DOI: 10.5061/dryad.pk0p2ngw5
title: Data to support: Anthropogenic influence on tropospheric reactive bromine since the pre-industrial: Implications for ice-core bromine trends

description: Tropospheric reactive bromine (Bry) influences the oxidation capacity of
 the atmosphere by acting as a sink for ozone and nitrogen oxides. Aerosol
 acidity plays a crucial role in Bry abundances through acid-catalyzed
 debromination from sea-salt-aerosol, the largest global source. Bromine
 concentrations in a Russian Arctic ice-core, Akademii Nauk, show a
 3.5-fold increase from pre-industrial (PI) to the 1970s (peak acidity,
 PA), and decreased by half to 1999 (present day, PD). Ice-core acidity
 mirrors this trend, showing robust correlation with bromine, especially
 after 1940 (r=0.9). Model simulations considering anthropogenic emission
 changes alone show that atmospheric acidity is the main driver of Bry
 changes, consistent with the observed relationship between acidity and
 bromine. The influence of atmospheric acidity and Bry should be considered
 in interpretation of ice-core bromine trends.
description: We use a global 3D chemical transport model GEOS-Chem (version
 11-02d, https://github.com/geoschem/geos-chem/tree/v11-02d-prelim) for historical simulations. The model is driven by MERRA-2 assimilated meteorological fields from the Goddard Earth Observing System (GEOS) (Gelaro et al., 2017), and contains detailed HO<sub>x</sub>-NO<sub>x</sub>-VOC-ozone-halogen-aerosol tropospheric chemistry (Wang et al., 2021) and fully coupled stratospheric chemistry (Eastham et al., 2014). Details of the modeled bromine chemistry are shown in Fig. S1‒S3.  Sea-salt-aerosol debromination occurs in both open ocean (Jaeglé et al., 2011) and blowing snow (Huang & Jaeglé, 2017) sourced sea-salt-aerosol. Following Zhai et al. (2023), ozone dry deposition velocity onto snow and ice is updated to 0.01 cm s<sup>−1</sup>, consistent with observations (Simpson et al., 2007). Snowpack bromine emissions (Swanson et al., 2022; Zhai et al., 2023) are not included in the model. Model simulations are performed under three anthropogenic emission scenarios: pre-industrial (PI, CE 1750), peak atmospheric acidity (PA, CE 1975), and present-day (PD, CE 1999). Anthropogenic and biomass-burning emissions vary between simulations to reflect their impacts on tropospheric bromine. Details of the emission setup can be found in Zhai et al. (2021), and trends of anthropogenic emissions of SO<sub>2</sub> and NO<sub>x</sub> can be found in Fig.S4. After a 1-year spin-up, each simulation is run for 1 year using 2007 meteorology and sea-ice extent. By using the same meteorology, we aim to isolate changes induced by anthropogenic emissions. All simulations are conducted at 4° × 5° horizontal resolution and 72 vertical levels up to 0.01 hPa.
description: # Data to support: Anthropogenic Influence on Tropospheric Reactive
 Bromine since the Pre-industrial: Implications for Ice-core Bromine Trends
 This data set contains
 modeling output to support the Article "Anthropogenic Influence on
 Tropospheric Reactive Bromine since the Pre-industrial: Implications for
 Ice-core Bromine Trends". ### Description of the data and file
 structure The dataset contains results from the 3 GEOS-Chem model
 simulations: PI (pre-industrial), PA (peak acidity) and PD (present day).
 Please refer to the article for detailed description of the simulation
 setup. Each model simulation contains 28 data files (all model outputs are
 monthly averaged values): 1.    PIconc.2007MMDD.nc: concentration files, 1
 file for every 3 months, 4 files in total for PI 2.    PAconc.2007MMDD.nc:
 concentration files, 1 file for every 3 months, 4 files in total for PA
 3.    PDconc.2007MMDD.nc: concentration files, 1 file for every 3 months,
 4 files in total for PD 4.    BrBudget.xlsx: excel file contains chemical
 reaction rates of each bromine reaction in the model, budget analysis for
 each bromine species, dry and wet deposition rates, and the burden of each
 bromine species. All values are the annual average over the 5-day back
 trajectory regions of the Akademii Nauk ice core (the 'TRJ sum
 99PD' tab) and the Col du Dome ice core (the 'CDD TRJ sum
 99PD' tab). Each calculation has 3 columns: ‘PI’, ‘PA’, and ‘PD’,
 which represent the three historical simulations in the model. For budget
 analysis tables, red font represents photolysis reactions, purple
 represents sea salt heterogeneous reactions, and green is multiphase
 reactions on cloud droplets. Gray italic font are summations of all
 sources or sinks. 5.    BrMapsBurden_TRJ region-1999PD.ipynb: Example
 python code (in jupyter notebook) to generate figures presented in the
 Article. ### Sharing/Access information GEOS-Chem is open software and
 available on . We used the
 version 11-02d. ### Code/Software Example python code (in jupyter
 notebook) to generate figures presented in the Article is also
 available:\\\ BrMapsBurden_TRJ region-1999PD.ipynb