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Science

Ozone Hole Larger in 2008 than in 2007, not in 2006

10237_web Living in Australia brings with it a wonderful set of environmental circumstances to live with. Not only do we have two weather patterns – El Nino/La Nina and the Indian Ocean Dipole – that are combining to lengthen our drought, but we’re one of the countries that suffer from the ever fluctuating ozone hole in the Southern Hemisphere.

This year, the ozone hole extended to approximately 27 million square kilometers. This compared to 2007’s 25 million square kilometers and 2006’s 29 million square kilometers.

Want a size comparison? That’s about the size of the North American continent!

Without the ozone layer protecting Earth, the planet would be bombarded with harmful ultraviolet rays which would kill us all. As it is, a diminishing of the ozone layer increases the risk of skin cancer and cataracts, as well as harming marine life.

During the southern hemisphere winter, the atmosphere above the Antarctic continent is kept cut off from exchanges with mid-latitude air by prevailing winds known as the polar vortex – the area in which the main chemical ozone destruction occurs. The polar vortex is characterized by very low temperatures leading to the presence of so-called stratospheric clouds (PSCs).

As the polar spring arrives in September or October, the combination of returning sunlight and the presence of PSCs leads to a release of highly ozone-reactive chlorine radicals that break ozone down into individual oxygen molecules. A single molecule of chlorine has the potential to break down thousands of molecules of ozone.

“In 2007 a weaker meridional heat transport was responsible for colder temperatures in the stratosphere over the Antarctic, leading to an intensified formation of PSCs in the stratosphere,” Meyer-Arnek said. “Therefore, we saw a fast ozone hole formation in the beginning of September 2007.”

“In 2008 a stronger-than-usual meridional heat transport caused warmer temperatures in the Antarctic stratosphere than usual, reducing the formation of PSCs. Consequently, the conversion of chemically inactive halogens into ozone-destroying substances was reduced. As a result in the beginning of September 2008, the ozone hole area was slightly smaller than average,” he continued.

“Since the polar vortex remained undisturbed for a long period, the 2008 ozone hole became one of the largest ever observed.”

Some parts adapted from ESA Press Relase

Image Credit: KNMI/ESA




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