Ozone Layer Hole Over Arctic Closed

• 28 Apr 2020

Why in News

Recently, the European Union’s Copernicus Atmosphere Monitoring Service (CAMS) announced that a hole in the Arctic ozone layer, believed to be the biggest reported over the Arctic, has closed.

• The ozone hole’s closing was because of a phenomenon called the polar vortex, and not because of reduced pollution levels due to Covid-19 lockdowns around the world.
• CAMS is one of six services that form Copernicus, the European Union's Earth observation programme.
  
  • It provides consistent and quality-controlled information related to air pollution and health, solar energy, greenhouse gases and climate forcing, everywhere in the world.

Key Points

• Ozone Hole:
  
  • It refers to a region in the stratosphere where the concentration of ozone becomes extremely low in certain months.
  • Ozone (chemically, a molecule of three oxygen atoms) is found mainly in the upper atmosphere, an area called the stratosphere, between 10 and 50 km from the earth’s surface.
  • Ozone absorbs the harmful UltraViolet (UV) radiations from the sun eliminating a big threat to life forms on earth. UV rays can cause skin cancer and other diseases and deformities in plants and animals.
• Reasons Behind the Biggest Ozone Hole over the Arctic:
  • In 2020, the ozone depletion over the Arctic was much larger. Before this year, the last sizable Arctic ozone hole was reported in 2011. 
  • The hole in the North Pole's ozone layer was first detected in February, 2020 had since reached a maximum extension of around 1 million sq km. 
  • Scientists believe that unusual atmospheric conditions, including freezing temperatures in the stratosphere, were responsible.
  • As per a European Space Agency report, cold temperatures (below -80°C), sunlight, wind fields and substances such as chlorofluorocarbons (CFCs) were responsible for the degradation of the Arctic ozone layer.
  • Although Arctic temperatures do not usually fall as low as in Antarctica, this year, powerful winds flowing around the North Pole trapped cold air within what is known as the polar vortex— a circling whirlpool of stratospheric winds.
  • However, the size of hole was still small compared to that usually observed in the southern hemisphere.
• Closing of the hole and Ozone recovery:
  
  • Scientists believe that the closing of the hole is because of the same polar vortex and not because of the lower pollution levels during the Covid-19 lockdown.
  • As per the Scientific Assessment of Ozone Depletion data of 2018:
    
    • The ozone layer in parts of the stratosphere has recovered at a rate of 1-3% per decade since 2000.
    • At these projected rates, the Northern Hemisphere and mid-latitude ozone is predicted to recover by around 2030, followed by the Southern Hemisphere around 2050, and polar regions by 2060.

Ozone holes over Antarctica

• The ozone holes most commonly refer to the depletions over Antarctica, forming each year in the months of September, October and November, due to a set of special meteorological and chemical conditions that arise at the South Pole, and can reach sizes of around 20 to 25 million sq km.
• Formation:
  
  • Polar vortex leads to the most depletion of stratospheric ozone. As winter arrives, a vortex of winds develops around the pole and isolates the polar stratosphere.
  • When temperatures drop below -78°C (-109°F), thin clouds form ice, nitric acid, and sulphuric acid mixtures.
  • Chemical reactions on the surfaces of ice crystals in the clouds release active forms of CFCs and ozone depletion begins.
  • In spring, temperatures begin to rise, the ice evaporates, and the ozone layer starts to recover.
• Such holes are much smaller in size in the North Pole due to the warmer temperatures than the South Pole.

Polar vortex

• A polar vortex is a large area of low pressure and cold air that surrounds both of Earth's poles.
• Polar vortexes always exist, but they typically weaken during the summer and strengthen in the winter.
• The polar vortex in the Arctic is typically weaker due to the presence of nearby land as well as mountain ranges that disturb the weather more so than its counterpart to the south.

Source: IE