The Role of Ozone Depletion in the Lack of Cooling in the Antarctic Upper Stratosphere during Austral Winter

Temperature trends in the upper stratosphere are investigated using satellite measurements from Stratospheric Sounding Unit (SSU) outputs and simulations from chemistry-climate models (CCMs) and the Coupled Model Intercomparison Project Phase 6 (CMIP6). Observational evidence shows a lack of cooling in the Antarctic, in contrast to strong cooling at other latitudes, during austral winter over 1979-97. Analysis of CCM simulations for a longer period of 1961-97 also shows a significant contrast in the upper stratospheric temperature trends between the Antarctic and lower latitudes. Results from two sets of model integrations with fixed ozone-depleting substances (ODSs) and fixed greenhouse gases (GHGs) at their 1960 levels suggest that the ODSs have made a major contribution to the lack of cooling in the Antarctic upper stratosphere. Results from CMIP6 simulations with prescribed GHGs and ozone confirm that changes in the dynamical processes associated with observed ozone depletion are largely responsible for the lack of cooling in the Antarctic upper stratosphere. The lack of cooling is found to be dynamically induced through increased upward wave activity into the upper stratosphere, which is attributed mainly to ODSs forcing. Specifically, the radiative cooling caused by the ozone depletion results in a stronger meridional temperature gradient between middle and high latitudes in the upper stratosphere, allowing more planetary waves propagating upward to warm the Antarctic upper stratosphere. These findings improve our understanding of the chemistry-climate coupling in the southern upper stratosphere.

Automated summary

Temperature trends in the upper stratosphere are examined using satellite measurements and simulations from climate models. Observational evidence reveals a lack of cooling in the Antarctic during austral winter over a specific period, while simulations over a longer period also show contrasting temperature trends between the Antarctic and lower latitudes. Further analysis suggests that ozone-depleting substances have contributed significantly to the lack of cooling in the Antarctic upper stratosphere.