Enormous Hole in the Ozone Appears Above Arctic in Rare Atmospheric Phenomenon

A huge hole in the ozone layer has appeared above the Arctic in a rare atmospheric phenomenon. Freezing temperatures have caused ozone levels to plummet, leaving a hole stretching from Hudson Bay to Russia's northern Arctic islands.

Images from NASA's Arctic Ozone Watch show how the hole has been growing since the start of March, with ozone levels dropping significantly. Blue and purple colors show where there is the least amount of ozone, while reds and yellows indicate where levels are higher.

Ozone is a gas made of three oxygen atoms. It is created naturally in the stratosphere, a layer of Earth's atmosphere that sits between seven and 25 miles above the surface of the planet. Ultraviolet rays from the sun break oxygen molecules into atoms. It is highly reactive and acts as a shield, protecting life on Earth from harmful UV rays.

It is a thin layer and is moved around by winds high in the atmosphere, and is depleted by both natural and manmade atmospheric gasses.

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A hole in the ozone layer appears above Antarctica each spring. In the 1980s, scientists noticed the layer in this region was thinning drastically. The cause was established to be the release into the atmosphere of manmade compounds called chlorofluorocarbons (CFCs). These chemicals were found to destroy ozone and, under the 1987 Montreal Protocol, are banned by 196 United Nations member states and the European Union. The hole still appears in Antarctica every year, but it is now healing.

Natural ozone depletion is driven by cold temperatures. Antarctica, which is surrounded by oceans, gets far colder than the Arctic. Freezing conditions in Antarctica means high-altitude clouds form and come together. These cloud formations lead to chemical reactions that cause ozone depletion.

The Arctic, however, is surrounded by mountainous continents, meaning temperatures normally do not plummet so low that these conditions are created. This year, however, temperatures dropped significantly, leading to the ozone depletion that was recorded.

John Pyle, an atmospheric scientist at the U.K.'s University of Cambridge, told Newsweek over email: "The low temperature condition (temperatures less than about 195k) in the Arctic are much less common. Interestingly, the Antarctic ozone hole last year was quite small; temperatures in the low stratosphere were higher than normal. In contrast, this Arctic winter/spring has seen a very strong lower stratospheric polar vortex and persistent, widespread very low temperatures. So, it's the meteorological conditions that set the condition—and this year's Arctic has been exceptional."

Markus Rex, an atmospheric scientist at the Alfred Wegener Institute in Potsdam, Germany, told Nature that there has been more cold air above the Arctic than any other winter for 40 years.

According to the magazine, measurements taken from weather balloons and observing stations in the region have shown a 90 percent drop in ozone levels. It is thought this could be one of the largest Arctic ozone holes on record.

"We have at least as much loss as in 2011, and there are some indications that it might be more than 2011," Gloria Manney, an atmospheric scientist at NorthWest Research Associates in Socorro, New Mexico, told Nature.

The hole is not a concern and it will likely start to repair over the coming weeks. Martyn Chipperfield, professor in atmospheric chemistry at the University of Leeds, U.K., told Newsweek: "We are entering spring. The atmosphere will warm up and the wind patterns will change. That will put a stop to the depletion and the depletion will repair itself."

He said it can be monitored with satellite observations and weather center forecasting models. "The 'hole,' or remnants of it, may move southwards but that is easily tracked," he said. "If needed alerts for high UV could be issued, but that is very unlikely to be necessary at this time of year."

The risk of large holes in the ozone appearing over the coming decades is also decreasing, as the bans introduced in the Montreal Protocol see levels of ozone-depleting chemicals drop even further, Chipperfield said.

"The scientific community has said for more than 20 years that, notwithstanding the Protocol, as we move towards recovery, very low temperatures in any particular year will lead to more ozone depletion in that year. So, this is exactly what we'd expect," Pyle added.