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| Titel |
Global volcanic CO2 fluxes have been underestimated due to neglect of light scattering processes |
| VerfasserIn |
Michael Burton, Giuseppe Salerno |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095864
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| Publikation (Nr.) |
 EGU/EGU2014-11340.pdf |
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| Zusammenfassung |
| Volcanic gas emissions reveal magma dynamics and affect climate. Recent estimates for global volcanic subaerial CO2 flux range from 0.1 PgC/yr to 0.15 PgC/yr, or ~1-2% of anthropogenic emissions, extrapolated from combined measurements of volcanic CO2/SO2 ratios and scattered sunlight UV measurements of SO2 flux. The latter are affected by light scattering into the UV spectrometer from below the volcanic plume, diluting the SO2 signal. Whilst the ‘light dilution’ effect was initially recognised, and has recently been placed on a sound theoretical basis, it has not yet been widely addressed in volcanic SO2 flux measurements, due to a lack of a suitable retrieval procedure. Here, we report a practical new SO2 retrieval process that addresses light dilution, and apply it to plume measurements on six volcanoes, including a year of data from Mt. Etna, Italy. We find light dilution-corrected SO2 fluxes are typically 2-4 times and occasionally 13 times greater than uncorrected fluxes. Light dilution produces a systematic bias, consistently underestimating the true flux when not corrected. The magnitude of this correction is a function of plume distance, plume aerosol optical depth, atmospheric aerosol load and SO2 abundance. We estimate conservative correction factors for all measured volcanic CO2 fluxes, and produce a new global volcanic CO2 flux of 0.5 PgC/yr, or 5% of anthropogenic emissions. This corrected volcanic CO2 source flux implies a larger land and ocean CO2 sink than previously thought, and hence a shorter atmospheric lifetime of CO2. These revised volcanic fluxes may significantly alter our understanding of the climate response to anthropogenic CO2 emissions. Our results demonstrate that the standard methodologies used in volcanic SO2 flux measurement can significantly underestimate the true flux, calling into question the 35 year old empirical foundation upon which much of our understanding of magmatic degassing is based. |
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