AS3.13
Orals: Mon, 24 Apr | Room 1.85/86
The eruption of the submarine Hunga Tonga Hunga Hapaii volcano on 15 January 2022 was associated with a powerful blast that injected sulfur and water to altitudes up to 58 km. In this study, we combine the data from various satellite instruments (MLS, OMPS-LP, CALIOP, SAGE III, Aeolus, COSMIC-2, ACE-FTS, GOES, Himawari), ground-based lidars at various locations, meteorological radiosoundings as well as model simulation using CLaMS chemistry-transport model to investigate the evolution of the stratospheric moisture and sulfate aerosol plume at a wide range of scales—from minutes and kilometres to monthly and planetary scale. We show that due to extreme altitude reach of the eruption, the volcanic plume has circumnavigated the Earth in only one week and dispersed nearly pole-to-pole in three months. The observations provide evidence for an unprecedented increase in the global stratospheric water mass by 13% as compared to climatological levels. As there are no efficient sinks of water vapour in the stratosphere, this perturbation is expected to persist several years. The eruption has also led to a 5-fold increase in the stratospheric aerosol load, the highest in the last three decades yet factor of 6 smaller than the previous major eruption of Mt Pinatubo in 1991.
The unique nature and magnitude of the global stratospheric perturbation by the Hunga eruption ranks it among the most remarkable climatic events in the modern observation era. Given the expected longevity of the stratospheric humidity perturbation, the Hunga eruption can be said to have initiated a new era in stratospheric gaseous chemistry and particle microphysics with a wide range of potential long-lasting repercussions for the global stratospheric composition and dynamics. The eruption has thus provided a unique natural testbed, lending itself to studies of climate sensitivity to strong change in both stratospheric gaseous and particulate composition.
Spanning more than one year, the satellite and ground-based observations available to-date enable the first accurate assessment of the annual-scale stratospheric aftermath of the Hunga Tonga eruption, uncovering its climate-altering capacity.
How to cite: Khaykin, S., Podglajen, A., Ploeger, F., Grooß, J.-U., Tence, F., Khlopenkov, K., Bedka, K., Rieger, L., Baron, A., Duflot, V., Clouser, B., Sakai, T., Godin-Beekmann, S., Bekki, S., and Querel, R.: Global perturbation of stratospheric water and aerosol burden by the Hunga Tonga eruption: a 1-year aftermath, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5957, https://doi.org/10.5194/egusphere-egu23-5957, 2023.
The stratospheric aerosol layer has witnessed large perturbations in the last couple of years. From extreme wildfires in North America and Australia to medium-size volcanic eruptions like Ambae, in July 2018, Raikoke, in 2019, and finally the Hunga-Tonga Ha’apai in January 2022. Reported as the largest marine eruption ever recorded, researchers used Microwave Limb Sounder (MLS) satellite data to reveal that this volcano injected the equivalent of 10% of the total stratospheric water vapor content (100 Tg) into the stratosphere. As a consequence, increased OH radicals from water vapor were reported to further reduce the SO2 lifetime by 50%.
Here we outline the ionic composition, in parallel with microphysical, chemical, and optical properties of stratospheric aerosols using balloon measurements from Brazil 5-7 months after the eruption, in comparison with satellite data and model simulations. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and ground-based lidar measurements revealed the existence of a volcanic plume between 20 and 25 km. Particle size information derived from balloon-borne optical counters showed the presence of aerosols with a size radius >0.3µm and their subsequent sedimentation. In addition, ion chromatographic analysis of samples collected within the plume using a light-weight aerosol sampler revealed the presence of ammonia (0.3 ng/m3), sulfate (0.4 ng/m3), nitrate (1 ng/m3), and nitrite (1 ng/m3) in addition to Potassium (0.14 ng/m3), magnesium (0.12 ng/m3), and calcium (0.2 ng/m3). One of the striking findings of our measurements was the existence of traces of Dimethylamine (DMA) in our flights alongside the above-mentioned ionic components. DMA is known to enhance new particle formation upon reacting with H2SO4 and could have played an important role in the volcanic plume microphysical evolution. Although satellite data have revealed the presence of SO2 it is still uncertain if the SO2 only evolved from the Hunga-Tonga itself or as a consequence of a marine eruption that could have emitted Dimethylsulfuroxide (DMSO) into the stratosphere resulting in sulfate production.
How to cite: Vernier, H., Quintão, D., Biazon, B., Landulfo, E., Souza, G., J. S. Lopes, F., Rastogi, N., Meena, R., Liu, H., Fadnavis, S., Mau, J., K. Pandit, A., Berthet, G., and Vernier, J.-P.: Understanding the impact of Hunga-Tonga undersea eruption on the stratospheric aerosol population using Balloon measurements, Satellite data, and model simulations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6882, https://doi.org/10.5194/egusphere-egu23-6882, 2023.
The evolution of volcanic clouds is sensitive to the initial three-dimensional (3D) distributions of volcanic material, which are often unknown. Here, we conduct inverse modeling of the fresh Mt. Pinatubo cloud to estimate the time-dependent emissions profiles and initial 3D spatial distributions of volcanic ash and SO2. We account for aerosol radiative feedback and dynamic lofting of volcanic ash. It results in a lower (by 1 km for ash) injection height than that without ash radiative feedback. The solution captures the elevated ash layer between 14 and 24 km and the meridional height gradient during the first two days after an eruption. A significant fraction of the emissions (i.e., 6/16.6 Mt of SO2 and 34/64.22 Mt of fine ash) did not reach the stratosphere. The results demonstrate that the Pinatubo eruption ejected ~78% of fine ash at 12 to 23 km, ~64% of SO2 at 17 to 23 km, and most of the ash and SO2 mass for the first two days after the eruption resides in the 15- to 22- km layer. 6 Mt of tropospheric SO2 oxidized into sulfate aerosol within a week. This outcome might help to explain the discrepancies between the observations and model simulations recently discussed in the literature. The long-term evolution of the Pinatubo aerosol optical depth simulated using the obtained ash and SO2 initial distributions converges with the available stratospheric aerosol and gas experiment (SAGE) observations a month after the eruption when the tropospheric aerosol cloud dissipated.
How to cite: Ukhov, A., Stenchikov, G., Osipov, S., Krotkov, N., Gorkavyi, N., Li, C., Dubovik, O., and Lopatin, A.: Inverse Modeling of the Initial Stage of the 1991 Pinatubo Volcanic Cloud Accounting for Radiative Feedback of Volcanic Ash, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12631, https://doi.org/10.5194/egusphere-egu23-12631, 2023.
Studying impacts of past volcanic eruptions on climate and society relies on volcanology, paleo proxies and archaeological records next to climate model simulations. Here we newly study the control of varying meteorological conditions and eruption source parameters on the volcanic forcing. Simulating explosive tropical and extratropical Northern Hemisphere (NH) volcanic eruptions are carried out by co-injecting sulfur and halogens into the stratosphere with the CESM2(WACCM) model including aerosol, chemistry, climate, and earth system processes. We consider different initial meteorological conditions (ENSO, QBO, and polar vortex states) and varying eruption source parameters injecting 17 Tg and 200 Tg of SO2 together with scaled halogens, at 24 km altitude and 15° N and 64° N latitude, during January and July pre industrial 1850 conditions. Varying initial meteorological conditions reveal a similar large impact on the volcanic forcing (SO2, SO4, aerosol optical depth, halogens) as varying source parameters for both tropical and NH extratropical eruptions. Our results are compared with available model experiments from MAECHAM5-HAM. Consequences and uncertainties of volcanic forcing and responses to past and future eruptions are discussed.
How to cite: Krüger, K., Zhuo, Z., Fuglestvedt, H., Mills, M., and Toohey, M.: Initial meteorological conditions and eruption source parameters control on volcanic forcing, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4474, https://doi.org/10.5194/egusphere-egu23-4474, 2023.
The evolution of the size distribution of stratospheric aerosols after volcanic eruptions is still not understood very well, due to the temporal sparsity of in situ measurements, the low spatial coverage by ground based observations and the difficulties to derive aerosol size information from satellite measurements. To contribute to this ongoing research, we show data from our aerosol size retrieval using SAGE III/ISS solar occultation measurements. Using a three wavelength extinction approach the parameters of assumed to be monomodal lognormal particle size distributions are retrieved.
Surprisingly we find that some volcanic eruptions can lead to a decrease in average stratospheric aerosol size, in this case the eruptions of Ambae in 2018, Ulawun in 2019 and La Soufrière in 2021, while other eruptions have a more expected increasing effect on the average particle size, like the 2019 Raikoke eruption. We show how different parameters like the median radius, the absolute mode width and the number density evolve after the mentioned eruptions.
Additionally, as a part of our ongoing research to understand the underlying mechanisms controlling the observed aerosol size reduction, we show simulations of the aforementioned volcanic eruptions using the aerosol-climate model MAECHAM5-HAM. Although the initial conditions in the model simulations are different from observations due to missing smaller emissions in the time before the eruptions, a good agreement in the perturbations of the extinction coefficient was achieved.
How to cite: Wrana, F., Niemeier, U., Wallis, S., and von Savigny, C.: Stratospheric aerosol size decrease after volcanic eruptions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5788, https://doi.org/10.5194/egusphere-egu23-5788, 2023.
We investigate how the global mean temperature responds to single volcanic events of different magnitudes and to multiple events occurring close in time. We are using the Community Earth System Model version 2 (CESM2) to simulate the Earth system forced only with stratospheric aerosols from explosive volcanoes, with the rest of the climate system fixed at 1850 conditions. The model is run with a dynamical ocean component, and the Whole Atmosphere Community Climate Model version 6 (WACCM6) atmosphere component using middle atmosphere chemistry.
Previous efforts of estimating a response function assume a linear relationship between the forcing and the deterministic temperature response to the forcing [1], defined as Tdet(t)=L[F(t)]. Studies also show that the forcing is similar across forcing agents [2] (although this is not a settled debate [3]), in which case volcanoes could provide a valuable means of estimating global temperature response to radiative forcing due to their short-lived and large temperature responses.
We present simulations of single volcano events with ejected sulphate aerosol loadings differing in orders of magnitude and simulations where two volcanic eruptions are close enough in time that the second eruption occurs as the temperature is still recovering from the first event.
We show that the functional form of the temperature response is similar for volcanic events of different magnitudes and that non-linearities are not important as a second eruption occurs when the temperature is well below equilibrium in a perturbed state. The results further suggest the global mean temperature time series may be reduced to a simple superposition of individual pulses, and thus that it may be described by a convolution between a linear response function and some forcing, analogous to the model used by [1].
[1] K. Rypdal and M. Rypdal, ‘Comment on “Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcing” by S. Lovejoy and C. Varotsos (2016)’, Earth System Dynamics, 2016, vol. 7, no. 3, pp. 597–609.
[2] T. B. Richardson et al., ‘Efficacy of Climate Forcings in PDRMIP Models’, Journal of Geophysical Research: Atmospheres, 2019, vol. 124, no. 23, pp. 12824–12844.
[3] P. Salvi, P. Ceppi, and J. M. Gregory, ‘Interpreting differences in radiative feedbacks from aerosols versus greenhouse gases’, Geophysical Research Letters, 2022, vol. 49, no. 8, p. e2022GL097766.
How to cite: Enger, E., Theodorsen, A., Rugenstein, M., and Graversen, R.: Insensitivity of global temperature response to the magnitude of volcanic eruptions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3331, https://doi.org/10.5194/egusphere-egu23-3331, 2023.
Several studies have reported anomalous precipitation in the years that follow large volcanic eruptions. Here we assess precipitation anomalies in post-eruption years according to their rarity in non-volcanic periods. Using global simulations of climate over the last millennium, we reevaluate the response of precipitation to volcanic aerosols in terms of novel metrics. In this approach, the magnitude of the precipitation response is contextualized through comparisons to internal variability. We also examine the connections between global and regional-scale precipitation anomalies. Finally, we assess to what extent a unique ‘fingerprint’ of eruptions can be seen in the observational precipitation record in spite of concurrent internal variability.
How to cite: McGraw, Z. and Polvani, L.: Reassessing post-eruption precipitation anomalies in the context of natural variability, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4691, https://doi.org/10.5194/egusphere-egu23-4691, 2023.
The record of the volcanic forcing of climate over the past 2500 years is reconstructed primarily from sulfate concentrations in ice cores. Of particular interest are stratospheric eruptions, as these afford sulfate aerosols the longest residence time and largest dispersion in the atmosphere, and thus the greatest impact on radiative forcing. Sulfur isotopes can be used to distinguish between stratospheric and tropospheric volcanic sulfate in ice cores since stratospheric sulfur aerosols are exposed to UV radiation which imparts a mass independent fractionation (Savarino et al., 2003). Thus, sulfur isotopes in ice cores provide a means to identify stratospheric eruptions and calculate the proportion of sulfate deposited from a volcanic event that came the stratosphere, allowing us to refine the historic record of explosive volcanism and its forcing of climate. Here we present high-resolution (sub-annual) sulfur isotope data from both Greenland and Antarctica across a suite of unidentified eruptions from the anomalously cold decades of the 530s CE, 1450s CE and 1600s CE, as well as the newly identified eruption of Okmok in 43 BC (McConnell et al., 2020), to investigate the stratospheric sulfur loading and climate forcing potential of these eruptions.
Savarino, J., Romero, A., Cole Dai, J., Bekki, S., & Thiemens, M. H. (2003). UV induced mass‐independent sulfur isotope fractionation in stratospheric volcanic sulfate. Geophysical Research Letters, 30(21). http://doi.org/10.1029/2003GL018134
McConnell, J. R., Sigl, M., Plunkett, G., Burke, A., Kim, W. M., Raible, C. C., et al. (2020). Extreme climate after massive eruption of Alaska’s Okmok volcano in 43 BCE and effects on the late Roman Republic and Ptolemaic Kingdom. Proc Natl Acad Sci USA, 117(27), 15443.
How to cite: Burke, A., Innes, H., Crick, L., Anchukaitis, K., Hutchison, W., McConnell, J., Rae, J., Sigl, M., and Wilson, R.: High-resolution sulfur isotopes from ice cores: improved estimates of the volcanic forcing of climate, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7109, https://doi.org/10.5194/egusphere-egu23-7109, 2023.
“Solar Radiation Management” aims to mitigate global warming by either seeding aerosols into clouds to change their radiative properties and occurrence frequency, or injecting sulfur into the atmosphere to shield the Earth’s surface from incoming solar radiation. These approaches are inspired, among other things, by the effect of volcanic eruptions on the climate system.
Here we provide a critical reassessment of a time period commonly referred to as the “Medieval Quiet Period”. For several centuries in early Medieval times (c. 750-1050 CE) the climate system was postulated to have been relatively unperturbed by natural climate forcing, resulting in a unique period of climate stability. We present evidence that just the opposite is true. In large parts of the Northern Hemisphere and in the Arctic, atmospheric aerosol loads were persistently high during this period as a result of increased volcanic activity, especially in Iceland.
Our new insight is supported by evidence taken from an array of synchronized ice cores from Greenland with high time-resolution records of a large suite of trace elements, including volcanic volatiles such as sulfur, chlorine, fluorine, and heavy metals. We use crypto-tephra in ice cores to provenance the sources of many volcanic eruptions and sulfur isotopes (33S, 34S) to delineate if volcanic gas emissions occurred above or below the ozone layer.
We define an “Iceland Active Period”, a time period of frequent and prolonged volcanic activity, producing persistently high levels in atmospheric aerosol burdens in the Northern Hemisphere Arctic’s preindustrial atmosphere lasting for decades to centuries. The frequency and cumulative amount of emissions of climate-impacting trace substances (e.g., sulfates, halogens, ash) is unprecedented in the late Holocene. It is exceeded at times only in the Anthropocene (since about 1900) and in the early-middle Holocene (e.g. during rapid deglaciation). We demonstrate that previous reconstructions of volcanic forcing used in PMIP3 and PMIP4 strongly underestimate volcanic aerosol emissions in the early Medieval and argue that this period should not be considered a reference climate state for the Common Era.
Finally, we investigate possible aerosol-climate interactions following these eruptions using climate proxies and state-of-the-art chemistry climate models with prognostic stratospheric aerosols and chemistry.
How to cite: Sigl, M., Gabriel, I., Abbott, P., Behrens, M., Burke, A., Chelman, N., Cook, E., Fleitmann, D., Fuglestvedt, H., Hörhold, M., Hutchison, W., Krüger, K., McConnell, J. R., Óladóttir, B. A., Plunkett, G., Preiser-Kapeller, J., and Zhuo, Z.: Solar radiation management from Icelandic volcanoes during the Medieval Quiet Period, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4536, https://doi.org/10.5194/egusphere-egu23-4536, 2023.
Posters on site: Tue, 25 Apr, 10:45–12:30 | Hall X5
Large high-latitude explosive volcanic eruptions remain less well understood than their low-latitude counterparts, despite their potential for strong hemispheric climate impacts. Using the high-top coupled Earth system model CESM2-WACCM6 with prognostic stratospheric aerosols and chemistry, we simulate Pinatubo-magnitude Northern Hemisphere (NH) volcanic eruptions at 64° N. We show how the SO2 lifetime and growth of volcanic sulphate aerosols are strongly modulated by the initial state of the NH polar vortex for eruptions at this latitude. The resulting variability of the volcanic forcing is of comparable magnitude to its sensitivity to varying the plume composition, eruption season, and plume height. We compare the modelled volcanic sulphate deposition over the Greenland ice sheet to that assumed in current forcing reconstructions of past NH extratropical eruptions and provide a new model-based estimate of the magnitude and uncertainty of the transfer function used to reconstruct sulphur injections from such eruptions. Our results demonstrate the great potential for improvement in understanding and reconstructing the climatic impacts of NH high-latitude eruptions.
How to cite: Fuglestvedt, H., Zhuo, Z., Toohey, M., and Krüger, K.: Revisiting the volcanic forcing of high-latitude Northern Hemisphere eruptions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7296, https://doi.org/10.5194/egusphere-egu23-7296, 2023.
Current reconstructions of volcanic forcing over the last 2000 years rely on scaling volcanic sulfate measured in ice cores to estimates of stratospheric sulfate burdens and optical properties using relationships derived from the 1991 eruption of Mt. Pinatubo. However, there are large uncertainties associated with these conversions and consequently a large uncertainty in the reconstructions. Here, we explore the relationship between ice sheet sulfate deposition and volcanic forcing in model simulations of the last millennium conducted using the UK Earth System Model with an interactive stratospheric aerosol scheme. Treating the model sulfate deposition timeseries as a measured ice-core record and using established conversions, we explore how many of the large-magnitude volcanic events simulated in the model are missed by looking at deposition alone, and how the volcanic forcing may be overpredicted or underpredicted compared to the model itself. These results will enable us to further explore uncertainty in these relationships, and aid in improving methods to calculate forcing for past eruptions.
How to cite: Marshall, L., Toohey, M., and Schmidt, A.: How much does ice sheet sulfate deposition tell us about volcanic forcing?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14017, https://doi.org/10.5194/egusphere-egu23-14017, 2023.
The climate impact of volcanic SO2 is strongly correlated with the injection height into the stratosphere. We have used a dataset created with the dispersion model FLEXPART by combining vertical information from the CALIOP lidar with horizontal SO2 information from AIRS [1]. So far, the dataset represents the eruptions of Sarychev in June 2009 with a vertical resolution of 200 m. The original dataset for SO2 used in WACCM releases all SO2 in one latitude and longitude gridbox, spanning an altitude of 11 to 15 km. Our dataset is distributed over several latitude and longitude gridboxes and spans an altitude of 7.6 to 18.6 km [1].
We have performed simulations in the Earth system model CESM2 WACCM with our dataset and WACCM’s original volcanic SO2 dataset. Aerosol distributions are compared with observations from the CALIOP lidar to investigate the impact of our dataset’s high vertical and horizontal resolution. We also compare outputs from simulations with the two datasets.
The first simulations with the two datasets show large differences in both horizontal and vertical SO2 distribution in the months following the eruption. This likely affects the duration of the radiative impact from sulfate particles formed from the SO2.
We are presently investigating differences in aerosol formation and concentrations, time evolution of volcanic sulfate, and climate impact of simulations with the two datasets. Future work involves creation of SO2 datasets for all volcanic eruptions since 2006, with the goal of providing better representation of volcanism in Earth system models.
References
[1] Sandvik, O. S., Friberg, J., Sporre, M. K., and Martinsson, B. G.: Methodology to obtain highly resolved SO2 vertical profiles for representation of volcanic emissions in climate models, Atmos. Meas. Tech., 14, 7153–7165, https://doi.org/10.5194/amt-14-7153-2021, 2021.
How to cite: Axebrink, E., Friberg, J., and Sporre, M. K.: Utilizing a high vertical and horizontal resolution dataset of SO2 for modelling volcanic eruptions in WACCM, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14847, https://doi.org/10.5194/egusphere-egu23-14847, 2023.
How to cite: Hollowed, J. and Jablonowski, C.: A Simple Model of Volcanic Aerosol Forcing Against an Idealized Climatological Background in Support of the DOE CLDERA Project, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1720, https://doi.org/10.5194/egusphere-egu23-1720, 2023.
Sulphate aerosol in the stratosphere recently became an interactive part of many global climate models and its uncertainties are not yet well constrained. Stratospheric sulphate aerosol is modulated by natural emissions of several sulphur-containing species, including volcanic eruptions, as well as anthropogenic emissions. If not directly injected into the stratosphere by large volcanic eruptions, sulphate aerosols and their precursors are transported into the stratosphere via the tropical tropopause. While there have been some model intercomparison activity for the large volcanic eruptions, the background conditions of sulphur species and in particular the stratospheric aerosol layer have thus far not been addressed at all. Evaluating the background conditions in global models allow to identify modelling issues that are usually masked by larger perturbations such as volcanic eruptions, yet may still be of importance after such a perturbation. Some key factors causing differences between models include different microphysical schemes, chemical schemes, as well as transport and cross-tropopause fluxes. In this work, we use 8 models and available observational data to quantify the full background atmospheric sulphur cycle (burdens, fluxes, and their variability) and investigate its uncertainties within the framework of the Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP). We focus on stratospheric aerosol and its transport with the Brewer-Dobson-Circulation, as well as the influence of the polar vortices. We find significant inter-model variations in the background burden of the major sulphur species. Seasonal cycles agree well in the southern hemisphere, whereas the northern hemisphere shows more inter-model differences due to the individual representations of the northern polar vortex.
How to cite: Brodowsky, C., Aquila, V., Bekki, S., Dhomse, S., Laakso, A., Mann, G., Niemeier, U., Quaglia, I., Rozanov, E., Sekiya, T., Tilmes, S., Timmreck, C., Yu, P., Zhu, Y., and Sukhodolov, T.: Evaluating the Uncertainties of the Global Atmospheric Sulphur Budget in a Multi-Model Framework, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14591, https://doi.org/10.5194/egusphere-egu23-14591, 2023.
The Raikoke volcano erupted on 21-22 June 2019 and emitted ~1.5 Tg volcanic ash into the atmosphere. Several previous studies have focused on the large-scale dispersion of volcanic aerosol plumes with space-borne observations and dispersion models. However, height-resolved ground-based observations are still necessary to trace and cross-check the 3-D evolution of aerosol plumes due to their complicated structures. Here, we present a rare ground-based lidar observation of Raikoke aerosol plumes in the mid-latitudes of the Northern Hemisphere (site: Wuhan; location: 30.5°N, 114.4°E) from 25 July to 30 September 2019. Two types of volcanic aerosol plumes were observed, including the main aerosol plume and a single impacted aerosol cloud (referred to as ‘CCC’, or coherent circular clouds). The main aerosol plume first arrived at Wuhan on 25 July and was intermittently observed during the following two months at altitudes of 15.0-20.5 km, with layer-integrated AODs (aerosol optical depths) of 0.001-0.017. From 22 August to 23 September, this aerosol plume underwent two quasi-elliptical transport pathways in East Asia driven by an Asian monsoon anticyclone. The CCC arrived at Wuhan twice at 20.2-21.7 km on 30 July and at 23.2-25.0 km on 24-26 August after self-lofting, corresponding to the former two circles of their transport around the Northern Hemisphere. Both arrivals of the CCC were closely followed by a thin and horizontally extended aerosol plume (named ‘trail’) with a duration of several days. The unique observation location provided us with an opportunity to study the evolution of the vertical distribution and optical properties of volcanic aerosols, which is anticipated to be a crucial supplement/reference for dispersion model simulation, data assimilation, and forecasting refinement.
How to cite: He, Y., Jing, D., and Yin, Z.: Evolution of aerosol plumes from 2019 Raikoke volcanic eruption observed with polarization lidar over central China, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13549, https://doi.org/10.5194/egusphere-egu23-13549, 2023.
Large tropical volcanic eruptions can significantly alter stratospheric water vapour either with direct injection or modifying entry pathways and the quantitative magnitude and time evolution of these changes remain uncertain. Using an ensemble volcanic forcing experiment carried out with version 1 of the UK Earth System Model (UKESM1), we explore the changes in the stratospheric water vapour (SWV) by a Pinatubo-like volcanic eruption via modification of the entry pathway. Our simulations show significant increases in SWV three months after the volcanic eruption for the ensemble mean. The increase peaks at 1 ppmv (~17% of the background levels) in the second post-eruption winter and then decays slowly, in accordance with the tropical cold point temperature anomalies. By decomposing the volcanic heating into diabatic aerosol heating and adiabatic dynamical heating, we show that the timing of tropopause heating after the eruption is determined by the seasonal variation of a general decelerated tropical upwelling imposed on the significant direct aerosol heating lasting two years.
How to cite: Zhou, X., Feng, W., Dhomse, S., Mann, G., and Chipperfield, M.: Analysing changes in stratospheric water vapour following Pinatubo-like volcanic eruption using UK Earth System Model, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15879, https://doi.org/10.5194/egusphere-egu23-15879, 2023.
We employ the ECHAM5/MESSy2 atmospheric chemistry general circulation model (EMAC)that incorporates calculations of gas-phase and heterogeneous chemistry coupled with the ozone cycle and aerosol formation, transport, and microphysics to calculate the 1991 Pinatubo volcanic cloud. We considered simultaneous injections of SO2, volcanic ash, and water vapor. We conducted multiple ensemble simulations with different injection configurations to test the evolution of SO2, SO4, ash masses, stratospheric aerosol optical depth, surface area density (SAD), and 24the stratospheric temperature response against available observations. We found that the volcanic cloud evolution is sensitive to the altitude where volcanic debris is initially injected and the initial concentrations of the eruption products that affect radiative heating and lofting of the volcanic cloud. The numerical experiments with the injection of 12 Mt SO2, 75 Mt of volcanic ash, and 150 Mt of water vapor at 20 km show the best agreement with the observation of aerosol optical depth and stratospheric temperature response. Volcanic water injected by eruptive jets and/or intruding through the tropopause accelerates SO2 oxidation. But the mass of volcanic water retained in the stratosphere is controlled by the stratospheric temperature at the injection level. For example, volcanic materials are released in the cold point above the tropical tropopause, and most of the injected water freezes and sediments as ice crystals. The water vapor directly injected into the volcanic cloud increases the SO2− mass and stratospheric aerosol optical depth by about 5%. The coarse 4ash comprises 98% of the ash injected mass. It sediments within a few days, but aged submicron ash could stay in the stratosphere for a few months providing SAD for heterogeneous chemistry. The presence of ash accelerates SO2 oxidation by 10%–20% due to heterogeneous chemistry, radiative heating, lofting, and faster dispersion of volcanic debris. Ash aging affects its lifetime and optical properties, almost doubling the radiative ash heating. The 2.5-year simulations show that the stratospheric temperature anomalies forced by radiative heating of volcanic debris in our experiments with the 20 km injection height agree well with observations and reanalysis data. This indicates that the model captures the long-term evolution and climate effect of the Pinatubo volcanic cloud. The volcanic cloud’s initial lofting, facilitated by ash particles’ radiative heating, controls the oxidation rate of SO2. Ash accelerates the formation of the sulfate layer in the first 2 months after the eruption. We also found that the interactive calculations of OH and heterogeneous chemistry increase the volcanic cloud sensitivity to water vapor and ash injections. All those factors must be accounted for in modeling the impact of large-scale volcanic injections on climate and stratospheric chemistry.
How to cite: AbdelKader, M., Stenchikov, G., Pozzer, A., Tost, H., and Lelieveld, J.: The effect of ash, water vapor, and heterogeneous chemistry on the evolution of a Pinatubo-size volcanic cloud, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11211, https://doi.org/10.5194/egusphere-egu23-11211, 2023.
In this presentation we present findings from a series of interactive stratospheric aerosol simulations of the Hunga-Tonga volcanic aerosol cloud with the UM-UKCA composition-climate model. The model experiments apply the same version of the UM-UKCA model published for the Agung, El Chichon and Pinatubo aerosol clouds (Dhomse et al., 2020), those runs aligned with the Historical Eruption SO2 emissions Assessment experiment within ISA-MIP (Timmreck et al., 2018).
A consistent feature of interactive stratospheric aerosol simulations of Pinatubo (e.g. Dhomse et al., 2014; Sheng et al., 2015; Mills et al., 2016) is an over-prediction of stratospheric AOD, for a given emission of SO2, requiring a downward-adjustment of emitted SO2 (e.g. Timmreck et al., 2018). Dhomse et al. (2020) indicated models may be missing an important removal process such as heterogeneous uptake of SO2 onto fine ash particles, the process recently demonstrated to have removed ~43% more sulphate than SO2-only simulations for the Kelut aerosol cloud (Zhu et al., 2020).
For Hunga-Tonga, any volcanic ash was likely removed within the initial days (Sellitto et al., 2022) and the co-emission of ~100Tg of water vapour (e.g. Carn et al., 2022) has been shown by Zhu et al. (2022) to increase the scattering efficiency of the Hunga-Tonga cloud, both via hygroscopic growth and changes in coagulation, leading to a potential systematic underestimation of stratospheric AOD among interactive stratospheric aerosol models.
In a series of UM-UKCA model experiments, we explore the unexpectedly strong optical depth from Hunga-Tonga aerosol via SO2-only simulations, increasing by a factor 2 and 3 the observed 0.4-0.5Tg of SO2 (Carn et al., 2022), and aligning with the protocol from a multi-model Hunga-Tonga aerosol intercomparison co-ordinated by the University of Colorado (Clyne et al., 2021). The Tonga-MIP protocol emits 0.5Tg of SO2 at 25-30km, within a 6-hour period, with models also enacting a meridional emission spread between 22S and 14S, matching approaches used to account for unresolved early-phase plume transport for Pinatubo (see e.g. Quaglia et al., 2022).
We evaluate the strength of the simulated Hunga-Tonga aerosol cloud in these SO2-only emission runs, comparing to the magnitude and timing of maximum strat-AOD observed from OMPS (Taha et al., 2022), and the altitude of the progressing aerosol cloud compared to ground-based lidar measurements from Reunion Island (Baron et al., 2022) and Sao Paulo (Landulfo et al., 2022).
How to cite: Mann, G., Dhomse, S., Shallcross, S., Bellouin, N., Abraham, L., Hatcher, R., Lister, G., Taha, G., Baron, A., Duflot, V., Lopes, F., and Landulfo, E.: Interactive stratospheric aerosol simulations of the Hunga-Tonga aerosol cloud re: stronger than expected observed mid-visible stratospheric AOD, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16560, https://doi.org/10.5194/egusphere-egu23-16560, 2023.
The 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano caused substantial impacts on the atmosphere, including a large increase of stratospheric aerosol at high altitudes and a massive injection of water vapor. We show results from application of a two-dimensional tomographic retrieval of aerosol extinction profiles from limb scattered sunlight made by the NASA OMPS Limb Profiler instrument. The tomographic retrieval substantially improves the agreement in magnitude and vertical structure with coincident lidar and occultation observations compared to the standard retrieval. We also show a secondary effect of bias from uncertainty in assumed particle size distribution parameters that results in a systematic underestimation of the aerosol extinction in the altitude region of the peak of the volcanic aerosol layer.
How to cite: Bourassa, A., Zawada, D., Rieger, L., and Degenstein, D.: Tomographic retrievals of Hunga Tonga-Hunga Ha’apai volcanic aerosol , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9208, https://doi.org/10.5194/egusphere-egu23-9208, 2023.
We present instantaneous forcing computed in a transient simulation with the chemistry climate model EMAC considering more than 600 explosive eruptions and plumes of major forest fires observed by limb scanning satellites in the period 1991 to 2021. If not available directly, perturbations of SO2 in the volcanic plumes, which we use as alternative to the "point source approach", were derived from observed extinctions. For the fires, black and organic carbon is injected at the top of the pyro-cumulonimbus and the resulting increase in extinction is compared with satellite data. Medium sized volcanic eruptions cause a total forcing of up to -0.35W/m2 at the top of the atmosphere while for the fires the forcing there can be positive (about 0.2W/m2).
How to cite: Brühl, C., Schallock, J., Lelieveld, J., and Rieger, L.: Radiative forcing by stratospheric aerosol from volcanoes and major fires for the last 3 decades, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3656, https://doi.org/10.5194/egusphere-egu23-3656, 2023.
In the AD 1450s, one of the three largest climate-forcing eruptions of the largest 1000 years took place, with similar impacts as the AD 1815 event of Tambora, Indonesia, that caused the ‘year without a summer’ of AD 1816. The submarine caldera of Kuwae, Vanuatu, has long been suggested to be the source of the AD 1450s eruption, but this is still highly debated.
Today, the 12-by-6 km large Kuwae caldera lies between the islands of Epi and Tongoa. Here, an eruption occurred in the 15th century eruption and locally caused devastation, covering the islands surrounding it with vast amounts of pyroclastic material. We present the first full stratigraphy of the event, enabling us to reconstruct the eruptive sequence. First, a small ash plume produced fine ash deposits overlying faulted soil sequences, indicating a low-energy, precursory phase. Afterwards, the eruption built a Plinian eruption column, causing lapilli fall in excess of 3 m in proximal locations, and sending volcanic particles and gases high up into the atmosphere. This column then collapsed, producing the first pyroclastic flows that devastated the islands surrounding the caldera, incorporating many trees that became charcoalised and are still fully preserved in the deposits. Following further pyroclastic flow activity, a massive lithic lag breccia contains megaclasts (>10 m breccia), recording the collapse of a pre-existent edifice. Later pumice-rich pyroclastic flows occurred bring the total thickness of the sequence to between 30 and >80 m in proximal locations.
These results are combined with initial results from a recent bathymetric study, mapping the submarine caldera floor, addressing the question of whether the entire caldera was generated during the mid-15th century event, or whether earlier eruptions have played a part in its collapse. This is essential for estimating the total collapse volume of the mid-15th century event at Kuwae, representative of the total erupted volume.
We will use information on a) the eruptive sequence (based on field observations), b) eruptive volume (based on bathymetry), c) total emitted sulphur (based on eruptive volume and preliminary geochemistry data), and d) the eruptive date (based on radiocarbon analysis of collected charcoal samples) to characterise the mid-15th century eruption of the Kuwae caldera and test whether it was the source of the AD 1450s volcanic event that had a global climate impact.
How to cite: Stern, S., Cronin, S., Bedford, S., Ballard, C., Henderson, R., and Yona, S.: Impacts of the mid-15th century eruption at Kuwae caldera, Vanuatu, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1789, https://doi.org/10.5194/egusphere-egu23-1789, 2023.
The Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP) is a protocol-driven international initiative under the umbrella of the sixth phase of the Coupled Model Intercomparison Project (CMIP6) aiming at coordinating the activities of different Research Institutes involved in numerical climate modelling focused on a multi-model assessment of climate models' performance under strong volcanic forcing conditions. The main objective of the initiative is to assess to what extent responses of the coupled ocean-atmosphere system to the same applied strong volcanic forcing are robustly simulated across state-of-the-art coupled climate models and identify the causes that limit robust simulated behavior, especially differences in their treatment of physical processes. To this purpose, four Tier-1 (mandatory) experiments branched into two main sets, named “volc-pinatubo” and “volc-long” were defined, together with eight more lower-priority experiments. Six years since the definition of the VolMIP protocol (Zanchettin et al., 2016), ensemble simulations of most of the mandatory VolMIP experiments have been completed and made publicly available through the Earth System Grid Federation open platform, with the first VolMIP results being currently published and several analyses in progress. The long turnover time between the experiment design, the integration of the simulations and the analysis of the output motivates an assessment of the overall effectiveness of the VolMIP strategy, particularly in the light of a possible second phase of the initiative.
In this contribution, we will illustrate the status of the initiative, highlight its major achievements and discuss its future perspective in the light of emergent scientific questions regarding volcanically forced climate variability.
Zanchettin, D., Khodri, M., Timmreck, C., Toohey, M., Schmidt, A., Gerber, E. P., Hegerl, G., Robock, A., Pausata, F. S. R., Ball, W. T., Bauer, S. E., Bekki, S., Dhomse, S. S., LeGrande, A. N., Mann, G. W., Marshall, L., Mills, M., Marchand, M., Niemeier, U., Poulain, V., Rozanov, E., Rubino, A., Stenke, A., Tsigaridis, K., and Tummon, F.: The Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP): experimental design and forcing input data for CMIP6, Geosci. Model Dev., 9, 2701–2719, https://doi.org/10.5194/gmd-9-2701-2016, 2016
How to cite: Zanchettin, D., Timmreck, C., Khodri, M., Hegerl, G., Krüger, K., Pausata, F. S. R., Robock, A., Schmidt, A., and Toohey, M.: The Model Intercomparison Project on the Climatic Response to Volcanic Forcing (VolMIP): Status and Future Perspectives of the Initiative, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2604, https://doi.org/10.5194/egusphere-egu23-2604, 2023.
Large explosive volcanic eruptions can have major impacts on global climate, affecting both radiative balance and inducing interannual-to-decadal dynamical alterations of the atmospheric and ocean circulation.
Despite some discrepancies across studies regarding the response of ENSO to volcanism based on paleoclimate data, the majority of ENSO reconstructions display an El Niño–like warming in the year of eruption, while none display a significant La Niña–like response, Furthermore, there has been an emerging consensus from the numerous coupled General Circulation Model studies investigating the impact of tropical volcanism on ENSO, with the overwhelming majority displaying an El Niño–like warming occurring in the year following the eruption. However, the mechanisms that trigger a change in the ENSO state following volcanic eruptions are still debated. The center of the argument is understanding how volcanism can affect the trade winds along the equatorial Pacific.
Here, we shed light on the processes that govern the ENSO response to tropical volcanic eruptions through a series of sensitivity experiments with an Earth System Model where a uniform stratospheric volcanic aerosol loading is imposed over different parts of the tropics. Three tropical mechanisms are tested: the “ocean dynamical thermostat” (ODT); the cooling of the Maritime Continent; and the cooling of tropical northern Africa (NAFR). We find that the NAFR mechanism plays the largest role, while the ODT mechanism is absent in our simulations as La Niña-like rather than El-Niño-like conditions develop following a uniform radiative forcing over the equatorial Pacific.
How to cite: Pausata, F. S. R., Zhao, Y., Zanchettin, D., Caballero, R., and Battisti, D.: Revisiting the mechanisms of ENSO response to tropical volcanic eruptions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3638, https://doi.org/10.5194/egusphere-egu23-3638, 2023.
The northerly Etesian winds are a stable summertime circulation system in the eastern Mediterranean, emerging from a steep pressure gradient between the central Europe and Balkans high-pressure and the Anatolian low pressure systems. Etesian winds are influenced by the variability in the Indian summer monsoon (ISM), but their sensitivity to external forcing on interannual and longer timescales is not well understood. Here we investigate the sensitivity of Etesian winds to large volcanic eruptions in a set of model simulations over the last millennium and reanalysis of the 20th century. We provide model evidence for significant volcanic signatures, manifested as a robust reduction in the wind speed and the total number of days with Etesian winds in July and August. These are robust responses to all strong eruptions in the last millennium, and in the extreme case of Samalas, the ensemble-mean response suggests a post-eruption summer without Etesians. The significant decline in the number of days with Etesian winds is attributed to the weakening of the ISM in the post-eruption summers, which is associated with a reduced large-scale subsidence and weakened surface pressure gradients in the eastern Mediterranean. Our analysis identifies a stronger sensitivity of Etesian winds to the Northern Hemisphere volcanic forcing, particularly for volcanoes before the 20th century, while for the latest large eruption of Pinatubo modelled and observed responses are insignificant.
How to cite: Misios, S., Logothetis, I., Knudsen, M. F., Karoff, C., Amiridis, V., and Tourpali, K.: Decline in the Mediterranean Etesian winds after large volcanic eruptions in the last millennium, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4560, https://doi.org/10.5194/egusphere-egu23-4560, 2023.
Large explosive volcanic eruptions are a potential source of uncertainty in future climate projections as they cannot be predicted in advance, but eventually will occur, causing short-term climatic impacts on both local and global scale. Still, an open topic is the volcanic impact on tropical climate variability, in particular El Niño Southern Oscillation (ENSO) and tropical precipitation and the combined effect of both. Sufficient large ensembles simulations with the same model and radiative forcing scenario but varying initial conditions have become a great tool in recent years to disentangle forced and internal variability). Here we use the EVA-ENS ensemble (Azoulay et al., 2021) which consists of 100-member ensembles of the MPI-ESM-LR for idealized equatorial Pinatubo-like eruptions of different eruption strength and an additional 100-member ensemble without forcing. We are in particular interested if there is a linear volcanic signal on tropical precipitation dependent on the eruption strength and when did it emerge from tropical internal variability.
Our results show that for Idealized tropical eruptions global and large hemispheric mean 2m temperature and precipitation anomalies seemed to be scalable with the sulfur emission strength above a certain threshold, except for tropical temperatures for an emission strength > 40 Tg sulfur (S). 10 Tg S emission, the upper estimate of the 1991 Pinatubo eruption, seems to be a threshold where the signal is discernible from internal variability. We also find that seasonal and ensemble mean pattern correlation of 2m temperature and precipitation anomalies are highly correlated in particular for larger emission strengths in the tropics and strongly modulated by ENSO. There is an increasing tendency for a warm ENSO increases with eruption strength. Emergence of the volcanic signal appears for smaller eruption strength when looking to ENSO composites. Emergence of cooling appears on a hemispheric scale, while precipitation response is more localized and mainly confined to the tropics and subtropics.
References:
Azoulay, A., Schmidt, H., and Timmreck, C.: The Arctic polar vortex response to volcanic forcing of different strengths, J. Geophys. Res., 126, e2020JD034450, doi.org/10.1029/2020JD034450, 2021.
How to cite: Timmreck, C., Olonscheck, D., Ballinger, A., D'Agostino, R., Fang, S.-W., Hegerl, G., and Schurer, A.: Linear precipitation response to increasingly strong volcanic eruptions and its emergence from internal variability , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5428, https://doi.org/10.5194/egusphere-egu23-5428, 2023.
Posters virtual: Tue, 25 Apr, 10:45–12:30 | vHall AS
Narrow field-of view spectral measurements of twilight sky brightness as a function of solar zenith angle in the 89°-95° range allow to retrieve lower stratospheric and tropospheric aerosol extinction profiles. The measurements were carried out over Tbilisi, Georgia, South Caucasus during 2021-2022 in the 700-800 nm wavelength range using a SBIG ST9 CCD camera and a SBIG SGS spectrograph. The Monte Carlo code Siro, developed in the Finnish Meteorological Institute was used to design a forward model. Aerosol extinction profiles at 780 nm were retrieved using the Levenberg–Marquardt algorithm.
Stratospheric aerosol loading was low in the considered period whereas the upper (about 9-10 km) and lower troposphere (about 4-5 km) were sometimes disturbed due to small volcanic eruptions and dust transport events. Particularly, ash clouds from Etna eruptions on 10 and 21 February were observed at about 9 km altitude.
How to cite: Mateshvili, N., Mateshvili, I., Baker, N., Berthelot, A., Bingen, C., Dekemper, E., Demoulin, P., Franssens, G., Fussen, D., Kyrölä, E., Paatashvili, T., Pieroux, D., and Vanhellemont, F.: Stratospheric aerosol extinction profiles retrieved from twilight sky spectral measurements above Georgia, South Caucasus in 2021-2022. , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13861, https://doi.org/10.5194/egusphere-egu23-13861, 2023.
