Has the Antarctic Vortex Split before 2002?

Abstract

In late September 2002, the Antarctic ozone hole was seen to split into two parts, resulting in large increases in ozone at some stations and the potential for significant modification of chlorofluorocarbon (CFC)-induced ozone loss. The phenomenon was dynamical (a split vortex), causing large increases in stratospheric temperature above stations normally within the vortex. Temperatures at Halley, Antarctica, at 30 hPa increased by over 60 K, and temperatures at South Pole at 100 hPa increased by over 25 K. It is important to know if this has happened before, since if it happens in the future, it would significantly alter the total hemispheric ozone loss due to chlorine from CFCs, particularly if it happens in August or September. Temperatures in winter and spring measured at Halley or the South Pole since 1957 and 1961, respectively, show no other comparable increases until the final warming in late spring, except for two dates in the 1980s at Halley when meteorological analyses show no vortex split. There are very few periods of measurements missing at both Halley and the South Pole, and analyses in those few periods show no vortex split. Measurements in August and September at sites normally near the edge of the vortex show very few suspicious dates, and analyses of those few suspicious dates again show no vortex split. It is concluded that the vortex has probably not split before the final warming since Antarctic records began in the late 1950s, and almost certainly not in August or September.