He ozone hole of Antarctica this 2020 is one of the largest and deepest in recent years. Since mid-August the hole has grown considerably and analyzes show that it has reached its maximum size, of around 24 million square kilometers. It currently covers 23 million square kilometers, above the average for the last decade.
“There is a lot of variability in the extent to which ozone hole events unfold each year. The 2020 ozone hole looks like the one in 2018, which was also quite a large hole, and it is definitely at the top of the pack. of the last fifteen years or so, “he explains in a statement Vincent-Henri Peuch, Director of the Copernicus Atmosphere Monitoring Service at ECMWF.
“With sunlight returning to the South Pole in recent weeks, we saw continued ozone depletion in the area. After the unusually small and short-lived ozone hole in 2019, which was driven by special weather conditions, we are recording one. quite large again this year, confirming that we must continue to apply the Montreal Protocol that prohibits emissions of chemicals that deplete the ozone layer, “says Peuch.
Since the prohibition of these chemicals, halocarbonos, the ozone layer has slowly recovered and the trend is for the hole area to keep decreasing. The latest scientific assessment of ozone depletion by the World Meteorological Organization (WMO) and the United Nations Environment Program, in 2018, concluded that the ozone layer is on the way to recovery and possible return, towards 2060, to the values of 1980.
Powered by the polar vortex
A strong, stable and cold polar vortex is what has aggravated the ozone hole of 2020. It constantly kept the temperature of the ozone layer over Antarctica cool.
Ozone deficiency is directly related to the temperature in the stratosphere, the layer of the atmosphere that is between 10 and 50 km above sea level. This is because polar stratospheric clouds, very important for the chemical destruction of ozone, only form at temperatures below -78 ° C.
These polar stratospheric clouds contain ice crystals that make it possible to convert non-reactive compounds into reactive ones. These then can destroy ozone when sunlight is available to initiate chemical reactions. This dependence on clouds and sunlight is the main reason why the ozone hole is only seen in late winter and early spring.
In the southern hemisphere spring season, from August to October, the Antarctic ozone hole grows and reaches its maximum between mid-September and mid-October. As temperatures in the stratosphere rise in late spring, ozone depletion slows, the polar vortex weakens, and eventually decomposes. And by the end of December, ozone levels return to normal.