Download or read book Atmospheric 14CO2 Constraints on and Modeling of Net Carbon Fluxes 06-ERD-031 An LLNL Exploratory Research in the Directorate's Final Report written by and published by . This book was released on 2009 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A critical scientific question is: 'what are the present day sources and sinks of carbon dioxide (CO2) in the natural environment, and how will these sinks evolve under rising CO2 concentrations and expected climate change and ecosystem response'? Sources and sinks of carbon dioxide impart their signature on the distribution, concentration, and isotopic composition of CO2. Spatial and temporal trends (variability) provide information on the net surface (atmosphere to ocean, atmosphere to terrestrial biosphere) fluxes. The need to establish more reliable estimates of sources and sinks of CO2 has lead to an expansion of CO2 measurement programs over the past decade and the development of new methodologies for tracing carbon flows. These methodologies include high-precision pCO2, [delta]13CO2, and [O2/N2] measurements on atmospheric constituents that, when combined, have allowed estimates of the net terrestrial and oceanic fluxes at decadal timescales. Major gaps in our understanding remain however, and resulting flux estimates have large errors and are comparatively unconstrained. One potentially powerful approach to tracking carbon flows is based on observations of the 14C/12C ratio of atmospheric CO2. This ratio can be used to explicitly distinguish fossil-fuel CO2 from other sources of CO2 and also provide constraints on the mass and turnover times of carbon in land ecosystems and on exchange rates of CO2 between air and sea. Here we demonstrated measurement of 14C/12C ratios at 1-2{per_thousand} on archived and currently collected air samples. In parallel we utilized the LLNL-IMPACT global atmospheric chemistry transport model and the TransCom inversion algorithm to utilize these data in inversion estimates of carbon fluxes. This project has laid the foundation for a more expanded effort in the future, involving collaborations with other air-sampling programs and modeling groups.