Scientists have discovered a hole in the atmosphere that allows ozone-depleting compounds and other chemicals to bypass the atmosphere’s natural “washing machine” layer.

The lowest layer of Earth's atmosphere, known as the troposphere, is full of hydroxyl (OH) radicals which are known as the detergent of the atmosphere. This is because OH is highly reactive and can break down all sorts of pollutants, chemicals and natural substances emitted by living organisms including humans, plants, animals, fungi, and microbes. The substances become water soluble and are washed out of the troposphere during rainstorms.

But when scientists sent weather balloons through the troposphere over the tropical Western Pacific, they discovered a 9-mile-high hole in this protective OH shield that extends over several thousand square miles. Because it has only just been discovered, researchers are as yet unsure what causes this hole. But by letting certain chemicals escape into the upper levels of the atmosphere, the OH gap could contribute to depletion of the ozone layer over the polar regions and influence worldwide climate.

Even where it is intact, the OH shield isn't 100 percent impenetrable. There are some chemicals that don’t interact as much with OH, and a small portion of them don't get filtered out. They are able to make it through into the next atmospheric layer, the stratosphere. Some of these chemicals – including halons, methyl bromide, and chlorofluorocarbons (CFCs) – are known to break down ozone. And because they degrade very slowly, generally over the course of years, they have time to spread out over the entire globe, depleting ozone in the upper atmosphere and contributing to the polar ozone holes.

But the Western Pacific OH hole allows these chemicals to pass straight into the stratosphere without being filtered out at all. The discovery of the hole has already helped solve a discrepancy in our understanding of the atmosphere. Measurements of ozone depletion have long been known to be more than they should from our theoretical models. When researchers put an OH hole into their simulations, the theoretical ozone depletion much more closely matched real-world data.