Supra-permafrost groundwater’s contribution to stream flow and
organic matter chemistry in the Arctic: estimation using combined
mechanistic and statistical approaches
Neelarun Mukherjee1, M. Bayani
Cardenas1, Jingyi Chen2, Bethany T.
Neilson3, and George Kling4.
- Department of Geological Sciences, University of Texas at Austin
- Aerospace Engineering Department, University of Texas at Austin
- Civil and Environmental Engineering, Utah State University
- Department of Ecology and Evolutionary Biology, University of Michigan
Abstract body:
Seasonally warm summers in the Arctic produce supra-permafrost aquifers
within the active layer. However, the magnitude of groundwater flow, the
amount of dissolved carbon and nutrients, and the solute flow paths are
largely unknown, but critical to quantifying downgradient contributions
to surface waters (lakes and rivers). To develop approachable methods to
quantify groundwater inputs in continuous permafrost watersheds, we
selected Imnavait Creek watershed on the North Slope of Alaska as a
representative headwater drainage. We conducted 1000 groundwater flow
simulations based on topography of the watershed and varying aquifer
hydraulic conductivity and saturated thickness values. We fitted a
lognormal distribution to the resulting 1000 model outputs, and we
derived n=1e6 possible discharge values based on Monte Carlo random
sampling on the model outputs. The groundwater discharge values
integrated across the watershed generally agree with observed streamflow
in Imnavait Creek over 2 months. When groundwater discharge estimates
were combined with in-situ measurements of groundwater dissolved organic
carbon and nitrogen concentrations, we found that Imnavait Creek’s
organic matter load is also dominantly sourced from groundwater. Thus,
riverine, and lacustrine ecological and biogeochemical processes relate
strongly to groundwater phenomena in these continuous permafrost
settings. As the Arctic warms and the active layer deepens, it will
become more important to understand and predict supra-permafrost aquifer
dynamics.