Recently, the European Union’s Copernicus Atmosphere Monitoring Service (CAMS) announced that a significant hole in the Arctic ozone layer had closed. This closure, however, is not due to reduced pollution levels from Covid-19 lockdowns worldwide but is attributed to a phenomenon known as the polar vortex. CAMS is a crucial part of Europe’s Earth observation program and provides critical information about air pollution, health, solar energy, greenhouse gases, and climate forcing.
Understanding the Ozone Hole
The “ozone hole” refers to an area in the stratosphere where the concentration of ozone becomes exceptionally low during specific months. Ozone, a molecule composed of three oxygen atoms, is primarily found in the stratosphere, which lies 10 to 50 km from the earth’s surface. Ozone plays a vital role in absorbing harmful Ultraviolet (UV) radiation from the sun, thereby protecting life on earth. Exposure to UV rays can lead to skin cancer and various diseases and deformities in plants and animals.
The Formation of the Largest Ozone Hole over the Arctic
In 2020, the ozone depletion over the Arctic significantly increased compared to previous years. The last large Arctic ozone hole occurred in 2011. However, scientists first detected a new hole in the North Pole’s ozone layer in February 2020, which eventually extended to approximately one million square kilometers. Unusual atmospheric conditions, such as freezing temperatures in the stratosphere, contributed to this development. Other factors responsible for the Arctic ozone layer’s degradation include sunlight, wind fields, and substances such as chlorofluorocarbons (CFCs).
The Role of Polar Vortex
A polar vortex is a large area of low pressure and cold air surrounding both of Earth’s poles. It exists year-round, but typically weakens in the summer and strengthens in winter. The polar vortex’s role in this context relates to the unusually powerful winds circulating around the North Pole, trapping cold air within the vortex. This led to massive ozone depletion in the Arctic. However, the size of this ozone hole was relatively small compared to those typically observed in the southern hemisphere.
Ozone Recovery and the Closure of the Hole
According to scientists, the closure of the ozone hole is due to the same polar vortex phenomenon rather than reduced pollution levels during the Covid-19 lockdown. The Scientific Assessment of Ozone Depletion’s 2018 data shows that parts of the stratosphere’s ozone layer have recovered at a rate of 1-3% per decade since 2000. If this trend continues, the Northern Hemisphere and mid-latitude ozone could recover by around 2030, followed by the Southern Hemisphere around 2050, and polar regions by 2060.
Ozone Holes over Antarctica
When people refer to “ozone holes,” they often mean the depletions over Antarctica. These depletions occur each year from September to November because of unique meteorological and chemical conditions at the South Pole and can reach sizes of around 20 to 25 million square kilometers. During winter, a vortex of winds develops around the pole and isolates the polar stratosphere. As the temperature drops below -78°C, thin clouds of ice, nitric acid, and sulphuric acid mixtures form. Chemical reactions on the surfaces of these ice crystals release active forms of CFCs, leading to ozone depletion. When temperatures rise in the spring, the ice evaporates, and the ozone layer starts recovering.
The polar vortexes are generally weaker at the North Pole compared to the South due to the presence of nearby land and mountain ranges that significantly disrupt weather patterns, leading to smaller ozone holes in the northern hemisphere.
