2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 102-1
Presentation Time: 8:00 AM


YOUNG, Michael, Bureau of Economic Geology, University of Texas at Austin, University Station, Box X, Austin, TX 78712, ABOLT, Charles J., Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, CALDWELL, Todd G., Jackson School of Geosciences, University of Texas at Austin, Bureau of Economic Geology, Univesity Station, Box X, Austin, TX 78758 and LARSON, Toti, Department of Geological Sciences, University of Texas at Austin, 10100 Burnet Road, Austin, TX 78713, michael.young@beg.utexas.edu

Perennially frozen soils cover ~17% of the global soil area and are estimated to hold over 1,000 Pg of soil organic carbon (SOC) within their top three meters, making it one of the world’s largest stocks of organic carbon. Studies predict varying extents to which ice-wedge polygons serve as carbon sources or sinks. Our goals are to generate a high-resolution data set of SOC stocks that incorporate the effects of cryoturbation and microtopographic land surface features and to use this information to predict mobility of carbon from soils within ice-wedge polygons to wetlands and thermokarst lakes in low-gradient watersheds. The field site is located 50 km south of Deadhorse, Alaska, within wetland tundra that contains extensive ice wedge polygon terrain. The study began in 2012 with high-resolution lidar acquisition (~20 points/m2) in a 480 km2 region, from which individual polygon morphology (e.g., high centered, low centered) could be discerned. In 2013, soil samples were collected from 101 pits within a (100 km2) subarea. Samples were analyzed for TOC, carbon isotopes, and soil texture. In 2014, we further reduced scale to 400 m2 using ground penetrating radar (GPR), cone penetrometry, methane and CO2 gas flux, dissolved and particulate organic carbon (DOC and POC) measurements and laboratory estimates of soil hydraulic and thermal properties. The results of these analyses are used to model carbon transport in aqueous and gaseous (CO2 or CH4) phases. Because this carbon loss may be coupled to direct erosion of ice wedge polygons, we developed a numerical model of soil polygon thermo-erosion, and used it to estimate potential carbon loss as polygons transition from low- to high-centered. GPR results show variability of the active layer thickness and potential flow paths for DOC, and the numerical model highlights the potential for soil erosion as a substantial source of carbon for hydrologic transport. Though results are preliminary, we show the value of coupling soil carbon stocks, hydraulic properties, and fluxes to estimate carbon dynamics.