28 Jun 2022
28 Jun 2022
Status: this preprint is currently under review for the journal ACP.

On the fingerprint of the Antarctica ozone hole in ice core nitrate isotopes: a case study based on a South Pole ice core

Yanzhi Cao1, Zhuang Jiang1, Becky Alexander2, Jihong Cole-Dai3, Joel Savarino4, Joseph Erbland4, and Lei Geng1,5,6 Yanzhi Cao et al.
  • 1Anhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui, China
  • 2Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
  • 3Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD USA
  • 4Univ. Grenoble Alpes, CNRS, IRD, G-INP, Institut des Géosciences de l’Environnement, Grenoble, France
  • 5CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei, Anhui, China
  • 6Qingdao National Laboratory for Marine Science and Technology, Qingdao, China

Abstract. Column ozone variability has important implications for surface photochemistry and climate. Ice-core nitrate isotopes are suspected to be influenced by column ozone variability and δ15N(NO3-) has been sought to serve as a proxy of column ozone variability. In this study, we examined the ability of ice-core nitrate isotopes to reflect column ozone variability by measuring δ15N(NO3-) and Δ17O(NO3-) in a shallow ice core drilled at the South Pole. The ice core covers the period of 1944 to 2005, and during this period δ15N(NO3-) was of large annual variability ((59.2 ± 29.3) ‰), but with no apparent response to the Antarctic ozone hole. Utilizing a snow photochemical model, we estimated 6.9 ‰ additional enrichments in δ15N(NO3-) could be caused by the development of the ozone hole. But this enrichment is nevertheless small and masked by the effects of snow accumulation rate variability in addition to that of the slightly increased snow accumulation rate at the South Pole over the same period of the ozone hole. The Δ17O(NO3-) record displays a decreasing trend by ~ 3.4 ‰ since 1976. This magnitude of change can’t be caused by enhanced post-depositional processing owing to the ozone hole. Instead, the Δ17O(NO3-) decrease was more likely due to the proposed decreases in O3 / HOx ratio in the extratropical Southern Hemisphere. Our results suggest ice-core δ15N(NO3-) is more sensitive to snow accumulation rate than to column ozone, but at sites with relatively constant snow accumulation rate, information of column ozone variability embedded in δ15N(NO3-) should be retrievable. In comparison with the South Pole, up to 21 ‰ additional δ15N(NO3-) enrichments can be caused by the ozone hole at Dome A and the signal would be possibly detected if where snow accumulation rate has stayed relatively constant.

Yanzhi Cao et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on Cao et al.', Anonymous Referee #1, 18 Jul 2022
  • RC2: 'Comment on acp-2022-417', Anonymous Referee #2, 19 Jul 2022

Yanzhi Cao et al.


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Short summary
We investigate the potential of ice-core preserved nitrate isotopes as proxies of stratospheric ozone variability by measuring nitrate isotopes in a shallow ice core from the South Pole. The large variability of snow accumulation rate and its slight increase after the 1970s masked any signals caused by ozone hole. Meanwhile, the nitrate oxygen isotope decrease may reflect changes in the atmospheric oxidation environment in the Southern Ocean.