2005 Antarctic Ozone Hole Rivals Deepest

October 20, 2005

According to NOAA's balloon soundings at the South Pole Station, this year's springtime Antarctic ozone hole was as severe as any on record in the past 10 years. The total column of ozone went from 266 Dobson Units (DU) on August 7 to a minimum of 110 DU on September 28 with the balloon ozonesondes indicating zero ozone in the 15-20 kilometer altitude range. The 2005 minimum was similar to that of 2003, the lowest in the 1994-2004 period. By contrast, the 2002 ozone hole minimum was about 165 DU and resulted in discussions of a possible recovery of the ozone hole.

The geographical area of the ozone hole in 2005 was also near record proportions of about 27 million square kilometers on 19 September as indicated by satellite measurements at the WMO. By comparison, North America is 24.2 million square kilometers in area. An animation of the development of the 2005 ozone hole from the NOAA balloon soundings.

Background: Ozone depletion is caused by man-made chlorine and bromine compounds that undergo chemical reactions which result in ozone loss. The ozone hole develops in spring because the ozone loss process requires sunlight. NOAA measurements show that most ozone-destroying atmospheric chemicals peaked in 1995 and are now declining. Ozone data from satellites and NOAA's global surface network is consistent with this as global ozone depletion appears to have at least stopped getting worse in the past 6-8 years.

In Antarctica however, the ozone depletion phenomenon is much more severe being related to the presence of polar stratospheric clouds which act as a catalyst in the chemical processes. The ozone destruction is totally saturated in the 15-20 kilometer altitude range as observed in 2005. It will be some years before the chlorine and bromine compounds decrease adequately for this region to support ozone in the springtime.

Significance: The stratospheric ozone layer protects all life from harmful solar ultraviolet (UV) radiation. Monitoring ozone, UV and ozone-depleting chemicals, in order to detect the expected recovery of the ozone layer during the next 50 years (model estimated total recovery time of the ozone layer), is an important element of NOAA's Climate Program. Both NOAA and NASA are mandated by the Clean Air Act of 1990 to conduct this research and to report to Congress on the progress of ozone layer recovery.

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