Volcanic activity in and around the year 536 CE led to severe cold and famine, and has been speculatively linked to large-scale societal crises around the globe. Using a coupled aerosol-climate ...model, with eruption parameters constrained by recently re-dated ice core records and historical observations of the aerosol cloud, we reconstruct the radiative forcing resulting from a sequence of two major volcanic eruptions in 536 and 540 CE. We estimate that the decadal-scale Northern Hemisphere (NH) extra-tropical radiative forcing from this volcanic “double event” was larger than that of any period in existing reconstructions of the last 1200 years. Earth system model simulations including the volcanic forcing show peak NH mean temperature anomalies reaching more than −2 °C, and show agreement with the limited number of available maximum latewood density temperature reconstructions. The simulations also produce decadal-scale anomalies of Arctic sea ice. The simulated cooling is interpreted in terms of probable impacts on agricultural production in Europe, and implies a high likelihood of multiple years of significant decreases in crop production across Scandinavia, supporting the theory of a connection between the 536 and 540 eruptions and evidence of societal crisis dated to the mid-6th century.
The Los Chocoyos (14.6°N, 91.2°W) supereruption happened ∼75,000 years ago in Guatemala and was one of the largest eruptions of the past 100,000 years. It emitted enormous amounts of sulfur, ...chlorine, and bromine, with multi‐decadal consequences for the global climate and environment. Here, we simulate the impact of a Los Chocoyos‐like eruption on the quasi‐biennial oscillation (QBO), an oscillation of zonal winds in the tropical stratosphere, with a comprehensive aerosol chemistry Earth System Model. We find a ∼10‐year disruption of the QBO starting 4 months post eruption, with anomalous easterly winds lasting ∼5 years, followed by westerlies, before returning to QBO conditions with a slightly prolonged periodicity. Volcanic aerosol heating and ozone depletion cooling leads to the QBO disruption and anomalous wind regimes through radiative changes and wave‐mean flow interactions. Different model ensembles, volcanic forcing scenarios and results of a second model back up the robustness of our results.
Plain Language Summary
Supereruptions are some of the most violent natural events on Earth which can erupt approximately every 100,000 to 200,000 years. Here, we investigate the impact of the Los Chocoyos (14.6°N, 91.2°W) eruption ∼75,000 years ago in Guatemala on the atmospheric circulation in the tropics (30°S to 30°N). The dominating circulation phenomenon in the tropical stratosphere, the second layer of the atmosphere at ∼16–50 km altitude in the tropics, is the quasi‐biennial oscillation (QBO) an approximately 28 months oscillation of alternating easterly or westerly winds occurring symmetrically between 15°S and 15°N. Using an Earth System Model taking volcanic aerosol chemistry climate interactions into account, we study the QBO response to this violent volcanic eruption. Our model results show a disruption of the QBO for up to 10 years before a return to a QBO regime with a slightly longer period. The direct injection of volcanic sulfur and halogens into the stratosphere leads to sulfuric acid droplet formation and ozone depletion impacting atmospheric radiation and dynamics which disturb the QBO wind system.
Key Points
Los Chocoyos sulfur‐ and halogen‐rich supereruption
Volcanic forcing changes chemistry, radiation, and dynamics
Super volcanic eruption disrupts the Quasi Biennial Oscillation
A major strong sudden stratospheric warming (SSW) occurred in the Southern
Hemisphere (SH) stratosphere in 2002 (hereafter referred to as SSW2002),
which is one of the most unusual winters in the SH. ...Following several
warmings, the polar vortex broke down in midwinter. Eastward-traveling waves
and their interaction with quasi-stationary planetary waves played an
important role during this event. This study analyzed the Japanese 55-year
reanalysis (JRA-55) dataset to examine the SSW event that occurred in the SH
in 2019 (hereafter referred to as SSW2019). In 2019, a rapid temperature
increase and decelerated westerly winds were observed at the polar cap,
but since there was no reversal of westerly winds to easterly winds at
60∘ S in the middle to lower stratosphere, the SSW2019 was
classified as a minor warming event. The results showed that quasi-stationary planetary waves of zonal wavenumber 1
developed during the SSW2019. The strong vertical component of the
Eliassen–Palm flux with zonal wavenumber 1 is indicative of pronounced
propagation of planetary waves to the stratosphere. The wave driving in
September 2019 was larger than that of the major SSW event in 2002. Major
SSWs tend to accompany preceding minor warmings, preconditioning, which
changes the zonal flow that weaken the polar night jet as seen in SSW2002. A
similar preconditioning was hardly observed in SSW2019. The strong wave
driving in SSW2019 occurred in high latitudes. Waveguides (i.e., positive
values of the refractive index squared) were found at high latitudes in the
upper stratosphere during the warming period, which provided favorable
conditions for quasi-stationary planetary waves to propagate upward and
poleward.
The current generation of Earth system models that participate in the Coupled Model Intercomparison Project phase 5 (CMIP5) does not, on average, produce a strengthened Northern Hemisphere (NH) polar ...vortex after large tropical volcanic eruptions as suggested by observational records. Here we investigate the impact of volcanic eruptions on the NH winter stratosphere with an ensemble of 20 model simulations of the Max Planck Institute Earth system model. We compare the dynamical impact in simulations of the very large 1815 Tambora eruption with the averaged dynamical response to the two largest eruptions of the CMIP5 historical simulations (the 1883 Krakatau and the 1991 Pinatubo eruptions). We find that for both the Tambora and the averaged Krakatau‐Pinatubo eruptions the radiative perturbation only weakly affects the polar vortex directly. The position of the maximum temperature anomaly gradient is located at approximately 30°N, where we obtain significant westerly zonal wind anomalies between 10 hPa and 30 hPa. Under the very strong forcing of the Tambora eruption, the NH polar vortex is significantly strengthened because the subtropical westerly wind anomalies are sufficiently strong to robustly alter the propagation of planetary waves. The average response to the eruptions of Krakatau and Pinatubo reveals a slight strengthening of the polar vortex, but individual ensemble members differ substantially, indicating that internal variability plays a dominant role. For the Tambora eruption the ensemble variability of the zonal mean temperature and zonal wind anomalies during midwinter and late winter is significantly reduced compared to the volcanically unperturbed period.
Key Points
Dynamical response to two eruption strengths is simulated with an Earth system model
Changes in wave propagation lead to strengthened polar vortex
Ensemble spread is reduced under very strong volcanic forcing
The supereruption of Los Chocoyos (14.6∘ N, 91.2∘ W) in Guatemala ∼84 kyr ago was one of the largest volcanic events of the past 100 000 years. Recent petrologic data show that the eruption released ...very large amounts of climate-relevant sulfur and ozone-destroying chlorine and bromine gases (523±94 Mt sulfur, 1200±156 Mt chlorine, and 2±0.46 Mt bromine). Using the Earth system model (ESM) of the Community Earth System Model version 2 (CESM2) coupled with the Whole Atmosphere Community Climate Model version 6 (WACCM6), we simulated the impacts of the sulfur- and halogen-rich Los Chocoyos eruption on the preindustrial Earth system. Our simulations show that elevated sulfate burden and aerosol optical depth (AOD) persists for 5 years in the model, while the volcanic halogens stay elevated for nearly 15 years. As a consequence, the eruption leads to a collapse of the ozone layer with global mean column ozone values dropping to 50 DU (80 % decrease) and leading to a 550 % increase in surface UV over the first 5 years, with potential impacts on the biosphere. The volcanic eruption shows an asymmetric-hemispheric response with enhanced aerosol, ozone, UV, and climate signals over the Northern Hemisphere. Surface climate is impacted globally due to peak AOD of >6, which leads to a maximum surface cooling of >6 K, precipitation and terrestrial net primary production decrease of >25 %, and sea ice area increases of 40 % in the first 3 years. Locally, a wetting (>100 %) and strong increase in net primary production (NPP) (>700 %) over northern Africa is simulated in the first 5 years and related to a southward shift of the Intertropical Convergence Zone (ITCZ) to the southern tropics. The ocean responds with pronounced El Niño conditions in the first 3 years that shift to the southern tropics and are coherent with the ITCZ change. Recovery to pre-eruption ozone levels and climate takes 15 years and 30 years, respectively. The long-lasting surface cooling is sustained by an immediate increase in the Arctic sea ice area, followed by a decrease in poleward ocean heat transport at 60∘ N which lasts up to 20 years. In contrast, when simulating Los Chocoyos conventionally by including sulfur and neglecting halogens, we simulate a larger sulfate burden and AOD, more pronounced surface climate changes, and an increase in column ozone. By comparing our aerosol chemistry ESM results to other supereruption simulations with aerosol climate models, we find a higher surface climate impact per injected sulfur amount than previous studies for our different sets of model experiments, since the CESM2(WACCM6) creates smaller aerosols with a longer lifetime, partly due to the interactive aerosol chemistry. As the model uncertainties for the climate response to supereruptions are very large, observational evidence from paleo archives and a coordinated model intercomparison would help to improve our understanding of the climate and environment response.
Volcanic eruptions impact the climate and environment. The volcanic forcing is determined by eruption source parameters, including the mass and composition of volcanic volatiles, eruption season, ...eruption latitude, and injection altitude. Moreover, initial atmospheric conditions of the climate system play an important role in shaping the volcanic forcing and response. However, our understanding of the combination of these factors, the distinctions between tropical and extratropical volcanic eruptions, and the co-injection of sulfur and halogens remains limited. Here, we perform ensemble simulations of volcanic eruptions at 15 and 64° N in January, injecting 17 Mt of SO2 together with HCl and HBr at 24 km altitude. Our findings reveal that initial atmospheric conditions control the transport of volcanic volatiles from the first month and modulate the subsequent latitudinal distribution of sulfate aerosols and halogens. This results in different volcanic forcing, surface temperature and ozone responses over the globe and Northern Hemisphere extratropics (NHET) among the model ensemble members with different initial atmospheric conditions. NH extratropical eruptions exhibit a larger NHET mean volcanic forcing, surface cooling and ozone depletion compared with tropical eruptions. However, tropical eruptions lead to more prolonged impacts compared with NH extratropical eruptions, both globally and in the NHET. The sensitivity of volcanic forcing to varying eruption source parameters and model dependency is discussed, emphasizing the need for future multi-model studies to consider the influence of initial conditions and eruption source parameters on volcanic forcing and subsequent impacts.
Halogenated very short-lived substances (VSLSs), such as bromoform
(CHBr3), can be transported to the stratosphere and contribute to the
halogen loading and ozone depletion. Given their highly ...variable emission
rates and their short atmospheric lifetimes, the exact amount as well as the
spatio-temporal variability of their contribution to the stratospheric halogen
loading are still uncertain. We combine observational data sets with
Lagrangian atmospheric modelling in order to analyse the spatial and
temporal variability of the CHBr3 injection into the stratosphere for
the time period 1979–2013. Regional maxima with mixing ratios of up to
0.4–0.5 ppt at 17 km altitude are diagnosed to be over Central America (1) and over the Maritime Continent–west Pacific (2), both of which are
confirmed by high-altitude aircraft campaigns. The CHBr3 maximum over
Central America is caused by the co-occurrence of convectively driven short
transport timescales and strong regional sources, which in conjunction
drive the seasonality of CHBr3 injection. Model results at a daily
resolution reveal isolated, exceptionally high CHBr3 values in this
region which are confirmed by aircraft measurements during the ACCENT
campaign and do not occur in spatially or temporally averaged model fields.
CHBr3 injection over the west Pacific is centred south of the Equator
due to strong oceanic sources underneath prescribed by the here-applied
bottom-up emission inventory. The globally largest CHBr3 mixing ratios
at the cold point level of up to 0.6 ppt are diagnosed to occur over the
region of India, Bay of Bengal, and Arabian Sea (3); however, no data from
aircraft campaigns are available to confirm this finding. Inter-annual
variability of stratospheric CHBr3 injection of 10 %–20 % is to a large
part driven by the variability of coupled ocean–atmosphere circulation
systems. Long-term changes, on the other hand, correlate with the regional
sea surface temperature trends resulting in positive trends of stratospheric CHBr3
injection over the west Pacific and Asian monsoon region and negative trends
over the east Pacific. For the tropical mean, these opposite regional trends
balance each other out, resulting in a relatively weak positive trend of
0.017±0.012 ppt Br per decade for 1979–2013, corresponding to 3 % Br per decade. The overall contribution of CHBr3 together with
CH2Br2 to the stratospheric halogen loading accounts for 4.7 ppt Br, in good agreement with existing studies, with 50 % and 50 % being
injected in the form of source and product gases, respectively.
During the summer monsoon, the western tropical Indian Ocean is predicted to be a hot spot for dimethylsulfide emissions, the major marine sulfur source to the atmosphere, and an important aerosol ...precursor. Other aerosol relevant fluxes, such as isoprene and sea spray, should also be enhanced, due to the steady strong winds during the monsoon. Marine air masses dominate the area during the summer monsoon, excluding the influence of continentally derived pollutants. During the SO234‐2/235 cruise in the western tropical Indian Ocean from July to August 2014, directly measured eddy covariance DMS fluxes confirm that the area is a large source of sulfur to the atmosphere (cruise average 9.1 μmol m−2 d−1). The directly measured fluxes, as well as computed isoprene and sea spray fluxes, were combined with FLEXPART backward and forward trajectories to track the emissions in space and time. The fluxes show a significant positive correlation with aerosol data from the Terra and Suomi‐NPP satellites, indicating a local influence of marine emissions on atmospheric aerosol numbers.
Plain Language Summary
The air‐sea flux trace gases and their transformation to aerosols and cloud condensation nuclei may be fundamental to cloud formation in the marine environment. Clouds and aerosol have an important influence on the radiative balance of the earth. The local coupling of air‐sea fluxes and the formation of aerosols and clouds over the ocean is still highly uncertain. This study combines directly measured air‐sea fluxes with satellite aerosol remote sensing. It is a novel, interdisciplinary approach where results from air‐sea gas transfer are combined with atmospheric chemistry satellite remote sensing using meteorological transport models. Our results strongly support a local influence of marine‐derived aerosol precursors on cloud condensation nuclei and aerosol optical depth above the tropical Indian Ocean.
Key Points
Linkage of sulfur source gases and remotely sensed aerosol numbers
Western tropical Indian Ocean DMS hot spot confirmed
First eddy covariance measurements of DMS in the Western Tropical Indian Ocean
In 1963 a series of eruptions of Mt. Agung, Indonesia, resulted in
the third largest eruption of the 20th century and claimed about 1900 lives. Two eruptions of this series injected SO2 into the
...stratosphere, which can create a long-lasting stratospheric
sulfate layer. The estimated mass flux of the
first eruption was about twice as large as the mass flux of the
second eruption. We followed the estimated emission profiles and
assumed for the first eruption on 17 March an injection rate of 4.7 Tg SO2 and 2.3 Tg SO2 for the
second eruption on 16 May. The injected sulfur forms a
sulfate layer in the stratosphere. The evolution of sulfur is
nonlinear and depends on the injection rate and aerosol background
conditions. We performed ensembles of two model experiments, one
with a single eruption and a second one with two eruptions. The two smaller
eruptions result in a lower sulfur burden, smaller aerosol particles, and 0.1 to 0.3 Wm−2 (10 %–20 %) lower radiative forcing in monthly mean
global average compared to the individual eruption experiment. The
differences are the consequence of slightly stronger meridional
transport due to different seasons of the eruptions, lower injection
height of the second eruption, and the resulting different aerosol
evolution. Overall, the evolution of the volcanic clouds is different in case
of two eruptions than with a single eruption only. The differences
between the two experiments are significant. We conclude that there
is no justification to use one eruption only and both climatic
eruptions should be taken into account in future emission datasets.
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