The impact of snow nitrate photolysis on boundary layer chemistry and the recycling and redistribution of reactive nitrogen across Antarctica and Greenland in a global chemical transport model

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Zatko, Maria, Geng, Lei, Alexander, Becky, Sofen, Eric, Klein, Katarina
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: COPERNICUS GESELLSCHAFT MBH 2016
• Subjects: Antarc*; Antarctica; Greenland; ice core
• Online Access: https://epic.awi.de/id/eprint/44764/; https://epic.awi.de/id/eprint/44764/1/acp-16-2819-2016.pdf; https://doi.org/10.5194/acp-16-2819-2016; https://hdl.handle.net/10013/epic.50999; https://hdl.handle.net/10013/epic.50999.d001

The formation and recycling of reactive nitrogen (NO, NO2, HONO) at the air–snow interface has implications for air quality and the oxidation capacity of the atmosphere in snow-covered regions. Nitrate (NO3−) photolysis in snow provides a source of oxidants (e.g., hydroxyl radical) and oxidant precursors (e.g., nitrogen oxides) to the overlying boundary layer, and alters the concentration and isotopic (e.g., δ15N) signature of NO3− preserved in ice cores. We have incorporated an idealized snowpack with a NO3− photolysis parameterization into a global chemical transport model (Goddard Earth Observing System (GEOS) Chemistry model, GEOS-Chem) to examine the implications of snow NO3− photolysis for boundary layer chemistry, the recycling and redistribution of reactive nitrogen, and the preservation of ice-core NO3− in ice cores across Antarctica and Greenland, where observations of these parameters over large spatial scales are difficult to obtain. A major goal of this study is to examine the influence of meteorological parameters and chemical, optical, and physical snow properties on the magnitudes and spatial patterns of snow-sourced NOx fluxes and the recycling and redistribution of reactive nitrogen across Antarctica and Greenland. Snow-sourced NOx fluxes are most influenced by temperature-dependent quantum yields of NO3− photolysis, photolabile NO3− concentrations in snow, and concentrations of light-absorbing impurities (LAIs) in snow. Despite very different assumptions about snowpack properties, the range of model-calculated snow-sourced NOx fluxes are similar in Greenland (0.5–11 × 108 molec cm−2 s−1) and Antarctica (0.01–6.4 × 108 molec cm−2 s−1) due to the opposing effects of higher concentrations of both photolabile NO3− and LAIs in Greenland compared to Antarctica. Despite the similarity in snow-sourced NOx fluxes, these fluxes lead to smaller factor increases in mean austral summer boundary layer mixing ratios of total nitrate (HNO3+ NO3−), NOx, OH, and O3 in Greenland compared to Antarctica because of ...