EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Understanding the evolution of atmospheric nitrous oxide over the last century from the stable isotopes of the firn air at Styx Glacier, East Antarctica

Sambit Ghosh1, Sakae Toyoda2, Jinho Ahn1, Youngjoon Jang1, and Naohiro Yoshida2,3,4
Sambit Ghosh et al.
  • 1School of Earth and Environmental Sciences, Seoul National University, Seoul, Republic of Korea (
  • 2Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama, Japan
  • 3Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
  • 4National Institute of Information and Communications Technology, Tokyo, Japan

The increase in mixing ratio of greenhouse gas (GHG) has been believed to be the primary driver for the ongoing global warming. Among the GHGs, the mixing ratio of nitrous oxide (N2O) has increased by 23% since 1750 CE. N2O has a long residence time of ca. 120 years, and a potential to destruct the ozone layer. The Global Warming Potential of N2O is about 300 times greater than that of CO2 over 100 years. However, the temporal changes in magnitude and geographic distribution of different N2O sources are uncertain, hence, understanding the dynamics of atmospheric N2O has been a challenge to the researcher during the last few decades. Here, we present new stable isotope data of N2O from the firn air at Styx Glacier, East Antarctica to comprehend the atmospheric evolution for the last 100 years. Our results show that the N2O mixing ratio has increased, whereas the δ15Nbulk (‰, AIR) and δ18O (‰, VSMOW) values decreased during the last 100 years, consistent with the existing firn air records. The progressive increase in the N2O mixing ratio and the decrease in the isotope ratios suggest a higher contribution from the anthropogenic sources assuming that the N2O flux from the natural sources is constant. Our box model analysis using the stable isotopes and mixing ratio data of N2O of Styx firn air suggests that anthropogenic N2O emission at 2014 CE was ca. 37.5% higher than 1919 CE. The box model calculation with Styx and other firn air and ice core data suggests that in comparison to the pre-industrial era, the total N2O emission is ca. 61% higher at present (2014 CE), where ca. 62% and 38% contributions are from natural and anthropogenic sources, respectively to the total N2O emission. The isotope-based mass-balance calculation indicates that continental emission was ca. 45% higher in 2014 CE than in 1919 CE. Although there is a large scatter in existing data, the site preference of 15N in N2O molecules (δ15NSP ‰, AIR) shows an increasing trend during the post-industrial era, which is consistent with the idea that enhanced fertilization increased soil N2O emissions by activating nitrification processes.

How to cite: Ghosh, S., Toyoda, S., Ahn, J., Jang, Y., and Yoshida, N.: Understanding the evolution of atmospheric nitrous oxide over the last century from the stable isotopes of the firn air at Styx Glacier, East Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9337,, 2021.

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