Ozone Day 2023: Why the South Pole has set alarm bells ringing this year

Subject: Environment

Section: Climate Change

Context:

September 16 is celebrated as World Ozone day. The 2023 winter season for the Antarctica region ended with a record-low sea ice cover in August. This coincided with the early opening of the ozone hole above the continent.

Antarctica sea ice:

This July, when the continent is in its peak winter, the sea ice extent was around 13.5 million sq km, the lowest since 1978.
Some scientists have statistically called it a five-sigma event, which means that without changes in the climate, such low sea ice cover would have happened once in 7.5 million years.
Sea ice forms and exists in the polar regions due to an interaction between the ocean and the atmosphere, both of which are showing changes due to global warming.
Global warming has also altered the position of the polar vortex, a large area of low pressure and cold air surrounding both of the Earth’s poles, which now has an increased southerly flow over the Antarctic sea ice, pushing more sea ice to the south.

Meridional overturning circulation:

The meridional overturning circulation is an underwater phenomenon where warm ocean water from the Equator travels to the North Atlantic and cold water flows back towards the Equator and then to Antarctica.
It completes the loop by travelling back to the tropics and becomes warm again. This circulation brings warmth to various parts of the globe and also carries nutrients necessary to sustain ocean life.

Ozone hole over Antarctica:

The Antarctic ozone hole is an annual thinning of the stratosphere’s ozone layer, which has a high concentration of ozone molecules that absorb ultraviolet radiation from the sun.
Every year, the ozone hole over Antarctica begins to form at the end of September, peaking in October before closing in November or December. This year the hole opened in August itself, triggering a fear that the world could see a larger-than-average hole.
The ozone hole is usually smaller during El Nino years.
The early opening up of the Antarctic ozone could be due to the eruption of the Hunga-Tonga volcano in January 2022.
- The increased water vapour in the stratosphere can lead to an enhanced formation of polar stratospheric clouds on which chloroflorocarbons can react to speed up ozone depletion.
- The water vapour could contribute to cooling the Antarctic stratosphere, enhancing the formation of these polar stratospheric clouds and resulting in a stronger polar vortex.

Ozone hole recovery:
- The hole in the ozone layer has been gradually healing since the 1987 Montreal Protocol.
- In October 2022, the World Meteorological Organization predicted that the entire world, barring the poles, would recover from the ozone hole by 2040. The poles should bounce back by 2066.