02 Mar 2022
02 Mar 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Influence of energetic particle precipitation on Antarctic stratospheric chlorine and ozone over the 20th century

Ville Maliniemi1, Pavle Arsenovic2,1, Annika Seppälä3, and Hilde Nesse Tyssøy1 Ville Maliniemi et al.
  • 1Birkeland Centre for Space Science, Department of Physics and Technology, University of Bergen, Norway
  • 2Risk Management Solutions, London, UK
  • 3Department of Physics, University of Otago, Dunedin, New Zealand

Abstract. Chlorofluorocarbon (CFC) emissions in the latter part of the 20th century reduced stratospheric ozone abundance substantially, especially in the Antarctic region. Simultaneously, polar stratospheric ozone is also destroyed catalytically by nitrogen oxides (NOx = NO + NO2) descending from the mesosphere and the lower thermosphere during winter. These are produced by energetic particle precipitation (EPP) linked to solar activity and space weather. NOx and active chlorine (ClOx = Cl + ClO) also react mutually and transform both reactive agents into reservoir gas chlorine nitrate, which buffers ozone destruction by both NOx and ClOx. We study the interaction between EPP produced NOx, ClO and ozone over the 20th century by using free running climate simulations of the chemistry-climate model SOCOL3-MPIOM. Substantial increase of NOx descending to polar stratosphere is found during winter, which causes ozone depletion in the upper and mid-stratosphere. However, in the Antarctic mid-stratosphere the EPP induced ozone depletion becomes less efficient after 1960s, especially during springtime. Simultaneously, significant decrease in stratospheric ClO and increase in chlorine nitrate between 10–30 hPa can be ascribed to EPP forcing. Hence, interaction between NOx and ClO likely suppressed the ozone depletion due to both EPP-NOx and ClO at these altitudes. Furthermore, at the end of the century significant ClO increase and ozone decrease is obtained at 100 hPa altitude during winter and spring. This lower stratosphere response is likely due to activation of chlorine from reservoir gases on polar stratospheric clouds. Our results show that EPP has been a significant modulator of reactive chlorine in the Antarctic stratosphere during the CFC era. With the implementation of the Montreal Protocol, stratospheric chlorine is estimated to return to pre-CFC era levels after 2050. Thus, we expect increased efficiency of chemical ozone destruction by EPP-NOx in the Antarctic upper and mid-stratosphere over coming decades. The future lower stratosphere ozone response by EPP is more uncertain.

Ville Maliniemi 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 acp-2022-151', Anonymous Referee #1, 31 Mar 2022
  • RC2: 'Comment on acp-2022-151', Anonymous Referee #2, 02 Apr 2022
  • AC1: 'Author responses to reviewer comments on acp-2022-151', Ville Maliniemi, 19 May 2022

Ville Maliniemi et al.

Ville Maliniemi et al.


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Short summary
We simulate effect of energetic particle precipitation (EPP) on Antarctic stratospheric ozone chemistry over the whole 20th century. We find significant increase of reactive nitrogen due to EPP which can deplete ozone via catalytic reaction. Furthermore, reduction of active chlorine is obtained related to production of chlorine nitrate buffering the ozone destruction of both nitrogen and chlorine. Our results show that EPP has been a significant modulator of ozone chemistry during the CFC era.