Surface fluxes and recycling of molecular halogens above the snowpack, in Utqiaġvik, AK

Halogen chemistry in the Arctic boundary layer catalytically destroys O3, and impacts the chemical lifetimes of methane and atmospheric mercury. Molecular halogens are produced from the sunlit surface snowpack above coastal tundra and sea ice. However, the magnitude of molecular halogen production from coastal snowpacks is not well constrained, and little is known about the extent of near-surface vertical mixing and the importance of recycling on aerosols. Here we present the first vertical profile measurements of molecular halogens extending to greater than 1 m above the snowpack, as well as the first high frequency (2 Hz) measurements of these molecular halogens, using chemical ionization mass spectrometry in Utqiaġvik, Alaska during March 2016. Eddy covariance fluxes of Cl2 have been calculated and used to inform one-dimensional modeling of near-surface halogen chemistry. Model results are compared to vertical profiles of Cl2 between 1 m and 7 m above the snowpack. These results are used to examine the sources, sinks, and recycling of halogens above the coastal Arctic snowpack.