Unusual polar vortex appears in Antarctica

Unusual warming and a strange polar vortex this year have changed the cycle of the ozone hole. Don't celebrate too soon, scientists warn.

Rare and unexpected warming events in Antarctica have affected the southern polar vortex , slowing the annual formation of the ozone hole above the icy continent.

Polar vortex appears in Antarctica this year (Photo: NASA Earth Observatory).

Ozone is a gas that forms a layer in the stratosphere, the middle layer of the atmosphere located between 20km and 50km above the ground. This ozone layer is the shield that protects life on Earth from the harmful effects of ultraviolet rays emitted by the Sun.

The ozone hole over Antarctica occurs every year during the southern hemisphere spring, which is from September to November. Data from 1979 to the present shows that the ozone layer over Antarctica usually begins to thin and break down in August, but this year the phenomenon appeared late, not starting until late August.

The cause is two warm spells that have altered the southern polar vortex. In July and August alone, temperatures in the stratosphere above Antarctica rose by 15 and 17 degrees Celsius. Such warm spells are rare over the continent, but they are becoming more frequent.

Scientists still don't know exactly what caused those two warming events, but they also noticed unusual weather conditions in the troposphere, the layer of the atmosphere just above the ground, over Antarctica in July with record-breaking temperatures.

"Sea surface temperatures also vary widely, but determining why these events occur is extremely difficult ," said atmospheric scientist Paul Newman at NASA's Goddard Space Flight Center.

The specific conditions for ozone holes to form are strong polar vortices, solar radiation, and ozone-depleting substances (ODS).

A strong polar vortex characterized by strong swirling winds and very low temperatures. These were the conditions that caused last year's ozone hole over Antarctica to be larger than the area of ​​North America.

Two images of air temperatures over Antarctica show how the vortex will behave in 2023 (left) and 2024 (right). (Image: NASA Earth Observatory)

However, instead of being round and strong, this year's polar vortex is weak and long , causing ozone depletion to slow down, even as the polar night ends and sunlight returns in August.

Ozone depletion typically begins in a belt around the edge of the vortex and spreads inward to form a hole that lasts through the southern spring. The hole disappears as temperatures rise during the southern hemisphere summer, usually in December.

The Antarctic ozone hole was first formed by humans pumping too many ODS chemicals into the atmosphere. Many countries have now signed international treaties banning these chemicals, including chlorofluorocarbons (CFCs), which were previously used in refrigerators and air conditioners.

There is evidence that the ozone hole is healing, but scientists say the fact that it is occurring slower than normal cannot immediately be considered a recovery of the ozone layer. The health of stratospheric ozone depends on a complex combination of chemical and meteorological factors.

If countries continue to comply with the ODS ban, the hole will theoretically close within 40 years. During that time, its size and activity will be influenced by meteorological fluctuations, anthropogenic and natural ODS sources, and the effects of climate change.