Antarctic ozone hole now larger, thinner & may take longer to recover. Mesosphere has a role to play: Study

Subject: Environment

Section: International convention

Context:

The ozone hole over the Antarctic has not only grown larger but also thinner throughout most of the spring, according to a new study.

Ozone Hole:

The ozone hole is a region of exceptionally depleted ozone in the stratosphere over the Antarctic. It happens at the beginning of the Southern Hemisphere spring from August through October.

Study findings:

Despite making a recovery in area and depth since the 2000s, the Antarctic ozone hole has been massive in the last four years.
There is much less ozone in the centre of the ozone hole compared to 19 years ago.
This reduction is despite the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, which regulates the production and consumption of human-generated chemicals known to deplete the ozone.
- The Montreal Protocol on Ozone Depleting Substances quadrennial assessment report of 2022 confirmed the phase-out of nearly 99 per cent of banned ozone-depleting substances.
The ozone layer is on track to recover within four decades, according to the United Nations Environment Programme (UNEP).
But, from 2020-22, the ozone hole has been remarkably large. The extent and duration of the 2022 hole were remarkably similar to the large holes of 2020 and 2021.

Factors responsible:

The ozone layer over the Antarctic is intrinsically linked to the climate and dynamics of the Southern Hemisphere.
Other factors like springtime temperature and wind patterns, aerosols from wildfires and volcanic eruptions, as well as changes in the solar cycle ozone hole development could also be responsible for the thinning of the ozone layer.
Role of Polar Vortex:
- The Antarctic ozone hole sits within the polar vortex, which is a circular pattern of wind in the stratosphere that forms during winter and is maintained until late spring.
- Within this vortex, the Antarctic air from the mesosphere (the atmospheric layer above the stratosphere) falls into the stratosphere.
- This intrusion of air brings natural chemicals (nitrogen dioxide, for example) which impact ozone chemistry in October.

For details of Montreal Protocol: Optimize Ias