Modeling Thermal and Biogeochemical Dynamics in Two Ponds Within Alaska's Yukon–Kuskokwim Delta: Impacts of Climatic Variability on Greenhouse Gas Fluxes

Abstract

Fluxes of carbon dioxide (CO₂) and methane (CH₄) from open water bodies are critical components of carbon-climate feedbacks in high latitudes. Processes governing the spatial and temporal variability of these aquatic greenhouse gas (GHG) fluxes are still highly uncertain due to limited observational data sets and lack of modeling studies incorporating comprehensive thermal and biochemical processes. This research investigates how slight variations in climate propagate through the biogeochemical cycles of ponds and resulting impacts on GHG emissions. We examine the thermal and biogeochemical dynamics of two ponds in the Yukon–Kuskokwim Delta, Alaska, under varying climatic conditions to study the impacts on CO₂, CH₄, and oxygen (O₂) concentrations and fluxes. We performed multiple numerical experiments, using the LAKE process-based model and field measurements, to analyze how these ponds respond to variations in air temperature, shortwave radiation, and snow cover. Our study demonstrates that ice cover duration and water temperature are primary climatic drivers of GHG fluxes. Climate experiments led to reductions in ice cover duration and increased water temperatures, which subsequently enhanced CH₄ and CO₂ gas emissions from two study ponds. On average, cumulative CH₄ and CO₂ emissions were 5% and 10% higher, respectively, under increases in air temperature and shortwave radiation. Additionally, we uncovered a need to incorporate groundwater influxes of dissolved gases and nutrients in order to fully represent processes governing aquatic biochemical activity. Our work highlights the importance of understanding local-scale processes in predicting future Arctic contributions to GHG emissions.