The effect of stratospheric ozone depletion on the phase of the Antarctic Oscillation

The effect of stratospheric ozone loss on Southern Hemispheric extratropical circulation is explored using an atmosphere‐only model. The main tropospheric response is a sudden shift in the leading mode of month‐to‐month variability, the Antarctic Oscillation, during November and December towards its high phase. Therefore, this change consists of a shift in atmospheric mass from high‐latitudes poleward of 60°S to a mid‐latitude band centred on 45°S. This response provides a plausible explanation for the increase in westerly circulation at 60°S observed since the early 1980's. There is also a strong response in January–March but this may be unrealistic as the observed lower stratospheric temperature changes are poorly simulated in that season.