The ozone hole over the Antarctic has widened and has reached its maximum size in 2020, according to the World Meteorological Organisation.
The ozone hole grew rapidly from mid August and peaked at around 24 million square kilometres in early October. The WMO said that the hole now covers 23 million square kilometres. It is above average for the last decade and spreading over most of the Antarctic continent, the WMO added.
WMO’s Global Atmosphere Watch programme in close association with Copernicus Atmospheric Monitoring Service, NASA, Environment and Climate Change Canada and others monitor the ozone layer.
Copernicus Atmosphere Monitoring Service Director Vincent-Henri Peuch said that there was much variability in the development of ozone hole each year. The Ozone depletion continued as sunlight returned to the South Pole, Peuch said and added they registered a rather large hole this year. This confirmed that the Montreal Protocol banning emissions of ozone depleting chemicals should continue. The director said.
The Montreal Protocol bans emissions of ozone depleting chemicals. The ozone layer slowly recovered after the ban on halocarbons. The WMO said that the large ozone hole was driven by a stable, strong and cold polar vortex. It said that ozone depletion was directly related to the temperature in the stratosphere. This is because polar stratospheric clouds, which have an important role in the chemical destruction of ozone, only form at temperatures below -78°C, the WMO said.
The polar stratospheric clouds contain ice crystals that turn non reactive compounds into reactive ones. These then rapidly destroy ozone as soon as light from the sun becomes available to start the chemical reactions. Polar stratospheric clouds and solar radiation was the main reason for the ozone hole, the WMO said.
The Weather organisation said that stratospheric ozone concentrations reduced to near-zero values over Antarctica around 20 to 25 km of altitude (50-100hPa), with the ozone layer depth coming just below 100 Dobson Units, about a third of its typical value outside of ozone hole events.
The ozone hole over the Antarctic increased in size during the spring season (August- October) in Southern Hemisphere. It reached a maximum between mid September and mid October.