Discovery of a large hole in the ozone layer over the Arctic

• Mario Molina. "We have corrected the ozone hole, but we have not yet solved climate change"
• Obituary: Sherwood Rowland dies, Nobel Prize in Chemistry for the ozone hole

A large hole has been detected in the ozone layer over the Arctic. It is the largest observed in the northern hemisphere and has surprised scientists, accustomed to monitoring the hole in the Antarctic ozone layer whose discovery in the 1970s caused great concern in the international community. However, thanks to the measures taken, that hole at the south pole has been recovering.

Ozone is the component of the atmosphere that protects life on Earth from harmful ultraviolet radiation emitted by the Sun. This gas forms a kind of protective blanket in the stratosphere, at an altitude of between 10 and 50 kilometers.

In 1974, chemists Frank Sherwood Rowland and Mario Molina discovered that the use of sprays and aerosols such as those used in the manufacture of lacquers, deodorants and refrigeration systems were destroying ozone. To prevent this protective layer from continuing to weaken, the international community signed in 1987 the historic Montreal Agreement that prohibited chlorofluorocarbon gases (CFCs), responsible for the destruction of that shield.

More than 30 years have passed since that decision and the hole over Antarctica is getting smaller. Last year it reached its minimum extent although, as Paul Newman, an atmospheric scientist at NASA's Goddard Space Center, recalls, the chemical compounds will not completely disappear for decades. Frank Sherwood Rowland and Mario Molina, by the way, won the Nobel Prize in Chemistry for their finding.

Three times bigger than Greenland

Now, the new hole detected in the Arctic ozone layer covers an area three times the size of Greenland. According to their discoverers in the journal Nature , they do not believe that this hole poses a direct threat to people's health, although the destruction of that natural filter that is the ozone layer is associated with an increased risk of skin cancer. Scientists believe that it will likely dissipate in the coming weeks but consider it an extraordinary atmospheric phenomenon that will figure in historical records.

"From my point of view, this is the first time that we can talk about a true hole in the ozone layer in the Arctic, " said Martin Dameris, atmospheric scientist at the German Aerospace Center in Oberpfaffenhofen.

Every year the low temperatures of the Antarctic winter promote the accumulation in the upper layers of the atmosphere of chemical compounds such as chlorine or bromine that come from industrial activities. So due to the formation of these clouds with chemical compounds, a hole is formed annually in the ozone layer over Antarctica.

Those circumstances sometimes occur, but less frequently in the Arctic. However, the strong winds from the west that have hit the North Pole and the particularly cold air masses that have been in this region this year - the coldest since 1979 - have caused clouds to form at high altitudes that have begun to destroy the ozone blanket and cause the arctic hole that has now been observed.

Fall in arctic ozone

Ozone levels in the atmosphere are measured with weather balloons at different Arctic observation stations, such as the one on the Polarstern icebreaker . It is a scientific research vessel that is anchored in the ice for a year to do polar science. At the end of March, the balloons measured a 90% drop in ozone 18 kilometers above sea level. In a region of the sky where balloons typically measure 3.5 parts per million ozone, they recorded just 0.3 parts per million on that date. A record that according to Markus Rex, a researcher at the Alfred Wegener Institute in Potsdam (Germany), "beats any measurement of ozone taken in the past." In 1997 and 2011, significant ozone losses were recorded, which have been exceeded in 2020

According to Rex, there is a small chance that in the next few weeks, the hole in the ozone layer will shift to lower, more densely populated latitudes. If that happens, the population should use more sun protection to protect themselves from radiation, so they do not consider that there will be more problems. Scientists believe that as temperatures rise in ozone levels, they will also rise, but the hole will close, but for now they are still pending to see how it evolves in the coming days.

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