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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 18 | Copyright
Atmos. Chem. Phys., 16, 12159-12176, 2016
https://doi.org/10.5194/acp-16-12159-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 28 Sep 2016

Research article | 28 Sep 2016

Future Arctic ozone recovery: the importance of chemistry and dynamics

Ewa M. Bednarz1, Amanda C. Maycock1,2,a, N. Luke Abraham1,2, Peter Braesicke1,2,b, Olivier Dessens3, and John A. Pyle1,2 Ewa M. Bednarz et al.
  • 1Department of Chemistry, University of Cambridge, Cambridge, UK
  • 2National Centre for Atmospheric Science – Climate, University of Cambridge, Cambridge, UK
  • 3University College London, London, UK
  • anow at: School of Earth and Environment, University of Leeds, Leeds, UK
  • bnow at: Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Karlsruhe, Germany

Abstract. Future trends in Arctic springtime total column ozone, and its chemical and dynamical drivers, are assessed using a seven-member ensemble from the Met Office Unified Model with United Kingdom Chemistry and Aerosols (UM-UKCA) simulating the period 1960–2100. The Arctic mean March total column ozone increases throughout the 21st century at a rate of  ∼ 11.5DUdecade−1, and is projected to return to the 1980 level in the late 2030s. However, the integrations show that even past 2060 springtime Arctic ozone can episodically drop by  ∼ 50–100DU below the corresponding long-term ensemble mean for that period, reaching values characteristic of the near-present-day average level. Consistent with the global decline in inorganic chlorine (Cly) over the century, the estimated mean halogen-induced chemical ozone loss in the Arctic lower atmosphere in spring decreases by around a factor of 2 between the periods 2001–2020 and 2061–2080. However, in the presence of a cold and strong polar vortex, elevated halogen-induced ozone losses well above the corresponding long-term mean continue to occur in the simulations into the second part of the century. The ensemble shows a significant cooling trend in the Arctic winter mid- and upper stratosphere, but there is less confidence in the projected temperature trends in the lower stratosphere (100–50hPa). This is partly due to an increase in downwelling over the Arctic polar cap in winter, which increases transport of ozone into the polar region as well as drives adiabatic warming that partly offsets the radiatively driven stratospheric cooling. However, individual winters characterised by significantly suppressed downwelling, reduced transport and anomalously low temperatures continue to occur in the future. We conclude that, despite the projected long-term recovery of Arctic ozone, the large interannual dynamical variability is expected to continue in the future, thereby facilitating episodic reductions in springtime ozone columns. Whilst our results suggest that the relative role of dynamical processes for determining Arctic springtime ozone will increase in the future, halogen chemistry will remain a smaller but non-negligible contributor for many decades to come.

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Future trends in springtime Arctic ozone, and its chemical dynamical and radiative drivers, are analysed using a 7-member ensemble of chemistry–climate model integrations, allowing for a detailed assessment of interannual variability. Despite the future long-term recovery of Arctic ozone, there is large interannual variability and episodic reductions in springtime Arctic column ozone. Halogen chemistry will become a smaller but non-negligible driver of Arctic ozone variability over the century.
Future trends in springtime Arctic ozone, and its chemical dynamical and radiative drivers, are...
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