SATURDAY, OCTOBER 31ST, 2020.-
Persistent cold temperatures and strong circumpolar winds, also known as the polar vortex, supported the formation of a large and deep Antarctic ozone hole that should persist into November, NOAA and NASA scientists reported.
The annual Antarctic ozone hole reached its peak size at about 9.6 million square miles (24.8 million square kilometers), roughly three times the area of the continental United States, on Sept. 20. Observations revealed the nearly complete elimination of ozone in a 4-mile-high column of the stratosphere over the South Pole.Where 2020’s Ozone Hole Ranks
The year 2020 will go down as having the 12th largest ozone hole by area in 40 years of satellite records, with the 14th lowest amount of ozone in 33 years of balloon-borne instrumental measurements, the scientists said. Ongoing declines in levels of ozone-depleting chemicals controlled by the Montreal Protocol prevented the hole from being as large as it would have been under the same weather conditions decades ago.
“From the year 2000 peak, Antarctic stratosphere chlorine and bromine levels have fallen about 16% towards the natural level,” said Paul A. Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We have a long way to go, but that improvement made a big difference this year. The hole would have been about a million square miles larger if there was still as much chlorine in the stratosphere as there was in 2000.”
What is the Ozone Hole and Why Does it Matter?
Ozone is composed of three oxygen atoms and is highly reactive with other chemicals. In the stratosphere, roughly 7 to 25 miles above Earth’s surface, the ozone layer acts like sunscreen, shielding the planet from ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and damage plants and sensitive plankton at the base of the global food chain. By contrast, ozone that forms closer to Earth’s surface through photochemical reactions between the sun and pollution from vehicle emissions and other sources, forms harmful smog in the lower atmosphere.
The Antarctic ozone hole forms during the Southern Hemisphere’s late winter as the returning Sun’s rays start ozone-depleting reactions. Cold winter temperatures persisting into the spring enable the ozone depletion process, which is why the “hole” forms over Antarctica. These reactions involve chemically active forms of chlorine and bromine derived from man-made compounds. The chemistry that leads to their formation involves chemical reactions that occur on the surfaces of cloud particles that form in cold stratospheric layers, leading ultimately to runaway reactions that destroy ozone molecules. In warmer temperatures fewer polar stratospheric clouds form and they don’t persist as long, limiting the ozone-depletion process.