Antarctic Ozone Hole on September 29, 2006

Greens and yellows show areas with the highest ozone amounts, while blues and purples show where ozone amounts are lowest. A purple veil of extremely low levels of ozone stretches across most of Antarctica, which is roughly centered in the image. The 2006 ozone hole is about  10.8 million square miles, which is larger than the entire continent of North America (about 9.5 million square miles).

 

Scientists generally use Dobson Units to describe ozone concentrations. The Dobson Unit describes how much ozone there would be in a column of the atmosphere if all the molecules were squeezed into a single layer. The average amount of ozone in the atmosphere is roughly 300 Dobson Units, equivalent to a layer 0.12 inches thick.  Any place where the concentration drops below 220 Dobson Units is considered part of the ozone hole.  Average ozone concentrations in the ozone hole are around 100 Dobson Units.

Related Information:

• Every year when daylight returns in spring (autumn in the northern hemisphere) to Antarctica, chemical processes begin that break down the ozone in the stratosphere, creating a hole in the ozone layer.  The hole begins to develop in mid-August each year and peaks in late September or early October.  When summer approaches, the conditions become less favorable for the ozone-destroying reactions and the size of the hole becomes stable.

• Scientists use the Dobson Units to describe the thickness of the ozone layer.  Ozone does not exist in the stratosphere as an actual layer, but is dispersed throughout.  Dobson Units take a column of air and describe how much ozone is in it.

• The average amount of ozone in the atmosphere is roughly 300 Dobson Units.  Any place where the concentration drops below 220 Dobson Units is considered part of the ozone hole.  Average ozone concentrations in the ozone hole are around 100 Dobson Units.

• The 2006 ozone hole is about  10.8 million square miles, which is larger than the entire continent of North America (about 9.5 million square miles).

• The ozone hole was first recognized in 1985 and by 1987 the cause of it was banned by the Montreal Protocol.  The culprit were chlorofluorocarbons (CFCs) and which are still present in the atmosphere today, despite the ban 19 years ago. 

• Due to the ban, scientists expect the ozone layer of the Antarctic to eventually recover and the hole to disappear, but it is a long process.  Current predictions put recovery in about the 2060’s.