Ozone super recovery cancelled in the Antarctic upper stratosphere

Abstract. Ozone is expected to fully recover from the CFC-era by the end of the 21st century. Furthermore, because of anthropogenic climate change, a cooler stratosphere accelerates ozone production and is projected to lead to a super recovery of ozone. We investigate the ozone distribution over the 21st century with four different future scenarios using simulations of the Whole Atmosphere Community Climate Model (WACCM). At the end of the 21st century, equatorial upper startosphere has roughly 0.5 to 1.0 parts per million more ozone in scenario with the highest greenhouse gas emissions compared to conservative scenario. Polar ozone levels exceed those in the pre CFC-era in scenarios that have the highest greenhouse gas emissions. This is true in the Arctic stratosphere and the Antarctic lower stratosphere. The Antarctic upper stratosphere is an exception, where different scenarios all have similar levels of ozone during winter, which do not exceed pre-CFC levels. Our results show that this is due to excess nitrogen oxides (NOx) descending from above in the stronger scenarios of greenhouse gas emissions. NOx is formed by energetic electron precipitation (EEP) in the thermosphere and the upper mesosphere, and descends faster through the mesosphere in stronger scenarios. This indicates that the EEP indirect effect will be important factor for the future Antarctic ozone evolution, and could potentially prevent a super recovery of ozone in the upper stratosphere.