| 1. |
- Arellano, Santiago, 1981, et al.
(författare)
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Synoptic analysis of a decade of daily measurements of SO2 emission in the troposphere from volcanoes of the global ground-based Network for Observation of Volcanic and Atmospheric Change
- 2021
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3516 .- 1866-3508. ; 13:3, s. 1167-1188
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Tidskriftsartikel (refereegranskat)abstract
- Volcanic plumes are common and far-reaching manifestations of volcanic activity during and between eruptions. Observations of the rate of emission and composition of volcanic plumes are essential to recognize and, in some cases, predict the state of volcanic activity. Measurements of the size and location of the plumes are important to assess the impact of the emission from sporadic or localized events to persistent or widespread processes of climatic and environmental importance. These observations provide information on volatile budgets on Earth, chemical evolution of magmas, and atmospheric circulation and dynamics. Space-based observations during the last decades have given us a global view of Earth's volcanic emission, particularly of sulfur dioxide (SO2). Although none of the satellite missions were intended to be used for measurement of volcanic gas emission, specially adapted algorithms have produced time-averaged global emission budgets. These have confirmed that tropospheric plumes, produced from persistent degassing of weak sources, dominate the total emission of volcanic SO2. Although space-based observations have provided this global insight into some aspects of Earth's volcanism, it still has important limitations. The magnitude and short-term variability of lower-atmosphere emissions, historically less accessible from space, remain largely uncertain. Operational monitoring of volcanic plumes, at scales relevant for adequate surveillance, has been facilitated through the use of ground-based scanning differential optical absorption spectrometer (ScanDOAS) instruments since the beginning of this century, largely due to the coordinated effort of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). In this study, we present a compilation of results of homogenized post-analysis of measurements of SO2 flux and plume parameters obtained during the period March 2005 to January 2017 of 32 volcanoes in NOVAC. This inventory opens a window into the short-term emission patterns of a diverse set of volcanoes in terms of magma composition, geographical location, magnitude of emission, and style of eruptive activity. We find that passive volcanic degassing is by no means a stationary process in time and that large sub-daily variability is observed in the flux of volcanic gases, which has implications for emission budgets produced using short-term, sporadic observations. The use of a standard evaluation method allows for intercomparison between different volcanoes and between ground- and space-based measurements of the same volcanoes. The emission of several weakly degassing volcanoes, undetected by satellites, is presented for the first time. We also compare our results with those reported in the literature, providing ranges of variability in emission not accessible in the past. The open-access data repository introduced in this article will enable further exploitation of this unique dataset, with a focus on volcanological research, risk assessment, satellite-sensor validation, and improved quantification of the prevalent tropospheric component of global volcanic emission. Datasets for each volcano are made available at https://novac.chalmers.se (last access: 1 October 2020) under the CC-BY 4 license or through the DOI (digital object identifier) links provided in Table 1.
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| 2. |
- Barrington, Charlotte, et al.
(författare)
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Wind Speed as a Dominant Source of Periodicities in Reported Emission Rates of Volcanic SO 2
- 2022
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Ingår i: Journal of Geophysical Research: Solid Earth. - 2169-9356 .- 2169-9313. ; 127:12
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Tidskriftsartikel (refereegranskat)abstract
- Volcanoes have been found to display periodicities or cyclic trends in a wide range of phenomena. These include the eruptive activity itself, but also in the time series of geophysical and geochemical monitoring data such as volcanic degassing. Here, we test the existence of periodicities of volcanic degassing at 32 volcanoes using the time series of sulfur dioxide (SO2) emission rates from data of the Network of Volcanic and Atmospheric Change (NOVAC). We use the Lomb-Scargle periodogram to analyze the SO2 data which allows efficient computation of a Fourier-like power spectrum from unevenly sampled data. We were able to calculate False-Alarm Probabilities in 28 of the 32 volcanoes, and we identified significant periodicities in the SO2 emission rates in 17 of the 28 volcanoes. However, we find that most of these periodicities are also present in the plume speeds used to determine SO2 emission rates. Periodicities at about 30–70, ∼120, and ∼180 days were identified at volcanoes located between 16°N and 16°S and are related to intraseasonality and interseasonality in global trade winds and not volcanic in origin. Periodicities between 30 and 70 days in both plume speed and SO2 emission rates are associated to the Madden-Julian Oscillation that is responsible for intraseasonal variability in the tropical atmosphere. Our study highlights the importance of using local wind data for deriving realistic SO2 emissions and the identification of short-term periodicity in volcanic behavior.
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| 3. |
- Galle, Bo, 1952, et al.
(författare)
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A multi-purpose, multi-rotor drone system for long-range and high-altitude volcanic gas plume measurements
- 2021
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 14:6, s. 4255-4277
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Tidskriftsartikel (refereegranskat)abstract
- A multi-rotor drone has been adapted for studies of volcanic gas plumes. This adaptation includes improved capacity for high-altitude and long-range, real-time SO2 concentration monitoring, long-range manual control, remotely activated bag sampling and plume speed measurement capability. The drone is capable of acting as a stable platform for various instrument configurations, including multi-component gas analysis system (MultiGAS) instruments for in situ measurements of SO2, H2S, and CO2 concentrations in the gas plume and portable differential optical absorption spectrometer (MobileDOAS) instruments for spectroscopic measurement of total SO2 emission rate, remotely controlled gas sampling in bags and sampling with gas denuders for posterior analysis on the ground of isotopic composition and halogens. The platform we present was field-tested during three campaigns in Papua New Guinea: in 2016 at Tavurvur, Bagana and Ulawun volcanoes, in 2018 at Tavurvur and Langila volcanoes and in 2019 at Tavurvur and Manam volcanoes, as well as in Mt. Etna in Italy in 2017. This paper describes the drone platform and the multiple payloads, the various measurement strategies and an algorithm to correct for different response times of MultiGAS sensors. Specifically, we emphasize the need for an adaptive flight path, together with live data transmission of a plume tracer (such as SO2 concentration) to the ground station, to ensure optimal plume interception when operating beyond the visual line of sight. We present results from a comprehensive plume characterization obtained during a field deployment at Manam volcano in May 2019. The Papua New Guinea region, and particularly Manam volcano, has not been extensively studied for volcanic gases due to its remote location, inaccessible summit region and high level of volcanic activity. We demonstrate that the combination of a multi-rotor drone with modular payloads is a versatile solution to obtain the flux and composition of volcanic plumes, even for the case of a highly active volcano with a high-altitude plume such as Manam. Drone-based measurements offer a valuable solution to volcano research and monitoring applications and provide an alternativespan idCombining double low line"page4256"/> and complementary method to ground-based and direct sampling of volcanic gases.
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| 4. |
- Galle, Bo, 1952, et al.
(författare)
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An algorithm for correction of atmospheric scattering dilution effects in volcanic gas emission measurements using skylight differential optical absorption spectroscopy
- 2023
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Ingår i: Frontiers in Earth Science. - 2296-6463. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Differential Optical Absorption Spectroscopy (DOAS) is commonly used to measure gas emissions from volcanoes. DOAS instruments measure the absorption of solar ultraviolet (UV) radiation scattered in the atmosphere by sulfur dioxide (SO2) and other trace gases contained in volcanic plumes. The standard spectral retrieval methods assume that all measured light comes from behind the plume and has passed through the plume along a straight line. However, a fraction of the light that reaches the instrument may have been scattered beneath the plume and thus has passed around it. Since this component does not contain the absorption signatures of gases in the plume, it effectively “dilutes” the measurements and causes underestimation of the gas abundance in the plume. This dilution effect is small for clean-air conditions and short distances between instrument and plume. However, plume measurements made at long distance and/or in conditions with significant atmospheric aerosol, haze, or clouds may be severely affected. Thus, light dilution is regarded as a major error source in DOAS measurements of volcanic degassing. Several attempts have been made to model the phenomena and the physical mechanisms are today relatively well understood. However, these models require knowledge of the local atmospheric aerosol composition and distribution, parameters that are almost always unknown. Thus, a practical algorithm to quantitatively correct for the dilution effect is still lacking. Here, we propose such an algorithm focused specifically on SO2 measurements. The method relies on the fact that light absorption becomes non-linear for high SO2 loads, and that strong and weak SO2 absorption bands are unequally affected by the diluting signal. These differences can be used to identify when dilution is occurring. Moreover, if we assume that the spectral radiance of the diluting light is identical to the spectrum of light measured away from the plume, a measured clean air spectrum can be used to represent the dilution component. A correction can then be implemented by iteratively subtracting fractions of this clean air spectrum from the measured spectrum until the respective absorption signals on strong and weak SO2 absorption bands are consistent with a single overhead SO2 abundance. In this manner, we can quantify the magnitude of light dilution in each individual measurement spectrum as well as obtaining a dilution-corrected value for the SO2 column density along the line of sight of the instrument. This paper first presents the theory behind the method, then discusses validation experiments using a radiative transfer model, as well as applications to field data obtained under different measurement conditions at three different locations; Fagradalsfjall located on the Reykjanaes peninsula in south Island, Manam located off the northeast coast of mainland Papua New Guinea and Holuhraun located in the inland of north east Island.
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| 5. |
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| 6. |
- Koenig, Alkuin M., et al.
(författare)
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Observed in-plume gaseous elemental mercury depletion suggests significant mercury scavenging by volcanic aerosols
- 2023
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Ingår i: Environmental Science: Atmospheres. - 2634-3606. ; 3:10, s. 1418-1438
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial volcanism is known to emit mercury (Hg) into the atmosphere. However, despite many years of investigation, its net impact on the atmospheric Hg budget remains insufficiently constrained, in part because the transformations of Hg in volcanic plumes as they age and mix with background air are poorly understood. Here we report the observation of complete gaseous elemental mercury (GEM) depletion events in dilute and moderately aged (& SIM;3-7 hours) volcanic plumes from Piton de la Fournaise on Reunion Island. While it has been suggested that co-emitted bromine could, once photochemically activated, deplete GEM in a volcanic plume, we measured low bromine concentrations in both the gas- and particle-phase and observed complete GEM depletion even before sunrise, ruling out a leading role of bromine chemistry here. Instead, we hypothesize that the GEM depletions were mainly caused by gas-particle interactions with sulfate-rich volcanic particles (mostly of submicron size), abundantly present in the dilute plume. We consider heterogeneous GEM oxidation and GEM uptake by particles as plausible manifestations of such a process and derive empirical rate constants. By extrapolation, we estimate that volcanic aerosols may scavenge 210 Mg y(-1) (67-480 Mg y(-1)) of Hg from the atmosphere globally, acting effectively as atmospheric mercury sink. While this estimate is subject to large uncertainties, it highlights that Hg transformations in aging volcanic plumes must be better understood to determine the net impact of volcanism on the atmospheric Hg budget and Hg deposition pathways.
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| 7. |
- Lages, J., et al.
(författare)
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Excess degassing drives long-term volcanic unrest at Nevado del Ruiz
- 2024
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Ingår i: Scientific Reports. - 2045-2322 .- 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- This study combines volcanic gas compositions, SO2 flux and satellite thermal data collected at Nevado del Ruiz between 2018 and 2021. We find the Nevado del Ruiz plume to have exhibited relatively steady, high CO2 compositions (avg. CO2/ST ratios of 5.4 ± 1.9) throughout. Our degassing models support that the CO2/ST ratio variability derives from volatile exsolution from andesitic magma stored in the 1–4 km depth range. Separate ascent of CO2-rich gas bubbles through shallow (< 1 km depth), viscous, conduit resident magma causes the observed excess degassing. We infer that degassing of ~ 974 mm3 of shallow (1–4 km) stored magma has sourced the elevated SO2 degassing recorded during 2018–2021 (average flux ~ 1548 t/d). Of this, only < 1 mm3 of magma have been erupted through dome extrusion, highlighting a large imbalance between erupted and degassed magma. Escalating deep CO2 gas flushing, combined with the disruption of passive degassing, through sudden accumulation and pressurization of bubbles due to lithostatic pressure, may accelerate volcanic unrest and eventually lead to a major eruption.
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| 8. |
- Liu, E. J., et al.
(författare)
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Aerial strategies advance volcanic gas measurements at inaccessible, strongly degassing volcanoes
- 2020
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Ingår i: Science advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 6:44
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Tidskriftsartikel (refereegranskat)abstract
- Volcanic emissions are a critical pathway in Earth's carbon cycle. Here, we show that aerial measurements of volcanic gases using unoccupied aerial systems (UAS) transform our ability to measure and monitor plumes remotely and to constrain global volatile fluxes from volcanoes. Combining multi-scale measurements from ground-based remote sensing, long-range aerial sampling, and satellites, we present comprehensive gas fluxes-3760 ± [600, 310] tons day-1 CO2 and 5150 ± [730, 340] tons day-1 SO2-for a strong yet previously uncharacterized volcanic emitter: Manam, Papua New Guinea. The CO2/ST ratio of 1.07 ± 0.06 suggests a modest slab sediment contribution to the sub-arc mantle. We find that aerial strategies reduce uncertainties associated with ground-based remote sensing of SO2 flux and enable near-real-time measurements of plume chemistry and carbon isotope composition. Our data emphasize the need to account for time averaging of temporal variability in volcanic gas emissions in global flux estimates.
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| 9. |
- Peltier, Aline, et al.
(författare)
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Volcano Crisis Management at Piton de la Fournaise (La Reunion) during the COVID-19 Lockdown
- 2021
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Ingår i: Seismological Research Letters. - : Seismological Society of America (SSA). - 1938-2057 .- 0895-0695. ; 92:1, s. 38-52
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Tidskriftsartikel (refereegranskat)abstract
- In March 2020, the coronavirus disease 2019 outbreak was declared a pandemic by the World Health Organization and became a global health crisis. Authorities worldwide implemented lockdowns to restrict travel and social exchanges in a global effort to counter the pandemic. In France, and in French overseas departments, the lockdown was effective from 17 March to 11 May 2020. It was in this context that the 2-6 April 2020 eruption of Piton de la Fournaise (La Reunion Island, Indian Ocean) took place. Upon the announcement of the lockdown in France, a reduced activity plan was set up by the Institut de Physique du Globe de Paris, which manages the Observatoire Volcanologique du Piton de la Fournaise (OVPF). The aim was to (1) maintain remote monitoring operations by teleworking and (2) authorize fieldwork only for critical reasons, such as serious breakdowns of stations or transmission relays. This eruption provided an opportunity for the observatory to validate its capacity to manage a volcanic crisis with 100% remotely operated monitoring networks. We thus present the longand short-term precursors to the eruption, and the evolution of the eruption recorded using the real-time monitoring data as communicated to the stakeholders. The data were from both continuously recording and transmitting field instruments as well as satellites. The volcano observatory staff remotely managed the volcano crisis with the various stakeholders based only on these remotely functioning networks. Monitoring duties were also assured in the absence of ad hoc field investigation of the eruption by observatory staff or face-to-face communications. The density and reliability of the OVPF networks, combined with satellite observations, allowed for trustworthy instrument-based monitoring of the eruption and continuity of the OVPF duties in issuing regular updates of volcanic activity in the context of a double crisis: volcanic and health.
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| 10. |
- Pfeffer, M. A., et al.
(författare)
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SO 2 emission rates and incorporation into the air pollution dispersion forecast during the 2021 eruption of Fagradalsfjall, Iceland
- 2024
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Ingår i: Journal of Volcanology and Geothermal Research. - 0377-0273. ; 449
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Tidskriftsartikel (refereegranskat)abstract
- During the low-effusion rate Fagradalsfjall eruption (19 March – 18 September 2021), the emission of sulfur dioxide (SO2) was frequently measured using ground-based UV spectrometers. The total SO2 emitted during the entire eruption was 970 ± 540 kt, which is only about 6% of the SO2 emitted during the similar length Holuhraun eruption (2014–2015). The eruption was divided into five phases based on visual observations, including the number of active vents and the occurrence of lava fountaining. The SO2 emission rate ranged from 44 ± 19 kg/s in Phase 2 to 85 ± 29 kg/s in Phase 5, with an average of 64 ± 34 kg/s for the entire eruption. There was notable variability in SO2 on short timescales, with measurements on 11 August 2021 ranging from 17 to 78 kg/s. SO2 flux measurements were made using scanning DOAS instruments located at different distances from and orientations relative to the eruption site augmented by traverses. Four hundred and forty-four scan and traverse measurements met quality criteria and were used, along with plume height and meteorological data, to calculate SO2 fluxes while accounting for wind-related uncertainties. A tendency for stronger SO2 flux concurrent with higher amplitude seismic tremor and the occurrence of lava fountaining was observed during Phases 4 and 5 which were characterized by intermittent crater activity including observable effusion of lava and gas release interspersed with long repose times. This tendency was used to refine the calculation of the amount of SO2 emitted during variably vigorous activity. The continuous seismic tremor time series was used to quantify how long during these eruption phases strong/weak activity was exhibited to improve the calculated SO2 flux during these Phases. The total SO2 emissions derived from field measurements align closely with results obtained by combining melt inclusion and groundmass glass analyses with lava effusion rate measurements (910 ± 230 kt SO2). Specifically, utilizing the maximum S content found in evolved melt inclusions and the least remaining S content in accompanying quenched groundmasses provides an identical result between field measurements and the petrological calculations. This suggests that the maximum SO2 release calculated from petrological estimates should be preferentially used to initialize gas dispersion models for basaltic eruptions when other measurements are lacking. During the eruption, the CALPUFF dispersion model was used to forecast ground-level exposure to SO2. The SO2 emission rates measured by DOAS were used as input for the dispersion model, with updates made when a significant change was measured. A detailed analysis of one mid-distance station over the entire eruption shows that the model performed very well at predicting the presence of volcanic SO2 when it was measured. However, it frequently predicted the presence of SO2 that was not measured and the concentrations forecasted had no correlation with the concentrations measured. Various approaches to improve the model forecast were tested, including updating plume height and SO2 flux source terms based on measurements. These approaches did not unambiguously improve the model performance but suggest that improvements might be achieved in more-polluted conditions.
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| 11. |
- Thivet, Simon, et al.
(författare)
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Evidences of Plug Pressurization Enhancing Magma Fragmentation During the September 2016 Basaltic Eruption at Piton de la Fournaise (La Réunion Island, France)
- 2020
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Ingår i: Geochemistry, Geophysics, Geosystems. - 1525-2027. ; 21:2
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Tidskriftsartikel (refereegranskat)abstract
- In September 2016, Piton de la Fournaise volcano, well known for its effusive and Hawaiian fountaining activity, produced, at the end of the eruption, an unusual phase of pulsating ash and bomb emission. Integration of geophysical data, with textural and petrological analysis of the samples, allowed us to constrain the main factors that controlled this sudden shift in activity, potentially dangerous for the tourist population that usually approach these “gentle” eruptive sites. Volcanic tremor, lava discharge rates, fountain heights, and SO2 emission changed rapidly during the eruption. Grain size and componentry of the tephra beds evolved from unimodal all along the sequence to bimodal on the last day of the activity, reflecting the contribution of both Hawaiian fountaining at the main vent (Vent A) and transient explosive activity at the second vent (Vent B). Hawaiian fountaining produced highly vesicular and almost microlite-free tephra (golden pumice and fluidal scoria) while transient explosive activity emitted denser and crystal-rich tephra (sideromelane and tachylite scoria) sometimes mingled with vesicular fragments. Permeability measurements on lapilli and bomb-sized samples reveal that golden pumice and fluidal scoria were more gas-permeable than the sideromelane and tachylite ones, while textural and chemical analyses of the ash support the hypothesis that these sideromelane and tachylite components were inherited from the subsurface crystallization of the initial golden pumice and fluidal scoria components. We thus suggest that Vent B accumulated a plug of degassed, cooled, and low-permeable magma, which modulated overpressure pulses under the late input of ascending magma.
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| 12. |
- Vásconez, Freddie, et al.
(författare)
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Linking ground-based data and satellite monitoring to understand the last two decades of eruptive activity at Sangay volcano, Ecuador
- 2022
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Ingår i: Bulletin of Volcanology. - : Springer Science and Business Media LLC. - 0258-8900 .- 1432-0819. ; 84:5
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Tidskriftsartikel (refereegranskat)abstract
- Sangay is one of the most active volcanoes in Ecuador, as it has been almost continuously erupting at least since the seventeenth century. However, because of its remote location and low associated risk to human population, little is known about its eruptions. Here we summarize Sangay’s volcanic activity from January 2001 to May 2020, based on ground-based data, satellite-derived observations and chemical analysis of its erupted products. During the analyzed period, Sangay’s activity changed from continuous to episodic, as revealed by seismic, thermal and ash emission data. We identified three main eruptive periods: the first, from 2001 to 2013, extruded a cumulative volume of 100 ± 50 million m3 of lava through long-lived activity; the second emitted 54 ± 27 million m3 in four short-lived episodes, which occurred once every year from 2015 to 2018; and finally, a third period since 2019, which has continuous but fluctuating intensity, and shows a significant increase in the extruded lava volume (172 ± 86 million m3 until May 31, 2020). Our results show a marked change in the eruption frequency and a significant increase in average discharge rate over time, although surface activity remained similar, with lava flows, small explosions and ash venting. We propose that three magmatic processes acted to explain the observed changes: between 2001 and 2013 the long-living low-intensity eruptions were promoted by buoyancy, while since 2019 similar but more intense activity was triggered by mass injections. In contrast, the episodic activity in between probably resulted from volatile exsolution due to crystallization (second boiling). Transitions between these three regimes are presumably the result of varying mass inflow rates. Our results provide insights into eruptive style transitions commonly observed at volcanoes of intermediate composition, such as Sangay, over a timescale of several years.
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| 13. |
- Verdurme, Pauline, et al.
(författare)
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Lava Volume from Remote Sensing Data: Comparisons with Reverse Petrological Approaches for Two Types of Effusive Eruption
- 2022
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Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 14:2
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Tidskriftsartikel (refereegranskat)abstract
- Five effusive eruptions of Piton de la Fournaise (La Réunion) are analyzed to investigate temporal trends of erupted mass and sulfur dioxide (SO2) emissions. Daily SO2 emissions are acquired from three ultraviolet (UV) satellite instruments (the Ozone Monitoring Instrument (OMI), the Ozone Mapping and Profiler Suite (OMPS), and the Tropospheric Monitoring Instrument (TROPOMI)) and an array of ground-based UV spectrometers (Network for Observation of Volcanic and Atmospheric Change (NOVAC)). Time-averaged lava discharge rates (TADRs) are obtained from two automatic satellite-based hot spot detection systems: MIROVA and MODVOLC. Assuming that the lava volumes measured in the field are accurate, the MIROVA system gave the best estimation of erupted volume among the methods investigated. We use a reverse petrological method to constrain pre-eruptive magmatic sulfur contents based on observed SO2 emissions and lava volumes. We also show that a direct petrological approach using SO2 data might be a viable alternative for TADR estimation during cloudy weather that compromises hot spot detection. In several eruptions we observed a terminal increase in TADR and SO2 emissions after initial emission of evolved degassed magma. We ascribe this to input of deeper, volatile-rich magma into the plumbing system towards the end of these eruptions. Furthermore, we find no evidence of volatile excess in the five eruptions studied, which were thus mostly fed by shallow degassed magma.
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