Ozone hole findings surprise researcher

University of Otago doctoral student Hannah Kessenich has discovered new developments in the...
University of Otago doctoral student Hannah Kessenich has discovered new developments in the Antarctic ozone hole. PHOTO: LINDA ROBERTSON
A University of Otago PhD student has discovered the ozone hole has been increasing in size — posing major issues for future climate patterns.

Hannah Kessenich said not only was the ozone hole remarkably large, it had been among the biggest on record over the past three years, and in two of the five years before that it was also deeper.

"We made connections between this drop in ozone and changes in the air that is arriving into the polar vortex above Antarctica. This reveals the recent large ozone holes may not be caused just by CFCs," she said.

Her research, which has been published in the journal Nature Communications, analysed the monthly and daily ozone changes, at different altitudes and latitudes within the Antarctic ozone hole, from 2004 to 2022.

"I started to notice we had been having these large and consistent ozone holes in the past few years.

"It seemed like something that needed to be looked into further."

Ms Kessenich said she was surprised by the findings.

"When I began, I thought the ozone hole issue had been solved ... I worried it would be a foregone conclusion.

"It was surprising to see the issue was more complicated than I thought."

It was not only CFCs that led to increases in the size of the ozone hole, she said.

"The ozone hole occurs within the polar vortex ... Air from above descends into the polar vortex. It reaches the ozone hole around October.

"That air descending is potentially changing things."

The Montreal Protocol on Substances that Deplete the Ozone Layer, which has been in place since 1987, regulates the production and consumption of man-made chemicals known to deplete the ozone, but Ms Kessenich and her fellow researchers believe other complex factors are also contributing to the ozone hole.

"The Montreal Protocol has been very successful in addressing the issue of CFCs, but there are other factors we need to consider.

"Each year we have an ozone hole. Particularly when it’s a large one, it impacts southern hemisphere climate."

Ms Kessenich said her research group hoped to better understand how big an impact the ozone hole would have on future climate patterns.

"Right now, the expected recovery date for the ozone hole is about 2065 — that’s about 40 years away, and it’s happening at the same time as we’re seeing a changing climate.

"If we can better understand the drivers, then we can better predict how these mechanisms will affect the climate."

Ms Kessenich said she enjoyed studying all the different data sets.

"It is exciting because it is this complex landscape ... It’s important to continue to observe the ozone hole.

"We want to see more people interested in it."