OBSERVATION AND POSSIBLE CAUSES OF NEW OZONE DEPLETION IN ANTARCTICA IN 1991

Local ozone reductions approaching 50% in magnitude were observed during the Antarctic spring in the 11-13 and 25-30 km altitude regions over South Pole and McMurdo Stations in 1991. These reductions, at altitudes where depletion has not been observed previously, resulted in a late September total ozone column 10-15% lower than previous years. The added depletion in the lower stratosphere was observed to coincide with penetration into the polar vortex of highly enhanced concentrations of aerosol particles from volcanic activity in 1991.