CO2 flux emissions from the Earth’s most actively degassing volcanoes, 2005–2015

Abstract

The global carbon dioxide (CO 2 ) 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 CO 2 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, CO 2 emissions from several remote degassing volcanoes worldwide can be predicted using regional/global relationships between the CO 2 /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 CO 2 /S T gas ratio of 34 top-degassing remote volcanoes with no available gas measurements. By scaling to volcanic SO 2 fluxes from a global catalogue, we estimate a cumulative “unmeasured” CO 2 output of 11.4 ± 1.1 Mt/yr (or 0.26 ± 0.02·10 12 mol/yr). In combination with the measured CO 2 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 CO 2 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).

Volcanic Gas Emissions Along the Colombian Arc Segment of the Northern Volcanic Zone (CAS‐NVZ): Implications for volcano monitoring and volatile budget of the Andean Volcanic Belt

“…We here use these estimations to infer a total volcanic CO 2 flux from the four most actively degassing CAS subaerial volcanoes at approximately 5,563 t/day. In perspective, this corresponds to more than 50% of present‐day (2005–2015) total volcanic CO 2 emissions from the active volcanoes of the Andean Volcanic Belt (derived at ~10,000 t/day from data in Aiuppa et al, ). Notably, Nevado del Ruiz and Galeras together contribute ~35% to the subaerial volcanic CO 2 emission budget in the Andean Volcanic Belt and are thus larger CO 2 sources than any other active volcano in Ecuador (Hidalgo et al, , ), Peru (Moussallam et al, 2017; Moussallam, Tamburello, et al, ), and Chile (Tamburello et al, ).…”

“…Estimated averages from this study are given in triangles, with reference literature averages for Colombia represented in squares. Other arc segments are plotted as follows: (i) In white Ecuador (Guagua Pichincha (Fischer & Chiodini, ); Cotopaxi [Hidalgo et al, 2017]; Tungurahua and Reventador (Aiuppa et al, )); (ii) in dark gray Peru (El Misti [Moussallam et al, 2017], Sabancaya and Ubinas [Moussallam, Tamburello, et al, ]); and (iii) in light gray Chile (Lascar and Lastarria, (Tamburello et al, ); Copahue (Tamburello et al, ); Isluga and Tacora (Schipper et al, ); Villarica (Aiuppa et al, )). Noticeable trends in CO 2 /S T plotting along the S T ‐CO 2 show along‐arc trends in volcanic gas compositions for the different segments (yellow graded areas represent, from the bottom, CO 2 /S T = 1, 2, and 5).…”

“…For Galeras, we report the more magmatic‐in‐nature CO 2 /S T ratio (green circle; October 2014) obtained throughout this investigation and compare it with the composition of high‐temperature gases collected during the 1989–1995 period of unrest (red circle; Fischer et al, ; Aiuppa, Fischer, et al, ). For Nevado del Ruiz, the original CO 2 /S T ratio quoted in Aiuppa et al () is shown for comparison. Both pressure‐compensated and uncorrected CO 2 /S T for Sabancaya and Ubinas (Peru; Moussallam, Tamburello, et al, ) are given for comparison.…”

“…Nevado del Huila (e.g. Pulgarín et al, ), another relevant subaerial emission source in the CAS, has been persistently degassing over the last decades, especially during its most recent eruptive period (2009–2012) when it emitted ~862 t/day of CO 2 (Aiuppa et al, ). We here use these estimations to infer a total volcanic CO 2 flux from the four most actively degassing CAS subaerial volcanoes at approximately 5,563 t/day.…”

“…Therefore, volcanic CO 2 flux estimates are typically derived indirectly by combining measurements of SO 2 flux and of CO 2 /SO 2 ratios in volcanic gases (e.g., Aiuppa et al, ; Shinohara et al, ). The latter measurements require in situ gas observations in hazardous and/or difficult to access volcanic craters, which have so far proven to be impossible for several volcano targets worldwide (Aiuppa et al, ), making the CO 2 budget inaccurately known for several arc segments (Shinohara , ), and globally (Aiuppa et al, ).…”