Canopy COS and CO 2 Flux Measurements

1. Quantifying Carbon-Climate Processes at the Regional Scale Using Atmospheric Carbonyl Sulfide 1Campbell, J.E., 2Berry, J.A. 3Seibt, U., 4Maseyk, K., 5Torn, M.S., 5Biraud, S.C., 5Fischer, M.L., 6Billesbach, D.P., 1Abu-Naser, M., 7Baker, I.1Sierra Nevada Research Institute, University of California, Merced, 2Dept. of Global Ecology, Carnegie Institution for Science, 3Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, 4Bioemco, Université Paris 6, France, 5Earth Sciences Division, Lawerence Berkeley National Laboratory, 6Biological Systems Engineering, University of Nebraska, Lincoln, 7Colorado State University, Fort Collins. Relationship of CO2 to Carbonyl Sulfide (COS) Canopy COS and CO2 Flux Measurements Regional Scale Flux Partitioning Oklahoma (SGP)Nebraska (BNE) Regional flux partitioning represents a critical knowledge gap due to a lack of robust methods for regional-scale analysis and large uncertainties in forecasting carbon-climate feedbacks. Atmospheric carbonyl sulfide (COS) has the potential capability for partitioning the regional carbon flux into respiration and photosynthesis components. This emerging approach is based on the observation that continental atmospheric CO2 gradients are dominated by net ecosystem fluxes while continental atmospheric COS gradients are dominated by photosynthesis-related plant uptake. Here we use a new COS eddy flux system, COS airborne monitoring data, and atmospheric modeling tools to quantify the climate sensitivity of carbon flux processes at the regional scale. The ARM Southern Great Plains site is hosting a spring field deployment of this new measurement system. The multi-scale analysis provides evidence to demonstrate the COS technique to the terrestrial ecology community and to provide an understanding of how COS can be incorporated into comprehensive investigations of ecosystem processes. Single ecosystem model pixel at SGP is aggregate of a heterogeneous landscape providing a challenge to scaling-up eddy flux. Re Ecosystem models (SiB, MODIS, CASA) have mixed results with respect to seasonality observed in eddy flux sites. f(GPP) GPP SiB used to generate global COS plant and soil fluxes. Soil sink is consistent with recent top-down and gas exchange experiments at other sites but not with SGP soil chambers. Airborne COS observations consistent with MODIS-driven GPP and select eddy flux sites, helping fill spatial scale gap. Airborne CO2 alone useful for NEE but not sufficient for GPP. • CO2 flux from TDLS and IRGA show agreement with respect to diurnal variation and magnitude of flux. • Significant diurnal variation in COS consistent with peak CO2 uptake • Scatter in COS reflective of large flux relative to background • Soil COS flux is a source, contrary to most chamber and atmospheric tracer studies which consider the soils to be a sink • Soil COS flux is small relative to canopy flux Experimental Approach • COS/CO2 Eddy Flux at SGP • Tunable diode laser spectrometer (TDLS) obsof COS and CO2 at 4 m • TDLS at 10 Hz has unprecedented resolution (COS ~15 ppt RMS)… opportunity for eddy flux • Comparison of TDLS and NOAA GC/MS flasks suggests reliability • SGP site: wheat peak growing season TDLS COS NOAA GC-MS(ppt) Chiller COS TDLS (ppt) Pump Line • Using COS Eddy Flux to Assess COS-GPP Model • Applying atmospheric COS to upscale CO2 eddy flux requires a model of the GPP-COS relationship • Leaf chamber measurements suggest a simple model: FCOS = FGPP * [COS]/[CO2] * V • We assess this model using SGP data and a canopy-scale version of the simple GPP-COS model: • (FCOS,canopy – FCOS,soil) = (FNEE – FRE) * [COS]/[CO2] * V • All parameters except V are estimated from SGP eddy flux data by daily mean (06:00 h-21:00 h) for all days. Preliminary fixed values for soil fluxes are assumed (FCOS,Soil = 0, FCO2,Soil = 2.5 pmol m-2 s-1). • Eddy flux yields V = 1.62 ± 0.43 which is remarkably similar to leaf chamber results V = 1.61 ± 0.26. • Soil Chamber Flux at SGP • Characterized LICOR for wall and temperature effects • TDLS measurements ~2 hr • Double-peak at SGP is broad geographic feature, distinct from adjacent single-peak region • Consistencies with agriculture extentsuggest role for COS in land use assessment. • CASA • Lag between FPAR and temperature causes double peak at SGP and adjacent ag pixels • Adjacent grassland pixels have single peak because FPAR and temperature are aligned • SiB • SiB3 runs driven by GIMMSg see only single-peak • New prognostic phenology in SiB may be more realistic and provides an opportunity to apply COS • Ecosystem Model Fluxes • COS plant uptake estimated directly from GPP using experimental leaf uptake observations: • COS plant+soil flux from process model (SiB) • Modeled and Observed Concentrations • Bi-monthly airborne COS and CO2 measured at SGP and other regional sites • Global PCTM model driven by SiB COS plant and soil uptake, Kettle anthropogenic, GFED biomass burning, and optimized ocean flux. • Regional STEM model driven by range of flux models (CASA/SiB/MODIS) in progress Soil COS Flux and Temperature References Blonquist, JM, Jr., et al., (2011), The potential of carbonyl sulfide as a proxy for gross primary production at flux tower sites, J. Geophys. Res., 116, G04019, doi:10.1029/2011JG001723. Campbell, JE, et. al. (2008), Photosynthetic control of atmospheric carbonyl sulfide during the growing season, Science, 322: 1085-1088. Montzka, SA, et al., (2007), On the global distribution, seasonality, and budget of atmospheric carbonyl sulfide (COS) and some similarities to CO2, J. Geophys. Res., 112(D9), doi:10.1029/2006JD007665. Eddy flux: SGP-Billesbach, Fischer, Torn; Walnut River-Coulter; Mead-Verma • At soil temperatures above 20°C, COS production dominates • Between 10-20°C soil can be a sink or source • Possibly both temperature and plant activity influence diurnal soil COS flux variations