| Summary: | In the Arctic, the stratospheric polar vortex usually breaks up between March and May in an event known as Final Stratospheric Warming (FSW). The polar vortex breakdown can induce anomalies at the surface, which depend to a large part on the timing of the FSW. Here, we investigate the importance of Arctic stratospheric ozone for the timing and surface impacts of FSWs under present-day and future conditions. In detail, we investigate the relationship between springtime ozone and the FSW in two Chemistry Climate Models using setups with fully interactive and prescribed climatological ozone for present-day and future conditions. For years with low springtime ozone concentrations in present-day conditions, we find that the FSW at 50 hPa is significantly delayed by 10-14 days and does not show robust effects on surface climate. In contrast, in years with high ozone concentrations, the FSW happens 9-16 days earlier than average and is followed by a negative Arctic Oscillation (AO) at the surface. Most importantly, stratospheric ozone anomalies contribute to the variability of FSWs and significantly enhance their surface effects in high ozone years in present-day conditions. These findings emphasise the importance of interactive ozone chemistry for subseasonal to seasonal predictions. For future conditions, we find that Arctic ozone variability is significantly reduced, as springtime ozone minima become smaller with declining abundances of ozone depleting substances. Consequences of a decrease in ozone variability on the connection between ozone and the timing of the FSW are discussed.
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