1971: Series of South Pole soundings before the ozone hole existed
1986: First year of continuous soundings at the South Pole
1993: Record low ozone hole related in part to the
eruption of Mt. Pinatubo, particles from which augmented polar stratospheric
clouds in the lower stratosphere. Ozone was nearly
2002: During this year, an unprecedented early warming of the stratosphere in the latter part of September displaced the ozone hole away from the South Pole. This warming elevated temperatures in the polar vortex so that when the vortex moved back over the South Pole ozone loss had stopped and minimum ozone amounts were the highest seen since 1988.
2003: Ozone hole levels are typical of the
Antarctic ozone hole. The next decade will likely show depletion levels
similar to 2003, after which declining
stratospheric chlorine, related to regulations on human-made CFC's
(CFC-11 vs. Time Plot and other CFC info) will
result in a slow recovery
Antarctic ozone depletion occurs primarily between the altitudes of 12 and 20 kilometers, a region where polar stratospheric clouds, necessary for the chlorine-catalyzed chemical ozone destruction process, readily form. This region is probed by high altitude balloon soundings carrying ozone sensing devices. In the figure, the amount of ozone, in Dobson Units (DU), observed by the balloonborne instruments in the 12 to 20 kilometer column at the South Pole is shown for several years during the July 1 to December 31 period. In recent years ozone in this region has been nearly totally destroyed, following sunrise in September.