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Massive Ozone hole closed over the Arctic; But how?

We all are well aware of the ozone layer in the stratosphere region of the earth’s atmosphere. The ozone layer lies typically in the stratosphere at 10 -50 km altitude. Upon reaction with sunlight, it absorbs the UV rays from entering into the atmosphere and reaching the earth’s surface ”life-sustaining” zone. 

But, the Ozone layer has been suffering damages for the last few years. These damages are severe near the poles. This has primarily happened due to different pollutants that contain nitrogen, chlorine, or bromine. 

A huge ozone hole appeared over the Antarctica region in 1980 winters. Since then, it has been continually appearing every year. 

However, the Montreal Protocol was signed in 1987 to reduce and ban the consumption of CFC substances, which cause the depletion of the ozone layer. Thanks to the protocol, the ozone hole is recovering, and it is expected that it will get recovered entirely by 2060. 

Scientists and experts claim that had it not been signed by 196 countries, we might have been facing various severe consequences of ozone depletion, including complete crop damage globally. 

Recently, a single hole appeared out of nowhere in the Arctic zone in the northern atmosphere in the last spring, causing worry for climate scientists all over the world, posing a threat to society. 

Image: 01st April 2020 (Blue Hole in the middle)

Source: NASA

But as the summer is approaching, the ozone hole is closed now by itself. This is good news that has been well-received among the scientific community across the globe. 

How does Ozone Depletion happen?

Usually, an ozone hole happens due to CFC (Chlorofluorocarbon) chemicals being more reactive in the Polar vortex layer in the upper region of the stratosphere. At lower temperatures, CFC is inert compounds, but due to the UV radiation coming via sun rays, they decompose to more reactive gases. This causes the formation of heavy polar stratospheric clouds. Such clouds form at a low temperature below -78 °C. Only. 

CFC chemicals from industries and human activities react more efficiently at higher levels and lower temperatures in the vortex zone to cause faster depletion. 

Ozone is measured in Dobson Units (DU). If the max ozone is above 220 DU, there is no ozone depletion in the region. Usually, in an ozone hole, the value drops as low as 100 DU varied over kilometres.

What Caused An Ozone Hole In The Arctic? 

This is the third time in history that the ozone hole has appeared over the Arctic region. Previously, a similar phenomenon was observed during the winters of 1996 and 2011. But, the depletion during the previous two times was too small to be called as significant Ozone holes. 

The current Ozone hole over the Arctic has been significant, approximately three times the size of Greenland. Due to higher landmasses in the Northern hemisphere near to the North Pole and high altitude mountains which disturb the airflow, unlike in the South Pole region, the polar vortex winds are not as strong as those of South Pole region.   

But, this year, there has been an unconventional and sudden increase in the strength of long-lived polar vortex, causing the normal phenomenon of the Antarctic region to appear. 

It is predicted that the cold air got trapped in the polar vortex region, causing a higher drop in the temperature in the area, and high-altitude cloud formation over the South Pole. 

The blue circle represents the ozone hole, which appeared out of nowhere in session 2019-20, significant in the red lines. The circle represents the sudden drop in the ozone levels in the polar vortex region. 

Reason for the disappearance of Arctic hole  

Misconception: Ozone layer recovery in the North Pole is due to the Covid-19 lockdown and reduction in pollution levels. 

Truth: There is no slightest relation between the COVID-19 lockdowns and the recovery of the ozone hole. It was predicted that as it appeared out of nowhere and cause is unknown, yet it will disappear in the same fashion. 

Copernicus Atmospheric Monitoring Service (CAMS – European Commission) announced the closure of the Arctic Ozone hole on April 23, 2020, on their official Twitter handle. 

Image: April 26, 2020 – No Hole

Source: NASA

On average, the polar vortex area is 14 million square kilometres. During this year it has reached a new high of 19 million square kilometres. 

Due to the increase in temperature and sun moving closer to the northern hemisphere, the polar vertex area has reduced significantly, weakening the intensity of polar vortex winds. This allows the ozone-deprived winds, which were trapped inside the polar vortex, to mix with the ozone-rich wind coming from the lower region in the stratosphere.

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