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Future Arctic ozone recovery: The importance of chemistry and dynamics

Bednarz, EM; Maycock, AC; Abraham, NL; Braesicke, P; Dessens, O; Pyle, JA; (2016) Future Arctic ozone recovery: The importance of chemistry and dynamics. Atmospheric Chemistry and Physics , 16 (18) pp. 12159-12176. 10.5194/acp-16-12159-2016. Green open access

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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 halogeninduced 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 (100-50 hPa). 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.

Type: Article
Title: Future Arctic ozone recovery: The importance of chemistry and dynamics
Open access status: An open access version is available from UCL Discovery
DOI: 10.5194/acp-16-12159-2016
Publisher version: http://dx.doi.org/10.5194/acp-16-12159-2016
Language: English
Additional information: Copyright © Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License (https://creativecommons.org/licenses/by/3.0/. Published by Copernicus Publications on behalf of the European Geosciences Union.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of the Built Environment
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of the Built Environment > Bartlett School Env, Energy and Resources
URI: https://discovery.ucl.ac.uk/id/eprint/1527456
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