratory, Utah State University
- Department of Ecology and Evolutionary Biology, University of Michigan
Supra-permafrost aquifers within the active layer are present in the Arctic during summer. Permafrost thawing due to Arctic warming can liberate previously frozen particulate organic matter (POM) in soils to leach into groundwater as dissolved organic carbon (DOC). DOC transport from groundwater to surface water is poorly understood due to the unquantified variability in subsurface properties and hydrological environments. These dynamics must be better characterized, as DOC transport to surface waters is critical to predicting the long-term fate of recently thawed carbon in permafrost environments.
Here, we used distributed Darcy’s Law calculations to quantify groundwater and DOC fluxes into Imnavait Creek, Alaska, a representative headwater stream in a continuous permafrost watershed. We developed a statistical ensemble approach to model parameter variability and range of potential contributions of steady-state groundwater flow to the creek. We quantified model prediction uncertainty using statistical sampling of in-situ active-layer soil hydro-stratigraphy (water table, ice table, and soil stratigraphy), high-resolution topography data, and DOC data.
Moreover, predicted groundwater discharge values representing all possible hydrologic conditions towards the end of the thawing season were also considered, given potential variability in saturation. Model predictions were similar to and span most of the observed range of Imnavait Creek streamflow, especially during recession but also including most floods.
As the Arctic warms and supra-permafrost aquifers deepen, groundwater flow is expected to increase, impacting river and lake biogeochemical processes by mobilizing more soil constituents in continuous permafrost regions. This study highlights how quantifying the uncertainty of hydro-stratigraphical input parameters helps in understanding and predicting supra-permafrost aquifer dynamics and connectivity to aquatic systems using a simple, scalable modeling approach.