Atmospheric ozone at South Pole, Antarctica, in 1986

Vertical‐profile ozone distributions and variations, as well as the annual course of total ozone, are described for South Pole, Antarctica, from observations made throughout 1986 with electrochemical concentration cell (ECC) ozonesondes and a Dobson spectrophotometer. Ozone decrease in the stratosphere in September and October months was the highlight of the measurements. From mid‐August to October 7, total ozone decreased by about 40%, with the bulk of the decrease occurring between 12 and 21 km. Within this region the maximum rate of ozone decrease, with an exponential decay half‐life of 11 days, was observed between September 20 and October 15, when column ozone and ozone volume mixing ratio at 16±1 km decreased by 78% and column ozone between 12 and 21 km decreased by 50%. This time interval was characterized by virtual cessation of ozone flux into the stratosphere above South Pole that might have resulted either from movement of the polar vortex or from ozone advection from lower latitudes. In contrast, ECC ozonesonde data obtained in 1971 show ozone to have arrived at South Pole above 30 mbar in mid‐September and above 100 mbar in late September, 6 and 3 weeks, respectively, earlier than it did in 1986. Supporting evidence for a temporal change in the timing of ozone transport to Antarctica by atmospheric circulation comes from 1974–1986 surface ozone observations at South Pole, which show a negative surface ozone growth rate during summer months, a positive growth rate during winter months, and an increase in the amplitude of the annual cycle by a factor of 2. A correspondence is shown between El Niño‐related highs in sea surface temperature anomalies in the equatorial Pacific Ocean and lows in October–December total ozone averages that were observed at South Pole in the 1960s and 1970s. Such ozone lows occurred during years of increased circumpolar vortex stability, late stratospheric warming, and late ozone arrival in Antarctica. It is suggested that the 1982–1983 El Niño, which was of unprecedented intensity, similarly affected the transport of ozone to Antarctica, thereby contributing to the observed springtime ozone decrease. The transport of air parcels from 50°–60°S latitude into the tropopause and low stratosphere region of Antarctica, as suggested by 10‐day, isobaric back trajectory analyses, may also contribute to the Antarctica springtime ozone decrease and warrants further investigation.