Carbon dioxide emissions in Yellowstone, United States, and Solfatara Volcano, Italy: Use of eddy covariance and mass flux modeling.

摘要

Carbon dioxide emissions are monitored in volcanic and hydrothermal areas to understand volcanic processes, to assess hazards in active regions, and to improve estimates of global volcanic and hydrothermal degassing. In this work, eddy covariance, a micrometeorological technique, was tested for the first time in volcanic and hydrothermal terrain to measure CO₂ fluxes over large land areas (km2). An eddy covariance (EC) station was deployed at Yellowstone National Park during August 1999 to determine if EC fluxes were consistent with surface flux measurements using the accumulation chamber technique in volcanic regions. A second deployment of EC at Solfatara Crater, Italy, June 8–25, 2001 assessed if EC could continuously measure CO₂ fluxes for volcanic hazards monitoring at this site. Turbulent (EC) fluxes were calculated in 30-minute averages and varied between 950 and 4460 g CO₂ m−2d−1 depending on location within Solfatara. Comparing turbulent fluxes with chamber measurements of surface fluxes using footprint models yielded an average difference of 0 ± 4%, indicating EC measurements were representative of surface fluxes at this hydrothermal site.; In conclusion, eddy covariance was found to provide reliable estimates of surface fluxes both at Solfatara, and Yellowstone, thereby providing a new technique for monitoring significantly larger areas than previous methods. Monitoring larger areas provides new insight to the temporal variability and spatial distribution of degassing in volcanic regions, and thus provides a new and useful technique for monitoring volcanic hazard.; CO₂ emissions were estimated for the Yellowstone volcanic/hydrothermal system using ground-based measurements and through modeling of the volcanic system. The estimates of degassing of Yellowstone were within an order of magnitude of one another, and indicate that Yellowstone likely emits 3.7 ± 1.3 × 1011 mol CO₂y−1. This estimate is significant in that it represents up to 16% of the global emission rate estimated for volcanic plumes, and up to 7% of global emissions from volcanic and hydrothermal environments estimated at 6–7 × 1012 mol CO₂ y−1, suggesting that more measurements are needed in hydrothermal regions to estimate global volcanic and hydrothermal emissions more accurately. (Abstract shortened by UMI.)