CO 2 flux emissions from the Earth’s most actively degassing volcanoes, 2005–2015

The global carbon dioxide (CO2) flux from subaerial volcanoes remains poorly quantified, limiting our understanding of the deep carbon cycle during geologic time and in modern Earth. Past attempts to extrapolate the global volcanic CO2 flux have been biased by observations being available for a relatively small number of accessible volcanoes. Here, we propose that the strong, but yet unmeasured, CO2 emissions from several remote degassing volcanoes worldwide can be predicted using regional/global relationships between the CO2/S-T ratio of volcanic gases and whole-rock trace element compositions (e.g., Ba/La). From these globally linked gas/rock compositions, we predict the CO2/S T gas ratio of 34 top-degassing remote volcanoes with no available gas measurements. By scaling to volcanic SO2 fluxes from a global catalogue, we estimate a cumulative "unmeasured" CO2 output of 11.4 +/- 1.1 Mt/ yr (or 0.26 +/- 0.02.10(12) mol/yr). In combination with the measured CO2 output of 27.4 +/- 3.6 Mt/yr (or 0.62 +/- 0.08.10(12) mol/yr), our results constrain the time-averaged (2005-2015) cumulative CO2 flux from the Earth's 91 most actively degassing subaerial volcanoes at 38.7 +/- 2.9 Mt/yr (or 0.88 +/- 0.06.10(12) mol/yr).