Flux Chamber Measurements of Methane Emissions and Stable Isotope Composition from an Arctic Wetland Using Field-Deployed Real-Time CRDS Vs Lab Measurements

Thursday, 18 December 2014
Hilary A Thompson1, Jennifer C Stern2, Heather V Graham2, Lisa M Pratt3 and Jeffrey R White1, (1)Indiana University Bloomington, School of Public and Environmental Affairs, Bloomington, IN, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)Indiana University Bloomington, Department of Geological Sciences, Bloomington, IN, United States
The emission of CH4 from Arctic landscapes under warming climate is an important feedback in Earth’s climate system. Studies of CH4 flux from Arctic wetlands have been growing in recent years, but few provide details on biogeochemical controls. Stable isotopic measurements help elucidate methane production and consumption pathways and offer important understanding about dynamics of CH4 cycling in Arctic systems. In order to demonstrate the possible instrumental approaches to measuring methane dynamics of wetlands in the Arctic, a fringing wetland of a small lake near the Russell Glacier in Southwestern Greenland was outfitted with static flux chambers and instrumented with a field-deployable Cavity Ring Down Spectrometer (CRDS) to measure real-time concentrations of CH4 and CO2 and their stable carbon isotopes. Several different wetland plant communities were included in the flux chamber experiments and field tests were conducted during several weeks in July 2014. Analytical measurements by CRDS were compared to batch samples analyzed in the laboratory using both Off-Axis Integrated Cavity Output Spectroscopy (ICOS) and Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry (GC-C-IRMS) with cryogenic pre-concentration. Results from flux chamber deployments will be presented and comparisons between the real-time field measurements and laboratory instrumental techniques will be evaluated.