Science on Ice: Shedding Light on Arctic Halogen Photochemistry (Invited Presentation)

Due to chemical interactions between the rapidly changing Arctic surface and the atmosphere, there is an urgent need to characterize the unique atmospheric chemistry due to interactions at the frozen snow-covered sea ice surface. Snowpack photochemistry has been shown as an efficient source of molecular halogens to the Arctic troposphere with significant impacts on the oxidation of ozone and mercury. Through chemical ionization mass spectrometry measurements near Utqiagvik, Alaska during winter-spring, we have shown the coastal snowpack to be a dominant source of molecular halogens, including Br₂, Cl₂, BrCl, and I₂. Both sunlit and artificial light experiments provide insights into molecular halogen production, and the first measurements of Br₂ and Cl₂ snowpack fluxes provide guidance for modeling efforts. Zero- and one-dimensional modeling are utilized to examine the resulting snowpack interstitial air and near-surface chemistry. Most notably, we recently showed the first atmospheric measurement of bromine atoms, which quantitatively explain the loss of ozone and elemental mercury in the springtime Arctic near-surface troposphere.