A hole in the Earth's ozone forms every year in the stratosphere over Antarctica, but this year it was slightly smaller than it has been in the past 10 years.
The ozone hole forms in August and September, the Antarctic spring. This year the average size of the hole was 8.1 million square miles, the hole has measured an average of 8.7 million square miles at its largest, a NASA news release reported.
At its largest this year, the hole measured 9.3 million square miles on Sept. 16, this is equivalent to the size of North America. At its largest ever, the hole was 11.5 million square miles on Sept. 9 2000.
The scientists would need to conduct observations longer than only one year of shrinking in order to determine the hole was healing itself.
"There was a lot of Antarctic ozone depletion in 2013, but because of above average temperatures in the Antarctic lower stratosphere, the ozone hole was a bit below average compared to ozone holes observed since 1990," Paul Newman, an atmospheric scientist and ozone expert at NASA's Goddard Space Flight Center in Greenbelt, Md, said.
The hole pops up in Antarctica when the Sun returns from its winter hiatus.
"Polar-circling winds keep cold air trapped above the continent, and sunlight-sparked reactions involving ice clouds and chlorine from manmade chemicals begin eating away at the ozone. Most years, the conditions for ozone depletion ease before early December when the seasonal hole closes," the news release reported.
Even though the researchers cannot confirm the hole is shrinking for good, there are less ozone-destroying chemicals in the atmosphere thanks to the 1987 Montreal Protocol. The Protocol is an international treaty that asks countries work to eliminate production of these chemicals. Since the protocol, the hole has stopped growing and researchers said it has stabilized.
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