The eruption of the Hunga Tonga-Hunga Ha’apai volcano in January 2023 injected a large amount of water vapor into the stratosphere (Photo by Maxar via Getty Images)
The delayed effect of the eruption of Tonga’s underwater Hunga volcano last year has caused an ozone hole over Antarctica to open weeks earlier than usual.
The hole in the ozone layer – the portion of the stratosphere that protects our planet from the Sun’s ultraviolet rays – has been gradually healing over the past few decades thanks to the 1987 Montreal Protocol’s phase-out of ozone-destroying chemicals like chlorofluorocarbons (CFCs).
Still, this layer thins every September to form an ‘ozone hole’ above the South Pole.
In recent years, the hole has started to open in mid-to-late August, when spring begins in the southern hemisphere.
The increasing sunlight also drives the ozone-destroying activity of the remaining CFCs in the atmosphere. It then closes in November or early December.
This year, the ozone hole has started to open several weeks earlier at the beginning of August. By August 10, it had already grown to over 3 million square kilometres in size.
In comparison, it was still completely closed on the same date in 2021 and 2022.
Chris Lucas at the Australian Bureau of Meteorology attributed this early opening to the eruption of the Hunga Tonga-Hunga Ha’apai volcano.
The eruption, considered the most explosive of the 21st century, injected vast amounts of water vapour into the stratosphere.
Above Antarctica, this water vapour has since turned into icy clouds that provide a surface on which CFCs can react with ozone, thereby speeding up its depletion, said Mr Lucas.
Another reason for the earlier opening in the ozone layer is the level of Antarctic sea ice being at a record low (Picture: Unsplash)
He added that water vapour from the eruption didn’t affect the ozone hole in 2022 because it didn’t reach Antarctica in time for its usual opening.
The early opening of the ozone hole this year could see it become one of the biggest on record.
‘We’re predicting a bigger ozone hole this year, comparable to some of the biggest ones we’ve seen,’ said Mr Lucas.
If the ozone hole also closes later this year, it could harm animals and plants that emerge later in spring or before summer, as there will be less ozone in the atmosphere to protect them from the Sun’s ultraviolet rays.
In the past three years, the ozone hole has closed later than normal due to extreme weather events like Australia’s bushfires in 2019, which released extreme amounts of ozone-destroying smoke.
Another reason for the earlier opening in the ozone layer is the level of Antarctic sea ice being at a record low.
Sea ice reflects sunlight, which helps to keep the Earth cool. However, with less of it, more sunlight is absorbed by the ocean, which warms the atmosphere and further depletes the ozone layer.
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There could be a bigger ozone hole this year.