Volcanic sulphur dioxide (SO₂), a precursor of sulphate aerosols, can have a deleterious impact on the atmosphere, ecosystems, and air quality at multiple scales. Knowledge of highly variable volcanic SO₂ emissions, i.e., mass flux rates and injection heights, would not only aid comprehension of such atmospheric implications but would also provide information on subterranean volcanological processes of magma transport. Furthermore, volcanic SO₂, which frequently co-exists in volcanic plumes with ash and sulphate aerosols, can pose a threat to aviation as ash and acidic aerosols are alarming to aircraft. Therefore, comprehensive knowledge of volcanic SO₂ emissions is essential for a thorough evaluation of near-source volcanic hazards and large-scale atmospheric impacts.

Hyper-spectral nadir-viewing UV and infrared satellite instruments record global SO2 mass-loadings on a daily or bi-daily basis. Geostationary sensors, on the other hand, deliver high temporal information on SO₂ emissions but with much lower sensitivity. Consequently, there are still gaps in our knowledge of volcanic SO₂ emissions and SO₂ to sulphate oxidation rates, notably inside tropospheric plumes, and hence volcanic sulphur-rich compound feedback on the atmosphere.

TROPOMI, a hyperspectral UV sensor with increased spatial and spectral resolution than that of the pre-existing UV (OMPS) sensor in the same orbit, was launched in 2017. We discuss how an inverse modelling approach that assimilates TROPOMI SO₂ column amounts (CA) improves the retrieval of hourly SO₂ emissions when compared to the assimilation of OMPS data acquired at approximately the same time and the new SO2 products (both SO₂ CA and layer heights) from IASI. The purpose of using IASI data is to assess the impact of assimilating SO2 data available bi-daily into inverse modelling with additional information on SO₂ layer height. The inverse modelling is performed utilizing a time series of daily or bi-daily SO₂ CA snapshots from the TROPOMI, OMPS, and IASI satellite instruments, respectively. Contrary to OMPS, which has 50x50 km² of spatial resolution, and IASI, which has a 12 km circular footprint, TROPOMI has an extraordinary spatial resolution of 5.5x3.5 km² (7x3.5 km² before August 2019). We find that because of their sensitivity to low-level SO₂ fluxes and thin SO₂ plumes, and the numerous SO₂-rich pixels defining dense parcels, TROPOMI observations enable better evaluation of SO₂ degassing during paroxysmal eruption phases, offering better-resolved SO₂ emissions by inverse modelling. However, if meteorological clouds hide the volcanic SO₂ plumes, the results can be inconsistent, especially if the clouds are near the source. So the additional data, the SO₂ height product from IASI observations, is used to reconcile and offer more robust SO₂ emissions. As a second step, we perform inverse modelling using both the SO₂ CA and layer heights from IASI. This research investigates the Mount Etna eruption in February 2021, the SO2 plume reaching France, and the 2018 Ambrym eruption, which was the top world-ranking SO₂ emitter. In the context of Etna eruption, we use ground-based OHP LIDAR aerosol height measurements to explore the presence of sulphate aerosols and their height in the SO₂ plume.

How to cite: Behera, A., Boichu, M., Thieuleux, F., Hioki, S., Clarisse, L., Khaykin, S., Xueref-Remy, I., Popovici, I., and Goloub, P.: Hourly SO2 emissions and plume dispersion simulated by inverse modelling using TROPOMI, OMPS, IASI, and ground-based LIDAR observations: case studies of the 2021 Etna and 2018 Ambrym eruptions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3847, https://doi.org/10.5194/egusphere-egu22-3847, 2022.

Bromine monoxide (BrO) is a halogen radical capable of influencing atmospheric chemical processes, in particular the abundance of ozone, e. g. in the polar boundary layer and above salt lakes, in the stratosphere as well as in volcanic plumes. Furthermore, the molar bromine to sulphur ratio in volcanic gas emissions is a proxy for the magmatic composition of a volcano and potentially an eruption forecast parameter.

To monitor volcanic activities on global scale, satellite measurements provide invaluable information. For these purposes, the TROPOspheric Monitoring Instrument (TROPOMI) onboard ESA’s S5-P satellite is particularly interesting: its high spatial resolution of up to 3.5x5.5km² and daily global coverage offer great potential to detect BrO and its corresponding ratio with sulphur dioxide (BrO/SO₂) even during minor eruptions and for continuous passive degassing volcanoes.

Here, we present a global overview of BrO/SO₂ molar ratios in volcanic plumes derived from a systematic long-term investigation covering four years (Januar 2018 to December 2021) of TROPOMI data.

We retrieved column densities of BrO and SO₂ using Differential Optical Absorption Spectroscopy (DOAS) and calculated mean BrO/SO₂ molar ratios for various volcanoes. The calculated BrO/SO₂ molar ratios differ strongly between different volcanoes, but also between measurements at one volcano at different points in time, ranging from several 10^-5 up to several 10^-4. In our four-year study of S5P/TROPOMI data we successfully recorded elevated BrO column densities at 506 volcanic events. We were able to derive significant BrO/SO₂ ratios at 26 different volcanoes on 378 occasions, thus adding an important volcanic parameter to these volcanoes.

In addition, this large data set of events allows to deduce time-series of several very active volcanoes, such as Mount Etna, Italy and Ambrym, Vanuatu.

How to cite: Warnach, S., Borger, C., Bobrowski, N., Sihler, H., Schöne, M., Beirle, S., Platt, U., and Wagner, T.: A global perspective on Bromine monoxide composition in volcanic plumes derived from S5-P/TROPOMI, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4983, https://doi.org/10.5194/egusphere-egu22-4983, 2022.

Submarine volcanic activity was observed in the Vestmannaeyjar archipelago off the south coast of Iceland in November 1963, at a location where the pre-eruption oceanic depth was 130 m.  The eruption continued until July 1967. As a result of the eruption, a volcanic island, Surtsey, and its short-lived satellite islands (Surtla, Syrtlingur, and Jólnir) were created.  The progression of the eruption was very well documented at the time.  However, data on structures below sea level has been limited to drillholes on the rim of the Surtur crater on the main Surtsey island.  In order to study the existence and possible location of pillow lava from the initial phases of the eruption and shallow intrusions within and below the edifices formed in 1963-1967, a six-hour-long aeromagnetic survey was completed in October 2021 over the Surtsey area. The survey is done using a Geometrics MagArrow drone magnetometer, here adapted for operation while fixed to an aircraft. The survey covered 60 km².  The spacing between profiles was 200 m and the flight elevation 100 m a.s.l. The MagArrow has a sampling frequency of 1000 Hz, which for an aircraft flying at 50 m/s gives a reading every 5 cm. To remove noise and perturbations from the aircraft, the data is low-pass filtered in two steps, firstly by averaging 50 measurements providing 20 Hz data, then by applying low pass filter with a cutoff frequency of 0.225 Hz, removing wavelengths smaller than 200-250m.  Initial data processing indicates some variations in the sources to the anomalies observed.  Major anomalies arise from the subaerial lavas on Surtsey itself, while the submarine remnants of the island Syrtlingur, active in 1965, show no anomalies.  This suggests that it is exclusively made of tuffs with no significant intrusions, similar to the structure of Surtsey itself below sea floor according to the drill cores obtained in 1979 and 2017.  In contrast, a clear anomaly is observed over the submarine remnants of the satellite island Jólnir, which was formed over several months in 1966. Apparently, this anomaly can only be explained by a magnetic body located no deeper than at 100 m depth below the seafloor at the eastern part of Jólnir, the same location as the vent active in 1966. 

How to cite: Sayyadi, S., Gudmundsson, M. T., White, J. D. H., Jónsson, T., and Jackson, M. D.: An aeromagnetic survey over the volcanic island of Surtsey off the south coast of Iceland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11029, https://doi.org/10.5194/egusphere-egu22-11029, 2022.

La Fossa volcano, located in the Vulcano Island of the Aeolian Archipelago, is the type locality of Vulcanian explosive eruptions. It last erupted in 1888-1890 and since then it is affected by an intense fumarolic activity from both the summit crater area and a hydrothermal site (Levante Beach) located very near to the main settlement of the island (Vulcano Porto). In Autumn 2021 a potential volcanic unrest crisis began with a strong increase of steam, CO₂ and SO₂ emission from the high-T crater fumaroles, ground uplift and episodic anomalous seismicity. Vulcano Porto inhabited area is exposed to gas hazard either from the wind dispersed crater fumarolic plume (mostly CO₂ and SO₂) and from anomalous diffuse soil gas emissions in Levante Beach and other zones of Vulcano Porto village (mostly CO₂ and eventually H₂S). The gas hazard of the village was considered so high that in December 2021 Civil Protection prohibited residents to stay at home during the night. In order to improve the monitoring of gas hazard we developed new stations continuously measuring the air concentration of CO₂ and SO₂. Each of these stations is operating with an electrochemical sensor for the measurement of SO₂ and a photoacoustic sensor for the measurement of CO₂. Moreover, atmospheric pressure, temperature and humidity are monitored in parallel to the gas measurements. The measured data are sent continuously via mobile data connection to a dedicated server. By this means the measured parameters can be monitored remotely, without the need to access the site personally. Three stations were installed (at 1 m from the ground) in mid-December 2021 in three sites of Vulcano Porto; two of them were located at the base of La Fossa cone in the sector most exposed to the crater gas plume, while a third station was located in the heart of the village, near the church. Results show that CO₂ exceeds of few hundreds ppm the normal air value of 400 ppm in all the stations. In some occasions, during night in absence of wind or with light wind blowing from SW, some peaks of both CO₂ and SO₂ were recorded in all the stations (CO₂ max 1500 ppm; SO₂ max 2 ppm). Additionally a future server sided extension to our system is planned, which integrates an early warning system, that can send email alerts, if certain thresholds are exceeded.

How to cite: Carapezza, M. L., Amend, D., Fisher, C., Pruiti, L., Ranaldi, M., Tarchini, L., and Weber, K.: New stations to monitor gas hazard in the ongoing volcanic unrest crisis of La Fossa volcano (Vulcano Island, Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12606, https://doi.org/10.5194/egusphere-egu22-12606, 2022.

Abstract: Volcanic aerosols can cool Earth’s surface on a global scale, with the largest eruptions (eg Toba 74kya) linked to especially severe impacts on ecosystems and human survival. However, global climate simulations of super-eruption impacts have disagreed widely on post-eruption temperatures. As no super-eruption has occurred in ~26,000 years, little is known of their aerosol byproducts other than mass estimates from ice cores. Here we use GISS ModelE climate simulations to demonstrate that unconstrained aerosol properties cause substantial radiative forcing uncertainty. By comparing ModelE sensitivity tests to previous modeling studies, we suggest that a lack of consensus on super-eruption aerosol properties is a major reason for the disagreement in post-eruption cooling.

How to cite: McGraw, Z., Dallasanta, K., Polvani, L., Tsigaridis, K., Orbe, C., and Bauer, S.: Aerosol properties crucial to reconciling supervolcanic cooling estimates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13498, https://doi.org/10.5194/egusphere-egu22-13498, 2022.

Magmatic gases that reach Earth’s surface are among the scarce sources of information on the planet’s interior. Their composition is dominated by H₂O, CO₂, and sulfur species and largely differs from that of today’s atmosphere of the Earth, particularly, by the amounts of oxygen. When magmatic gases are emitted directly to the atmosphere (e.g. at lava lakes), the process is further characterised by huge temperature gradients (hundreds to more than a thousand K per metre). The rapid cooling and fast mixing with atmospheric oxygen defines an early phase in the lifetime of a volcanic plume, which can crucially influence the plume’s later composition. Few attempts have been made to include the often extreme dynamics of this early plume phase into the scope of volcanic gas studies.

Naturally, magmatic degassing processes are difficult to study and thus bound to large uncertainties in crucial parameters, such as gas temperature, gas composition, and mixing. Further, heterogeneous processes involving ash and aerosols might have a strong impact on the processes.

We developed a model to study the C-H-O-S gas phase reaction kinetics of the first seconds of a volcanic gas emission. The entire cooling process of the volcanic gases is covered and studied considering its dynamics and regarding large ranges of mixing scenarios, gas compositions and emission temperatures.

We find that many major processes are far from (the often assumed) thermal equilibrium (TE). Particularly, large amounts of HO_X (OH + HO₂), exceeding TE by orders of magnitude, form at high temperature as soon as sufficient O₂ entered the plume. High OH levels lead to rapid oxidation of emitted species, such as CO, H₂, and SO₂. Strikingly, CO levels can be both, reduced and enhanced by high temperature processing, depending on the assumed initial conditions. Moreover, we observe that the enthalpy change associated with the chemical conversions can lead to a significant net heating of the plume.

Overall, and despite of the simplifications made, our model indicates a major influence of the dynamics within the interface between magma and the atmosphere (i.e. the early volcanic plume). The composition of gas samples that interacted only a tenth of a second with the atmosphere might substantially differ from the magmatic gas composition. This would lead to enhanced uncertainties in the quantification of magmatic parameters (such as temperature and redox state), when derived from measurements of gas ratios in the volcanic plume. 

How to cite: Kuhn, J., Bobrowski, N., and Platt, U.: The interface between magma and Earth’s atmosphere and its influence on the gas composition of volcanic plumes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2882, https://doi.org/10.5194/egusphere-egu22-2882, 2022.

Explosive volcanic eruptions are risk to human population, buildings, and infrastructure. One consequence of volcanic ash in the built environment, as seen graphically during the recent (2021) St. Vincent and La Palma eruptions, is that it collects on roofs, sometimes overtopping the host building completely. If enough ash collects then the weight on the roof can cause collapse, damaging the structure and endanger people. While it is known that snow loading of roofs is a hazard and is regulated for in EN 1991 Eurocode 1, no guidance currently exists in the Eurocodes for volcanic ash deposition, although during prolonged eruptions loading impact from ash can exceed structural guidelines and recommended safety criteria for exceptional snow loads. One of the main reasons for lack of including is data availability. For snow load calculations the Eurocodes can draw on approximately 2600 weather station that are constantly monitored. Volcanic eruptions are significantly less frequent.  To remedy this, we present a computer-based mathematical model for testing stress and deformation levels due to volcanic ash deposition on flat concrete roofs. The mathematical model can take account of variable factors. Using computer models, we can assess the interactions of many variables simultaneously, without the need to perform complex physical experiments. Results show that the stress on concrete roofs due to the weight of accumulating ash can exceed the safety requirements set out in EN1991 Eurocode 1. While more research is needed, our results shows the need to revise the current codes for the built environment in volcanic prone areas of Europe.

How to cite: Quainoo, P. K., Petford, N., Kaczmarczyk, S., and Thomas, M.: Modelling the effects of volcanic ash on the strength and likely collapse of concrete roofs: implications for EU Building Code EN1991., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8731, https://doi.org/10.5194/egusphere-egu22-8731, 2022.

Volcanic ash can act as ice-nucleating particles (INPs), which by triggering freezing of supercooled water droplets in the atmosphere, can profoundly influence clouds and thereby climate [1]. Volcanoes worldwide sporadically emit large amounts of ash into the atmosphere including at middle to high latitudes (30-90° N/S) where, importantly, other major types of INPs such as windblown Saharan dust from low latitudes are less abundant. A recent study found that windblown Icelandic dust of volcanic and glacio-fluvial origin could episodically dominate INP concentrations between 3 to 5.5 km above sea level over the North Atlantic and Arctic [2]. However, it remains unexplored how volcanic ash emissions from explosive eruptions, which typically occur every 3 to 5 years in Iceland, affect INP concentrations in these regions. Here we investigated the Eyjafjallajökull eruption from 14 April to 22 May 2010 and Eyjafjallajökull ash resuspension events (by wind) thereafter as sources of INPs to the atmosphere. Specifically, by combining ash concentration and temperature data from Lagrangian particle dispersion model simulations (Numerical Atmospheric dispersion Modelling Environment [3]) with a laboratory-derived parameterisation of the ice-nucleating activity of this ash [2,4-5], we calculated INP concentrations up to 10 km above sea level across the Northern Hemisphere during and following the Eyjafjallajökull eruption. In late April 2010, the erupted ash produced INP concentrations >0.01 L^-1 (potentially capable of affecting cloud liquid water content) in up to ~14 vol% of air masses at temperatures between 0 and -35 °C and latitudes between 45 and 90° N. In contrast, the contribution of resuspended ash to the atmospheric INP population in subsequent months was up to several orders of magnitude smaller, partly because resuspended ash particles more seldomly reached altitudes where temperatures were low enough for ice nucleation. Findings of this case study and perspectives on further integrating model and laboratory data to improve understanding of the impacts of volcanic ash on clouds and climate will be discussed.

[1] Murray, B. J., Carslaw, K. S, Field, P. R. (2021) Atmospheric Chemistry and Physics, 21, 665-679, doi:10.5194/acp-21-665-2021.

[2] Sanchez-Marroquin, A., Arnalds, O., Baustian-Dorsi, K. J., Browse, J., Dagsson-Waldhauserova, P., Harrison, A. D., Maters, E. C., Pringle, K. J., Vergara-Temprado, J., Burke, I. T., McQuaid, J. B., Carslaw, K. S., Murray, B. J. (2020) Science Advances, 6, eaba8137, doi:10.1126/sciadv.aba8137.

[3] Jones, A., Thomson, D., Hort, M., Devenish, B. (2007) In: Borrego, C., Norman, A.-L. (Eds) Air Pollution Modelling and its Application XVII, Springer, Boston, 580-589, doi:10.1007/978-0-387-68854-1_62

[4] Hoyle, C. R., Pinti, V., Welti, A., Zobrist, B., Marcolli, C., Luo, B., Höskuldsson, Á., Mattsson, H. B., Stetzer, O., Thorsteinsson, T., Larsen, G., Peter, T. (2011) Atmospheric Chemistry and Physics, 11, 9911-9926, doi:10.5194/acp-11-9911-2011.

[5] Steinke, I., Möhler, O., Kiselev, A., Niemand, M., Saathoff, H., Schnaiter, M., Skrotzki, J., Hoose, C., Leisner, T. (2011) Atmospheric Chemistry and Physics, 11, 12945-12958, doi:10.5194/acp-11-12945-2011.

How to cite: Maters, E., de Leeuw, J., Beckett, F., Sanchez-Marroquin, A., Witham, C., Murray, B., Carslaw, K., and Schmidt, A.: Impacts of erupted and resuspended volcanic ash from the 2010 Eyjafjallajökull eruption, Iceland, on atmospheric ice-nucleating particle concentrations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5832, https://doi.org/10.5194/egusphere-egu22-5832, 2022.

The Neapolitan volcanic area is by far the highest volcanic risk one in the World, due to the presence of three active volcanic areas (Vesuvius, Campi Flegrei, Ischia) with an extreme population density: three millions people live within 20 km from a possible volcanic vent. Volcanic risk in these areas is strictly associated to seismic risk, and to other secondary risks as landslides and flooding.

The mitigation of such an extreme risk can only be afforded by considering volcanological, as well as economical, urbanistic  and social issues. All these highly multidisciplinary aspects must be jointly recognized and shared by both volcanologists and decision makers, in a global, effective risk reduction policy.

We start considering the very high number of people living in the ‘red zones’ (the most risky areas, in terms of the actual emergency plans) of Vesuvius and Campi Flegrei, and the economic losses linked to a complete evacuation of these areas. We then demonstrate, from volcanological considerations, that evacuated people could not come back in the red zones in short times, but rather after years or decades, perhaps never again.From such basic considerations, we proceed to propose a multidisciplinary, effective mitigation strategy and emergency planning, which can significantly decrease the volcanic and associated risks in the area and to make effectively feasible and sustainable an evacuation, in case of high probability for an impending eruption. The proposed strategy also uses the most advanced Artificial Intelligence methodologies to plan an optimal, complete relocation of the population living in the most risky areas, in case of sudden as well as progressive evacuation. In addition, our mitigation strategy takes into account other key demographic and economic issues: problems affecting several internal areas of Southern Italy, which can help to handle the problem of risk mitigation, and to possibly jointly solve them.

How to cite: Troise, C., De Natale, G., Somma, R., Buscema, M., Maurelli, G., Giannola, A., and Petrazzuoli, S.: Mitigating the highest volcanic risk in the World: a multidisciplinary strategy for the Neapolitan area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12949, https://doi.org/10.5194/egusphere-egu22-12949, 2022.

Tourism is one of the economic activities of reference throughout the world despite the consequences of SARS-CoV-2. Within the new tourism products, geotourism is a relatively new modality and alternative to mass tourism in mature destinations. One example of this is the creation and rise of the global and European networks of geoparks. In the case of the Canary Islands, this fact can also be seen in the increase in tourist activities related to volcano tourism as an alternative product to sun and beach tourism. In this sense, the main objective of this study is to identify, inventory, select, characterize and evaluate geomorphosites with geotouristic interest on the Canary Island of La Palma following the methodology proposed by Reynard et al (2007 and 2017), based on the evaluation of scientific and added values. A total of 47 geomorphosites of geotourism interest (Ligts) that host the geodiversity of volcanic and non-volcanic forms and processes of La Palma have been studied. The main results after applying the assessment is that the scientific values ​​(0.53) are above the added values ​​(0.43). Among the first, the paleogeographic interest stands out (0.61) and of the added ones, that of the protection of the site (0.71). All these evaluations show that the geomorphological sites studied are representative of the natural and cultural heritage of La Palma, but also that they are conserved, protected and that they contribute to explain the geological and geomorphological evolution of the island. These aspects are essential to be able in the future to propose itineraries or georoutes of volcano tourist interest.

How to cite: Hernández, W., Dóniz, J., Hernández, P. A., and Pérez, N. M.: Volcanic geomorphosites, places of geotouristic interest and geo-routes in La Palma (Canary, Spain) , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8057, https://doi.org/10.5194/egusphere-egu22-8057, 2022.