NASA’s Arctic Ozone Watch has reported the formation of a large hole in the ozone layer above the North Pole that may be the biggest on record in the north. During March, weather balloon reports revealed a drop of 90 percent in ozone at the core of the layer.
While the situation is still being assessed, this is likely the biggest reduction of ozone in the region ever. The two previous ones in 2011 and 1997 are considered mini-holes as their depletion was not considered severe enough to qualify as a fully-fledged hole like the one witnessed over the South Pole.
“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.
We have known since the late 1970s that several manufactured chemicals have depleted the layer of ozone that protects life on our planet from dangerous ultraviolet radiation from the Sun. A consequence of this depletion is the formation of the ozone holes over the polar regions.
The ozone hole over Antarctica forms every winter and its size has only begun to decline thanks to the adoption of the Montreal Protocol in 1987, which set deadlines for the phase-out of various ozone-depleting gasses, most famously chlorofluorocarbons (CFCs). The Antarctic hole shrank to its smallest size yet in 2019, showing the world that we can work together to achieve huge goals.
The extreme depletion is due to those industrial chemicals and very particular conditions that happen at the poles. When the cold temperature plummets, it allows for the formation of high-altitude clouds rich in ice crystals. The chemicals and CFCs in the atmosphere trigger a reaction on the surface of the clouds that eats away at the ozone layer. These are perfect grounds for accelerating the reaction and thus more efficiently getting rid of the ozone. Antarctica has much lower temperatures than the Arctic and for this reason, the hole has been a consistent feature in the south but not so much in the north.
However, this year, unusually low temperatures gripped the North Pole, creating the conditions for a huge new hole to open up there. It's unclear how the situation will evolve over the next couple of weeks as the Northern hemisphere becomes more illuminated by the Sun, so scientists are keeping an eye on it.
“Right now, we’re just eagerly watching what happens,” Ross Salawitch, an atmospheric scientist at the University of Maryland in College Park told Nature. “The game is not totally over.”