Arctic Soil Column Saturation & Drainage Experiment for Biogeochemical Redox Dynamics; Council, Alaska 2020-2022

Land subsidence and changing hydrology due to permafrost thaw causes saturated thermokarst channels to develop across many Arctic landscapes. Formation of thermokarst channels shifts soil biogeochemical redox dynamics and impacts carbon dioxide (CO2) and methane (CH4) fluxes. This experimental study explores how soil saturation and drainage drives biogeochemical redox cycling and carbon decomposition in two soil types collected from the NGEE-Arctic field site in Council, Alaska. Soil cores were collected from a wet, upland soil overlain by low shrubs and tussocks and a saturated, thermokarst soil dominated by sedge. After removing surface vegetation, two cores for each soil type were homogenized across geochemically similar depth increments and packed into a PVC tube instrumented with volumetric water content (VWC) sensors, oxygen (O2) sensors, temperature sensors, and microrhizon porewater samplers. Then each experiment (upland and thermokarst) underwent three experimental phases: drainage 1, saturation, and drainage 2. During the 90 day experiments, VWC and O2 were measured continuously and porewater samplers were used for discrete measurements of pH, ferrous and total iron (Fe), dissolved organic carbon (DOC) and SUVA, and other dissolved species. Headspace samples in the the column were used to determine fluxes of CO2 and CH4. This dataset includes initial soil core geochemical characterization and column experiment continuous sensor measurements, outflow and porewater measurements, and gas flux measurements. Additional datasets include pre and post experiment soil geochemical measurements and microbial community analysis. The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).