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

Abstract

Quantifying the global volcanic CO2 output from subaerial volcanism is key for a better understanding of rates and mechanisms of carbon cycling in and out of our planet and their consequences for the long‐term evolution of Earth's climate over geological timescales. Although having been the focus of intense research since the early 1990s, and in spite of recent progress, the global volcanic CO2 output remains inaccurately known. Here we review past developments and recent progress and examine limits and caveats of our current understanding and challenges for future research. We show that CO2 flux measurements are today only available for ~100 volcanoes (cumulative measured flux, 44 Tg CO2/year), implying that extrapolation is required to account for the emissions of the several hundred degassing volcanoes worldwide. Recent extrapolation attempts converge to indicate that persistent degassing through active crater fumaroles and plumes releases ~53–88 Tg CO2/year, about half of which is released from the 125 most actively degassing subaerial volcanoes (36.4 ± 2.4 Tg CO2/year from strong volcanic gas emitters, Svge). The global CO2 output sustained by diffuse degassing via soils, volcanic lakes, and volcanic aquifers is even less well characterized but could be as high as 83 to 93 Tg CO2/year, rivaling that from the far more manifest crater emissions. Extrapolating these current fluxes to the past geological history of the planet is challenging and will require a new generation of models linking subduction parameters to magma and volatile (CO2) fluxes.

Late Pleistocene Carbon Cycle Revisited by Considering Solid Earth Processes

“…Our constant flux of background volcanic activity with a CO 2 emission of about 9 ⋅ 10 12 mol C/yr falls in the upper part of the range of fluxes compiled (1-12 ⋅ 10 12 mol C/yr) in the review of Burton et al (2013), in which the upper end refers to the best guess of the authors. A recent review (Fischer & Aiuppa, 2020) derives a total sum of volcanic subaerial CO 2 emissions that is with 3-4 ⋅ 10 12 mol C/yr smaller than our value, but this review also denotes that only Burton et al (2013) covers the most comprehensive attempt of volcanic CO 2 emissions, since it compiles all available fluxes, including volcanic lakes, as well as diffuse emissions. We therefore consider our assumptions to be in line with other evidence, although the uncertainties here are high.…”

BVLOS UAS Operations in Highly-Turbulent Volcanic Plumes

“…Volcanic environments present challenging environments in which to make scientific measurements, particularly at high altitude, densely vegetated, or highly active volcanoes. These sampling limitations have led to significant bias in estimates of global volcanic gas emissions toward a relatively small number of accessible, passively degassing volcanoes (Fischer and Aiuppa, 2020 ). By enabling proximal sampling of remote or hazardously accessible volcanic plumes, instrumented UAS are now targeting gaps in our knowledge of gas emissions at some of the major remaining “known unknown” volcanic emitters.…”

First In-Situ Measurements of Plume Chemistry at Mount Garet Volcano, Island of Gaua (Vanuatu)

“…Our inferred CO 2 fluxes are especially relevant because they contribute new data to recent cataloguing efforts [19][20][21]29] [20,29] is~320 t d −1 ). Notably, our measured Gaua CO 2 flux is a factor~3 lower than the CO 2 flux (~745 t d −1 ) predicted by Aiuppa et al [21].…”

“…In addition to their great potential in eruption forecasting, these portable units have revolutionized our understanding of along-arc chemistry of volcanic gases at different regions of the world. Moreover, when combined with remotely sensed SO 2 fluxes, these measurements provide a means to constrain volcanic gas fluxes, especially CO 2 [17][18][19][20][21][26][27][28][29].…”