How frequent are Antarctic sudden stratospheric warmings in present and future climate?

Abstract

The stratospheric polar vortex forms in the winter hemisphere due to the lack of solar heating at high latitudes and the resulting strong equator-to-pole temperature gradient. In the Northern Hemisphere (NH), strong and planetary scale waves originating in the troposphere from orographic forcing and land-sea contrast periodically propagate upward into the stratosphere and perturb the polar vortex via momentum deposition, when the waves break (Charney & Drazin, 1961;Eliassen & Palm, 1960;Matsuno, 1971). In extreme cases, this disruption of the polar vortex leads to a rapid warming and reversal of wind directions in the polar stratosphere, a so-called (major) sudden stratospheric warming (SSW) (Butler et al., 2015). These SSWs occur around every other winter in the NH.However, over the six decades that we have station records (and later satellite observations) of the Southern Hemisphere (SH) polar vortex, only one such wind reversal has been recorded in 2002(Esler et al., 2006Roscoe et al., 2005). This event substantially decreased the size of the ozone hole, thanks to higher than usual stratospheric polar temperatures and transport of ozone-rich air from lower latitudes into the polar regions (Figure S2a) (Stolarski et al., 2005). There was also a dynamical effect of the 2002 SSW at the surface, as an extreme negative polarity of the southern annular mode (SAM) was recorded at the surface for the 10-90-day period following the event . Even though no wind reversal at 60°S and 10 hPa was registered in 2019, the polar vortex in this more recent event weakened dramatically and also lead to a smaller ozone hole (Figure S2b), with almost 30% higher total column ozone values compared to the previous decade (Safieddine et al., 2020). The event has also been linked to the severe bushfire season in South Eastern Australia the following spring and summer (Lim et al., 2021).

Comparison of Arctic and Antarctic Stratospheric Climates in Chemistry Versus No‐Chemistry Climate Models

“…This is the vortex breakup and major stratospheric warming of 2002 which at the time was considered very unusual as it had never before been seen in the observational record (Newman & Nash, 2003). Both chemistry (UKESM1, SOCOL) and no‐chemistry (CESM2) models exhibit similar extremely warm episodes around this time of the year, meaning that some CMIP6/CCMI2 models can qualitatively simulate such events (Jucker et al., 2021).…”

Introduction to Special Collection “The Exceptional Arctic Stratospheric Polar Vortex in 2019/2020: Causes and Consequences”

“…While Antarctic SSWs are expected to become much less likely in the next century, with an accompanying strong and longer‐lived austral polar vortex, it is unclear what may happen in the Arctic—while the results of Jucker et al. (2021) do not suggest a large change in Arctic SSW frequency in the future, other studies show disagreement even in the sign of the SSW frequency response across models (e.g., Ayarzagüena et al., 2019, 2020; Rao & Garfinkel, 2021a; papers not in this special collection). Correspondingly, we have no consensus as to whether exceptionally strong vortices such as that in 2019/2020 may become more or less common in the future.…”

“…The work of Jucker et al. (2021) relates to questions of how extreme stratospheric vortex states may change in the future. They focus primarily on assessing the likely frequency of future SSWs in the Antarctic with comparison to the Arctic.…”

Southern Hemisphere Stratospheric Warmings and Coupling to the Mesosphere‐Lower Thermosphere

“…However, the warming occurred earlier in September than the 2002 warming and at a time when the stratospheric winds were still large, so the deceleration of the westward flow was insufficient to reverse the mean zonal flow at 10 hPa (Liu, Hirooka, et al., 2021). Nevertheless, the deceleration of the vortex at 10 hPa was as drastic as that of the 2002 SSW (Jucker et al., 2021). As Lim et al.…”