Whenever we post about the Earth's ozone layer, we don't have great news. Continuous cold temperatures and vibrant circumpolar winds, also called the polar vortex, led to a deeper and bigger Antarctic ozone hole that is expected to persist into November 2020, as reported by NASA in October 2020. The annual Antarctic ozone hole reached its apex at about 9.6 million square miles (24.8 million square kilometers), around three times the continental United States area, in September. Observations exposed the nearly complete removal of ozone in a 4-mile-high column of the stratosphere over the South Pole.
The Rising Ozone Concern
With the recurring sunlight into the South Pole in the last weeks, the continued ozone depletion has been observed over the area. After the substantial small and fleeting ozone hole in 2019, which resulted from special meteorological conditions, a large one is being registered again this year, which reveals that we need to make efforts to keep enforcing the Montreal Protocol banning emissions of ozone-depleting chemicals.
The ozone layer is critically important since it protects the Earth from hazardous ultraviolet radiation. In the late 20th century, the ozone layer was spoiled by the human release of ozone-depleting halocarbons. However, the size of the ozone hole is also affected every year by persistent weather conditions. This year, a strong polar vortex has frozen the air above Antarctica, and steadily cold air creates perfect ozone depletion conditions.
Where the Ozone Hole of 2020 Ranks?
The year 2020 will go down as witnessing the 12th biggest ozone hole by area in 40 years of satellite records, with the 14th lowest ozone amount in 33 years of balloon-borne instrumental measurements. Continuously declining levels of ozone-depleting chemicals controlled by the Montreal Protocol helped the hole prevent being as big as it would have been under similar weather conditions years ago.
Since the year 2,000, the Antarctic stratosphere Chlorine and Bromine levels have declined by almost 16% towards the natural level. We have a long way to go, but that development made a vast difference this year. The hole would have been about a million square miles bigger if there could still be as much chlorine in the stratosphere as it was in 2000.
The Condition of the polar vortex
The weather systems minimizing the ozone reduction in September, called "sudden stratospheric warming" events, were strangely robust this year. Around 12 miles above Earth's surface, temperatures during September were 29 degrees higher than average, as reported by NASA, which was recorded as the warmest in the 40-year historical record for September by a significant margin.
As can happen with stratospheric warming scenarios in the Northern Hemisphere, this weather system helped to deteriorate the Antarctic polar vortex, a ribbon of high-speed air surrounding the South Pole that usually converges the coldest air near or over the pole itself.