Satellite-derived SO<sub>2</sub> flux time-series and magmatic processes during the 2015 Calbuco eruptions

Abstract

Abstract. Quantifying time-series of sulphur dioxide (SO2) emissions during explosive eruptions provides insight into volcanic processes, assists in volcanic hazard mitigation, and permits quantification of the climatic impact of major eruptions. While volcanic SO2 is routinely detected from space during eruptions, the retrieval of plume injection height and SO2 flux time-series remains challenging. Here we present a new numerical method based on forward-and backwardtrajectory analyses which enable such time-series to be robustly determined. The method is applied to satellite images of 10 volcanic eruption clouds through the integration of the HYSPLIT software with custom-designed Python routines in a fully automated manner. Plume injection height and SO2 flux time-series are computed with a period of ~10 minutes with low computational cost.Using this technique, we investigated the SO2 emissions from two sub-Plinian eruptions of Calbuco, Chile, produced in April 2015. We found a mean injection height above the vent of ~15 km for the two eruptions, with 15 overshooting tops reaching ~20 km. We calculated a total of 300±46 kt of SO2 released almost equally during both events, with 160±30 kt produced by the first event and 140±35 kt by the second. The retrieved SO2 flux time-series show an intense gas release during the first eruption (average flux of 2560 kt day -1 ), while a lower SO2 flux profile was seen for the second (average flux 560 kt day -1 ), suggesting that the first eruption was richer in SO2. This result is exemplified by plotting SO2 flux against retrieved plume height above the vent, revealing distinct trends for the two events. We propose that a pre-20 erupted exsolved volatile phase was present prior to the first event, which could have led to the necessary overpressure to trigger the eruption. The second eruption, instead, was mainly driven by syneruptive degassing. This hypothesis is supported by melt inclusion measurements of sulfur concentrations in plagioclase phenocrysts and groundmass glass of tephra samples through electron microprobe analysis.This work demonstrates that detailed interpretations of sub-surface magmatic processes during eruptions are 25 possible using satellite SO2 data. Quantitative comparisons of high temporal resolution plume height and SO2 flux timeseries offer a powerful tool to examine processes triggering and controlling eruptions. These novel tools open a new frontier in space-based volcanological research, and will be of great value when applied to remote, poorly monitored volcanoes, and to major eruptions that can have regional and global climate implications through, for example, influencing ozone depletion in the stratosphere and light scattering from stratospheric aerosols. 30Solid Earth Discuss., https://doi

Observing the Impact of Calbuco Volcanic Aerosols on South Polar Ozone Depletion in 2015

“…Additionally, although there is a significant difference in the amount of SO 2 Calbuco injected into the stratosphere (0.4 Tg) (Nicarnica Aviation, ; Pardini et al, ), compared to the Pinatubo eruption (14–23 Tg) (Guo et al, ), comparisons of model‐derived SAD between the Pinatubo years of 1991–1993 and the Calbuco year of 2015 at 60°S and 100 hPa show similar values. This suggests that the location of the eruption is an important factor regarding the influence of volcanic aerosols in the stratosphere.…”

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“…The stratospheric aerosol had a cooling effect of the Earth, which in terms of radiative forcing, is estimated to -0. Prata and Bernardo (2007) b Carn and Prata (2010) c Thomas et al (2011) 5 d Carn et al (2009) e Lopez et al (2013) f Haywood et al (2010) g Surono et al (2012) h Clarisse et al (2012) 10 i Li et al (2017) j Pardini et al(2017) …”

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“…The Calbuco eruptions also entailed substantial co-located emissions of SO 2 at 15 km a. v.l. in the range of 300 kt for the two phases according to GOME-2 satellite images (Pardini et al, 2017).…”