The effect of representing bromine from VSLS on the simulation and evolution of Antarctic ozone

Oman, Luke D.; Douglass, Anne R.; Salawitch, R. J.; Canty, T. P.; Ziemke, J. R.; Manyin, Michael

doi:10.1002/2016gl070471

Cited by 32 publications

(33 citation statements)

References 34 publications

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“…While VSLS have a large impact on Antarctic ozone depletion during the ozone hole period, i.e., during times with high-stratospheric chlorine loading from about the late 1970s to the second half of the 21st century (e.g., Fernandez et al, 2017;Oman et al, 2016;Sinnhuber and Meul, 2015;Yang et al, 2014), we find that by the end of the 21st century VSLS have less impact on total Antarctic stratospheric ozone depletion under low chlorine loading, although their importance relative to the total stratospheric halogen load is increasing (about 40 % in accordance to Fernandez et al, 2017). Assuming an adherence to the Montreal Protocol, stratospheric volume mixing ratios of Cl y will decrease exponentially in the course of the 21st century from its peak values in 2000.…”

Section: Implications On Ozone Depletionmentioning

confidence: 99%

“…Catalytic cycles involving bromine and mixed halogen reactions, namely with chlorine, efficiently deplete ozone (e.g., Sinnhuber et al, 2009). The ozone depletion efficiency of bromine is strongly related to the available amount of activated chlorine in the atmosphere (Yang et al, 2014;Sinnhuber and Meul, 2015;Oman et al, 2016). Long-lived, anthropogenically emitted, halogenated source gases (SG), e.g., CH 3 Br and halons, have been restricted by the Montreal Protocol and its amendments.…”

Section: Introductionmentioning

confidence: 99%

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Brominated VSLS and their influence on ozone under a changing climate

et al. 2017

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Abstract. Very short-lived substances (VSLS) contribute as source gases significantly to the tropospheric and stratospheric bromine loading. At present, an estimated 25 % of stratospheric bromine is of oceanic origin. In this study, we investigate how climate change may impact the oceanatmosphere flux of brominated VSLS, their atmospheric transport, and chemical transformations and evaluate how these changes will affect stratospheric ozone over the 21st century.Under the assumption of fixed ocean water concentrations and RCP6.0 scenario, we find an increase of the oceanatmosphere flux of brominated VSLS of about 8-10 % by the end of the 21st century compared to present day. A decrease in the tropospheric mixing ratios of VSLS and an increase in the lower stratosphere are attributed to changes in atmospheric chemistry and transport. Our model simulations reveal that this increase is counteracted by a corresponding reduction of inorganic bromine. Therefore the total amount of bromine from VSLS in the stratosphere will not be changed by an increase in upwelling. Part of the increase of VSLS in the tropical lower stratosphere results from an increase in the corresponding tropopause height. As the depletion of stratospheric ozone due to bromine depends also on the availability of chlorine, we find the impact of bromine on stratospheric ozone at the end of the 21st century reduced compared to present day. Thus, these studies highlight the different factors influencing the role of brominated VSLS in a future climate.

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Section: Implications On Ozone Depletionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Brominated VSLS and their influence on ozone under a changing climate

et al. 2017

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“…Nonetheless, model simulations predict that the Antarctic ozone hole will continue to occur for decades (e.g. WMO, 2014;Oman et al, 2016;Fernandez et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

Müller¹,

Grooß²,

Zafar

et al. 2018

Atmos. Chem. Phys.

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Abstract. The Antarctic ozone hole arises from ozone destruction driven by elevated levels of ozone destroying ("active") chlorine in Antarctic spring. These elevated levels of active chlorine have to be formed first and then maintained throughout the period of ozone destruction. It is a matter of debate how this maintenance of active chlorine is brought about in Antarctic spring, when the rate of formation of HCl (considered to be the main chlorine deactivation mechanism in Antarctica) is extremely high. Here we show that in the heart of the ozone hole (16-18 km or 85-55 hPa, in the core of the vortex), high levels of active chlorine are maintained by effective chemical cycles (referred to as HCl null cycles hereafter). In these cycles, the formation of HCl is balanced by immediate reactivation, i.e. by immediate reformation of active chlorine. Under these conditions, polar stratospheric clouds sequester HNO 3 and thereby cause NO 2 concentrations to be low. These HCl null cycles allow active chlorine levels to be maintained in the Antarctic lower stratosphere and thus rapid ozone destruction to occur. For the observed almost complete activation of stratospheric chlorine in the lower stratosphere, the heterogeneous reaction HCl + HOCl is essential; the production of HOCl occurs via HO 2 + ClO, with the HO 2 resulting from CH 2 O photolysis. These results are important for assessing the impact of changes of the future stratospheric composition on the recovery of the ozone hole. Our simulations indicate that, in the lower stratosphere, future increased methane concentrations will not lead to enhanced chlorine deactivation (through the reaction CH 4 + Cl −→ HCl+CH 3 ) and that extreme ozone destruction to levels below ≈ 0.1 ppm will occur until mid-century.

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“…Very short-lived brominated gases have predominately natural sources, and therefore cannot be regulated by international agreements (Oman et al, 2016;Butler et al, 2007).…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

“…The wide range of VSLS atmospheric lifetimes allow at least some of the emitted material to reach the upper troposphere, particularly over geographical regions where there is rapid, deep convection (Penkett et al, 1998; Yang et al, 2005; Warwick et al, 2006;Levine et al, 2007;Pisso et al, 2010;Hosking et al, 2010; Carpenter et al, 2014; 50 Hossaini et al, 2016a; Butler et al, 2016). Here, we use aircraft observations of bromoform (CHBr 3 ) and dibromomethane (CH 2 Br 2 ) collected over the western Pacific Ocean to infer, using an inverse model, the magnitude and distribution of ocean emissions of these gases.There are a wide range of VSLS that are beginning to limit the recovery of stratospheric 55 ozone (e.g., Read et al, 2008;Hossaini et al, 2015;Oman et al, 2016). Chlorine VSLS are typically dominated by anthropogenic sources, but the fraction depends on the species (Hossaini et al, 2016b).…”

mentioning

confidence: 99%

Surface fluxes of bromoform and dibromomethane over the tropical western Pacific inferred from airborne in situ measurements

Li¹,

Palmer²,

Butler³

et al. 2017

Preprint

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Abstract. We infer surface fluxes of bromoform (CHBr3) and dibromoform (CH2Br2) from aircraft observations over the western Pacific using a tagged version of the GEOS-Chem global 3-D atmospheric chemistry model and a Maximum A Posteriori inverse model. The distribution of a priori ocean emissions of these gases are reasonably consistent with observed atmospheric mole fractions of CHBr3 (r&#8201;=&#8201;0.62) and CH2Br2 (r&#8201;=&#8201;0.38). These a priori emissions result in a positive model bias in CHBr3 peaking in the marine boundary layer, but capture observed values of CH2Br2 with no significant bias by virtue of its longer atmospheric lifetime. Using GEOS-Chem, we find that observed variations in atmospheric CHBr3 are determined equally by sources over the western Pacific and those outside the study region, but observed variations in CH2Br2 are determined mainly by sources outside the western Pacific. Numerical closed-loop experiments show that the spatial and temporal distribution of boundary layer aircraft data have the potential to substantially improve current knowledge of these fluxes, with improvements related to data density. Using the aircraft data, we estimate aggregated regional fluxes of 3.6&#8201;&#177;&#8201;0.3&#8201;&#215;&#8201;108&#8201;g/month and 0.7&#8201;&#177;&#8201;0.1&#8201;&#215;&#8201;108&#8201;g/month for CHBr3 and CH2Br2 over 130&#176;&#8211;155&#176;&#8201;E and 0&#176;&#8211;12&#176;&#8201;N, respectively, which represent reductions of 20&#8211;40&#8201;% and substantial spatial deviations from the a priori inventory. We find no evidence to support a robust linear relationship between CHBr3 and CH2Br2 oceanic emissions, as used by previous studies.

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The effect of representing bromine from VSLS on the simulation and evolution of Antarctic ozone

Cited by 32 publications

References 34 publications

Brominated VSLS and their influence on ozone under a changing climate

Brominated VSLS and their influence on ozone under a changing climate

The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

Surface fluxes of bromoform and dibromomethane over the tropical western Pacific inferred from airborne in situ measurements

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