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Ozone Hole Detected over Antarctica

Context:

According to a recent study, published in Nature Communications, stated that the Antarctic Ozone Hole has been massive in the last four years.

Relevance:

GS I- Geography

Dimensions of the Article:

  1. What is Ozone Layer and what are Ozone Holes?
  2. Ozone creation and destruction
  3. Ozone Holes Grow and Shrink Every Year
  4. Causes of the Giant Ozone Hole in 2023
  5. Is Climate Change Reopening Ozone Holes?

What is Ozone Layer and what are Ozone Holes?

  • Ozone layer, also called ozonosphere, is a region of the upper atmosphere, between roughly 15 and 35 km (9 and 22 miles) above Earth’s surface which contains relatively high concentrations of ozone molecules (O3).
  • Approximately 90 percent of the atmosphere’s ozone occurs in the stratosphere, the region extending from 10–18 km (6–11 miles) to approximately 50 km (about 30 miles) above Earth’s surface.
  • The ozone layer effectively blocks almost all solar radiation of wavelengths less than 290 nanometres from reaching Earth’s surface, including certain types of ultraviolet (UV) and other forms of radiation that could injure or kill most living things.
What are Ozone Holes?
  • The ‘ozone hole’ is not really a hole — it refers to a region in the stratosphere where the concentration of ozone becomes extremely low in certain months.
  • The ‘ozone holes’ most commonly talked about are 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.
  • Such holes are also spotted over the North Pole, but owing to warmer temperatures than the South Pole, the depletions here are much smaller in size.

Ozone creation and destruction

  • The production of ozone in the stratosphere results primarily from the breaking of the chemical bonds within oxygen molecules (O2) by high-energy solar photons. This process, called photodissociation, results in the release of single oxygen atoms, which later join with intact oxygen molecules to form ozone.
  • The amount of ozone in the stratosphere varies naturally throughout the year as a result of chemical processes that create and destroy ozone molecules and as a result of winds and other transport processes that move ozone molecules around the planet.
  • Over the course of several decades, however, human activities substantially altered the ozone layer.
  • Ozone depletion, the global decrease in stratospheric ozone observed since the 1970s, is most pronounced in polar regions, and it is well correlated with the increase of chlorine and bromine in the stratosphere.
  • Those chemicals, once freed by UV radiation from the chlorofluorocarbons (CFCs) and other halocarbons (carbon-halogen compounds) that contain them, destroy ozone by stripping away single oxygen atoms from ozone molecules.
  • As the amount of stratospheric ozone declines, more UV radiation reaches Earth’s surface, and scientists worry that such increases could have significant effects on ecosystems and human health.

Ozone Holes Grow and Shrink Every Year:

  • The size of the ozone hole over Antarctica changes annually, typically opening in August and closing in November or December.
  • It’s caused by special winds over Antarctica due to the Earth’s rotation, creating a shield over the continent that prevents mixing with surrounding air. When the winds calm down, the hole closes.

Causes of the Giant Ozone Hole in 2023:

  • The large ozone hole this year may be linked to volcanic eruptions at Hunga Tonga in Tonga during December 2022 and January 2023.
  • Normally, gas from volcanic eruptions stays below the stratosphere, but this one released a lot of water vapor into the stratosphere.
  • The water vapor, through chemical reactions, impacted the ozone layer and altered its heating rate. It also contained elements like bromine and iodine that can deplete ozone.
  • There isn’t strong evidence to attribute this ozone hole to human activities.

Is Climate Change Reopening Ozone Holes?

  • Ozone depletion isn’t a primary driver of global climate change, but rising temperatures could have an influence on ozone holes.
  • Mitigation efforts for ozone holes were effective since the 1980s, but the 2020 and 2021 ozone holes were unusually deep and long-lasting, with wildfires in southeastern Australia contributing to the 2020 hole.
  • The impact of ozone holes on Earth’s climate is not entirely clear; some data suggests they might have cooling effects by reducing the greenhouse gas effect.

-Source: Down To Earth


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