[A-CC37] [EJ] Ice cores and past environmental changes

[ACC37-03] A 60-year record of isotopic compositions of nitrate preserved in the high-accumulation dome ice core, South East Greenland

*Shohei Hattori¹, Asuka Tsuruta¹, Iizuka Yoshinori², Ryu Uemura³, Sumito Matoba², Naohiro Yoshida¹ (1.Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2.Institute of Low Temperature Science, Hokkaido University, 3.University of Ryukyus)

Keywords:stable isotope, nitrate

Nitrate (NO₃^-) is one of the major anions found in snow. NO₃^- deposition results from reactions between nitrogen oxides (NOx = NO + NO₂) and atmospheric oxidants. Global main sources of NOx are fossil fuel and biomass burning, biogenic soil emissions, and lightning, and a recent increase in NO₃^- in ice cores has been associated with increasing anthropogenic emissions of NOx. Based on the changes in NO₃^- concentration, however, it is difficult to identify specific sources of NOx which takes into account for the changes in NO₃^- concentrations, hindering the development of mitigation policy of anthropogenic pollution and its effect on the environment.
Isotopic compositions of NO₃^- reveal changes in the nitrogen source and its formation pathways, but ice core records for NO₃^- concentrations and its isotopic compositions are problematic because of post depositional loss of NO₃^- via photolysis. In this study, we analyzed isotopic compositions of NO₃^- preserved in the high-accumulation dome ice core, South East Greenland. South East Greenland has a dome whose elevation is higher than 3000 m a.s.l. with high accumulation rate (about 1 m yr^-1) in water equivalent. High elevation and accumulation rate gives high-time resolution reconstruction of past environment, and provides negligible effect of the post depositional loss of nitrate (NO₃^-). In fact, the nitrogen isotopic compositions for NO₃^- are generally lower than those reported in Summit, Greenland, suggesting negligible effect of post depositional loss of NO₃^- in this site. In the presentation, we present changes in NO₃^- concentration and its isotopic composition through recent 60 years, and discuss the changes in the source and formation pathways of nitrate.