A ‘record breaking’ ozone hole has emerged over the Arctic due to a ‘polar vortex’ caused by freezing temperatures in the atmosphere
- In contrast to the hole in the ozone layer in Antarctica, this will probably no longer occur next year
- Researchers say it was caused by freezing temperatures in the stratosphere
- Occasionally holes appear in the Arctic ozone layer, but this is larger than normal
A hole in the ozone layer above the Arctic has been created as a result of a “polar vortex” that causes unusual freezing temperatures in parts of the atmosphere.
The European Space Agency supported Copernicus Atmosphere Monitoring Service (CAMS) has been tracking the ‘unusual ozone hole’ since it was first formed.
It comes as record-breaking low ozone levels are recorded in the northernmost part of the Earth at about 11 miles above the surface – the lowest levels since 2011.
The hole above Antarctica in the Southern Hemisphere forms annually, but a hole above the Arctic is rare, according to ESA.
Occasionally holes appear above the Arctic, but this is the largest discovered so far and is due to a colder-than-normal ‘polar vortex’ in the stratosphere.
These images show the ozone above the Arctic in April and March, revealing lower than normal levels recorded by Copernicus satellites
ESA says atmospheric conditions are to blame for the new new one – caused by an extremely strong polar vortex mixed with sunlight after winter.
HOW IS THE HOLE FORMED IN THE OZONE?
Chlorine and bromine-containing substances accumulate in the polar vortex and remain chemically inactive in the dark.
Temperatures in the vortex can drop below -108 degrees Fahrenheit and ice crystals can form in polar stratospheric clouds, which play an important role in the chemical reactions.
As the sun rises above the pole, the sun’s energy releases chemically active chlorine and bromine atoms into the vortex that quickly destroy ozone molecules, creating the hole.
The new Arctic hole is a fraction of the size of Antarctica and is expected to close in mid-April.
“Our predictions suggest that temperatures have now begun to rise in the polar vortex,” said Vincent-Henri Peuch, director of the Copernicus Atmosphere Monitoring Service.
“This means that ozone depletion will slow down and eventually stop, as polar air will mix with ozone-rich air of lower latitudes,” he said.
“It is very important to continue to make international efforts to monitor annual ozone hole events and the ozone layer over time.”
Ozone concentrations above the Arctic are at a very low level – the last time it was so bad was in the spring of 2011 and this year seems to be even worse, ESA said.
“While we are used to ozone holes that develop over Antarctica each year during the Australian spring, the conditions necessary for such a strong ozone depletion are not normally found in the Northern Hemisphere,” the Copernicus team wrote.
The ozone hole over Antarctica is primarily caused by man-made chemicals, including chlorine and bromide, that migrate to the stratosphere.
This is a layer of the atmosphere about 6 to 30 miles above sea level.
These chemicals accumulate in the strong polar vortex that develops over Antarctica every winter, where they remain chemically inactive in the dark.
Temperatures in the vortex can drop below -108 degrees Fahrenheit and polar stratospheric clouds (PSCs) can form.
These clouds play an important role in chemical reactions involving the man-made chemicals that lead to degradation of the ozone layer as soon as sunlight returns to the area.
“This depletion has caused an ozone hole to develop annually for the past 35 years, but the Antarctic ozone hole in 2019 was actually one of the smallest we’ve seen in that time,” the team wrote.
The graph shows the Arctic’s ozone column over the past year, with decade comparisons to the black line showing low-record 2020 levels
The Arctic stratosphere is typically less isolated than its Antarctica counterpart, as the presence of nearby land masses and mountain ranges disrupts weather patterns more than in the Southern Hemisphere.
This explains why the polar vortex in the Northern Hemisphere is usually weaker than in the Southern Hemisphere, and the temperature does not drop so low.
In 2020, the Arctic vortex was exceptionally strong and long-lived, with temperatures in the Arctic stratosphere dropping low enough for several months in early 2020 to allow for PSC formation.
“The ozone depletion above the Arctic in 2020 was so severe that most of the ozone layer in the layer between 80 and 50 hPa (about 11 miles) is depleted,” the Copernicus team wrote in a blog post.
Satellite measurements are combined with computer models of the atmosphere in a similar way to weather forecasts to monitor the ozone layer.
Monitoring the ozone hole is important because the stratospheric ozone layer acts as a shield and protects all life on Earth from potentially harmful ultraviolet rays.
WHAT IS THE OZONE COAT?
Ozone is a molecule made up of three oxygen atoms that naturally occur in small amounts.
In the stratosphere, about seven to forty miles above the Earth’s surface, the ozone layer acts as a sunscreen, protecting the planet from potentially harmful ultraviolet rays that can cause skin cancer and cataracts, suppress the immune system and also damage plants.
It is produced in tropical latitudes and distributed all over the world.
Closer to the ground, ozone can also form from photochemical reactions between the sun and pollution from vehicle emissions and other sources, creating harmful smog.
Although warmer-than-average stratospheric weather conditions have reduced ozone depletion over the past two years, the current ozone hole area is still large compared to the 1980s when the ozone depletion was first discovered over Antarctica.
In the stratosphere, about seven to 25 miles above the Earth’s surface, the ozone layer acts as a sunscreen and protects the planet from potentially harmful ultraviolet rays
This is because the content of ozone-depleting substances such as chlorine and bromine remains high enough to cause significant ozone loss.
In the 1970s, it was recognized that chemicals called CFCs, used for example in refrigeration and aerosols, destroy ozone in the stratosphere.
Agreement was reached in 1987 on the Montreal Protocol, which led to the phasing out of CFCs and, recently, the first signs of recovery from the Antarctic ozone layer.
The upper stratosphere at lower latitudes also shows clear signs of recovery, proving that the Montreal Protocol is working well.
But the new study, published in Atmospheric Chemistry and Physics, found that it is unlikely to recover at latitudes between 60 ° N and 60 ° S (London is 51 ° N).
The cause is not certain, but the researchers think climate change may change the pattern of atmospheric circulation, causing more ozone to drain from the tropics.
Another possibility, they say, is that very short-lived substances (chlorine and bromine) could destroy ozone in the lower stratosphere.
VSLSs include chemicals used as solvents, paint strippers, and as degreasers.
One is even used in the production of an ozone-friendly replacement for CFCs.