The Antarctic 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 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) and should reach maximum levels in the stratosphere near the turn of the century. It is anticipated that the recovery of the Antarctic Ozone Hole can then begin; however, because of the slow rate of healing, it is expected that the beginning of this recovery will not be conclusively detected for a decade or more into the next century, and that complete recovery of the Antarctic ozone layer will not occur until the year 2050 or later. The exact date of recovery will depend on the effectiveness of present and future regulations on the emission of CFCs and their replacements, which, while more ozone-friendly, will also require regulation during the next century. It will also depend on climate change in the intervening years. For example, a colder stratosphere would exacerbate ozone loss and prolong recovery.
GMD's history in the South Pole ozone program
Ozone monitoring by NOAA and its predecessors at the Amundsen-Scott South Pole Station goes back to 1961 when the first Dobson spectrophotometer measurements were made. These continue to the current date, providing a 37 year record. Dobson instruments, as well as satellite instruments such as TOMS, measure ozone by detecting the amount of solar ultraviolet radiation able to penetrate through the stratospheric ozone layer. Reduced ozone results in increased ultraviolet (the reason that the ozone layer is important). Since these instruments are inoperable at the South Pole during the dark winter, the NOAA Climate Monitoring and Diagnostics Laboratory began weekly ozone balloon soundings from the South Pole in 1986. During the austral spring (September to November), the sounding frequency is increased to about 3 per week in an ongoing study of the Antarctic Ozone Hole. These soundings have revealed total destruction of springtime ozone in the 14 to 19 km altitude region of the stratosphere. The lowest springtime total ozone measured during the 1986-1997 period at the South Pole was 89 Dobson Units (DU) on October 12, 1993. This may be compared with values of about 300 DU in October 1970. This page presents both historical and recent data from NOAAs South Pole ozone measurement program, which will be monitoring the recovery of the Antarctic Ozone Hole. Stay Tuned!
GMD Publications Concerning Antarctic Ozone Depletion
Hofmann, D. J., S. J. Oltmans, J. M. Harris, B. J. Johnson, and J. A. Lathrop, Ten years of ozonesonde measurements at the South Pole: Implications for recovery of springtime Antarctic ozone loss, J. Geophys. Res., in press, 1997.
Hofmann, D. J., The 1996 Antarctic ozone hole, Nature, 383, 129, 1996.
Hofmann, D. J., Recovery of the Antarctic ozone hole, Nature, 384, 222-223, 1996.
Vömel, H., S. J. Oltmans, D. J. Hofmann, T. Deshler, and J. M. Rosen, The evolution of the dehydration in the Antarctic stratospheric vortex, J. Geophys. Res., 100., 13919-13926, 1995.
Hofmann, D. J., S. J. Oltmans, B. J. Johnson, J. A. Lathrop, J. M. Harris, and H. Vömel, Recovery of ozone in the lower stratosphere at the south pole during the spring of 1994, Geophys. Res. Lett., 22, 2493-2496, 1995.
Vömel, H., S. J. Oltmans, D. J. Hofmann, J. M. Harris, Evidence for midwinter chemical ozone destruction over Antarctica, Geophys. Res. Lett., 22, 2381-2384, 1995.
Hofmann, D. J., S. J. Oltmans, J. A. Lathrop, J. M. Harris, and H. Vömel, Record low ozone at the south pole in the spring of 1993, Geophys. Res. Lett., 21, 421-424, 1994.
Oltmans, S. J., D. J. Hofmann, W. D. Komhyr, and J. A. Lathrop, Ozone Vertical Profile Changes over South Pole, Proc. 1992 Quadrennial Ozone Symposium, Charlottesville, VA, 13 June, 1992, 578-581, 1994.
Hofmann, D. J., and S. J. Oltmans, Anomalous Antarctic ozone during 1992: Evidence for Pinatubo volcanic aerosol effects, J. Geophys. Res., 98, 18,555-18,561, 1993.
Hofmann, D. J., S. J. Oltmans, J. M. Harris, S. Solomon, T. Deshler, and B. J. Johnson, Observation of New Ozone Depletion in Antarctica in 1991, Nature, 359, 283-287, 1992.
Hofmann, D. J., S. J. Oltmans, and T. Deshler, Simultaneous Balloonborne Measurements
of Stratospheric Water Vapor and Ozone in the Polar Regions, Geophys. Res.
Lett., 18, 1011-1014, 1991.