Displays

Stratospheric water vapor (SWV) is important not only for stratospheric ozone chemistry but also due to its influence on the atmospheric radiation budget.

After volcanic eruptions, SWV is known to increase due to two different mechanisms: First, water within the volcanic plume is directly injected into the stratosphere during the eruption itself. Second, the volcanic aerosols lead to a warming of the lower stratosphere including the tropopause layer. The increased temperature of the cold point allows an increased water vapor transit from the troposphere to the stratosphere. Not much is known about this process as it is obscured by internal variability and observations are scare.

To better understand the increased SWV entry via the indirect pathway after volcanic eruptions we employ a suite of large volcanically perturbed ensemble simulations of the MPI-ESM1.2-LR for five different eruptions strengths (2.5 Mt, 5 Mt, 10 Mt, 20 Mt and 40 Mt sulfur). Each ensemble consists of 100 realizations for a time period of 3 years.

Our work mainly focuses on the tropical tropopause layer (TTL) quantifying changes in relevant parameters such as the atmospheric temperature profile and the consequent increase in SWV. A maximum increase of up to 4 ppmm in the first two years after the eruption is found in the case of the 40 Mt eruption. Furthermore the large ensemble size additionally allows for an analysis of the statistical significance and influence of variability, showing that SWV increases can already be detected for the 2.5 Mt eruption in the ensemble mean, for single ensemble members the internal variability dominates the SWV entry up to an eruption strength of 10 Mt to 20 Mt depending on the season and time after the eruption. The study is complemented by investigations using the 1D radiative convective equilibrium model konrad to understand the radiative effects of the SWV increase.

How to cite: Kroll, C., Azulay, A., Schmidt, H., and Timmreck, C.: Volcanically induced stratospheric water vapor changes , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8333, https://doi.org/10.5194/egusphere-egu2020-8333, 2020.

More than 2,000 analyses of beryllium‐10 (¹⁰Be) and sulphate concentrations were performed at a nominal subannual resolution on an ice core covering the last millennium as well as on shorter records from three sites in Antarctica (Dome C, South Pole, and Vostok) to better understand the increase in ¹⁰Be deposition during stratospheric volcanic eruptions.

A significant increase in ¹⁰Be concentration is observed in 14 of the 26 volcanic events studied. The slope and intercept of the linear regression between ¹⁰Be and sulphate concentrations provide different and complementary information. Slope is an indicator of the efficiency of the draining of ¹⁰Be atoms by volcanic aerosols depending on the amount of sulphur dioxide (SO₂) released and on the altitude it reaches in the stratosphere. The intercept provides an appreciation of the ¹⁰Be production in the stratospheric reservoir, ultimately depending on solar modulation (Baroni et al., 2019, JGR).

Among all the identified events, the Samalas event (1257 CE) stands out as the biggest eruption of the last millennium with the lowest positive slope. It released (158 ± 12) Tg of SO₂ up to an altitude of 43 km in the stratosphere (Lavigne et al., 2013, PNAS ; Vidal et al., 2016, Sci. Rep.). We hypothesize that the persistence of volcanic aerosols in the stratosphere after the Samalas eruption has drained the stratospheric ¹⁰Be reservoir for a decade.

The persistence of Samalas sulphate aerosols might be due to the increase of SO₂ lifetime because of: (i) the exhaustion of the OH reservoir required for sulphate formation (e.g. (Bekki, 1995, GRL; Bekki et al., 1996, GRL; Savarino et al., 2003, JGR); and/or, (ii) the evaporation followed by photolysis of gaseous sulphuric acid back to SO₂ at altitudes higher than 30 km (Delaygue et al., 2015, Tellus; Rinsland et al., 1995, GRL). In addition, the lifetime of air masses increases to 5 years above 30 km altitude compared with 1 year for aerosols and air masses in the lower stratosphere (Delaygue et al., 2015, Tellus). When this high-altitude SO₂ finally returns below the 30 km limit, it could be oxidized back to sulphate and forms new sulphate aerosols. These processes could imply that the ¹⁰Be reservoir is washed out over a long time period following the end of the eruption of Samalas.

This would run counter to modelling studies that predict the formation of large particle sizes and their rapid fall out due to the large amount of SO₂, which would limit the climatic impact of Samalas-type eruptions (Pinto et al., 1989, JGR; Timmreck et al., 2010, 2009, GRL).

How to cite: Baroni, M., Bard, E., Petit, J.-R., Viseur, S., and Team, A.: Persistent draining of the stratospheric 10Be reservoir after the Samalas volcanic eruption (1257 CE), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12957, https://doi.org/10.5194/egusphere-egu2020-12957, 2020.

The relationship between volcanic stratospheric aerosol optical depth (SAOD) and volcanic forcing is key to quantify the climate impacts of volcanic eruptions. In their fifth assessment report, the Intergovernmental Panel on Climate Change uses a single scaling factor between volcanic SAOD and effective radiative forcing (ERF) based on climate model simulations of the 1991 Mt. Pinatubo eruption, which may not be appropriate for eruptions of different magnitudes. Using a large-ensemble of aerosol-chemistry-climate simulations of eruptions with different SO₂ emissions, latitudes, emission altitudes and seasons, we find that the effective radiative forcing is on average 21% less than the instantaneous radiative forcing, predominantly due to a positive shortwave cloud adjustment.  In our model, the volcanic SAOD to ERF relationship is non-unique and depends strongly on eruption latitude and season. We recommend a power law fit in the form of ERF = -15.1 × SAOD^0.88 to convert SAOD (in the range of 0.01-0.7) to ERF.

How to cite: Marshall, L., Smith, C., Forster, P., Aubry, T., and Schmidt, A.: Large variations in volcanic aerosol forcing efficiency due to eruption source parameters and rapid adjustments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5254, https://doi.org/10.5194/egusphere-egu2020-5254, 2020.

The mechanisms through which volcanic eruptions impact the El Niño-Southern Oscillation (ENSO) state are still controversial. Previous studies have invoked direct radiative forcing, an ocean dynamical thermostat (ODT) mechanism and shifts of the Intertropical Convergence Zone (ITCZ), among others, to explain the ENSO response to tropical eruptions. Here, these mechanisms are tested using ensemble simulations with an Earth System Model in which volcanic aerosols from a Tambora-like eruption are confined either in the Northern or the Southern Hemisphere. We show that the primary drivers of the ENSO response are the shifts of the ITCZ together with extratropical circulation changes, which affect the tropics; the ODT mechanism does not operate in our simulations. Our study highlights the importance of initial conditions in the ENSO response to tropical volcanic eruptions and provides explanations for the predominance of post-eruption El Niño events and for the occasional post-eruption La Niña in observations and reconstructions.

How to cite: Pausata, F. S. R., Zanchettin, D., Karamperidou, C., Caballero, R., and Battisti, D. S.: ITCZ shift and extratropical teleconnections drive ENSO response to volcanic eruptions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2067, https://doi.org/10.5194/egusphere-egu2020-2067, 2020.

The societal impacts of climate change during the late Holocene leads to regional anthropogenic changes over the Nile region floodplain and could have acted in tandem with natural factors like major volcanic eruptions on the regional climate system to magnify the local climatic impacts. This study aims to explore and investigate the sensitivity of climatic changes to the regional anthropogenic changes due to various factors over the Nile river floodplains during the late-Holocene (2.5K years before present). The GISS ModelE Earth system model will be used to simulate the various scenarios of regional increasing/decreasing river fraction, changes in vegetation type and cover, along with changes in land surface type against the no-changes scenario in absence of volcanic eruptions. The spatial coverage of the Nile river basin is estimated using the GIS shapefile based on elevation data from Shuttle Radar Topography Mission (SRTM) at 3 Arc-seconds (approx. 90-meter) horizontal resolution. The extent of flooding in the model grid (2.0°x2.5° in latitude and longitude) is estimated using the existing high-resolution (0.125°x0.125°) gridded topographic elevation information and mapped over the Nile river floodplains. This study also focuses on evaluating the NASA GISS ModelE for resolving the climate feedbacks and response on climate system due to anthropogenic changes and volcanic eruptions. It is also aimed to analyze and quantify the impact of various anthropogenic factors over the African monsoon system and rainfall over the region, which feeds the Nile River.

How to cite: Singh, R., LeGrande, A. N., and Tsigaridis, K.: Influence of regional anthropogenic changes over Nile region on the climate system during the late Holocene (~2500 years before present), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12338, https://doi.org/10.5194/egusphere-egu2020-12338, 2020.

This paper capitalizes upon the recent availability of much-improved ice-core chronologies of explosive volcanism for the first millennium BCE in combination with the remarkable record of meteorological data preserved in Babylonian astronomical diaries, written on cuneiform tablets spanning 652-61BC and now housed in the British Museum. These diaries comprise systematic economic data on agricultural prices, weather observations at an hourly resolution, river heights for the Euphrates and other phenomena. Our initial results reveal strong correspondences between multiple previously unrecognized accounts of solar dimming, extreme cold weather and major ice-core volcanic signals. We also observe anomalously high spring floods of the Euphrates at Babylon, following major tropical eruptions, which is consistent with climate modelling of anomalously elevated winter precipitation in the headwaters of the Euphrates and Tigris in northeastern Turkey. With the astronomical diaries also providing systematic meteorological information (unparalleled in resolution and scope until at least the Early Modern period) ranging from wind direction and intensity, to the level of cloud cover and references to atmospheric clarity (clear vs. dusty skies), to the general conditions (temperature and precipitation) for all seasons, these sources can in combination with natural archives such as ice-cores open an unprecedented window into the Middle Eastern climate of the first millennium BCE.

Nor are these or other written sources from the region silent on the societal consequences of extreme weather and other climatic shocks. We will thus finish our paper with a brief case study of responses to the climatic impacts of explosive volcanism during the reign of Esarhaddon, ruler of Assyria, who's reign from 672 BCE suddenly became a troubled one. Contemporary prophecies indicated a loss of cattle, the failure of dates and sesame and the arrival of locusts. Such prophecies were often descriptions of events already occurring and along with predictions dated to 671 of 'darkness in the land', crop failure and famine, there is definite evidence that Esarhaddon resorted to the ritual of placing a substitute (sacrificial) ruler on the throne for 100 days. This did not, however, resolve the dangers perceived by the Assyrian ruler and he repeated the ritual in 670, along with apotropaic rituals against malaria and plague. That year, nevertheless, saw revolt. Herdsmen refused to supply oxen and sheep to the government officials, who could not travel the land without armed escort. Regional governors appropriated revenues and construction workers halted brick production. Esarhaddon acted decisively in late 670, early 669, executing a large number of rebellious Assyrian nobles. 669 and 668 remained troubled, however, with prophecies of locusts and plague among cattle and humans, while in 667 Egypt revolted against Assyria in the context of possible shortages of barely and straw.

This paper is a contribution to the Irish Research Council-funded “Climates of Conflict in Ancient Babylonia” (CLICAB) project.

How to cite: Ludlow, F., Kostick, C., McGovern, R., and Farrelly, L.: Volcanic Impacts on Climate and Society in First Millennium BCE Babylonia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22127, https://doi.org/10.5194/egusphere-egu2020-22127, 2020.

    During the last 2 years (2018-2019) a series of volcanic eruptions led to remarkable enhancements in stratospheric aerosol load. These are eruptions of Ambae (July 2018, Vanuatu), Raikoke (June 2019, Russia) and Ulawun (July 2019, Papua New Guinea). In this study we examine the evolution of the stratospheric aerosol bulk optical properties following these events in consideration of large-scale stratospheric circulation. We use long-term aerosol records by ground-based lidars in both hemispheres together with global observations by various satellite missions (OMPS-LP, SAGE III, OSIRIS, CALIOP) and discuss the consistency between these datasets.  In addition, we evaluate the preliminary lower stratosphere aerosol product by ESA Aeolus mission through intercomparison with ground-based lidars.

   The 28-yr Observatoire de Haute Provence (OHP) lidar record shows that Raikoke eruption has led to the strongest enhancement of stratospheric aerosol optical depth (SAOD) in the northern extratropics since Pinatubo eruption. Satellite observations suggest that the stratospheric plume of Raikoke has dispersed throughout the entire Northern hemisphere and ascended up to 27 km altitude. The eruption of Ulawun in the tropics has further boosted the stratospheric aerosol load and by Fall 2019, the global mean SAOD was a factor of 2.5 higher than its background level.

    At the turn of the year 2020, while both Raikoke and Ulawun aerosols were still present in the stratosphere, a dramatic bushfire event accompanied by vigorous fire-induced thunderstorms (PyroCb) in eastern Australia caused a massive injection of smoke into the stratosphere. The early detections of stratospheric smoke by OMPS-LP suggest that the zonal-mean SAOD perturbation caused by this event exceeds the previous record-breaking PyroCb-related perturbation after the British Columbia fires in August 2017. We use satellite observations of aerosol and trace gases (H2O, CO) to characterize the stratospheric impact of the wildfires and contrast it with that of volcanic eruptions.

How to cite: Khaykin, S., Godin-Beekmann, S., Taha, G., Feofilov, A., Bourassa, A., Rieger, L., and Hauchecorne, A.: Recent evolution of stratospheric aerosol load from ground-based lidars and satellites: impact of volcanic eruptions and wildfires. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11246, https://doi.org/10.5194/egusphere-egu2020-11246, 2020.

Using a combination of satellite, ground-based and in-situ observations, and radiative transfer modelling, we quantify the impact of the most recent moderate volcanic eruptions (Ambae, Vanuatu in July 2018; Raikoke, Russia and Ulawun, New Guinea in June 2019) on the global stratospheric aerosol layer and climate.

For the Ambae volcano (15°S and 167°E), we use the Stratospheric Aerosol and Gas Experiment III (SAGE III), the Ozone Mapping Profiler Suite (OMPS), the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Himawari geostationary satellite observations of the aerosol plume evolution following the Ambae eruption of July 2018. It is shown that the aerosol plume of the main eruption at Ambae in July 2018 was distributed throughout the global stratosphere within the global large-scale circulation (Brewer-Dobson circulation, BDC), to both hemispheres. Ground-based LiDAR observations in Gadanki, India, as well as in-situ Printed Optical Particle Spectrometer (POPS) measurements acquired during the BATAL campaign confirm a widespread perturbation of the stratospheric aerosol layer due to this eruption. Using the UVSPEC radiative transfer model, we also estimate the radiative forcing of this global stratospheric aerosol perturbation. The climate impact is shown to be comparable to that of the well-known and studied recent moderate stratospheric eruptions from Kasatochi (USA, 2008), Sarychev (Russia, 2009) and Nabro (Eritrea, 2011). Top of the atmosphere radiative forcing values between -0.45 and -0.60 W/m², for the Ambae eruption of July 2018, are found.

In a similar manner the dispersion of the aerosol plume of the Raikoke (48°N and 153°E) and Ulawun (5°S and 151°E) eruptions of June 2019 is analyzed. As both of those eruptions had a stratospheric impact and happened almost simultaneously, it is challenging to completely distinguish both events. Even though the eruptions occurred very recently, first results show that the aerosol plume of the Raikoke eruption resulted in an increase in aerosol extinction values, double as high as compared to that of the Ambae eruption. However, as the eruption occurred on higher latitudes, the main bulk of Raikoke aerosols was transported towards the northern higher latitude’s in the stratosphere within the BDC, as revealed by OMPS, SAGE III and a new detection algorithm for SO₂ and sulfate aerosol using IASI (Infrared Atmospheric Sounder Interferometer). Even though the Raikoke eruption had a larger impact on the stratospheric aerosol layer, both events (the eruptions at Raikoke and Ambae) have to be considered in stratospheric aerosol budget and climate studies.

How to cite: Kloss, C., Sellitto, P., Legras, B., Vernier, J.-P., Jégou, F., Ratnam, M. V., Kumar, B. S., Madhavan, B. L., Eremenko, M., and Berthet, G.: Impact of the Ambae, Raikoke and Ulawun eruptions in 2018-2019 on the global stratospheric aerosol layer and climate, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2406, https://doi.org/10.5194/egusphere-egu2020-2406, 2020.

Volcanic eruptions pose a serious threat to the aviation industry causing widespread disruption. To identify any potential impacts, nine Volcanic Ash Advisory Centres (VAACs) provide global monitoring of all eruptions, informing stakeholders how each volcanic eruption might interfere with aviation. Numerical dispersion models represent a vital infrastructure when assessing and forecasting the atmospheric conditions from a volcanic plume.

In this study we investigate the 2019 Raikoke eruption, which emitted approximately 1.5 Tg of sulfur dioxide (SO₂) representing the largest volcanic emission of SO₂ into the stratosphere since the Nabro eruption in 2011. Using the UK Met Office’s Numerical Atmospheric-dispersion Modelling Environment (NAME), we simulate the evolution of the volcanic gas and aerosol particle plumes (SO₂ and sulfate, SO₄) across the Northern Hemisphere between 21^st June and 17^th July. We evaluate the skills and limitations of NAME in terms of modelling volcanic SO₂ plumes, by comparing our simulations to high-resolution measurements from the Tropospheric Monitoring Instrument (TROPOMI) on-board the European Space Agency (ESA)’s Sentinel 5 – Precursor (S5P) satellite.

Our comparisons show that NAME accurately simulates the observed location and shape of the SO₂ plume in the first few weeks after the eruption. NAME also reproduces the magnitude of the observed SO₂ vertical column densities, when emitting 1.5 Tg of SO₂, during the first 48 hours after the eruption. On longer timescales, we find that the model-simulated SO₂ plume in NAME is more diffuse than in the TROPOMI measurements, resulting in an underestimation of the peak SO₂ vertical column densities in the model. This suggests that the diffusion parameters used in NAME are too large in the upper troposphere and lower stratosphere.

Finally, NAME underestimates the total mass of SO₂ when compared to estimates from TROPOMI, however emitting 2 Tg of SO₂ in the model improves the comparison, resulting in very good agreement with the satellite measurements.

How to cite: de Leeuw, J., Schmidt, A., Witham, C., Theys, N., Pope, R., Haywood, J., Osborne, M., and Kristiansen, N.: Dispersion Model Evaluation for the Sulfur Dioxide Plume from the 2019 Raikoke Eruption using Satellite Measurements., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16028, https://doi.org/10.5194/egusphere-egu2020-16028, 2020.

Constraining emission inventories into chemistry-transport models (CTM) is essential. In addition to anthropogenic emissions, natural sources of pollutants must be considered. Among them, volcanoes are large emitters of gases, including sulfur dioxide (SO₂), a volatile species, causing environmental and health issues.

Volcanic SO₂ emission inventories are usually integrated in global CTMs, in order to improve the modelling of chemical species in the atmosphere. Here, we use the model MOCAGE, developed at CNRM, which currently uses Andres & Krasgnoc’s inventory (1998); a temporal average of emission on some 40 volcanoes, monitored through the synergy of satellite data and surface remote sensing instruments, for 25 years (from 1970’s to 1997). However, this inventory is now quite old and is therefore no longer sufficiently accurate.

Thanks to the development of new satellite observations, it has become possible to produce such inventories with an improved accuracy. The global coverage and higher sensitivity of these instruments has allowed to reference more emission sources (hard-to-access volcanoes, small eruptions or even passive degassing). Hence, a new inventory of Carn et al (2016,2017) based on satellite observations has been implemented in MOCAGE. Besides being recent (from 1978 up to 2015), it combines eruption and passive degassing over more than 160 volcanoes. Passive degassing fluxes are provided as annual averages and eruption fluxes as daily total quantities (in case of events). In addition, information on volcanoes vent altitude and eruptive plume heights is available, which has been used to better constraints the model.

We focus our study at the global scale. The years 2013 and 2014 were chosen as the years with the lowest and highest total eruptive emissions respectively, in Carn's inventory. Thus, 2013 highlights mainly the impact of passive degassing, while 2014 provides additional information on eruptions.

For each of the years studied, the sulfur species budget in MOCAGE simulation is increased when the inventory is updated and therefore the relative contribution of volcanic sulfur emissions is larger. We note the global increase in sulfur dioxide and sulfate aerosol burdens; an increase even more significant when the injection heights of the emissions are taken into account.

How to cite: Lamotte, C., Marécal, V., and Guth, J.: Update of the volcanic sulfur emission inventory in MOCAGE CTM and its impact on the budget of sulfur species in the atmosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4791, https://doi.org/10.5194/egusphere-egu2020-4791, 2020.

Satellite remote sensing has been widely used to make measurements of sulphur dioxide (SO₂) emissions from volcanoes. The Infrared Atmospheric Sounding Interferometer (IASI) is one such instrument that has been used to examine the emissions from large explosive eruptions.  Much less work has been done using IASI to study the emissions from smaller eruptions, non-eruptive degassing or anthropogenic sources, and similarly it is rarely used for examining long term trends in activity.  Now, when there are three IASI instruments in orbit and with over ten years of data, is the perfect opportunity to explore these topics. This study applied a ‘fast’ linear retrieval developed for IASI in Oxford, across the globe for a ten-year period. Global annual averages were dominated by the emissions from large eruptions (e.g. Nabro in 2011) but elevated signals could also be identified from smaller volcanic sources and industrial centres, suggesting the technique has promise for detecting lower level emissions. A systematic approach was then taken, rotating the linear retrieval output for each orbit at over 100 volcanoes worldwide, with the wind direction at the volcano’s vent, or in cases where the plume was emitted at a greater height, using the observed plume direction. This isolates the elevated signal downwind of the volcano. The rotated outputs were then averaged over monthly, annual and multi-annual time periods. Analysis of the upwind and downwind values establishes whether there is an elevated signal and its intensity. An inventory was then constructed from these observations which show how these emissions varied over a ten-year period. Trends in SO₂ emission were compared against fluxes generated for the Ozone Monitoring Instrument (OMI) and the number of thermal anomalies detected by the MODVOLC algorithm developed for MODIS.  It was identified for example, that long term trends are more easily identified at high altitude volcanoes such as Popocatepetl, Sabancaya and Nevado del Ruiz. This is consistent with the idea that the instrument performs better in regions with lower levels of water vapour (e.g. above the boundary layer).

How to cite: Taylor, I., Carboni, E., Mather, T. A., and Grainger, R. G.: Monitoring volcanic SO2 emissions with the Infrared Atmospheric Sounding Interferometer, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-797, https://doi.org/10.5194/egusphere-egu2020-797, 2020.

Around the world, there are a number of volcanoes which are passively degassing, chronically exposing communities to potentially-harmful gases and aerosols. The medical evidence, to date, is unclear about the long-term health impacts of such exposures, but there is evidence that people experience an exacerbation of existing respiratory disease, such as asthma, bronchitis, and COPD. In addition, there are a range of physiological and psychological symptoms which even otherwise healthy people experience, which can impact their lives and livelihoods. In Hawaii, prior to the end of the 2018 Lower East Rift Zone eruption crisis of Kīlauea Volcano, communities downwind of the vents were frequently exposed to volcanic pollution or ‘vog’, with exposures worsening during the 2018 crisis. Local emergency and health agencies provided generic advice on measures to reduce exposure but the usefulness and uptake of the advice was unknown. A survey of Hawai’i island residents in 2015, highlighted the range and severity of symptoms that they perceived to be caused by vog exposures, and exposed a lack of application of the official advice. Some respondents described how their lifestyles (e.g., the open structure of their homes and availability of air conditioning) didn’t allow them to implement key strategies such as closing doors and windows and staying indoors. The perceived irrelevance of official advice, and a perception, by some, that vog information was suppressed due to political pressures, led to mistrust in the official agencies by a subset of the population. The survey also revealed undocumented strategies that individuals were using to protect themselves and cope with symptoms of vog exposure. In partnership with local agencies, we rewrote the guidance to be more applicable to the local situation. Revised guidance incorporated successful local practices, where medical evidence of efficacy could be found. We also developed an online interagency ‘vog dashboard’ that provided a comprehensive source for vog information and advice. The ‘Vog Talk’ Facebook page was also initiated to provide a forum for informal discussion amongst community members and between communities and agency representatives. During the 2018 eruption crisis, these resources were extensively utilised and were considered primary sources of information for Hawaii residents, tourists and the world’s media. The experience in Hawaii demonstrates the importance of a multi-disciplinary approach to engaging communities, with health management professionals, physical and social scientists, and community representatives working together to ensure that issued advice is trusted, relevant and practical.

How to cite: Horwell, C. J. and Elias, T.: ‘This advice is absurd’: issues with providing generic advice on community protection from chronic volcanic degassing, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16190, https://doi.org/10.5194/egusphere-egu2020-16190, 2020.

Volcanoes emit a chemically complex cocktail of gases and aerosols into the atmosphere, which can affect Earth’s climate (1) and human health. The vast majority of volcanogenic fatalities involve the obvious thermal and physical injuries resulting from an eruption, but many of the emissions from volcanoes are toxic and include compounds such as sulfates and metals, which are known to disrupt biological systems (2). Yet, there is a lack of knowledge on the toxicity of compounds found in volcanic plumes and their fate in the atmosphere.

Research has focussed on the impacts of large-magnitude explosive eruptions. While emissions from many non-explosive eruptions are continuous and prolonged, their climatic and potential effects on human health have not been studied extensively. Once the plume disperses in the atmosphere, the aerosol particle components can mix and interact with oxidants and organic compounds present in the atmosphere. How these chemical components interact and how the interactions affect the Earth’s climate, particle toxicity and human health is largely unknown especially for trace metals.

In the framework of the EPL-REFLECT (Etna Plume Lab – near-source estimations of Radiative EFfects of voLcanic aErosols for Climate and air quality sTudies), a field campaign on Mount Etna was done in July 2019 in which samples of atmospheric aerosol were collected during non-explosive degassing activity. Samples were collected both at the crater and in a transect following the volcanic plume down slope to the closest inhabited areas. Samples were analysed for trace metals and organic compounds, including solubility tests (3) to assess how tropospheric processing of the aerosol affects metal bioavailability and potentially the toxicity of the aerosol.

(1) von Glasow, R. 2010. Atmospheric chemistry in volcanic plumes. Proceedings of the National Academy of Sciences, vol. 107, pp. 6594–6599., DOI: 10.1073/pnas.0913164107

(2) Weinstein, P., Horwell, C.J., Cook, A. 2013. Volcanic Emissions and Health. In: Essentials of Medical Geology, Springer Netherlands, Dordrecht, pp. 217–238., DOI: 10.1007/978-94-007-4375-5_10

(3) Tapparo, A., Di Marco, V., Badocco, D., D’Aronco, S., Soldà, L., Pastore, P., Mahon, B.M., Kalberer, M., Giorio, C. 2019. Formation of metal-organic ligand complexes affects solubility of metals in airborne particles at an urban site in the Po Valley. Chemosphere, in press., DOI: 10.1016/j.chemosphere.2019.125025

How to cite: Giorio, C., D'Aronco, S., Soldà, L., Giammanco, S., La Spina, A., Salerno, G., Donatucci, A., Caltabiano, T., and Sellitto, P.: Solubility of metals in aerosol samples from Mount Etna during the EPL-REFLECT campaign, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9858, https://doi.org/10.5194/egusphere-egu2020-9858, 2020.

The 2018 eruption of Kīlauea volcano, Hawai'i, resulted in enormous gas emissions from the Lower East Rift Zone (LERZ) of the volcano. This led to important changes to air quality in downwind communities. We analyse and present measurements of atmospheric sulfur dioxide (SO₂) and aerosol particulate matter < 2.5 µm (PM_2.5) collected by the Hawai'i Department of Health (HDOH) and National Park Service (NPS) operational air quality monitoring networks between 2007 and 2018; and a community-operated network of low-cost PM_2.5 sensors on the Island of Hawai'i. During this period, the two largest observed increases in Kīlauea's volcanic emissions were: the summit eruption that began in 2008 (Kīlauea emissions averaged 5 – 6 kt/day SO₂ over the course of the eruption) and the LERZ eruption in May-August 2018 when SO₂ emission rates likely reached 200 kt/day in June. Here we focus on characterising the airborne pollutants arising from the 2018 LERZ eruption and the spatial distribution and severity of air pollution events across the Island of Hawai'i. The LERZ eruption caused the most frequent and severe exceedances of Environmental Protection Agency 24-hour-mean PM_2.5 air quality thresholds in Hawai'i since 2010. In Kona, for example, there were eight exceedances during the 2018 LERZ eruption, where there had been no exceedances in the previous eight years as measured by the HDOH and NPS networks. SO₂ air pollution during the LERZ eruption was most severe in communities in the south and west of the island, with maximum 24-hour-mean mass concentrations of 728 µg/m³ recorded in Ocean View (100 km west of the LERZ emission source) in May 2018. Data from the low-cost sensor network correlated well with data from the HDOH PM_2.5 instruments (Kona station, R² = 0.89), demonstrating that these low-cost sensors provide a viable means to rapidly augment reference-grade instrument networks during crises.

How to cite: Whitty, R., Ilyinskaya, E., Mason, E., Wieser, P., Liu, E., Schmidt, A., Roberts, T., Pfeffer, M., Brooks, B., Mather, T., Edmonds, M., Elias, T., Schneider, D., Oppenheimer, C., Dybwad, A., Nadeau, P., and Kern, C.: Spatial and temporal variations in ambient SO2 and PM2.5 levels influenced by Kīlauea Volcano, Hawai'i, 2007 - 2018, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-405, https://doi.org/10.5194/egusphere-egu2020-405, 2020.

The ca. 74 ka BP ‘‘super-eruption’’ of Toba volcano in Sumatra is the largest known Quaternary eruption. It expelled an estimated of 2800 km³ of dense rock equivalent, creating a caldera of 100 x 30 km. The eruption is estimated to have been 3500 greater than the Tambora eruption that created the “year without summer” in 1816 in Europe (Oppenheimer, 2002). However, the consequences of this “mega-eruption” on the climate and human evolution that could be expected for such eruption are still debated and uncertain. There is no evidence that this eruption has triggered any catastrophic climate change such as a “nuclear winter”. One of such lack of evidence lies in the ice.

In the ice core community, this eruption still remains a mystery. Indeed, the estimated size of the eruption should have left a gigantic mark in the ice, at least in the form of a huge sulfuric acid layer but none of the ice records covering this period show any such singularity. The sulfate record seems so common that it is in fact difficult to allocate a specific sulfate peak to this event.

In an effort to synchronize the Vostok ice core and the EPICA Dome C core, (Svensson et al., 2013) have identified three possible sulfuric acid layers for the Toba eruption in the Vostok ice core. In order to see if one of such event could have been the Toba eruption, we have performed the sulfur  & oxygen isotope analysis of these three sulfuric acid layers in the hope that it could reveal some particularity. The sulfur results show that 1- all these three events have injected their products in the stratosphere and 2- the sulfur isotopic compositions of these three events share a common array, array that is in lines with other stratospheric eruptions, however one of the three acid layers shows an extremely and unusual weak oxygen anomaly, potentially indicating a major eruption. In order to remove the last doubts about the existence or not of one or a series of eruptions related to TOBA, the geochemical analysis of volcanic glasses trapped in the ice will be performed and presented.

How to cite: Savarino, J., Gautier, E., Caillon, N., Albalat, E., Albarède, F., Hattori, S., Petit, J.-R., and Lipenkov, V.: Where is the Toba eruption in the Vostok ice core? Clues from tephra, O and S isotopes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4, https://doi.org/10.5194/egusphere-egu2020-4, 2020.

Volcanic eruptions trigger a broad spectrum of climatic responses. For example, the Mount Pinatubo eruption in 1991 forced an El Niño and global cooling, and the Tambora eruption in 1815 caused the "Year Without a Summer." Especially grand eruptions such as Toba around 74,000 years ago can push the Earth's climate into a volcanic winter state, significantly lowering the surface temperature and precipitation globally. Here we present a new, previously overlooked element of the volcanic effects spectrum: the radiative mechanism of stratospheric ozone depletion. We found that the volcanic plume of Toba enhanced the UV optical depth and suppressed the primary formation of stratospheric ozone from O₂ photolysis. Sulfate aerosols additionally reflect the photons needed to break the O₂ bond (λ < 242 nm), otherwise controlled by ozone absorption and Rayleigh scattering alone during volcanically quiescent conditions. Our NASA GISS ModelE simulations of the Toba eruption reveal up to 50% global ozone loss due to the overall photochemistry perturbations of the sulfate aerosols. We also consider and quantify the radiative effects of SO₂, which partially compensated for the ozone loss by inhibiting the photolytic O₃ sink.

Our analysis shows that the magnitude of the ozone loss and UV-induced health-hazardous effects after the Toba eruption are similar to those in the aftermath of a potential nuclear conflict. These findings suggest a “Toba ozone catastrophe" as a likely contributor to the historic population decline in this period, consistent with a genetic bottleneck in human evolution.

How to cite: Osipov, S., Stenchikov, G., Tsigaridis, K., LeGrande, A., Bauer, S., Fnais, M., and Lelieveld, J.: Toba volcano super eruption destroyed the ozone layer and caused a human population bottleneck, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4131, https://doi.org/10.5194/egusphere-egu2020-4131, 2020.

The major eruption of the Cerro Blanco Volcanic Complex (CBVC), in the Central Volcanic Zone of the Andes, NW Argentina, dated at 4410–4150 a cal BP, was investigated confirming that is the most important of the three major Holocene felsic eruptive events identified in the southern Puna (Fernandez-Turiel et al., 2019). Identification of pre–, syn–, and post–caldera products of CBVC allowed us to estimate the distribution of the Plinian fallout during the paroxysmal syn–caldera phase of the eruption. Results provide evidence for a major rhyolitic explosive eruption that spread volcanic deposits over an area of about 500,000 km², accumulating >100 km³ of tephra (bulk volume). This last value exceeds the lower threshold of Volcanic Explosive Index (VEI) of 7. Ash-fall deposits mantled the region at distances >400 km from source and thick pyroclastic-flow deposits filled neighbouring valleys up to several tens of kilometres from the vent. This eruption is the largest documented during the past five millennia in the Central Volcanic Zone of the Andes, and is probably one of the largest Holocene explosive eruptions in the world.

The implications of the findings of the present work reach far beyond having some chronostratigraphic markers. Further interdisciplinary research should be performed in order to draw general conclusions on these impacts in local environments and the disruptive consequences for local communities. This is invaluable not just for understanding how the system may have been affected over time, but also for evaluating volcanic hazards and risk mitigation measures related to potential future large explosive eruptions.

Financial support was provided by the ASH and QUECA Projects (MINECO, CGL2008–00099 and CGL2011–23307). We acknowledge the assistance in the analytical work of labGEOTOP Geochemistry Laboratory (infrastructure co–funded by ERDF–EU Ref. CSIC08–4E–001) and DRX Laboratory (infrastructure co–funded by ERDF–EU Ref. CSIC10–4E–141) (J. Ibañez, J. Elvira and S. Alvarez) of ICTJA-CSIC, and EPMA and SEM Laboratories of CCiTUB (X. Llovet and J. Garcia Veigas). This study was carried out in the framework of the Research Consolidated Groups GEOVOL (Canary Islands Government, ULPGC) and GEOPAM (Generalitat de Catalunya, 2017 SGR 1494).

Fernandez–Turiel, J.L., Perez–Torrado, F.J., Rodriguez–Gonzalez, A., Saavedra, J., Carracedo, J.C., Rejas, M., Lobo, A., Osterrieth, M., Carrizo, J.I., Esteban, G., Gallardo, J., Ratto, N., 2019. The large eruption 4.2 ka cal BP in Cerro Blanco, Central Volcanic Zone, Andes: Insights to the Holocene eruptive deposits in the southern Puna and adjacent regions. Estudios Geologicos 75, e088.

How to cite: Fernandez-Turiel, J.-L., Perez-Torrado, F.-J., Rodríguez-Gonzalez, A., Ratto, N., Rejas, M., and Lobo, A.: The 4.2 ka cal BP major eruption of Cerro Blanco, Central Andes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5038, https://doi.org/10.5194/egusphere-egu2020-5038, 2020.

Explosive eruptions of the Plinian type inject large amounts of particles (pumice, ash, aerosols) and volatile species into the atmosphere. They result from the rapid discharge of a magma chamber and involve large volumes of magma (from a km³ to hundreds of km³). Such eruptions correspond to a rapid ascent of magma in the conduit driven by the exsolution of volatile species. If the magma supply is continuous, this jet produces a convective eruptive column that can reach tens of km in height and transports gas and particles (pumice, ash, aerosols) directly into the stratosphere. Depending on the latitude of the volcano, the volume of implied magma, the height of the eruptive plume and the composition of the released gaseous and particulate mixture, these events can strongly affect the environment at the local or even at a global scale. Almost all studies on global impacts of volcanic eruptions have largely focused on the sulfur component. Volcanoes are also responsible for the emission of halogens which have a crucial impact on the ozone layer and therefore the climate.

The objective of our project is to revisit the issue of the impact of volcanism on the atmosphere and climate by considering not only the sulfur component but also the halogen component. We will provide field work-based constraints on the strength of halogen (Cl and Br) emissions and on degassing processes for key eruptions, we will characterise the dynamics of volcanic plumes, notably the vertical distribution of emissions and we will explore and quantify the respective impacts of sulfur and halogen emissions on the ozone layer and climate.

Here we will shed light on the methodology that will combine field campaign, laboratory analysis of collected samples and a hierarchy of modelling tools to study. We use an approach combining field studies, petrological characterization, geochemical measurements including isotopic data, estimation of the volume of involved magma and the height of injection of gases and particles by modelling the eruptive plume dynamic and numerical simulation of the impacts at the plume scale and at the global scale.  The first halogen budget will also be presented.

How to cite: Balcone-Boissard, H., D'Augustin, T., Boudon, G., Bekki, S., Bonifacie, M., Boudouma, O., Bouvier, A.-S., Carazzo, G., Deloule, E., Fialin, M., and Rividi, N.: Impact of volcanic halogens on the ozone layer and climate, a look to the past to highlight the present , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19275, https://doi.org/10.5194/egusphere-egu2020-19275, 2020.

The large VEI= 6 explosive eruption of the Laacher See volcano dated to c. 13,000 yrs BP (Reinig et al., 2020) marks the end of explosive volcanism in the East Eifel volcanic zone (Germany). It has previously been argued that this eruption temporarily impacted Northern Hemisphere climate (Graf and Timmreck, 2001), environments (Baales et al., 2002) and human communities (e.g. Blong et al., 2018). It has also recently been suggested again that the eruption may in fact be implicated in the onset of the Younger Dryas. Recent advances in the modelling of volcanically-induced climatic forcing warrant renewed attention to the eruption’s potential influence on Northern Hemisphere climate. Detailed reconstructions of its eruption dynamics have been proposed. The eruption might have lasted several weeks, most likely with a short (~10h) intense initial phase. A bipartite NE- and S- plume deposited tephra to the north-east the volcano towards the Baltic Sea and to the south towards Italy (Riede et al., 2011). 
In revisiting the eruption’s potential influence on Northern Hemisphere climate, we here present revised model simulations of the radiative impacts of the LSE using a global stratospheric aerosol model and new sulphur dioxide (SO2) emission estimates. The simulations were performed with the general circulation model MAECHAM5-HAM, which is coupled to an aerosol microphysical model. This allows us to simulate the evolution of the volcanic sulfur cloud and the transport of the ash cloud. The position of the observed deposits of the LSE depend on the weather and the wind direction during the eruption, demanding specific weather conditions to simulate similar locations of the observed deposits. Our models provide significantly improved insights into the meteorological situation during the eruption event as well as its impacts on Northern Hemisphere climate, with attendant implications for ecological and cultural impacts.

References
Baales, M., Jöris, O., Street, M., Bittmann, F., Weninger, B. and Wiethold, J.: Impact of the Late Glacial Eruption of the Laacher See Volcano, Central Rhineland, Germany, Quaternary Research, 58(3), 273–288, doi:10.1006/qres.2002.2379, 2002.
Blong, R. J., Riede, F. and Chen, Q.: A fuzzy logic methodology for assessing the resilience of past communities to tephra fall: a Laacher See eruption 13,000 year BP case, Volcanica, 1(1), 63–84, doi:https://doi.org/10.30909/vol.01.01.6384, 2018.
Graf, H.-F. and Timmreck, C.: A general climate model simulation of the aerosol radiative effects of the Laacher See eruption (10,900 B.C.), Journal of Geophysical Research, 106(14), 14747–14756, doi:0148-0227/01/2001JD900152, 2001.
Reinig, F., Cherubini, P., Engels, S., Esper, J., Guidobaldi, G., Jöris, O., Lane, C., Nievergelt, D., Oppenheimer, C., Park, C., Pfanz, H., Riede, F., Schmincke, H.-U., Street, M., Wacker, L. and Büntgen, U.: Towards a dendrochronologically refined date of the Laacher See eruption around 13,000 years ago, Quaternary Science Reviews, 229, 106128, doi:10.1016/j.quascirev.2019.106128, 2020.
Riede, F., Bazely, O., Newton, A. J. and Lane, C. S.: A Laacher See-eruption supplement to Tephrabase: Investigating distal tephra fallout dynamics, Quaternary International, 246(1–2), 134–144, doi:doi: 10.1016/j.quaint.2011.06.029, 2011.

How to cite: Niemeier, U., Riede, F., Timmreck, C., and Zernack, A.: Revisiting the climate impact of the ~13,000 yr BP Laacher See eruption, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8656, https://doi.org/10.5194/egusphere-egu2020-8656, 2020.

Several uncertainties affect the simulation of the climatic response to strong volcanic forcing by coupled climate models, which primarily stem from model specificities and intrinsic variability. To better understand the relative contribution of both sources of uncertainties, the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP) has been initiated as part of the CMIP6 protocol. VolMIP has defined a coordinated set of idealized volcanic perturbation experiments with prescription of the same volcanic forcing and coherent sampling of initial conditions to be performed to the different participating coupled climate models. However, as the VolMIP effort focuses on comparison across different models, an open question remains about how different configurations of the same model affect the comparability of results.

 Here, we present first results of CMIP6 VolMIP simulations performed with the MPIESM1.2 in two resolutions. The low resolution (LR) configuration employs an atmospheric resolution of T63 (~200 km), and nominal ocean resolution of 1.5°. The high resolution (HR) configuration employs twice of the horizontal resolution of its atmospheric component (T127 ~100 km)   with a spontaneously generated QBO, and an eddy-permitting ocean resolution of  0.4°.

In this contribution we illustrate results from the volc-pinatubo experiments, which focus on the assessment of uncertainty in the seasonal-to-interannual climatic response to an idealized 1991 Pinatubo-like eruption, and from the volc-long experiments, which are designed to investigate the long-term dynamical climate response to volcanic eruptions. We compare responses of different climate variables, e.g. near-surface air temperature, precipitation and sea ice on global and regional scale.  Special emphasis will be placed on the volcanic impact on the tropical hydrological cycle.

How to cite: Timmreck, C., Toohey, M., and Zanchettin, D.: On the dependency of simulated volcanically-forced variability to model configuration , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4045, https://doi.org/10.5194/egusphere-egu2020-4045, 2020.

Radiative forcing from stratospheric volcanic sulfate aerosols is a key driver of climate variability. However, climate change may also impact volcanic forcing which remains largely unexplored. Atmospheric processes indeed control virtually all mechanisms that govern volcanic forcing, such as the rise of the volcanic column, the chemical and microphysical evolution of volcanic aerosols and their transport in the atmosphere.

Accordingly, we present novel numerical experiments combining chemistry-climate and volcanic plume modelling to investigate how climate change will affect volcanic forcing. We compare the aerosol evolution and radiative forcing following two eruption cases in two different climates (historical 1990’s and SSP5 8.5 2090’s). We chose two tropical eruptions: i) a strong intensity (i.e., mass flux), Pinatubo-like eruption emitting 10 Tg of sulfur dioxide (SO₂); and ii) a moderate intensity eruption emitting 1 Tg of SO₂, similar to eruptions such as those of Merapi in 2010, Nabro in 2011 or Kelud in 2014, which have had major impacts on the stratospheric aerosol background and are thought to have contributed to the global temperature hiatus in the early 21^st century. The chemistry-climate model that we use (UM_UKCA version 11.2) has the capacity to interactively simulate the chemical and microphysical evolution of stratospheric sulfate aerosol given an initial injection of SO₂. Furthermore, we use a plume model to calculate SO₂ injection heights for a given eruption intensity and atmospheric conditions simulated by UM-UKCA.

In our experiments, the peak stratospheric aerosol optical depth (SAOD) of the high-intensity, Pinatubo-like eruption increases by 10% in the SSP5 8.5 2090 climate compared to the historical 1990 climate. Furthermore, the peak global-mean top-of-the-atmosphere radiative forcing of the same eruption increases by 30%. In contrast, the peak SAOD of the moderate intensity eruption decreases by a factor of 4 (with radiative forcing being small compared to simulated natural variability). Our results thus suggest that volcanic forcing will become more extreme and polarized in the future, with the forcing associated with moderate-intensity and relatively frequent eruptions being muted, but the forcing associated with high-intensity and relatively rare eruptions being amplified. We analyze which mechanisms are responsible for the simulated impacts of climate change on volcanic forcing, and discuss potential additional feedbacks expected in our future ocean-atmosphere coupled simulations.

How to cite: Aubry, T., Schmidt, A., and Haywood, J.: Interactive stratospheric aerosol model experiments suggest a strong impact of climate change on the aerosol evolution and radiative forcing from future eruptions., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3464, https://doi.org/10.5194/egusphere-egu2020-3464, 2020.

Large volcanic eruptions can affect the global climate through changes in atmospheric and ocean circulation. Understanding the influence of volcanic eruptions on the hydroclimate over monsoon regions is of great scientific and social importance. The South America Monsoon System (SAMS) is the most important climatic feature of the continent. Both the Intertropical and the South Atlantic wind convergence zones (ITCZ and SACZ, respectively) are fundamental components of the SAMS. They show variations on a broad range of scales, dependent on complex multi-system interactions with the adjacent Atlantic Ocean and teleconnections. Also driven by the winds, the Atlantic Subtropical Cell (STC) is the link between the subduction zone in the subtropical gyre with the tropics. Hence, the STC influence equatorial sea surface temperature variability on interannual to decadal scales in the tropical Atlantic Ocean. In order to improve our understanding of the responses of the ocean-atmosphere system to the volcanic forcing, we aim to identify the dominant mechanisms of seasonal-to-interdecadal variability of the SAMS and the Atlantic STC after large Pinatubo-like (1991) and Tambora-like (1815) eruptions relying on the VolMIP model intercomparison project experiments.

How to cite: Sobral Verona, L., Wainer, I., and Khodri, M.: How volcanism impact on the variability of the South American Monsoon System and the associated Atlantic Subtropical Cell, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-289, https://doi.org/10.5194/egusphere-egu2020-289, 2020.

Large tropical volcanic eruptions are well known to change the global climate and maybe even interfere with some natural modes of variability such as El Niño Southern Oscillation. As they inject a high amount of sulfur gas into the stratosphere, sulfate aerosol loading increases a few months after the eruption, which is then transported globally. Large tropical events may, therefore, affect extratropical climate variability. For example, temperature changes have been identified in Antarctica after the Pinatubo eruption in 1991, as warming in the peninsula. However, a causal link with the eruption and, more generally, a possible influence of large tropical volcanic eruptions on the Southern Hemisphere climate are still open questions. In this study we aim to focus on the five biggest eruptions of the historical period (Krakatau — Aug/1883, Santa María — Oct/1902, Mt Agung — Mar/1963, El Chichón — Apr/1982 and Pinatubo — Jun/1991) by assessing two CMIP6 class models (IPSL-CM6A-LR Large Ensemble and BESM) and two Reanalyses (NOAA 20th Century Reanalysis and ECMWF's ERA 20th Century).

How to cite: Silva, N., Wainer, I., and Khodri, M.: Antarctic climate response to large volcanic eruptions in the historical period, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-291, https://doi.org/10.5194/egusphere-egu2020-291, 2020.

In this study we investigate the the South Atlantic Ocean response to large tropical volcanic eruptions for the historial periods. In particular, we analyse the changes in the coupling of the ocean and the atmosphere over that ocean basin triggered by changes in the amount of incoming shortwave radiation.

The analysis consists of averaging the response of the five biggest eruptions in the last 200 years, namely, Krakatoa (1883), Santa Maria (1902), Agung (1963), El Chichón (1982) and Pinatubo (1991), represented by the IPSL-CMP6-LR Large Ensemble, from the Institut Pierre Simon Laplace, and the BESM-CMIP6, from INPE-CPTEC. We perform the same analysis on reanalysis products as well, such as the HadISST and NOAA's ERSSTv5.

In order to capture the interannual change in the climate variability, we use two climate indices that assess the coupling of ocean and atmosphere over this timescale, namely, the Atlantic Meridional Mode (AMM) and the South Atlantic Subtropical Dipole (SASD). We compute their time series from the model output and calculate their regression to the SST and precipitation fields.

Such analysis should yield more insights on how the interaction between the ocean and the atmosphere responds to external forcings, providing a better understanding of the processes that control the climate variability over the South Atlantic Ocean basin.

How to cite: Lobo Lopes, E., Elazari Klein Coaracy Wainer, I., and Khodri, M.: Investigating the volcanic impacts on Tropical South Atlantic modes of variability for the Historical period using the IPSL-CM6-LR Large Ensemble and INPE-BESM, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1132, https://doi.org/10.5194/egusphere-egu2020-1132, 2020.

The 2018 eruption on the Lower East Rift Zone of Kilauea volcano, Hawai’i released unprecedented fluxes of gases (>200 kt/d SO₂) and aerosol into the troposphere [1,2]. The eruption affected air quality across the island and lava flows reached the ocean, forming a halogen-rich plume as lava rapidly boiled and evaporated seawater.

We present the at-source composition – gas and size-segregated aerosol – of both the magmatic plume (emitted from ‘Fissure 8’, F8) and the lava-seawater interaction plume (ocean entry, OE), including major gas species, and major and trace elements in non-silicate aerosol. Trace metal and metalloid (TMM) emissions during the 2018 eruption were the highest recorded for Kilauea, and the magmatic ‘fingerprint’ of TMMs (X/SO₂ ratios) in the 2018 plume is consistent with measurements made at the summit lava lake in 2008 [3], and with other rift and hotspot volcanoes [4,5].

We show that the OE plume composition predominantly reflects seawater composition with a small contribution from plagioclase +/- ash. However, elevated concentrations of some TMMs (Bi, Cd, Cu, Zn, Ag) with affinity for Cl-speciation in the gas phase cannot be accounted for by the silicate correction and therefore may derive from degassing of lava in the presence of elevated Cl^-. In the case of silver and copper, concentrations in the OE plume are elevated above both the F8 plume and seawater.

At-vent speciation of TMMs in the F8 plume during oxidation (following a correction for ash contributions) was assessed using a Gibbs Energy Minimization algorithm (HSC chemistry, Outotec Research). We also demonstrate the sensitivity of speciation in the plume to the concentration of common ligand-forming elements, chlorine and sulfur. These results could be used as initial conditions in atmospheric reaction models to investigate how plume composition evolves as low-temperature chemistry takes over.

References:

[1] Neal C et al. (2019) Science

[2] Kern C et al. (2019) AGU Fall meeting abstract V43C-0209

[3] Mather T et al. (2012) GCA 83:292-323

[4] Zelenzki et al. (2013) Chem Geol 357:95-116

[5] Gauthier P-J et al. (2016) J Geophys 121:1610-1630

How to cite: Mason, E., Wieser, P., Liu, E., Ilyinskaya, E., Edmonds, M., Whitty, R. C. W., Mather, T., Elias, T., Nadeau, P. A., Kern, C., Schneider, D. J., and Oppenheimer, C.: Trace element emissions during the 2018 Kilauea Lower East Rift Zone eruption, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-162, https://doi.org/10.5194/egusphere-egu2020-162, 2020.

Volcanic gas emissions, in particular, of sulphur and halogen species, play an important role in atmospheric chemistry. Due to the complex reaction kinetics of halogen radicals inside the volcanic plume, many properties like e.g. chemistry limiting factors and timescales of reactions, are still not well understood.
Imaging techniques based on optical remote sensing can get valuable insights into the study of both volcanic degassing fluxes and chemical conversions within the plume that continuously mixes with the atmosphere. However, state-of-the-art techniques are either too slow to resolve plume chemistry processes on its intrinsic time scales (e.g. DOAS) or show many cross sensitivities and hence are limited to rather high trace gas concentrations (e.g. SO₂ cameras). 

We introduce a novel technique for volcanic trace gas imaging, which, by employing a Fabry-Perot interferometer (FPI), uses detailed spectral information for the detection of the target trace gas. Cross sensitivities are thereby drastically reduced, allowing for the detection of much lower SO₂ concentrations and imaging of other trace gas species like, e.g., BrO, OClO. Furthermore, the inherent calibration of the new techniques avoids the requirement of additional DOAS measurements or gas cells for calibration.

We present the first measurements of volcanic SO₂ with an imaging Fabry-Perot interferometer correlation spectroscopy (IFPICS) prototype. The sensitivity of ≈ 10¹⁹ cm² molec^-1 is comparable to filter based SO₂ cameras, whereas the selectivity is much higher (e.g. no ozone interference). This will largely increase the accuracy of SO₂ emission rates, which are routinely used to approximate fluxes of other volcanic gas emissions into the atmosphere.

Additionally, sensitivity studies for further trace gases combining laboratory measurements and radiation transfer modelling show promising prospected BrO detection limits of < 10¹⁴ molec cm^-², corresponding to mixing ratios of 10 to 100 ppt in volcanic plumes. The direct visualisation of BrO within the volcanic plume mixing with the ambient atmosphere will give important insights into the plume’s halogen chemistry and, thereby, its impact on the atmosphere.

How to cite: Fuchs, C., Kuhn, J., Bobrowski, N., and Platt, U.: A novel technique for studying volcanic gas chemistry and dispersion on short time scales, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1008, https://doi.org/10.5194/egusphere-egu2020-1008, 2020.

Condensation of sulfuric acid formed from the co-injected sulfur dioxide on volcanic ash particles, so-called chemical aging, increases the particle size and changes their microphysical and optical properties. The larger aged particles have a higher removal rate, which reduces their lifetime. On the other hand, the aging increases the scattering cross-section, and therefore the ash optical depth is increasing due to aging. The uptake of sulfuric acid by volcanic ash delays the formation of new sulfate particles depending on the level of aging, which is characterized by the number of sulfuric acid layers coating a single ash particle (i.e., monolayers). Both the formation of sulfate aerosols and sulfuric acid uptake by ash particles affect the development of a volcanic plume and its radiative impact.

We employ the ECHAM5/MESSy atmospheric chemistry general circulation model (EMAC) to simulate the chemical aging of volcanic ash in the 1991 Pinatubo eruption volcanic plume. We emit 17Mt of SO₂ and 75Mt of fine ash. Two aerosol modes represent ash size distribution: accumulation and coarse with 0.23 and 3.4 um median radii, respectively. We allow the sulfuric acid to condense on the ash particles and assume different levels of aging (from not aged to highly aged). We use independent observations for sulfur dioxide, volcanic ash mass, volcanic ash optical depth, and plume coverage area from the Advanced Very-High-Resolution Radiometer (AVHRR) observations and total optical depth from the Stratospheric Aerosol and Gas Experiment II (SAGE II). We constrain the number of monolayers on ash particles by testing simulated ash surface area and optical depth calculated within a fully coupled online stratospheric-tropospheric chemistry model against observations. The level of volcanic ash aging strongly affects the surface area of the volcanic ash plume, ranging from 3x10⁶ km² to 6x10⁶ km², compared to 3.8x10⁶km² from AVHRR retrievals. The volcanic ash optical depth, averaged over the volcanic plume area, ranges between 2 and 3.6. Using five monolayer coating assumption allows us to better reproduce the observed SO₂ mass, its decay rate, total plume surface area, and ash optical depth. Most of the coarse ash particles are removed within a week after the eruption reducing the amount of sulfuric acid within the volcanic plume. The smaller particles have much longer residence time and continue to uptake sulfuric acid for more than three months.

How to cite: AbdelKader, M., Stenchikov, G., Bruhl, C., and Lelieveld, J.: Volcanic ash chemical aging from multiple observational constraints for the Pinatubo eruption, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2623, https://doi.org/10.5194/egusphere-egu2020-2623, 2020.

The formation of Earth atmosphere and oceans have been primarily deeply influenced by volcanic emissions. In addition, the planet radiative balance and stratospheric chemistry can be affected by materials injected into the atmosphere by large explosive eruptions. Volcanic emission often contain water vapor (H2O), carbon dioxide (CO2), and depending on the type of volcano they may contain varying proportions of toxic/corrosive gases such as Sulphur dioxide (SO2), hydrogen fluoride (HF) and silicon tetrafluoride (SiF4). CO2 is generally the most abundant gas with the lowest solubility among the volatile compounds of magmatic liquids and the less susceptible than most other magmatic substances such as SO2 and HF. Thanks to those properties, the volcanic CO2 emission rates could play an important role for assessing volcanic hazards and for constraining the role of magma degassing in the biogeochemical cycle of carbon. However, measurements of CO2 emission rates from volcanoes remain challenging, mainly due to the difficulty of measuring volcanic CO2 against the high level of CO2 in the atmosphere. Thermal Infrared (TIR) imaging is now a well-established tool for the monitoring of volcanic activity since many volcanic gases such as CO2 and SO2 are infrared-active molecules. High speed broadband cameras give valuable insight into the physical processes taking place during volcanic activity, while spectrally resolved cameras allow to assess the composition of volcanic gases.

In this work we conducted TIR imaging and quantification of CO2 passive degassing at Sulphur Banks from Kilauea volcano using Telops Midwave Infrared time-resolved multispectral imager. The imager allows synchronized acquisition on eight channels, at a high frame rate, using a motorized filter wheel. Using appropriate spectral filters measurements allows estimation of the gas emissivity parameters in addition to providing selectivity regarding the chemical nature of the emitted gases. Our results show CO2 measurements within the volcano’s plume from its distinct spectral feature. Quantitative chemical maps with local CO2 concentrations of few hundreds of ppm was derived and mass flow rates of few g/s were also estimated. The results show that thermal infrared multispectral imaging provides unique insights for volcanology studies.

How to cite: Boubanga Tombet, S., Gatti, S., Eisele, A., and Morton, V.: Observation and Quantification of CO2 passive degassing at sulphur Banks from Kilauea Volcano using thermal Infrared Multispectral Imaging, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4816, https://doi.org/10.5194/egusphere-egu2020-4816, 2020.

Atmospheric modelling allows to study large spatial scale events such as volcanic eruptions, which can emit large amounts of plume-confined particulate matter and gases, to evaluate their transport in the atmosphere and their subsequent impacts. However, to study more precisely these events, different issues have to be addressed. One notable example of these issues is the well-known excessive numerical diffusion in the atmospheric column in Eulerian models leading to excessive plume dispersion misrepresentation of the plume three-dimensional morphology and subsequent geographical extent of its impacts. Mount Etna volcano’s moderate eruption of March 18, 2012, which released about 3kT of sulphure dioxide in the atmosphere, has been simulated in this study with the CHIMERE chemistry-transport model. The simulated plume has been observed and tracked with satellite instruments (OMI and IASI) for several days during its transport over the Mediterranean Sea in order to compare with model outputs.

Sensitivity tests have been performed to evaluate the impact of injection altitude and profile shape on the subsequent trajectory of the plume. It was shown that altitude is the most sensitive parameter when results remain weakly sensitive to the vertical shape of injection.

In order to effectively address the problem of excessive numerical diffusion, we have included a new antidiffusive transport scheme in the vertical direction and a new strategy to use directly the vertical wind field provided by the forcing meteorological model. We show that both these improvements permit a substantial reduction in numerical diffusion. The use of the new antidiffusive vertical scheme has brought the strongest improvement in our model outputs. To a lesser extent, a more realistic representation of the vertical wind field has also been shown to reduce volcanic plume spreading. In summary, we show that these two improvements bring an improvement in the representation of the plume which is as strong as the improvement brought by increasing the number of vertical levels, but without an additional burden in computational power.

This study has been supported by AID (Agence de l'Innovation de Défense) under grant TROMPET.

How to cite: Lachatre, M., Mailler, S., Menut, L., Turquety, S., Sellitto, P., Guermaz, H., Salerno, G., and Carboni, E.: New strategies for chemistry-transport modelling of volcanic plumes: application to the case of Mount Etna eruption in March 18, 2012, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7036, https://doi.org/10.5194/egusphere-egu2020-7036, 2020.

Raikoke volcano (Kuril Islands, Russia) eruption on 21 June 2019 sent an ash plume at 10-13 km altitude, which is higher than the local tropopause.  Volcanic aerosols were transported around the globe, causing spectacular purple twilights. We will present ground-based measurements of monochromatic twilight sky brightnesses at 780 nm wavelength in two geographical points: Tbilisi, Georgia (41° 43’ N, 44° 47° E) and Halle, Belgium (50° 44′ N, 4° 14′ E).  Aerosol extinction vertical profiles in the lower stratosphere-upper troposphere were retrieved with the help of the Levenberg–Marquardt algorithm. Monte Carlo code Siro was used to design a forward model. Raikoke aerosols observed above the both sites have shown essentially cloudy and variable structure. Multiple layers were observed between 10 and 17 km with extinction up to 0.01 km-1.  We will present Raikoke aerosol cloud evolution in the period July 2019 –January 2020.

How to cite: Mateshvili, N., Fussen, D., Mateshvili, I., Vanhellemont, F., Bingen, C., Paatashvili, T., Kyrölä, E., Robert, C., and Dekemper, E.: Raikoke aerosol clouds observed from Tbilisi, Georgia and Halle, Belgium using ground-based twilight sky brightness spectral measurements., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7548, https://doi.org/10.5194/egusphere-egu2020-7548, 2020.

The aerosol properties of Mount Etna’s passive degassing plume and its short-term processes and radiative impact were studied in detail during the EPL-RADIO/REFLECT campaigns (summer 2016, 17 and 19), using a synergistic combination of remote-sensing and in situ observations, and radiative transfer modelling. Summit observations show extremely high particulate matter concentrations, with no evidence of secondary sulphate aerosols (SA) formation. Marked indications of secondary SA formation, i.e. by the conversion of volcanic SO2 emissions, are found at larger spatial scales (<20 km downwind craters). Using portable photometers, the first mapping of small-scale spatial variability of the average size and burden of volcanic aerosols is obtained, as well as different longitudinal, perpendicular and vertical sections. A substantial variability of the plume properties is found at these spatial scales, revealing that processes (e.g. new particle formation and coarse aerosols sedimentation) are at play, which are not represented with current regional scale modelling and satellite observations. Vertical structures of typical passive degassing plumes are also obtained using observations from a fixed LiDAR station constrained with quasi-simultaneous photometric observations. These observations are used as input to radiative transfer calculations, to obtain the shortwave top of the atmosphere (TOA) and surface radiative effects of the plume. Moreover, the radiative impact of Mount Etna’s emissions is studied using a medium-term time series (a few months during summer 2019) of coupled aerosol optical properties and surface radiative flux at a fixed station on Etna’s eastern flank. These are the first available estimations in the literature of the radiative impact of a passive degassing volcanic plume and are here critically discussed. Cases of co-existent volcanic aerosol layers and aerosols from other sources (Saharan dust transport events, wildfire from South Italy and marine aerosols) are also presented and discussed.

How to cite: Sellitto, P., Salerno, G., La Spina, A., Caltabiano, T., Scollo, S., Boselli, A., Leto, G., Zanmar Sanchez, R., Sannino, A., Crumeyrolle, S., Hanoune, B., Giorio, C., Giammanco, S., Roberts, T., di Sarra, A., Legras, B., and Briole, P.: Small-scale volcanic aerosols variability, processes and direct radiative impact at Mount Etna during the EPL-RADIO/REFLECT campaigns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8337, https://doi.org/10.5194/egusphere-egu2020-8337, 2020.

New particle formation (NPF) is an important source of aerosol particles at  global scale, including, in particular, cloud condensation nuclei (CCN). NPF has been observed worldwide in a broad variety of environments, but some specific conditions, such as those encountered in volcanic plumes, remain poorly documented in the literature. Yet, these conditions could promote the occurrence of the process, as recently evidenced in the volcanic eruption plume of the Piton de la Fournaise (Rose at al. 2019); a dominant fraction of the volcanic particles was moreover found to be of secondary origin in the plume, further highlighting the importance of the particle formation and growth processes associated to the volcanic plume eruption. A deeper comprehension of such natural processes is thus essential to assess their climate-related effects at present days but also to better define pre-industrial conditions and their variability in climate model simulations.

Sulfuric acid (SA) is commonly accepted as one of the main precursors for atmospheric NPF, and its role could be even more important in volcanic plume conditions, as recently evidenced by the airborne measurements conducted in the passive volcanic plumes of Etna and Stromboli (Sahyoun et al., 2019). Indeed, the flights performed in the frame of the STRAP campaign have allowed direct measurement of SA in such conditions for the first time, and have highlighted a strong connection between the cluster formation rate and SA concentration. Following these observations, the objective of the present work was to further quantify the formation of new particles in a volcanic plume and assess the effects of the process at a regional scale. For that purpose, the new parameterisation of nucleation derived by Sahyoun et al. (2019) was introduced in the model WRF-Chem, further optimized for the description of NPF. The flight ETNA13 described in detail in Sahyoun et al. (2019) was used as a case study to evaluate the effect of the new parameterisation on the cluster formation rate and particle number concentration in various size ranges, including CCN (i.e. climate-relevant) sizes.

References:

Sahyoun, M., Freney, E., Brito, J., Duplissy, J., Gouhier, M., Colomb, A., Dupuy, R., Bourianne, T., Nowak, J. B., Yan, C., Petäjä, T., Kulmala, M., Schwarzenboeck, A., Planche, C., and Sellegri, K.: Evidence of new particle formation within Etna and Stromboli volcanic plumes and its parameterization from airborne in-situ measurements, J. Geophys. Res.-Atmos., 124, 5650–5668, https://doi.org/10.1029/2018JD028882, 2019.

Rose, C., Foucart, B., Picard, D., Colomb, A., Metzger, J.-M., Tulet, P., and Sellegri, K.: New particle formation in the volcanic eruption plume of the Piton de la Fournaise: specific features from a long-term dataset, Atmos. Chem. Phys., 19, 13243–13265, https://doi.org/10.5194/acp-19-13243-2019, 2019.

How to cite: Planche, C., Rose, C., Banson, S., Lupascu, A., Gouhier, M., and Sellegri, K.: Modelling new particle formation in a passive volcanic plume using a new parameterisation in WRF-Chem - effects on climate-relevant variables at the regional scale, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8470, https://doi.org/10.5194/egusphere-egu2020-8470, 2020.

Volcanoes are a large global source of almost every element, including ~20 environmentally reactive trace elements classified as metal pollutants (e.g. selenium, cadmium and lead). Fluxes of metal pollutants from individual eruptions can be comparable to total anthropogenic emissions from large countries such as China.

The 2018 Lower East Rift Zone eruption of Kīlauea, Hawaii produced exceptionally high emission rates of major and trace chemical species compared to other basaltic eruptions over 3 months (200 kt/day of SO₂; Kern et al. 2019). We tracked the volcanic plume from vent to exposed communities over 0-240 km distance using in-situ sampling and atmospheric dispersion modelling. This is the first time that trace elements in volcanic emissions (~60 species) are mapped over such distances. In 2019, we repeated the field campaign during a no-eruption period and showed that volcanic emissions had caused 3-5 orders of magnitude increase in airborne metal pollutant concentrations across the Island of Hawai’i.

We show that the volatility of the elements (the ease with which they are degassed from the magma) controls their particle-phase speciation, which in turn determines how fast they are depleted from the plume after emission. Elements with high magmatic volatilities (e.g. selenium, cadmium and lead) have up to 6 orders of magnitude higher depletion rates compared to non-volatile elements (e.g. magnesium, aluminium and rare earth metals).

Previous research and hazard mitigation efforts on volcanic emissions have focussed on sulphur and it has been assumed that other pollutants follow the same dispersion patterns. Our results show that the atmospheric fate of sulphur, and therefore the associated hazard distribution, does not represent an accurate guide to the behaviour and potential impacts of other species in volcanic emissions. Metal pollutants are predominantly volatile in volcanic plumes, and their rapid deposition (self-limited by their volatility) places disproportionate environmental burdens on the populated areas in the immediate vicinity of the active and, in turn, reduces the impacts on far-field communities.

Reference: Kern, C., T. Elias, P. Nadeau, A. H. Lerner, C. A. Werner, M. Cappos, L. E. Clor, P. J. Kelly, V. J. Realmuto, N. Theys, S. A. Carn, AGU, 2019; https://agu.confex.com/agu/fm19/meetingapp.cgi/Paper/507140.

How to cite: Ilyinskaya, E., Mason, E., Wieser, P., Holland, L., Liu, E., Mather, T. A., Edmonds, M., Whitty, R., Elias, T., Nadeau, P., Schneider, D., McQuaid, J., Allen, S., Oppenheimer, C., Kern, C., and Damby, D.: Self-limiting atmospheric lifetime of environmentally reactive elements in volcanic plumes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19656, https://doi.org/10.5194/egusphere-egu2020-19656, 2020.

Etesians winds are northerly winds in the lower atmosphere, blowing over the Aegean basin from early summer to early autumn, regulating summer time heating levels. The interannual variability of Etesians is thought to be linked to the extended Indian Summer Monsoon and tropical Pacific Region. Here, we are investigating the response of Etesians to major volcanic eruptions with the aid of ensembles of historical simulations. Specifically, we are making use of the CESM Last Millennium and Large Ensemble simulations to investigate modelled Etesian changes in the post-eruption one to three years. We find consistent changes for all major eruptions over the last millennium of reduced amplitude peaking in the first year after the eruption. Interestingly, the Laki eruption shows a similar signal to the other major tropical Eruptions. Modelled results are compared to signals in the observational record and a possible mechanism connecting Etesians to the Indian Monsoon region is discussed.

How to cite: Misios, S., Logothetis, I., Knudsen, M. F., Karoff, C., and Tourpali, K.: Etesian winds after major volcanic eruptions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20415, https://doi.org/10.5194/egusphere-egu2020-20415, 2020.

The WCRP-SPARC initiative on stratospheric sulphur (SSiRC) has begun a new activity to recover past observational datasets of the stratospheric aerosol layer.

The data rescue activity aims to provide additional constraints for volcanic impacts on climate and is organised into three time-periods:

1. The quiescent period prior to the major eruption 1963 Agung eruption,
2. The period of strong volcanic activity during 1963-1969,
3. The Jul-Dec 1991 period after Pinatubo when the SAGE-II signal was saturated.

A new page within the SSiRC website gives further information on the datasets within this activity ( http://www.sparc-ssirc.org  --> Activities --> Data Rescue).

In this presentation, we explain the 1963-1969 component of the data rescue, and compare the CMIP5 and CMIP6 volcanic aerosol datasets during this period, post-Agung interactive stratospheric aerosol model simulations and a preliminary analysis of 15-year global-mean surface temperature trends from CMIP6 historical integrations for 1950-1980.

The 1960s was a strongly volcanically active decade, with the major 1963 Agung eruption and tropical stratosphere-injecting eruptions in 1965 (Taal), 1966 (Awu) and 1968 (Fernandina) generating a prolonged period of strong natural surface cooling.

Less than a year after the Agung eruption, the first in-situ measurements of a major volcanic aerosol cloud were made with dust-sondes from Minneapolis measuring aerosol particle concentrations with 10 soundings between 1963 and 1965 (6 in 1963-4).

Global surveys with the U-2 aircraft were equipped with impactors to measure stratospheric aerosol particle size distribution and composition, for example detecting the presence of volcanic ash within the Agung volcanic plume.

Early ground-based active remote sensing measurements (lidar, searchlight) also measured the vertical profile of the Agung-enhanced stratospheric aerosol layer.

The main purpose of the SSiRC data rescue is to provide constraints for interactive stratospheric aerosol models, aligning with the ISA-MIP activity, which could potentially lead to new volcanic forcing datasets for climate models, ultimately thereby aiming to improve attribution of anthropogenic change and future projections.

How to cite: Mann, G., Antuna Marrero, J. C., Maycock, A., McKenna, C., Shallcross, S., Dhomse, S., Thomason, L., Luo, B., Deshler, T., and Rosen, J.: Recovered measurements of the 1960s stratospheric aerosol layer for new constraints for volcanic forcing in the years after 1963 Agung, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21721, https://doi.org/10.5194/egusphere-egu2020-21721, 2020.

Large volcanic eruptions influence climate on both annual and decadal time scales due to dynamical interactions of different climate components in the Earth's system. It is well established that the North Atlantic Oscillation (NAO) tends to shift towards its positive phase during the winter season in the first 1–2 years after large tropical volcanic eruptions, causing warming over Europe. However, other North Atlantic circulation regimes such as Atlantic Ridge or zonal regime have received less attention. This study explores the volcanic fingerprint in terms of patterns and mechanisms on the North Atlantic atmospheric circulation in IPSL-CM6A-LR model simulations for tropical eruptions of the last millennium using dedicated sensitivity experiments and observations.

How to cite: Feng, Y., Khodri, M., Li, L., Sicre, M.-A., and Lebas, N.: The influence of volcanic eruptions on circulation regimes over the North Atlantic and their impact on European climate, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17415, https://doi.org/10.5194/egusphere-egu2020-17415, 2020.