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Context

• The Antarctic ozone hole grew to 10 million square miles in size at its largest on September 21, 2023.
• This data comes from an analysis of satellite and balloon-based observations by the United States National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA).

Details

About Ozone

• An oxygen molecule, which we breathe in every day, is typically composed of two oxygen atoms (O2 illustrating two oxygen atoms).
• However, ozone, another oxygen-containing molecule, includes three oxygen atoms (O3) instead.
• Oxygen (O2) accounts for 21% of the Earth's atmosphere, while ozone accounts for less than 0.001%.

Production

• The interaction of ultraviolet (UV) energy from the Sun with O2 molecules produces ozone molecules.
• After splitting an O2 molecule, the two liberated oxygen atoms join with additional O2 molecules to generate O3 molecules.

The ozone layers

• Because UV light is more powerful at higher altitudes where the air is thinner, most ozone is created in the stratosphere, giving rise to the ozone layer.
• The ozone layer has an altitude range of roughly 10 to 40 kilometers, with a maximum of about 25 kilometres.

Significance

• The ozone layer is critical for life on Earth because it absorbs the most harmful kind of UV radiation, UV-B radiation.
• The wavelength of this is between 280 and 315 nanometres.
• Because most skin cancers are caused by excessive UV radiation, anything that protects us from UV rays helps reduce cancer rates.
• When UV radiation is absorbed by ozone in the stratosphere, it heats the surrounding air, resulting in a stratospheric temperature inversion.

Measuring stratospheric ozone

• In Dobson units, ozone is defined as the total amount contained in a column of an overlying atmosphere.
• One Dobson unit represents the amount of ozone present if it formed a 0.01mm thick layer at typical sea-level pressure and temperature.

Where does Ozone come from?

• The majority of stratospheric ozone is created at tropical latitudes, but high-altitude winds carry it all over the world.
• It is constantly forming and decomposing, and its distribution across the world is neither uniform nor consistent.
• In the long run, the natural processes of formation and breakdown are balanced.
• Human activities have just recently caused ozone to be destroyed considerably quicker than it can be created.
• Ozone can also form at ground level, resulting in 'photochemical smog,' and because ozone is a poisonous gas, large quantities of ozone pose a health risk.
• This problem arises primarily in cities with heavy traffic during the summer when sunlight mixes with nitrogen oxide-containing car exhaust emissions.

About Ozone Hole

• An ozone hole is a region of the stratosphere over Antarctica in which the ozone layer is extremely depleted.
• The ozone hole is not a "hole" where no ozone exists, but rather a region of extremely depleted ozone in the stratosphere over Antarctica.
• The ozone hole is the region over Antarctica with total ozone of 220 Dobson Units or lower.

Reasons

• The ozone hole has developed as a result of human pollution of the atmosphere with chlorine and bromine-containing compounds.
• Chlorofluorocarbons (CFCs), halons, and carbon tetrachloride are the key compounds involved.
• The cause of ozone depletion was not particles in aerosol cans, but rather the propellants we utilize as gases to propel the solutions inside.
• These gaseous propellants contain chlorine, which depletes the ozone layer when released high in the stratosphere.

Steps were taken to reduce the Ozone Hole

• The Montreal Protocol was established in 1987 to protect the ozone layer by phasing out the production of these hazardous compounds.

Growing Ozone Hole in Antarctica

• The Antarctic ozone hole grew to be 10 million square miles in size at its largest on September 21, 2023.
• This data comes from an analysis of satellite and balloon-based observations by the United States National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA).
• The annual maximum size of the hole in 2023 was the 12th largest since records began back in 1979, the organizations noted.
• This year, during the critical period between September 7 and October 13, when ozone depletion is most pronounced, the ozone hole remained on average at 8.9 million square miles.
• This expansive area mirrors the vast geographical footprint of North America.
• In 2022, the average size of the ozone hole over Antarctica was 8.91 million square miles, and in 2021, it was 8.99 million square miles.

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 special 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 this year's massive ozone hole?

• Scientists believe this year's large ozone hole is the result of volcanic eruptions at Hunga Tongan Tonga in December 2022 and January 2023.
• Under normal circumstances,the gas emitted by a volcanic eruption remains below the stratosphere's level, however, this eruption emitted a large amount of water vapour.
• Through chemical processes, the water influenced the ozone layer and altered its heating rate.
• Other components that can deplete ozone, such as bromine and iodine, were also present in the water vapor.
• There is little evidence that humans are responsible for the ozone hole.

Is climate change causing ozone holes to reopen?

• Scientists believe that ozone depletion is not the primary cause of global warming.
• Experts believe there are indicators that rising global temperatures may be affecting ozone holes.
• Since the 1980s, mitigation of the ozone hole has been effective, but the 2020 ozone hole was unusually deep and long-lasting. The same was true in 2021.
• According to research, the main cause of the huge ozone hole in 2020 was wildfires in southeastern Australia that year.
• It is less apparent how ozone gaps affect the Earth's temperature.
• According to certain statistics, ozone holes actually contribute to cooling by reducing the greenhouse gas effect.

PRACTICE QUESTION Examine the causes and consequences of the expanding ozone hole over Antarctica. (150 words)