The Coastal Post - August 2000

Mini Ozone Holes Outside the Ozone Hole

By Jim Scanlon

Looking through NASA's Web Site from July 14 through July 19th one can follow the development of what appears to be a another new development in ozone depletion in the southern hemisphere.

Large areas of the stratosphere are currently showing significant ozone depletion between 52 and 60 S. Right now, this is the depth of winter with just a few hours of weak sunlight outside permanent winter darkness Such early ozone depletion is unprecedented. Last year there were small patches of ozone depletion outside the area traditionally depleted within the Antarctic Circle. These persisted throughout the fall.

The current depletion goes from between 225 to 250 Dobson Units on the 14th to from 200 to 250 DUs on the 19th. It moves along Drakes Passage to the south east. (The convention for an "ozone hole" is below 220 Dobson Units). On July 11 there was also a mini ozone hole.

This is an ominous sign. Weak sunlight will return to Antarctica in August and this year's ozone hole will fully develop in September. They have been larger, more intense and have been lasting longer over the last ten years. They may now be starting earlier at lower mid latitudes, and/or may be on their way to becoming year round.

In 1999 the Antarctic Ozone only passed over the populated portion on southern South America once. Normally they pass over that area several times in the springtime. Summertime levels are now lower than normal after the Ozone Hole breaks up. Ultraviolet levels have been measured and found to be increasing in Southern South America and New Zealand. The results of these measurements have been published in peer reviewed journals in the US

Last year the US and the European Union completed large scale scientific field measurements confirming the existence of a rapid downward trend in ozone depletion over northern high latitudes over the last ten years. Ultraviolet radiation levels are expected to increase significantly over the next twenty years---not just at high levels---according to recent estimates in Geophysical Research Letters a highly regarded journal of the Earth Sciences.

There is a definite pattern emerging. First one end of the planet, then the other. Will the middle go next?

Stay tuned. This is your life.

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