A recent article in PNAS (Contrasts between Antarctic and Arctic ozone depletion) reminded me that we’re getting to the time of year when the ozone hole reaches its minimum.

Abstract: This work surveys the depth and character of ozone depletion in the Antarctic and Arctic using available long balloon-borne and ground-based records that cover multiple decades from ground-based sites. Such data reveal changes in the range of ozone values including the extremes observed as polar air passes over the stations. Antarctic ozone observations reveal widespread and massive local depletion in the heart of the ozone “hole” region near 18 km, frequently exceeding 90%. Although some ozone losses are apparent in the Arctic during particular years, the depth of the ozone losses in the Arctic are considerably smaller, and their occurrence is far less frequent. Many Antarctic total integrated column ozone observations in spring since approximately the 1980s show values considerably below those ever observed in earlier decades. For the Arctic, there is evidence of some spring season depletion of total ozone at particular stations, but the changes are much less pronounced compared with the range of past data. Thus, the observations demonstrate that the widespread and deep ozone depletion that characterizes the Antarctic ozone hole is a unique feature on the planet.

And some pictures in case you don’t like all those words.

DU means Dobson unit, and in general the higher the better. It’s clear that from 1980 until 1995 the minimum ozone amounts were decreasing. Since then, they have remained relatively constant. The same thing is seen in the area of the ozone hole. Those interested in the chemistry of stratospheric ozone should read this paper by Mario Molina.

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