The emissions of CO2 and other volatiles from the world’s subaerial volcanoes

Abstract

Volcanoes are the main pathway to the surface for volatiles that are stored within the Earth. Carbon dioxide (CO2) is of particular interest because of its potential for climate forcing. Understanding the balance of CO2 that is transferred from the Earth’s surface to the Earth’s interior, hinges on accurate quantification of the long-term emissions of volcanic CO2 to the atmosphere. Here we present an updated evaluation of the world’s volcanic CO2 emissions that takes advantage of recent improvements in satellite-based monitoring of sulfur dioxide, the establishment of ground-based networks for semi-continuous CO2-SO2 gas sensing and a new approach to estimate key volcanic gas parameters based on magma compositions. Our results reveal a global volcanic CO2 flux of 51.3 ± 5.7 Tg CO2/y (11.7 × 1011 mol CO2/y) for non-eruptive degassing and 1.8 ± 0.9 Tg/y for eruptive degassing during the period from 2005 to 2015. While lower than recent estimates, this global volcanic flux implies that a significant proportion of the surface-derived CO2 subducted into the Earth’s mantle is either stored below the arc crust, is efficiently consumed by microbial activity before entering the deeper parts of the subduction system, or becomes recycled into the deep mantle to potentially form diamonds.

AGU Centennial Grand Challenge: Volcanoes and Deep Carbon Global CO2 Emissions From Subaerial Volcanism—Recent Progress and Future Challenges

“…Another aspect related to the high flux estimates of Burton et al () is that the data used are often biased toward measurements obtained during periods of high volcanic activity when CO 2 fluxes are high. The recent compilation by Werner et al () and Fischer et al () use longer‐term satellite‐based SO 2 flux averages that result in overall lower fluxes as discussed in detail below.…”

“…The measured 57 volcanic sources of Aiuppa et al () contribute a cumulative “measured” flux of 27.4 ± 3.6 Tg CO 2 /year. Overall, Werner et al () estimated a total global flux of 88 ± 21 Tg CO 2 /year for passive degassing from volcanic craters, and Fischer et al () estimated 51.3 ± 5.7 Tg CO 2 /year for global passive degassing from volcanic craters (Table ).…”

“…The Aiuppa et al () approach has been elaborated further by Fischer et al (). These authors refined estimates for the 2005–2015 averaged global volcanic SO 2 flux (24.9 ± 2.3 Tg SO 2 /year; it was 23 ± 2 Tg SO 2 /year in Carn et al, ), by including new OMI data and ground‐based SO 2 flux data from the Network for Volcanic and Atmospheric Change (NOVAC) (Galle et al, ) for 35 additional volcanoes.…”

“…This category includes those volcanoes that are weak emitters of SO 2 (undetectable from space; here referred to as W vge 1) and those hydrothermal‐stage volcanoes that emit no SO 2 at all but may still be contributing CO 2 via low‐temperature fumaroles, steaming ground, and bubbling pools (here referred to as W vge 2). The challenge here is that (1) the number of weakly degassing volcanoes measured for their CO 2 flux is very low (38 volcanoes Fischer et al, ), which means that (2) the “characteristic” CO 2 flux for such category of volcanoes is poorly known, and (3) the total number of weakly degassing volcanoes worldwide is similarly poorly constrained.…”

“…The most complete and recent attempt to quantify the global CO 2 output from W vge is that of Fischer et al (). These authors applied a graphical statistical approach (GSA) method to the CO 2 flux population of 38 W vge , from which they assigned the “characteristic” CO 2 fluxes of 431 and 36 t/day to W vge 1 and W vge 2, respectively.…”