Groundwater-Dependent Fluxes of Water and Organic Carbon in a Permafrost Watershed Across Hydrologic States
Authors
Neelarun Mukherjee1* (neelarun@utexas.edu), Jingyi Chen1, Bethany T. Neilson2, George W. Kling3, M. Bayani Cardenas1
Institutions
1University of Texas−Austin, TX; 2Utah State University, Logan, UT; 3University of Michigan, Ann Arbor, MI
Abstract
Suprapermafrost aquifers within the active layer are present in the Arctic during summer. The exacerbated permafrost thaw rate due to global warming in the Arctic will liberate previously frozen particulate organic matter (POM). The POM leaches dissolved organic carbon (DOC), which gets transported through groundwater flow. How much DOC is delivered by groundwater into surface water remains uncertain. This input is critical to landscape budgets and for predicting the long term fate of carbon. The team quantified groundwater and DOC fluxes into a representative headwater stream of a continuous permafrost watershed—the Imnavait Creek (IC) in Alaska. This was done across thousands of scenarios represented by steady groundwater flow simulations based on high-resolution topography combined with aquifer transmissivity and DOC data. The predicted groundwater discharge values, which represent all possible hydrologic conditions excluding the freshet, are similar to and span the range of IC streamflow. Researchers also found that IC’s DOC may be entirely 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 suprapermafrost aquifer dynamics.