The hole in the ozone layer over Antarctica has become larger – Les Échos

Published November 25, 2023 at 10:01 am.

26 million square kilometers, about three times the size of Brazil! The images from the Copernicus Sentinel-5P satellite are not encouraging. They show that the ozone hole has continued to grow over Antarctica this year.

“The 2023 ozone hole started early and has grown rapidly since mid-August,” says Antje Inness, senior scientist at the European Union (ESA) Copernicus Atmosphere Monitoring Service (CAMS). On September 16, it reached an area of ​​more than 26 million square kilometers, making it one of the largest ozone holes ever.”

Although these data are impressive, they do not call into question the restoration of our atmosphere. The stratospheric ozone layer, a natural protective barrier against the sun’s ultraviolet rays, located between 11 and 40 kilometers above the Earth’s surface, is still “on the road to recovery,” UN experts said last January.

The influence of an underwater volcanic eruption

So how can we explain the gap observed this year? The gigantic eruption of the underwater volcano Hunga-Tonga-Hunga-Ha’apai in the Pacific in January 2022 could be one of the causes. A recent study published in the journal PNAS shows that the eruption reduced ozone levels in the stratosphere.

This eruption “ejected a lot of water vapor into the stratosphere, which only reached the southern polar regions after the end of the ozone hole in 2022. The water vapor may have led to increased cloud formation in polar stratosphere regions where chlorofluorocarbons (CFCs) can react and accelerate the depletion of the ozone layer,” explains Antje Inness, who states that the exact effects of the eruption are “still the subject of ongoing research.” are.

“Unusual years”

Another study published this Tuesday in Nature Communications supports this hypothesis. It shows that “the reappearance of large, long-lived ozone holes over Antarctica” observed in recent years “would not be caused exclusively by CFCs,” which were identified in the mid-1970s as major culprits in ozone layer thinning, which led to their ban by the 1987 Montreal Protocol, although they were previously widely used in aerosols and refrigerators.

“It could be that something else is happening in the atmosphere – perhaps due to climate change – and is masking some of the recovery,” says Annika Seppala from the University of New Zealand’s physics department. of Otago, co-author of the book Study.

For Susan Solomon, a leading ozone specialist, we must take into account the fact that “the last few years have been quite unusual”. The chemist had previously shown that the hole in the ozone layer increased by 10% in 2020 under the impact of the huge bushfires in Australia.