Comparison of model and ground observations finds snowpack and blowing snow aerosols both contribute to Arctic tropospheric reactive bromine

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Swanson, William, F., Holmes, Chris, D., Simpson, William, R., Confer, Kaitlyn, Marelle, Louis, Thomas, Jennie, L., Jaeglé, Lyatt, Alexander, Becky, Zhai, Shuting, Chen, Qianjie, Wang, Xuan, Sherwen, Tomás
• Other Authors: Department of Chemistry and Biochemistry Fairbanks, University of Alaska Fairbanks (UAF), Geophysical Institute Fairbanks, Department of Earth, Ocean and Atmospheric Science Tallahassee (FSU, Florida State University Tallahassee (FSU), Department of Atmospheric Sciences Seattle, University of Washington Seattle, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Department of Civil and Environmental Engineering Hong Kong (CEE), The Hong Kong Polytechnic University Hong Kong (POLYU), School of Energy and Environment Hong Kong, City University of Hong Kong Hong Kong (CUHK), National Centre for Atmospheric Science York (NCAS), University of York York, UK, Department of Chemistry York, UK
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Arctic; Arctic Ocean; Sea ice; Alaska
• Online Access: https://insu.hal.science/insu-03578658; https://insu.hal.science/insu-03578658v2/document; https://insu.hal.science/insu-03578658v2/file/acp-22-14467-2022.pdf; https://doi.org/10.5194/acp-22-14467-2022

International audience ReactivehalogensplayaprominentroleintheatmosphericchemistryoftheArcticduringspringtime. Field measurements and modeling studies suggest that halogens are emitted into the atmosphere from snowpack and reactions on wind-blown snow-sourced aerosols. The relative importance of snowpack and blowing snow sources is still debated, both at local scales and regionally throughout the Arctic. To understand the implications of these halogen sources on a pan-Arctic scale, we simulate Arctic reactive bromine chemistry in the atmospheric chemical transport model GEOS-Chem. Two mechanisms are included: (1) a blowing snow sea salt aerosol formation mechanism and (2) a snowpack mechanism assuming uniform molecular bromine production from all snow surfaces. We compare simulations including neither mechanism, each mechanism individually, and both mechanisms to examine conditions where one process may dominate or the mechanisms may interact. We compare the models using these mechanisms to observations of bromine monoxide (BrO) derived from multiple- axis differential optical absorption spectroscopy (MAX-DOAS) instruments on O-Buoy platforms on the sea ice and at a coastal site in Utqiag ̇vik, Alaska, during spring 2015. Model estimations of hourly and monthly average BrO are improved by assuming a constant yield of 0.1 % molecular bromine from all snowpack surfaces on ozone deposition. The blowing snow aerosol mechanism increases modeled BrO by providing more bromide-rich aerosol surface area for reactive bromine recycling. The snowpack mechanism led to increased model BrO across the Arctic Ocean with maximum production in coastal regions, whereas the blowing snow aerosol mechanism increases BrO in specific areas due to high surface wind speeds. Our uniform snowpack source has a greater impact on BrO mixing ratios than the blowing snow source. Model results best replicate several features of BrO observations during spring 2015 when using both mechanisms in conjunction, adding evidence that these mechanisms ...