Anthropogenic Impacts on Tropospheric Reactive Chlorine Since the Preindustrial

Zhai, Shumenghui; Wang, Xuan; McConnell, J. R.; Geng, Lei; Cole‐Dai, Jihong; Sigl, Michael; Chellman, Nathan; Sherwen, Tomás; Pound, Ryan; Fujita, Koji; Hattori, Shohei; Moch, Jonathan M.; Zhu, Lei; Evans, M. J.; Legrand, Michel; Liu, Pengfei; Pasteris, D.; Chan, Yuk‐Chun; Murray, Lee T.; Alexander, Becky

doi:10.1029/2021gl093808

Cited by 11 publications

(19 citation statements)

References 105 publications

(114 reference statements)

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“…Our model does not include anthropogenic inorganic chlorine sources, which could however be important in polluted continental boundary layer regions as seen in atmospheric observations (Wang et al, 2016;Tham et al, 2016;Lee et al, 2018;Zhou et al,2018;Yun et al, 2018;Peng et al, 2020;Thornton et al, 2010;Wang et al, 2020;Gunthe et al, 2021). Here we focus on a more global perspective.…”

Section: Inorganic Chlorine Gases (Cl Y )mentioning

confidence: 99%

Global tropospheric halogen (Cl, Br, I) chemistry and its impact on oxidants

et al. 2021

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Abstract. We present an updated mechanism for tropospheric halogen (Cl + Br + I) chemistry in the GEOS-Chem global atmospheric chemical transport model and apply it to investigate halogen radical cycling and implications for tropospheric oxidants. Improved representation of HOBr heterogeneous chemistry and its pH dependence in our simulation leads to less efficient recycling and mobilization of bromine radicals and enables the model to include mechanistic sea salt aerosol debromination without generating excessive BrO. The resulting global mean tropospheric BrO mixing ratio is 0.19 ppt (parts per trillion), lower than previous versions of GEOS-Chem. Model BrO shows variable consistency and biases in comparison to surface and aircraft observations in marine air, which are often near or below the detection limit. The model underestimates the daytime measurements of Cl2 and BrCl from the ATom aircraft campaign over the Pacific and Atlantic, which if correct would imply a very large missing primary source of chlorine radicals. Model IO is highest in the marine boundary layer and uniform in the free troposphere, with a global mean tropospheric mixing ratio of 0.08 ppt, and shows consistency with surface and aircraft observations. The modeled global mean tropospheric concentration of Cl atoms is 630 cm−3, contributing 0.8 % of the global oxidation of methane, 14 % of ethane, 8 % of propane, and 7 % of higher alkanes. Halogen chemistry decreases the global tropospheric burden of ozone by 11 %, NOx by 6 %, and OH by 4 %. Most of the ozone decrease is driven by iodine-catalyzed loss. The resulting GEOS-Chem ozone simulation is unbiased in the Southern Hemisphere but too low in the Northern Hemisphere.

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Section: Inorganic Chlorine Gases (Cl Y )mentioning

confidence: 99%

Global tropospheric halogen (Cl, Br, I) chemistry and its impact on oxidants

et al. 2021

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“…2d) show how chlorine is correlated with atmospheric acidity (Fig. 2e) since the preindustrial, and atmospheric models indicate this correlation is due to acidity reacting with sea-salt aerosols (Zhai et al 2021).…”

Section: Ice-core Records Of Atmospheric Composition and Chemistrymentioning

confidence: 94%

Ice-core records of atmospheric composition and chemistry

2022

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“…(2011). To simulate a preindustrial atmosphere, all anthropogenic emissions are turned off (Zhai et al., 2021). We use meteorology and volcanic SO 2 emissions from the year 2013, during which passive and eruptive volcanic SO 2 emissions in regions affecting the Arctic (i.e., Kamchatka, Alaska, and Iceland) were similar to the 2004–2017 median.…”

Section: Comparing Ice Core Sulfate To a Global Modelmentioning

confidence: 99%

Underestimated Passive Volcanic Sulfur Degassing Implies Overestimated Anthropogenic Aerosol Forcing

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Cole‐Dai

et al. 2023

Geophysical Research Letters

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The Arctic is warming at almost four times the global rate. An estimated sixty percent of greenhouse‐gas‐induced Arctic warming has been offset by anthropogenic aerosols, but the contribution of aerosols to radiative forcing (RF) represents the largest uncertainty in estimating total RF, largely due to unknown preindustrial aerosol abundance. Here, sulfur isotope measurements in a Greenland ice core show that passive volcanic degassing contributes up to 66 ± 10% of preindustrial ice core sulfate in years without major eruptions. A state‐of‐the‐art model indicates passive volcanic sulfur emissions influencing the Arctic are underestimated by up to a factor of three, possibly because many volcanic inventories do not include hydrogen sulfide emissions. Higher preindustrial volcanic sulfur emissions reduce modeled anthropogenic Arctic aerosol cooling by up to a factor of two (+0.11 to +0.29 W m−2), suggesting that underestimating passive volcanic sulfur emissions has significant implications for anthropogenic‐induced Arctic climate change.

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Anthropogenic Impacts on Tropospheric Reactive Chlorine Since the Preindustrial

Abstract: Chlorine (Cl) in polar ice cores can provide information about past SSA abundance since the main source of ice-core Cl is from the emission and transport of sea-salt-aerosol (SSA). Reactive gaseous chlorine

Cited by 11 publications

References 105 publications

Global tropospheric halogen (Cl, Br, I) chemistry and its impact on oxidants

Global tropospheric halogen (Cl, Br, I) chemistry and its impact on oxidants

Ice-core records of atmospheric composition and chemistry

Underestimated Passive Volcanic Sulfur Degassing Implies Overestimated Anthropogenic Aerosol Forcing

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