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Abstract:
Bromine chemistry in the springtime Arctic causes ozone depletion events, altering the oxidative capacity of the lower atmosphere. As the Arctic continues to warm, changes in snowmelt, sea ice distribution, sea-salt aerosol particle production, snow salinity, and boundary layer dynamics will influence this halogen chemistry. During the CHemistry in the Arctic: Clouds, Halogens, and Aerosols field campaign, which took place in Utqiagvik, Alaska during the spring of 2022, the Heidelberg Airborne Imaging DOAS Instrument (HAIDI) was used to measure the reactive halogen species bromine monoxide (BrO) from the Purdue University Airborne Laboratory for Atmospheric Research (ALAR) across Northern Alaska. More than 240 high-resolution BrO profiles were recorded over a two-month period. We often observed the largest BrO mixing ratios at the snow surface, likely due to heterogenous chemistry on the snow surface and the extreme stability of the Arctic atmosphere. Although these surface-peaked observations were common, it is important to note that our flights were biased towards clear-sky conditions, due to flight condition requirements. On one hazy flight day, we observed lofted BrO profiles associated with a lofted aerosol particle layer. Flights near oil extraction facilities reveal the interactions between reactive halogen chemistry and anthropogenic pollution. We use observations from other instruments and back-trajectory analyses to interpret the BrO observations retrieved throughout the campaign. These observations demonstrate that airborne measurements of bromine monoxide provide insights into vertical structures of reactive halogens and can help inform the role of snow, pollution, and particle surfaces on halogen chemistry.
