Hans Brenna

• Brenna, Hans; Kutterolf, Steffen & Krüger, Kirstin (2019). Global ozone depletion and increase of UV radiation caused by pre-industrial tropical volcanic eruptions. Scientific Reports.  ISSN 2045-2322.  9(1) . doi: 10.1038/s41598-019-45630-0

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• Brenna, Hans; Kutterolf, Steffen; Mills, Michael; Niemeier, Ulrike; Timmreck, Claudia & Krüger, Kirstin (2019). The Los Chocoyos super volcanic eruption disrupts the Quasi-Biennial Oscillation. Vis sammendrag

  The Los Chocoyos super eruption happened ~81 kyrs ago in Guatemala, and was one of the largest eruptions of the past 100,000 years. The eruption emitted enormous amounts of sulfur, chlorine and bromine, with multi-decadal consequences for the global climate and environment (Brenna et al 2019 ACPD). In this paper, we simulate the impact of this sulfur- and halogen-rich super-eruption on the quasi-biennial oscillation (QBO), an oscillation of the zonal winds in the tropical stratosphere, with the comprehensive aerosol chemistry Earth System Model CESM2(WACCM6). We find a ~10 year disruption of the QBO before returning to QBO conditions with a slightly prolonged periodicity. Volcanic induced aerosol heating and ozone depletion cooling leads through radiative changes and wave-mean flow interactions to the QBO disruption and anomalous wind regimes. Different model ensembles, volcanic forcing scenarios and one other model backs up the robustness of our results.

• Brenna, Hans; Kutterolf, Steffen & Krüger, Kirstin (2018). Global ozone depletion and increase of UV radiation caused by pre-industrial tropical volcanic eruptions. Vis sammendrag

  Abstract Large explosive tropical volcanic eruptions inject significant amounts of gases into the stratosphere, where they disperse globally through the large-scale meridional circulation. Halogens from tropical eruptions have been thought to be negligible based on observations of the largest eruptions of the satellite era, and thus most studies focus on sulfuric acid aerosols. More recent observations and plume modeling indicate that explosive volcanism can be a big source of halogens to the stratosphere. Here, we present the first study, based on observations, of sulfur, chlorine and bromine releases from tropical volcanic eruptions from the Central American Volcanic Arc over the last 200 ka combined with state-of-the-art coupled chemistry climate model simulations using CESM1(WACCM). The simulations reveal global, long-lasting impact on the ozone layer affecting atmospheric composition and circulation for a decade. Column ozone drops below 220 DU (ozone hole conditions) in the tropics, Arctic and Antarctica, increasing biologically active UV by 80 to 400%. Given the current decline in anthropogenic chlorine, halogen and sulfur rich explosive tropical eruptions may become the major threat to the future ozone layer.

• Brenna, Hans; Kutterolf, Steffen; Mills, Michael J & Krüger, Kirstin (2018). Are we ready for the next big sulfur-and-halogen-rich eruption in the tropics?. Vis sammendrag

  Large Plinian volcanic eruptions inject large amounts of gases (e.g. S, Cl, Br) and solid particles into the stratosphere. If the eruption occurs in the tropics, it can have a global impact due to the dispersal through the large scale meridional overturning circulation. Previous modeling studies mainly concentrate on the sulfate aerosol effects on climate and ozone. In contrast, the role of volcanic halogens from tropical eruptions is believed to play an insignificant role for the global atmosphere, based on observations from the 1982 El Chichón and 1991 Pinatubo eruptions. New measurements regarding the halogen release by paleo Plinian eruptions (Kutterolf et al. 2015), as well as recent volcanic plume observations and model simulations facilitate our investigation into what effect the combined sulfur, chlorine and bromine emissions from large tropical eruptions have on ozone and the atmosphere in general. The post-Pinatubo period has been volcanically relatively quiet. This means that there are few well-observed large eruptions that can be used as input to modeling studies. Using the large and almost complete eruptive data set from the Central American Volcanic Arc (CAVA) of the last 200 ka, we can construct well constrained input-values to chemistry-climate model simulations. This past record suggests that a future Plinian CAVA eruption will release large amounts of sulfur and halogen. As the chlorine content of the atmosphere decreases during the 21th century future sulfur-and-halogen-rich eruptions will have a large impact on stratospheric ozone and climate. We will present results from the coupled chemistry climate model CESM(WACCM) of different CAVA eruption strength containing sulfur, chlorine and bromine and their impact on stratospheric ozone. We argue that if humanity wants to be prepared for the next big tropical eruption we need also take volcanic halogens into account due to their potentially large impact on stratospheric composition and chemistry.

• Brenna, Hans; Kutterolf, Steffen; Mills, Michael J & Krüger, Kirstin (2018). Atmospheric, climatic and environmental effects of the super-size Los Chocoyos eruption 84 kyrs ago. Vis sammendrag

  The Los Chocoyos eruption (Magnitude ~8, dated to 84 kyrs before present) was one of the largest volcanic eruptions during the past 100,000 years. Originating from present-day Guatemala, the eruption formed the current stage of the large Atitlán caldera. Los Chocoyos released more than ~1100 km3 of tephra and the eruption is used as a widespread stratigraphic key marker during that time. The ash layers can be found in marine deposits from offshore Ecuador to Florida over an area of more than 107 km2. Using the new erupted magma mass from Kutterolf et al (2016) and recent volatile measurements (Metzner et al 2014, Krüger et al 2015, Kutterolf et al 2015) we estimate that the Los Chocoyos eruption released >1045 Mt SO2, ~1200 megatons of chlorine, and ~2 megatons of bromine, which classifies it as a super-size eruption. Considering these volatile emissions, the eruption must have caused massive effects on the atmosphere, climate and environment at that time, e.g. pronounced and long lasting ozone depletion with impacts on surface ultraviolet radiation. We will present results of the impact of volatile injections from the super-size Los Chocoyos eruption on atmospheric composition, chemistry and radiation. We will use the newly developed coupled chemistry climate model CESM2(WACCM) taking the combined effect of both sulfur and halogen interactively into account. The model results will be compared with a sulfur-rich only volcanic eruption. The analysis will focus in particular on halogen and ozone chemistry, radiation, atmospheric circulation and surface climate changes.

• Brenna, Hans; Krüger, Kirstin & Kutterolf, Steffen (2017). A new threat to the future ozone layer? Halogen and sulfur rich explosive eruptions in the tropics. Vis sammendrag

  Large Plinian volcanic eruptions inject large amounts of atmosphere-relevant gases (e.g. S, Cl, Br) and solid particles into the stratosphere. If the eruption occurs in the tropics, it can have a global impact due to the dispersal through the large scale meridional overturning circulation. Previous modelling studies mainly concentrate on the sulfate aerosol effects on climate and ozone. In contrast, the role of volcanic halogens from tropical eruptions is believed to play an insignificant role for the global atmosphere, based on observations from the recent El Chichon and Pinatubo eruptions. New results regarding the halogen release by paleo Plinian eruptions, as well as recent volcanic plume observations and model simulations facilitate our investigation into what effect the combined chlorine and bromine emissions from large tropical eruptions have on ozone and the atmosphere in general. Here, we present the first study of combined chlorine, bromine from a tropical halogen and sulfur rich volcanic eruption using a state-of-the-art coupled chemistry climate model. A complete halogen and sulfur data set for the last 200ka (Metzner et al, 2013; Kutterolf et al., 2013, 2015), derived by the petrological method from paleo-eruptions of the Central American Volcanic Arc (CAVA), are used to force simulations with WACCM (Whole Atmosphere Community Climate Model). Using the petrological data we simulated 3 forcing scenarios: Sulfur, halogen and combined injections. The goal is to quantify the impact of volcanic halogen and sulfur on the preindustrial atmosphere when the background chlorine levels were low compared to the present day with the main focus on stratospheric ozone. We carried out 5 model simulations of each of the 3 forcing scenarios assuming that 10% of the Cl and Br emitted from the average CAVA eruption is injected into the tropical stratosphere during January. The model response reveals a global impact on the ozone layer affecting, through radiation, atmospheric circulation as well for more than 7 years. Total ozone drops below 220 DU, the present-day ozone hole threshold, in the tropics, Arctic and Antarctica. The increase in biologically active UV caused by the global ozone depletion is found to be more than 80% over much of the northern hemisphere during the first two years post eruption. Given the current decline in anthropogenic chlorine, halogen and sulfur rich explosive tropical eruption will become a major threat for the future ozone layer.

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