Kirstin Krüger

Publications

Peer-reviewed publications:

• Brenna, H., Kutterolf, S., Mills, M. J., and Krüger, K.: The potential impacts of a sulfur- and halogen-rich supereruption such as Los Chocoyos on the atmosphere and climate, Atmos. Chem. Phys., 20, 6521–6539, https://doi.org/10.5194/acp-20-6521-2020, 2020.
• Brenna, H., Kutterolf, S., and Krüger, K. Global ozone depletion and increase of UV radiation caused by pre-industrial tropical volcanic eruptions. Sci Rep 9, 9435, https://doi.org/10.1038/s41598-019-45630-0, 2019.
• Toohey, M., Krüger, K., Schmidt, H. et al. Disproportionately strong climate forcing from extratropical explosive volcanic eruptions. Nature Geosci 12, 100–107, https://doi.org/10.1038/s41561-018-0286-2, 2019.
• Ziska, F., Quack, B., Tegtmeier, S., Stemmler, I., and Krüger, K., Future emissions of marine halogenated very-short lived substances under climate change, J Atmos Chem 74, 245–260, https://doi.org/10.1007/s10874-016-9355-3, 2017.
• Hossaini, R., Patra, P. K., Leeson, A. A., Krysztofiak, G., Abraham, N. L., Andrews, S. J., Archibald, A. T., Aschmann, J., Atlas, E. L., Belikov, D. A., Bönisch, H., Carpenter, L. J., Dhomse, S., Dorf, M., Engel, A., Feng, W., Fuhlbrügge, S., Griffiths, P. T., Harris, N. R. P., Hommel, R., Keber, T., Krüger, K., Lennartz, S. T., Maksyutov, S., Mantle, H., Mills, G. P., Miller, B., Montzka, S. A., Moore, F., Navarro, M. A., Oram, D. E., Pfeilsticker, K., Pyle, J. A., Quack, B., Robinson, A. D., Saikawa, E., Saiz-Lopez, A., Sala, S., Sinnhuber, B.-M., Taguchi, S., Tegtmeier, S., Lidster, R. T., Wilson, C., and Ziska, F.: A multi-model intercomparison of halogenated very short-lived substances (TransCom-VSLS): linking oceanic emissions and tropospheric transport for a reconciled estimate of the stratospheric source gas injection of bromine, Atmos. Chem. Phys., 16, 9163–9187, https://doi.org/10.5194/acp-16-9163-2016, 2016.
• Toohey, M., K. Krüger, M. Sigl, F. Stordal, and H. Svensen, Climatic and societal impacts of a volcanic double event at the dawn of the Middle Ages, Climatic Change, 136, 401–412, https://doi.org/10.1007/s10584-016-1648-7, 2016.
• Krüger, K., Kutterolf, S., T.H., Hansteen, Chapter 16: Halogen release from Plinian eruptions and depletion of stratospheric Ozone, Volcanism and global environmental change, Cambridge University Press, ISBN: 9781107058378, Ed. A. Schmidt et al., PP. 244-259, 2015.
• Sigl, M., J.R. McConnell, M. Toohey, M. Curran, S.B. Das, R. Edwards, E. Isaksson, K. Kawamura, S. Kipfstuhl, K. Krüger, L. Layman, O. Maselli, Y. Motizuki, H. Motoyama, D. Pasteris, M. Severi,  Insights from Antarctica on volcanic forcing during the Common Era. Nature Clim Change 4, 693–697, https://doi.org/10.1038/nclimate2293, 2014.
• Ziska, F., Quack, B., Abrahamsson, K., Archer, S. D., Atlas, E., Bell, T., Butler, J. H., Carpenter, L. J., Jones, C. E., Harris, N. R. P., Hepach, H., Heumann, K. G., Hughes, C., Kuss, J., Krüger, K., Liss, P., Moore, R. M., Orlikowska, A., Raimund, S., Reeves, C. E., Reifenhäuser, W., Robinson, A. D., Schall, C., Tanhua, T., Tegtmeier, S., Turner, S., Wang, L., Wallace, D., Williams, J., Yamamoto, H., Yvon-Lewis, S., and Yokouchi, Y.: Global sea-to-air flux climatology for bromoform, dibromomethane and methyl iodide, Atmos. Chem. Phys., 13, 8915–8934, https://doi.org/10.5194/acp-13-8915-2013, 2013.
• Montzka, S., S. Reimann, S. O'Doherty, A. Engel, K. Krüger, and W.T., Sturges:, Chapter 1: Ozone-Depleting Substances and Related Chemicals, Scientific Assessment of Ozone Depletion: 2010, PP 112, 2011.
• Butchart, N, A. Charlton-Perez, I., Cionni, S.C., Hardiman, Krüger, K. et al., Chapter 4: Stratospheric Dynamics, SPARC CCMVal Report on the Evaluation of Chemistry-Climate Models, SPARC No. 5, WCRP-132, WMO/TD-No. 1526, PP 109-148, 2010.

• Brenna, Hans; Kutterolf, Steffen; Mills, Michael; Niemeier, Ulrike; Timmreck, Claudia & Krüger, Kirstin (2021). Decadal Disruption of the QBO by Tropical Volcanic Supereruptions. Geophysical Research Letters.  ISSN 0094-8276.  48(5), s 1- 13 . doi: 10.1029/2020GL089687 Show summary

  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.

• Brenna, Hans; Kutterolf, Steffen; Mills, Michael J. & Krüger, Kirstin (2020). The potential impacts of a sulfur- And halogen-rich supereruption such as Los Chocoyos on the atmosphere and climate. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  20(11), s 6521- 6539 . doi: 10.5194/acp-20-6521-2020 Full text in Research Archive.
• Tegtmeier, Susann; Anstey, James; Davis, Sean; Dragani, Rossana; Harada, Yayoi; Ivanciu, Ioana; Pilch Kedzierski, Robin; Krüger, Kirstin; Legras, Bernard; Long, Craig S.; Wang, James S.; Wargan, Krzysztof & Wright, Jonathon S. (2020). Temperature and tropopause characteristics from reanalyses data in the tropical tropopause layer. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  20(2), s 753- 770 . doi: 10.5194/acp-20-753-2020 Full text in Research Archive.
• Tegtmeier, Susann; Atlas, Elliot; Quack, Birgit; Ziska, Franziska & Krüger, Kirstin (2020). Variability and past long-term changes of brominated very short-lived substances at the tropical tropopause. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  20, s 7103- 7123 . doi: 10.5194/acp-20-7103-2020 Full text in Research Archive.
• Wright, Jonathon S.; Sun, Xiaoyan; Konopka, Paul; Krüger, Kirstin; Legras, Bernard; Molod, Andrea; Tegtmeier, Susann; Zhang, Guang J. & Zhao, Xi (2020). Differences in tropical high clouds among reanalyses:origins and radiative impacts. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  20, s 8989- 9030 . doi: 10.5194/acp-20-8989-2020 Full text in Research Archive.
• 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 . doi: 10.1038/s41598-019-45630-0 Full text in Research Archive.
• Niemeier, Ulrike; Timmreck, Claudia & Krüger, Kirstin (2019). Revisiting the Agung 1963 volcanic forcing - Impact of one or two eruptions. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  19(15), s 10379- 10390 . doi: 10.5194/acp-19-10379-2019 Full text in Research Archive.
• Toohey, Matthew; Krüger, Kirstin; Schmidt, Hauke; Timmreck, Claudia; Sigl, Michael; Stoffel, Markus & Wilson, Rob (2019). Disproportionately strong climate forcing from extratropical explosive volcanic eruptions. Nature Geoscience.  ISSN 1752-0894.  12, s 100- 107 . doi: 10.1038/s41561-018-0286-2 Show summary

  Extratropical volcanic eruptions are commonly thought to be less effective at driving large-scale surface cooling than tropical eruptions. However, recent minor extratropical eruptions have produced a measurable climate impact, and proxy records suggest that the most extreme Northern Hemisphere cold period of the Common Era was initiated by an extratropical eruption in 536 ce. Using ice-core-derived volcanic stratospheric sulfur injections and Northern Hemisphere summer temperature reconstructions from tree rings, we show here that in proportion to their estimated stratospheric sulfur injection, extratropical explosive eruptions since 750 ce have produced stronger hemispheric cooling than tropical eruptions. Stratospheric aerosol simulations demonstrate that for eruptions with a sulfur injection magnitude and height equal to that of the 1991 Mount Pinatubo eruption, extratropical eruptions produce time-integrated radiative forcing anomalies over the Northern Hemisphere extratropics up to 80% greater than tropical eruptions, as decreases in aerosol lifetime are overwhelmed by the enhanced radiative impact associated with the relative confinement of aerosol to a single hemisphere. The model results are consistent with the temperature reconstructions, and elucidate how the radiative forcing produced by extratropical eruptions is strongly dependent on the eruption season and sulfur injection height within the stratosphere.

• Vogel, Andreas; Durant, Adam; Cassiani, Massimo; Clarkson, Rory J.; Slaby, Michal; Diplas, Spyridon; Krüger, Kirstin & Stohl, Andreas (2019). Simulation of volcanic ash ingestion into a large aero engine: particle–fan interactions. Journal of turbomachinery.  ISSN 0889-504X.  141(1) . doi: 10.1115/1.4041464 Show summary

  Volcanic ash (VA) clouds in flight corridors present a significant threat to aircraft operations as VA particles can cause damage to gas turbine engine components that lead to a reduction of engine performance and compromise flight safety. In the last decade, research has mainly focused on processes such as erosion of compressor blades and static components caused by impinging ash particles as well as clogging and/or corrosion effects of soft or molten ash particles on hot section turbine airfoils and components. However, there is a lack of information on how the fan separates ingested VA particles from the core stream flow into the bypass flow and therefore influences the mass concentration inside the engine core section, which is most vulnerable and critical for safety. In this numerical simulation study, we investigated the VA particle–fan interactions and resulting reductions in particle mass concentrations entering the engine core section as a function of particle size, fan rotation rate, and for two different flight altitudes. For this, we used a high-bypass gas-turbine engine design, with representative intake, fan, spinner, and splitter geometries for numerical computational fluid dynamics (CFD) simulations including a Lagrangian particle-tracking algorithm. Our results reveal that particle–fan interactions redirect particles from the core stream flow into the bypass stream tube, which leads to a significant particle mass concentration reduction inside the engine core section. The results also show that the particle–fan interactions increase with increasing fan rotation rates and VA particle size. Depending on ingested VA size distributions, the particle mass inside the engine core flow can be up to 30% reduced compared to the incoming particle mass flow. The presented results enable future calculations of effective core flow exposure or dosages based on simulated or observed atmospheric VA particle size distribution, which is required to quantify engine failure mechanisms after exposure to VA. As an example, we applied our methodology to a recent aircraft encounter during the Mt. Kelud 2014 eruption. Based on ambient VA concentrations simulated with an atmospheric particle dispersion model (FLEXPART), we calculated the effective particle mass concentration inside the core stream flow along the actual flight track and compared it with the whole engine exposure.

• Fiehn, Alina; Quack, Birgit; Marandino, Christa A. & Krüger, Kirstin (2018). Transport Variability of Very Short Lived Substances From the West Indian Ocean to the Stratosphere. Journal of Geophysical Research (JGR): Space Physics.  ISSN 2169-9380.  123(10), s 5720- 5738 . doi: 10.1029/2017JD027563 Full text in Research Archive. Show summary

  Halogen- and sulfur-containing compounds are supersaturated in the surface ocean, which results in their emission to the atmosphere. These compounds can be transported to the stratosphere, where they impact ozone, the background aerosol layer, and climate. In this study we calculate the seasonal and interannual variability of transport from the West Indian Ocean (WIO) surface to the stratosphere for 2000–2016 with the Lagrangian transport model FLEXPART using ERA-Interim meteorological fields. We investigate the transport relevant for very short lived substances (VSLS) with tropospheric lifetimes corresponding to dimethylsulfide (1 day), methyl iodide (CH3I, 3.5 days), bromoform (CHBr3, 17 days), and dibromomethane (CH2Br2, 150 days). The stratospheric source gas injection of VSLS tracers from the WIO shows a distinct annual cycle associated with the Asian monsoon. Over the 16-year time series, a slight increase in source gas injection from the WIO to the stratosphere is found for all VSLS tracers and during all seasons. The interannual variability shows a relationship with sea surface temperatures in the WIO as well as the El Niño–Southern Oscillation. During boreal spring of El Niño, enhanced stratospheric injection of VSLS from the tropical WIO is caused by positive sea surface temperature anomalies and enhanced vertical uplift above the WIO. During boreal fall of La Niña, strong injection is related to enhanced atmospheric upward motion over the East Indian Ocean and a prolonged Indian summer monsoon season. Related physical mechanisms and uncertainties are discussed in this study. 1.

• Fiehn, Alina; Quack, Birgit; Stemmler, Irene; Ziska, Franziska & Krüger, Kirstin (2018). Importance of seasonally resolved oceanic emissions for bromoform delivery from the tropical Indian Ocean and west Pacific to the stratosphere. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  18(16), s 11973- 11990 . doi: 10.5194/acp-18-11973-2018 Full text in Research Archive. Show summary

  Oceanic very short-lived substances (VSLSs), such as bromoform (CHBr3), contribute to stratospheric halogen loading and, thus, to ozone depletion. However, the amount, timing, and region of bromine delivery to the stratosphere through one of the main entrance gates, the Indian summer monsoon circulation, are still uncertain. In this study, we created two bromoform emission inventories with monthly resolution for the tropical Indian Ocean and west Pacific based on new in situ bromoform measurements and novel ocean biogeochemistry modeling. The mass transport and atmospheric mixing ratios of bromoform were modeled for the year 2014 with the particle dispersion model FLEXPART driven by ERA-Interim reanalysis.We compare results between two emission scenarios: (1) monthly averaged and (2) annually averaged emissions. Both simulations reproduce the atmospheric distribution of bromoform from ship- and aircraft-based observations in the boundary layer and upper troposphere above the Indian Ocean reasonably well. Using monthly resolved emissions, the main oceanic source regions for the stratosphere include the Arabian Sea and Bay of Bengal in boreal summer and the tropical west Pacific Ocean in boreal winter. The main stratospheric injection in boreal summer occurs over the southern tip of India associated with the high local oceanic sources and strong convection of the summer monsoon. In boreal winter more bromoform is entrained over the west Pacific than over the Indian Ocean. The annually averaged stratospheric injection of bromoform is in the same range whether using monthly averaged or annually averaged emissions in our Lagrangian calculations. However, monthly averaged emissions result in the highest mixing ratios within the Asian monsoon anticyclone in boreal summer and above the central Indian Ocean in boreal winter, while annually averaged emissions display a maximum above the west Indian Ocean in boreal spring. In the Asian summer monsoon anticyclone bromoform atmospheric mixing ratios vary by up to 50% between using monthly averaged and annually averaged oceanic emissions. Our results underline that the seasonal and regional stratospheric bromine injection from the tropical Indian Ocean and west Pacific critically depend on the seasonality and spatial distribution of the VSLS emissions.

• Zavarsky, Alex; Booge, Dennis; Fiehn, Alina; Krüger, Kirstin; Atlas, Elliot & Marandino, Christa (2018). The influence of air-sea fluxes on atmospheric aerosols during the summer monsoon over the Indian Ocean. Geophysical Research Letters.  ISSN 0094-8276.  45(1), s 418- 426 . doi: 10.1002/2017GL076410
• Fiehn, Alina; Quack, Birgit; Hepach, Helmke; Fuhlbrugge, Steffen; Tegtmeier, Susann; Toohey, Matthew; Atlas, Elliot L & Krüger, Kirstin (2017). Delivery of halogenated very short-lived substances from the west Indian Ocean to the stratosphere during the Asian summer monsoon. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  17, s 6723- 6741 . doi: 10.5194/acp-17-6723-2017 Full text in Research Archive. Show summary

  Halogenated very short-lived substances (VSLS) are naturally produced in the ocean and emitted to the atmosphere. When transported to the stratosphere, these compounds can have a significant influence on the ozone layer and climate. During a research cruise on RV Sonne in the subtropical and tropical West Indian Ocean in July and August 2014, we measured the VSLS, methyl iodide (CH3I) and for the first time bromoform (CHBr3) and dibromomethane (CH2Br2), in surface seawater and the marine atmosphere to derive their emission strengths. Using the Lagrangian transport model Flexpart with ERA-Interim meteorological fields, we calculated the direct contribution of observed VSLS emissions to the stratospheric halogen burden during Asian summer monsoon. Furthermore, we compare the in situ calculations with the interannual variability of transport from a larger area of the West Indian Ocean surface to the stratosphere for July 2000-2015. We found that the West Indian Ocean is a strong source region for CHBr3 (910 pmol m 2 h 1), very strong for CH2Br2 (930 pmol m 2 h 1), and average for CH3I (460 pmol m 2 h 1). The atmospheric transport from the tropical West Indian Ocean surface to the stratosphere experiences two main pathways. On very short timescales, especially relevant for the shortest-lived compound CH3I (3.5 days lifetime), convection above the Indian Ocean lifts oceanic air masses and VSLS towards the tropopause. On a longer timescale, the Asian summer monsoon circulation transports oceanic VSLS towards India and Bay of Bengal, where they are lifted with the monsoon convection and reach stratospheric levels in the southeastern part of the Asian monsoon anticyclone. This transport pathway is more important for the longer-lived brominated compounds (17 and 150 days lifetime for CHBr3 and CH2Br2). The entrainment of CHBr3 and CH3I from the West Indian Ocean to the stratosphere during Asian summer monsoon is less than from previous cruises in the tropical West Pacific Ocean during boreal autumn/early winter, but higher than from the tropical Atlantic during boreal summer. In contrast, the projected CH2Br2 entrainment was very high because of the high emissions during the West Indian Ocean cruise. The 16-year July time series shows highest interannual variability for the short-lived CH3I and lowest for the long lived CH2Br2. During this time period, a small increase of VSLS entrainment from the West Indian Ocean through the Asian monsoon to the stratosphere is found. Overall, this study confirms that the subtropical and tropical West Indian Ocean is an important source region of halogenated VSLS, especially CH2Br2, to the troposphere and stratosphere during the Asian summer monsoon.

• Fujiwara, Masatomo; Wright, Jonathon S.; Manney, Gloria L.; Gray, Lesley J.; Anstey, James; Birner, Thomas; Davis, Sean; Gerber, Edwin P.; Harvey, V. Lynn; Hegglin, Michaela I.; Homeyer, Cameron R.; Knox, John A.; Krüger, Kirstin; Lambert, Alyn; Long, Craig S.; Martineau, Patrick; Molod, Andrea; Monge-Sanz, Beatriz M.; Santee, Michelle L.; Tegtmeier, Susann; Chabrillat, Simon; Tan, David G.H.; Jackson, David R.; Polavarapu, Saroja; Compo, Gilbert P.; Dragani, Rossana; Ebisuzaki, Wesley; Harada, Yayoi; Kobayashi, Chiaki; McCarty, Will; Onogi, Kazutoshi; Pawson, Steven; Simmons, Adrian; Wargan, Krzysztof; Whitaker, Jeffrey S. & Zou, Cheng-Zhi (2017). Introduction to the SPARC Reanalysis Intercomparison Project (S-RIP) and overview of the reanalysis systems. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  17(2), s 1417- 1452 . doi: 10.5194/acp-17-1417-2017 Full text in Research Archive.
• Lennartz, Sinikka T.; Marandino, Christa A.; von Hobe, Marc; Cortes, Pau; Quack, Birgit; Simo, Rafel; Booge, Dennis; Pozzer, Andrea; Steinhoff, Tobias; Arevalo-Martinez, Damian L.; Kloss, Corinna; Bracher, Astrid; Atlas, Elliot & Krüger, Kirstin (2017). Direct oceanic emissions unlikely to account for the missing source of atmospheric carbonyl sulfide. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  17, s 385- 402 . doi: 10.5194/acp-17-385-2017 Full text in Research Archive.
• Schlundt, Cathleen; Tegtmeier, Susann; Lennartz, Sinikka T.; Bracher, Astrid; Cheah, Wee; Krüger, Kirstin; Quack, Birgit & Marandino, Christa A. (2017). Oxygenated volatile organic carbon in the western Pacific convective center: Ocean cycling, air-sea gas exchange and atmospheric transport. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  17(17), s 10837- 10854 . doi: 10.5194/acp-17-10837-2017 Full text in Research Archive.
• Vogel, Andreas; Diplas, Spyridon; Durant, Adam; S. Azar, Amin; Sunding, Martin Fleissner; Rose, William I.; Sytchkova, Anna Krasilnikova; Bonadonna, Costanza; Krüger, Kirstin & Stohl, Andreas (2017). Reference data set of volcanic ash physicochemical and optical properties. Journal of Geophysical Research (JGR): Atmospheres.  ISSN 2169-897X.  122(17), s 9485- 9514 . doi: 10.1002/2016JD026328 Full text in Research Archive.
• Bittner, Matthias; Timmreck, Claudia; Schmidt, Hauke; Toohey, Matthew & Krüger, Kirstin (2016). The impact of wave-mean flow interaction on the Northern Hemisphere polar vortex after tropical volcanic eruptions. Journal of Geophysical Research (JGR): Atmospheres.  ISSN 2169-897X.  121(10), s 5281- 5297 . doi: 10.1002/2015JD024603
• Fuhlbrugge, Steffen; Quack, Birgit; Atlas, Elliot; Fiehn, Alina; Hepach, Helmke & Krüger, Kirstin (2016). Meteorological constraints on oceanic halocarbons above the Peruvian upwelling. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  16(18), s 12205- 12217 . doi: 10.5194/acp-16-12205-2016
• Fuhlbrugge, Steffen; Quack, Birgit; Tegtmeier, Susann; Atlas, Elliot; Hepach, Helmke; Shi, Qiang; Raimund, Stefan & Krüger, Kirstin (2016). The contribution of oceanic halocarbons to marine and free tropospheric air over the tropical West Pacific. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  16(12), s 7569- 7585 . doi: 10.5194/acp-16-7569-2016
• Hepach, Helmke; Quack, Birgit; Tegtmeier, Susann; Engel, Anja; Bracher, Astrid; Fuhlbrugge, Steffen; Galgani, Luisa; Atlas, Elliot L; Lampel, Johannes; Frieß, Udo & Krüger, Kirstin (2016). Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  16(18), s 12219- 12237 . doi: 10.5194/acp-16-12219-2016
• Hossaini, R*; Patra, P.K.; Leeson, AA; Krysztofiak, G.; Abraham, NL; Andrews, SJ; Archibald, A.T.; Aschmann, J; Atlas, E.L.; Belikov, DA; Bönisch, H.; Carpenter, LJ; Dhomse, S.; Dorf, M; Engel, A.; Feng, W.; Fuhlbrügge, S.; Griffiths, PT; Harris, N. R. P.; Hommel, R; Keber, T.; Krüger, Kirstin; Lennartz, ST; Maksyutov, S.; Mantle, H; Mills, GP; Miller, B; Montzka, SA; Moore, F.; Navarro, MA; Oram, DE; Pfeilsticker, K.; Pyle, JA; Quack, B; Robinson, A.D.; Saikawa, E.; Saiz-Lopez, A; Sala, S; Sinnhuber, BM; Taguchi, S; Tegtmeier, S.; Lidster, RT; Wilson, C & Ziska, F. (2016). A multi-model intercomparison of halogenated very short-lived substances (TransCom-VSLS): Linking oceanic emissions and tropospheric transport for a reconciled estimate of the stratospheric source gas injection of bromine. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  16(14), s 9163- 9187 . doi: 10.5194/acp-16-9163-2016
• Toohey, Matthew; Krüger, Kirstin; Sigl, Michael; Stordal, Frode & Svensen, Henrik (2016). Climatic and societal impacts of a volcanic double event at the dawn of the Middle Ages. Climatic Change.  ISSN 0165-0009.  136(3), s 401- 412 . doi: 10.1007/s10584-016-1648-7
• Ziska, Franziska; Quack, Birgit; Tegtmeier, Susann; Stemmler, Irene & Krüger, Kirstin (2016). Future emissions of marine halogenated very-short lived substances under climate change. Journal of Atmospheric Chemistry.  ISSN 0167-7764. . doi: 10.1007/s10874-016-9355-3
• Krüger, Kirstin; Kutterolf, Steffen & Hansteen, Thor H. (2015). Halogen release from Plinian eruptions and depletion of stratospheric ozone, In Anja Schmidt; Kirsten Fristad & Linda T. Elkins-Tanton (ed.),  Volcanism and global environmental change.  Cambridge University Press.  ISBN 9781107058378.  16.  s 244 - 259
• Kutterolf, Steffen; Hansteen, Thor H.; Freundt, Armin; Wehrmann, Heidi; Appel, Karen; Krüger, Kirstin & Pérez, Wendy (2015). Bromine and chlorine emissions from Plinian eruptions along the Central American Volcanic Arc: From source to atmosphere. Earth and Planetary Science Letters.  ISSN 0012-821X.  429, s 234- 246 . doi: 10.1016/j.epsl.2015.07.064
• Lennartz, ST; Krysztofiak, G.; Marandino, C.A.; Sinnhuber, BM; Tegtmeier, S.; Ziska, F.; Hossaini, R.; Krüger, Kirstin; Montzka, SA; Atlas, E.; Oram, DE; Keber, T.; Bönisch, H. & Quack, B (2015). Modelling marine emissions and atmospheric distributions of halocarbons and dimethyl sulfide: The influence of prescribed water concentration vs. prescribed emissions. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  15(20), s 11753- 11772 . doi: 10.5194/acp-15-11753-2015
• Tegtmeier, S.; Ziska, Franziska; Pisso, Ignacio; Quack, B; Velders, G. J. M.; Yang, X. & Krüger, Kirstin (2015). Oceanic bromoform emissions weighted by their ozone depletion potential. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  15(23), s 13647- 13663 . doi: 10.5194/acp-15-13647-2015 Full text in Research Archive.
• Sigl, M; McConnell, Joseph R.; Toohey, Matthew; Curran, Mark A.J.; Das, Sarah B.; Edwards, Ross; Isaksson, Elisabeth; Kawamura, Kenji; Kipfstuhl, Sepp; Krüger, Kirstin; Layman, Lawrence; Maselli, Olivia J.; Motizuki, Yuko; Motoyama, H; Pasteris, Daniel & Severi, M (2014). Insights from Antarctica on volcanic forcing during the common era. Nature Climate Change.  ISSN 1758-678X.  4(8), s 693- 697 . doi: 10.1038/nclimate2293
• Hepach, Helmke; Quack, Birgit; Ziska, F.; Fuhlbrügge, S.; Atlas, Elliot; Krüger, Kirstin; Peeken, Ilka & Wallace, Douglas W.R. (2014). Drivers of diel and regional variations of halocarbon emissions from the tropical North East Atlantic. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  14(3), s 1255- 1275 . doi: 10.5194/acp-14-1255-2014
• Rex, M.; Wohltmann, I.; Ridder, T; Lehmann, R; Rosenlof, Karen H.; Wennberg, P; Weisenstein, D; Notholt, J; Krüger, Kirstin; Mohr, V & Tegtmeier, S. (2014). A tropical West Pacific OH minimum and implications for stratospheric composition. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  14(9), s 4827- 4841 . doi: 10.5194/acp-14-4827-2014
• Toohey, Matthew; Krüger, Kirstin; Bittner, Matthias; Timmreck, Claudia & Schmidt, Hauke (2014). The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  14, s 13063- 13079 . doi: 10.5194/acp-14-13063-2014
• Hossaini, R*; et al., , & Krüger, Kirstin (2013). Evaluating global emission inventories of biogenic bromocarbons. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  13, s 11819- 11838 . doi: 10.5194/acp-13-11819-2013
• Tegtmeier, S.; Krüger, Kirstin & et al., , (2013). The contribution of oceanic methyl iodide to stratospheric iodine. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  13, s 11869- 11886 . doi: 10.5194/acp-13-11869-2013
• Toohey, M*; Hegglin, M. I.; Tegtmeier, S.; Anderson, J; Anel, J.A.; Bourassa, A. & Krüger, Kirstin (2013). Characterizing sampling biases in the trace gas climatologies of the SPARC Data Initiative. Journal of Geophysical Research (JGR): Atmospheres.  ISSN 2169-897X.  118(20), s 11,847- 11,862 . doi: 10.1002/jgrd.50874

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• Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Høeg, Helge I.; Bakke, Jostein; Støren, Eivind N.; Loftsgarden, Kjetil; Iversen, Frode; Hagopian, William Martin; Jahren, Anne Hope; Svensen, Henrik Hovland & Krüger, Kirstin (2021). Instability or adaptation of the pre-Viking society to the climate variability of the Late Antiquity?. Show summary

  Understanding how agricultural societies were impacted and adapted to past climate variations is critical to adapt to contemporary climate change and guaranty the food security. However, linking climate and change in the behaviour of a population are difficult to evidence. Here, we studied the climate variations of the period between 200 and 1300 CE and its impact on the pre-Viking and Viking societies in south Norway. We used a retrospective approach combining a multi-proxy analysis of lake sediments, including geochemical and palynological analyses, to reconstruct past changes in temperature and agricultural practices during the period 200-1300 CE. We associated variations in Ca/Ti ratio as a result of change in lake productivity with the temperature. The periods 200-300 and 800-1300 CE were warmer than the period between 300 and 800 CE, which is known as the “Dark Ages Cold Period” in the Northern Hemisphere. During this colder period, phases dominated by grazing activities (280-420 CE, 480-580 CE, 700-780 CE) alternated with phases dominated by the cultivation of cereals and hemp (before 280 CE, 420-480 CE, 580-700 CE, and after 800 CE). The alternation of these phases is synchronous of temperature changes. Cold periods are associated to livestock farming, and warmer periods to crop farming. This result suggests that when temperature no longer allowed crop farming, the food production specialized in animal breeding. The development of activities reached a maximum between 400 and 550 CE and a minimum between 680 and 800 CE, in agreement with archaeological findings. The Viking Age (800-1000 CE) started with an increase in temperature and corresponds to the warmest period between 200 and 1300 CE, allowing a larger development of the agriculture practices and society. Our results prove that the pre-Viking society adapted their agricultural practices to the climate variability of the Late Antiquity and that the Vikings expanded with climate warming.

• Fuglestvedt, Herman; Krüger, Kirstin; Zhuo, Zhihong; Sigl, Michael; Toohey, Matthew & Mills, Michael J. (2021). Modelling high-latitude explosive eruptions and their atmospheric and environmental impacts.
• Zhuo, Zhihong; Fuglestvedt, Herman; Toohey, Matthew; Mills, Michael J. & Krüger, Kirstin (2021). Model comparison of volcanic aerosol forcing and climate impact of tropical and extratropical eruptions.
• Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Støren, Eivind Wilhelm Nagel; Bakke, Jostein; Høeg, Helge Irgens; Loftsgarden, Kjetil; Iversen, Frode; Hufthammer, Anne Karin & Krüger, Kirstin (2020). Record of climate and environmental changes in a dead-ice lake close to Gardermoen told by a 10 000 years old freshwater fish and a Viking King. Show summary

  We studied a six-meter long sediment sequence retrieved from the kettle lake Ljøgottjern, close to Oslo-Gardermoen Airport, to reconstruct environmental and climate changes during the last millennia. The lake is 18 m depth and located at 185 m a.s.l., under the maximum postglacial sea level. The largest burial mound of Northern Europe was built in the mid-6th century on the shore of this lake allegedly for King Rakni and makes this place ideal to study human-environment interactions in a paleo-perspective approach. Using a multi-proxy sedimentological analysis of this record, including 14C dating, paleo-secular variations, XRF and CT scans, and pollen, this study highlights different climate patterns throughout the Holocene. At the bottom of the core, a carbonated sandy-clayey layer with centimetric twigs overlays an organic rich black peaty-type layer, suggesting a continental environment. On top of that, a disturbed clay layer containing fish bones from a freshwater Carpinidae species was found. The fish could have been buried by the massive (70 cm) sandy carbonated deposit covering it. A sharp transition separates a clay cap on top of the deposit and the start of a finely laminated lacustrine sedimentation dated 9.3 ka cal. BP. The massive deposit could be associated to the outburst flood from the glacial lake Nedre Glomsjø dated 10-10.4 ka cal BP (Longva, 1984; Høgaas and Longva, 2016). A major change in the sedimentation occurred around 8 ka cal. BP, with darker sediments and a lower sedimentation rate. This change could be related to a warming climate and stabilization of the catchment by soil and forest development around the lake in the mid-Holocene. The sedimentation rate increased again between 2000 and 3000 years cal. BP as a result of the development of first human activities and major change in the vegetation (Høeg, 1997). We reconstructed temperature changes during the first millennia and compared it to societal dynamics. The period between 300 and 800 years cal. CE is colder than the period 800-1300 years cal. CE. After 1600 years cal. CE, an increase in erosion could be associated to the extension of the population and agriculture in Scandinavia and revealed a chronicle of the major floods in this area. The presence of freshwater fish older than 9,3 ka attests of their early and natural colonization of Scandinavian lakes. The comparison of this record with archaeological data will allow us to discuss socio-environmental dynamics following the deglaciation in the area. References: Smith, A.A. 2010. CO2 stor¬age. Journal of Sciences 32, 10-20. Høeg, H.I., 1997. Pollenanalytiske undersøkelser på Øvre Romerike : Ullensaker og Nannestad, Akershus fylke : Gardermoprosjektet, Varia (Universitetets oldsaksamling : trykt utg.). Universitetets oldsaksamling, Oslo. Høgaas, F., Longva, O., 2016. Mega deposits and erosive features related to the glacial lake Nedre Glomsjø outburst flood, southeastern Norway. Quat. Sci. Rev. 151, 273–291. https://doi.org/10.1016/j.quascirev.2016.09.015 Longva, O., 1984. Romeriksmjelen danna ved ein storflaum på Austlandet for vel 9000 år siden. Norges geologiske undersøkelse, Årsmelding 1984 8–11.

• Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Støren, Eivind Wilhelm Nagel; Bakke, Jostein; Høeg, Helge Irgens; Loftsgarden, Kjetil; Iversen, Frode & Krüger, Kirstin (2020). Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE.
• Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Støren, Eivind Wilhelm Nagel; Bakke, Jostein; Høeg, Helge Irgens; Loftsgarden, Kjetil; Iversen, Frode; Svensen, Henrik & Krüger, Kirstin (2020). Tracing socio-environmental dynamics and climate changes in the period 300-1300 CE in Scandinavia from lake sediments. Show summary

  Understanding large volcanic eruptions impacts on environments and societies is necessary to consider future climate and socio-environmental interactions. Lake sediments can record these dynamics on a continuous long time scale and include at the same time footprints from volcanic eruptions, climate changes and human activities. We analysed the sediments of Lake Ljøgottjern, located southeastern Norway. The largest burial mound of Northern Europe was built in the mid-6th century on the shore of this lake and makes this place an ideal site to study human-environmental interactions throughout the last millennia. Using a multi-proxy analysis of this sedimentary record, including 14C dating, geochemistry, as well as palynological data, we reconstructed temperature and socio-environmental changes in this area between 300 and 1300 CE (Common Era). We associated changes in Ca/Ti ratio with changes in temperature. The period between 300 and 800 CE was colder than the periods 200-300 and 800-1300 CE. Five abrupt cooling events seem to be linked to weakened positive NAO (North Atlantic Oscillation) phases, and two of them can also be linked to the two largest volcanic events of the period (i.e. the 536/540 CE double event, and 1257 CE eruption of Samalas). Palynological data indicate a decrease of the human activities and reforestation of the area in the 6th century. This abandonment is consistent with archaeological findings and could be related to the 536/540 cooling event. Very little activities are then recorded between 700 and 850 CE. Agricultural activities start again strongly in the Viking age with increase in temperature.

• Krüger, Kirstin (2020). Volcanic Eruptins and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE. Show summary

  This multi-disciplinary project aims to understand the role of volcanic eruptions and climate change in shaping the early history of Europe. The period 500-1250 CE is characterized by natural disasters, societal unrest, Viking expansion, emerging kingship – and large volcanic eruptions evidenced by geochemical markers in natural archives. Contemporary reports of a mysterious cloud which dimmed the light of the sun for at least a year were written at the dawn of the Middle Ages which marked the beginning of an unusual cold period in the mid of the 6th century due to the double volcanic eruption event in 536/540 CE. The social structure of Scandinavian society was radically changed between 500 and 750 CE. Population levels were reduced by plague and agriculture had to be adapted to a colder climate. Tree ring and climate model data from Scandinavia identify a prolonged period of cooling which may have lasted over a century. Following is a period of volcanic activity which was thought to be more quiescent in a global sense and is marked by the onset of the medieval warm period (c. 950 -1250 CE). However, volcanic eruptions in Iceland were frequently active during 700 to 1100 CE and must have had severe impacts on climate, environment and society in Northern Europe, which is not supported by available records. This presentation aims to shed more light into the background of this early Common Era period based on revised volcanic forcing, complex earth system climate model, proxy, and archaeology data.

• Van Dijk, Evelien Jacoba Cornelia & Krüger, Kirstin (2020). Impact of the 536/540 CE double eruption event on the 6th -7th century climate using model and proxy data.
• Van Dijk, Evelien Jacoba Cornelia & Krüger, Kirstin (2020). Impact of the 536/540 CE double volcanic eruption event on the 6th-7th century climate using model and proxy data.
• Van Dijk, Evelien Jacoba Cornelia & Krüger, Kirstin (2020). The impact of the 536/540 CE double volcanic eruption event on the climate.
• Brenna, Hans; Kutterolf, Steffen; Mills, Michael; Niemeier, Ulrike; Timmreck, Claudia & Krüger, Kirstin (2019). The Los Chocoyos super volcanic eruption disrupts the Quasi-Biennial Oscillation. Show summary

  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.

• Fouilloux, Anne Claire; Iaquinta, Jean & Krüger, Kirstin (2019). Towards an infrastructure for Earth system modelling in Norway.
• Fouilloux, Anne Claire; Krüger, Kirstin & Iaquinta, Jean (2019). Climate Analysis with Galaxy. Show summary

  Advance in the development of climate models and associated data viewers and processing tools has achieved unprecedented maturity in the environmental scientific community. This progress was accompanied by the standardization of model output formats (conventions for Climate and Forecast metadata), the availability of open databases (i.e., the Earth System Grid Federation), and of the climate model codes themselves. However, scientific communities are not fully realizing the benefits of such advances because of the complexity for both running and analysing climate models. Using Galaxy makes it possible to share tools and easily (re-)run climate model runs or analyse climate data thus opening new opportunities for multidisciplinary research for instance ecology, social and human sciences. In this presentation, we will show how climate models can be run out-of-the-box, without much effort, using Galaxy platform. We will show how climate model outputs can be visualized using the same web portal.

• Krüger, Kirstin (2019). The sulfur- and halogen-rich super eruption Los Chocoyos and its impacts on climate, environment, and circulation. Show summary

  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 consequences for the global climate, environment and atmospheric circulation. Using the Earth System Model CESM2(WACCM6) we simulate the impacts of this super eruption on the pre-industrial Earth System. Our model results show that the ozone layer nearly collapses, with large impacts on UV and the biosphere, and the surface climate cools globally with >6 K. Recovery to pre-eruption ozone levels and climate takes 15 and 30 years respectively. The quasi-biennial oscillation (QBO), an oscillation of the zonal winds in the tropical stratosphere with ~28 month periodicity, reveals a 10 year disruption before returning to QBO conditions with a slightly prolonged periodicity. Different model ensembles, volcanic forcing scenarios and comparison with other models are used to test the robustness of our results.

• Krüger, Kirstin (2019). Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE.
• Krüger, Kirstin (2019). Working Group Overview. Show summary

  VIKINGS/NFR TACCO INES KeyCLIM

• Krüger, Kirstin & Bajard, Manon Julietto Andree (2019). Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE. Show summary

  VIKINGS(NFR) TACCO(Notur/NorStore)

• Krüger, Kirstin; Sigl, Michael; Toohey, Matthey & Iversen, Frode (2019). Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE.
• Brenna, Hans; Kutterolf, Steffen & Krüger, Kirstin (2018). Global ozone depletion and increase of UV radiation caused by pre-industrial tropical volcanic eruptions. Show summary

  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?. Show summary

  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. Show summary

  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.

• Fiehn, Alina; Krüger, Kirstin; Stemmler, Irene; Quack, Birgit & Ziska, Franziska (2018). Importance of seasonally resolved oceanic emissions for bromoform delivery to the stratosphere through the Asian monsoon. Show summary

  Very short-lived substances (VSLS) of marine origin, such as bromoform (CHBr3), contribute to stratospheric bromine loading and, thus, to ozone depletion. However, amount, timing, and region of bromine delivery to the stratosphere through one of the main entrance gates, the Asian monsoon circulation, are still uncertain. The atmospheric distribution of bromoform and its delivery to the stratosphere have been the topic of several chemistry transport and chemistry climate modeling studies, but only few studies considered seasonally varying surface water concentrations or emissions in their model simulations. In this study, we create two bromoform emission inventories with monthly resolution for the tropical Indian Ocean and West Pacific based on new in situ bromoform measurements in the tropical West Indian Ocean (Fiehn et al., 2017) incorporated into the observation based climatology (Ziska et al., 2013), and the ocean biogeochemistry modeling (Stemmler et al., 2015) of bromoform. Mass transport and atmospheric mixing ratios of bromoform are simulated for the year 2014 with the particle dispersion model FLEXPART driven by ERA-Interim reanalysis. Model experiments are performed with two emission scenarios: (1) monthly varying emissions and (2) constant emissions over the whole year. We compare these model results with ship- and aircraft-based observations in the boundary layer and upper troposphere lower stratosphere. Using monthly emissions, main oceanic source regions for the stratosphere include the Arabian Sea and Bay of Bengal in boreal summer and the tropical west Pacific Ocean in boreal winter. The corresponding main stratospheric injection occurs over the southern tip of India in boreal summer associated with the high local oceanic sources and strong convection of the summer monsoon. The annually averaged stratospheric injection of bromoform is in the same range independent of temporal resolution of the emissions. However, monthly emissions result in highest mixing ratios within the Asian monsoon anticyclone in boreal summer and above the central Indian Ocean in boreal winter, while constant emissions show a maximum above the West Indian Ocean in boreal spring. Our results for the Asian monsoon circulation underline that the seasonal and regional stratospheric bromine injection from the tropical Indian Ocean and west Pacific critically depends on the seasonality and spatial distribution of the VSLS emissions next to the variability in the atmospheric transport. Finally, we discuss our results with respect to circulation changes of the Asian monsoon which shows an increase in bromoform delivery between 2000 and 2015.

• Krüger, Kirstin (2018). Does the ocean impact the ozone layer?. Show summary

  Natural, halogenated very short-lived substances (VSLS) with an atmospheric lifetime τ<0.5 yr play an important role in the stratospheric ozone budget besides the anthropogenic long-lived chlorine- and brominefluorocarbons. The tropical oceans are a known source of reactive iodine and bromine to the atmosphere such as the VSLS methyl iodide (CH3I), bromoform (CHBr3), and dibromomethane (CH2Br2). They contribute to the halogen loading of the stratosphere if they are transported fast enough within, i.e., deep tropical convection. The tropical West Pacific and Indian Ocean are of special interest since the oceanic compounds of the VSLS are projected to have hot spots for both their emissions and transport pathways to the stratosphere. This study will give an overview of 10 years of research work on VSLS sources in the tropical oceans and their transport pathways and contribution to the stratospheric halogen level to answer the question.

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

  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.

• Fiehn, Alina; Gjermo, Sarah; Fuhlbrugge, Steffen; Quack, Birgit; Marandino, Christa A.; Atlas, Elliot L & Krüger, Kirstin (2017). SO243 ASTRA-OMZ: Does ENSO influence the transport of halogenated very short-lived substances above the tropical East Pacific?.
• Fiehn, Alina & Krüger, Kirstin (2017). Transport of very short-lived substances from the Indian Ocean to the stratosphere through the Asian monsoon.
• Fiehn, Alina; Quack, Birgit; Stemmler, Irene & Krüger, Kirstin (2017). What drives the seasonal cycle of stratospheric entrainment of oceanic halogenated VSLS through the Asian monsoon?.
• Krüger, Kirstin & Gjermo, Sarah (2017). Transport of very short lived halogenated substances from the tropical East Pacific to the stratosphere and the influence of El Niño 2015/16.
• Fiehn, Alina; Hepach, Helmke; Atlas, Elliot L; Quack, Birgit; Tegtmeier, Susann & Krüger, Kirstin (2016). Transport of halogenated very short-lived substances from the Indian Ocean to the stratosphere through the Asian monsoon circulation.
• Fiehn, Alina; Hepach, Helmke; Atlas, Elliot L; Quack, Birgit; Tegtmeier, Susann & Krüger, Kirstin (2015). Transport of bromoform from the Indian Ocean to the stratosphere during Asian summer monsoon. Show summary

  Bromoform and other halogenated very short-lived substances (VSLS, atmospheric lifetime less than half a year) are naturally produced in the ocean and emitted to the atmosphere. If transported to the stratosphere, they take part in ozone depletion. The Asian summer monsoon circulation and the deep convection over India may provide an efficient pathway for compounds from the Indian Ocean. We use the Lagrangian transport model FLEXPART with ERA-Interim meteorological fields to discern transport properties during Indian summer monsoon season.

• Fiehn, Alina; Hepach, Helmke; Atlas, Elliot L; Quack, Birgit; Tegtmeier, Susann & Krüger, Kirstin (2015). Transport of halogenated VSLS from the Indian Ocean to the stratosphere through the Asian monsoon circulation.
• Fiehn, Alina; Hepach, Helmke; Atlas, Elliot L; Quack, Birgit; Tegtmeier, Susann & Krüger, Kirstin (2015). Transport of halogenated VSLS from the Indian Ocean to the stratosphere through the Asian monsoon circulation.
• Wærsted, Eivind Grøtting Grøtting & Krüger, Kirstin (2015). Timescales of surface-to-tropopause transport in the tropics, using Flexpart.

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