Ozone Layer and Ozone Hole Formation

Ozone Layer and Ozone Hole

• The ozone layer is a thin shield of gas in the Earth's stratosphere that absorbs the sun's ultraviolet rays.
• Nearly 90% of the Earth's ozone resides in the stratosphere.
• The ozone hole is a region of exceptionally depleted ozone in the stratosphere over the Antarctic and Arctic.
• The ozone hole denotes areas where ozone levels drop below 220 Dobson Units.

Ozone-Depleting Substances (ODSs)

• ODSs are human-made gases that reach the stratosphere and break apart ozone molecules through catalytic cycles.
• Major ODSs include chlorine, bromine, CFCs, carbon tetrachloride, and halons.

Status of Ozone Layer Recovery

• The ozone layer is on track to recover within 4 decades according to the United Nations Environment Programme.

Potential Drivers of Ozone Hole over Antarctica

• Changes in the Antarctic polar vortex, which leads to the formation of polar stratospheric clouds (PSCs).
• PSCs, also known as nacreous clouds or mother of pearl, form below -78°C and trap outgoing longwave radiation.
• PSCs can destroy ozone by providing a surface for the conversion of benign chlorine forms into reactive, ozone-destroying forms.
• PSCs can also remove nitrogen compounds that moderate the destructive impact of chlorine.

Other Factors Affecting Ozone Layer

• Changes in the solar cycle.
• Increased atmospheric abundance of Chlorofluorocarbons (CFCs).
• Volcanic eruptions, such as the Hunga Tonga-Hunga Ha'apai Volcano eruption in January 2022, may potentially impact the ozone layer.

Recent Developments

• From 2020 to 2022, the ozone hole has grown larger and thinner over Antarctica.
• The average thickness of the ozone layer over Earth is 300 Dobson Units.