Last week, the European Union’s Copernicus Atmosphere Monitoring Service (CAMS) announced that a hole in the Arctic ozone layer, believed to be the biggest reported, has closed.
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.
The ozone hole’s closing was because of a phenomenon called the polar vortex, and not because of reduced pollution levels due to Covid-19 lockdowns around the world.
The hole in the North Pole’s ozone layer, which was first detected in February, had since reached a maximum extension of around 1 million sq km.
Ozone (chemically, a molecule of three oxygen atoms) is found mainly in the upper atmosphere, an area called the stratosphere, between 10 and 50 km from the earth’s surface. Though it is talked of as a layer, ozone is present in the atmosphere in rather low concentrations. Even at places where this layer is thickest, there are not more than a few molecules of ozone for every million air molecules.
But they perform a very important function. By absorbing the harmful ultraviolet radiations from the sun, the ozone molecules eliminate a big threat to life forms on earth. UV rays can cause skin cancer and other diseases and deformities in plants and animals.
Ozone 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. Before this year, the last sizable Arctic ozone hole was reported in 2011.
As per a European Space Agency report, cold temperatures (below -80°C), sunlight, wind fields and substances such as chlorofluorocarbons (CFCs) were responsible for the degradation of the Arctic ozone layer.
Although Arctic temperatures do not usually fall as low as in Antarctica, this year, powerful winds flowing around the North Pole trapped cold air within what is known as the polar vortex, a circling whirlpool of stratospheric winds.
Scientists believe that the closing of the hole is because of the same polar vortex and not because of the lower pollution levels during the coronavirus lockdown.