‘Antarctic ozone hole — one of the largest, deepest — closes’

Context

The annually occurring ozone hole over the Antarctic had rapidly grown from mid-August and peaked at around 24 million square kilometres — one of the largest so far — in early October 2020. 

About

What is Ozone hole?

  • An ozone hole is the thinning of the ozone layer boosted in size by colder temperatures.
  • As the temperature high up in the stratosphere starts to rise, ozone depletion slows, the polar vortex weakens and breaks down.
  • By the end of December, ozone levels return to normal. This time around, however, the process took longer. 
  • The formation of ozone hole in the Antarctic has been an annual occurrence and has been recorded for the last 40 years.
  • Human-made chemicals migrate into the stratosphere and accumulate inside the polar vortex.
  • It begins to shrink in size as warmer temperatures dominate

The science behind ozone depletion

  • Ozone depletion occurs when chlorofluorocarbons (CFCs) and halons (gases formerly found in aerosol spray cans and refrigerants) are released into the atmosphere.
  • Ozone sits in the upper atmosphere and absorbs ultraviolet radiaton, another type of solar energy that's harmful to humans, animals and plants.
  • CFCs and halons cause chemical reactions that break down ozone molecules, reducing ozone's ultraviolet radiation-absorbing capacity.

What led to the expansion?

  • The expansion of the hole was driven by a strong, stable and cold polar vortex and very cold temperatures in the stratosphere.
  • The same meteorological factors also contributed to the record 2020 Arctic ozone hole, which has also closed.

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