South Pole Ozone Hole

The Antarctic Ozone Hole was discovered by the British Antarctic Survey from data obtained with a Dobson ozone spectrophotometer at Halley Bay station in the 1981-1983 period. They reported the October ozone loss in 1985. Satellite measurements then confirmed that the springtime ozone loss was a continent-wide feature. Research conducted during the National Ozone Expeditions to the U.S. McMurdo Station in 1986 and 1987, and NASA stratospheric aircraft flights into the Antarctic region from Chile in 1987 showed conclusively that the ozone loss was related to halogen (chlorine)-catalyzed chemical destruction which takes place following spring sunrise in the Antarctic polar region. The chlorine is derived from manmade chlorofluorocarbons (CFCs) which have migrated to the stratosphere and have been broken down by solar ultraviolet light, freeing chlorine atoms. The cold dark Antarctic winter, with its stratospheric ice clouds mixed with manmade chlorine, sets the stage for springtime chemical ozone destruction when the missing ingredient in the photochemical reactions, sunlight, appears.

Owing to Montreal Protocal regulations on the production of certain ozone-destroying, chlorinated compounds, which went into effect in January 1996, the atmospheric concentration of some of these man-made substances has begun to decline (CFC-11 vs. Time Plot and other CFC info). The recovery from the ozone hole is a slow process. In order to easily understand this process, NOAA has developed an index, the Ozone Depleting Gas Index (ODGI), which relates the current ozone measurements to the pre-ozone hole era (circa 1980). The index is calculated directly from observations at Earth's surface of the most abundant long-lived, chlorine and bromine containing gases regulated by the Montreal Protocol (15 individual chemicals).