Large Ozone Hole detected over Antarctica

What’s in today’s article?

• Why in news?
• What is Ozone?
• Where is ozone produced?
• What is Ozone Hole?
• News Summary: Large ozone hole detected over Antarctica
• Ozone holes grow and shrink every year
• What caused the giant ozone hole this year?
• Is climate change reopening ozone holes?

Why in news?

• Satellite measurements over Antarctica have detected a giant hole in the ozone layer.
  • The European Space Agency Copernicus Sentinel-5P satellite made the recordings as part of the EU’s environmental monitoring program.
• The hole, which scientists call an “ozone-depleted area” was 26 million square kilometers in size, roughly three times the size of Brazil.

What is Ozone?

• About
  • Typically, an oxygen molecule which we breathe in every day is made of two oxygen atoms (O2 showing two oxygen atoms). 
  • However, ozone, which is also a molecule containing oxygen, contains three oxygen atoms instead (O3).
  • Oxygen (O2) makes up 21% of the Earth’s atmosphere, and ozone makes up less than 0.001%.
• Production
  • Ozone molecules are created by the interaction of ultra-violet (UV) radiation from the Sun with O2 molecules.
  • An O2 molecule is split, the two free oxygen atoms bond with other O2 molecules to form O3 molecules.
• Ozone layer
  • Because UV radiation is more intense at higher altitudes where the air is thinner, it is in the stratosphere where most of the ozone is produced, giving rise to what is called the ‘ozone layer’.
  • The ozone layer extends between about 10 and 40km altitude, peaking at about 25km.
• Significance
  • The ozone layer is very important for life on Earth because it has the property of absorbing the most damaging form of UV radiation, UV-B radiation.
    • This has a wavelength of between 280 and 315 nanometres.
• Most skin cancers are caused by exposure to high amounts of UV radiation, so anything that shields us from UV rays helps reduce cancer rates.
• As UV radiation is absorbed by ozone in the stratosphere, it heats up the surrounding air to produce the stratospheric temperature inversion.
• Measuring stratospheric ozone
  • Ozone is measured as the total amount that is present in a column of overlying atmosphere in Dobson units.
  • One Dobson unit can be thought of as the amount of ozone that would be present if it formed a layer 0.01mm thick at average sea-level pressure and temperature.

Where is Ozone produced?

• Most of the stratospheric ozone is produced at tropical latitudes, but high-altitude winds spread it over the whole planet.
• It is continually forming and breaking down, and its distribution over the planet is not uniform or constant.
• Over the long run the natural processes of formation and breakdown are balanced.
  • It is only in recent decades that human activities have led to ozone being destroyed much faster than it can be formed.
• Ozone can also be formed at ground level to produce ‘photochemical smog’; and, as ozone is a toxic gas, there is a health hazard when ozone reaches high levels.
  • This problem occurs primarily in the summer in cities with a high amount of traffic when sunlight interacts with car exhaust fumes containing nitrogen oxides.

What is Ozone Hole?

• About
  • An ozone hole is a region of the stratosphere over Antarctica where the ozone layer is exceptionally depleted.
    • The ozone hole is not technically a “hole” where no ozone is present, but is actually a region of exceptionally depleted ozone in the stratosphere over the Antarctic.
• The ozone hole is the region over Antarctica with total ozone of 220 Dobson Units or lower.
• Reasons
  • The ozone hole has developed because people have polluted the atmosphere with chemicals containing chlorine and bromine. 
  • The primary chemicals involved are chlorofluorocarbons (CFCs for short), halons, and carbon tetrachloride.
  • The culprit behind ozone depletion was not aerosols in aerosol cans, but the propellants we use as gases to propel the solutions inside. 
  • These gaseous propellants contain chlorine, which is released high in the stratosphere and depletes the ozone.
• Steps taken
  • In 1987, The Montreal Protocol was created to protect the ozone layer by phasing out the production of these harmful substances.

Large Ozone Hole detected over Antarctica

Ozone holes grow and shrink every year:

• The size of the ozone hole over Antarctica fluctuates each year, opening each year in August and closing again in November or December.
• As per experts, the ozone hole opens up because of the rotation of the Earth causing specials winds over the closed landmass of Antarctica. 
• The winds create a mini climate, creating a shield over Antarctica preventing it from mixing with surrounding air. When the winds die down, the hole closes.

What caused the giant ozone hole this year?

• Scientists believe this year’s big ozone hole could be due to the volcanic eruptions atHunga Tongain Tonga during December 2022 and January 2023.
• Under normal conditions, gas released from a volcanic eruption stays below the level of the stratosphere, but this eruption sent a lot of water vapor into the stratosphere.
• The water had an impact on the ozone layer through chemical reactions and changed its heating rate. 
• The water vapor also contained other elements that can deplete ozone like bromine and iodine.
  • There is not much evidence the ozone hole is due to humans.

Is climate change reopening ozone holes?

• Scientists agree that ozone depletion is not a principal cause of global climate change.
• However, experts believe there are signs that rising global temperatures could be having an impact on ozone holes.
  • Mitigation of the ozone hole was working well since the 1980s, but the 2020 ozone hole was very deep and long lasting. The same was true for 2021. 
  • Research showed that the main reason for the large ozone hole in 2020 was due to the wildfires in southeastern Australia that year.
• It is less clear what impact ozone holes have on the Earth’s climate.
• Some data shows that ozone holes actually contribute to cooling effects, as they reduce the greenhouse gas effect.

Q1) What is Hunga Tongain Tonga?

Hunga Tonga-Hunga Ha'apai is a submarine volcano in the South Pacific Ocean. It's located 65 km northwest of Tongatapu, the main island of Tonga. The volcano is part of the Tonga–Kermadec Islands volcanic arc, which extends from New Zealand to Fiji.

Q2) What is climate change?

Climate change is a long-term change in average weather conditions, such as temperature, precipitation, and wind patterns. Climate change can occur over years, decades, centuries, or longer.

Climate change is different from natural weather variability because it's a longer-term trend. Climate change can cause weather patterns to be less predictable.

Source: Large ozone hole detected over Antarctica: Is it a matter of concern? | NASA | Discovering Antarctica