Antarctic Ozone Hole in 2021 | UPSC
Antarctic ozone hole
WHY IN NEWS:
The Antarctic ozone hole — one of the deepest, largest gap in the ozone layer in the last 40 years — has closed.
SYLLABUS COVERED: GS 1 : Geography : Ozone Hole
WHAT IS THE OZONE HOLE AND WHY DOES IT MATTER?
- Ozone is composed of three oxygen atoms and is highly reactive with other chemicals.
- These harmful radiations 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 forms harmful smog in the lower atmosphere.
ANTARCTIC OZONE HOLE
- The Antarctic ozone hole forms during the Southern Hemisphere’s late winter as the returning Sun’s rays start ozone-depleting reactions.
- 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.
ANTARCTIC OZONE HOLE IN 2021
- The Antarctic ozone hole — one of the deepest, largest gap in the ozone layer in the last 40 years — has closed, according to World Meteorological Organization (WMO) January 6, 2021.
- The annually occurring ozone hole over the Antarctic had rapidly grown from mid-August and peaked at around 24 million square kilometres — one of the largest so far — in early October 2020.
SOURCES : NASA
EXPANSION AND CONTRACTION OF OZONE HOLE
- The expansion of the hole was driven by a strong, stable and cold polar vortex and very cold temperatures in the stratosphere.
- The same meteorological factors also contributed to the record 2020 Arctic ozone hole, which has also closed.
- During winters, the polar vortex at the North Pole expands, sending cold air southward.
- An ozone hole is the thinning of the ozone layer boosted in size by colder temperatures.
- As the temperatures high up in the stratosphere starts to rise, ozone depletion slows, the polar vortex weakens and breaks down.
- By the end of December, ozone levels return to normal.
SIGNIFICANT CHANGES IN 2020
- This time around, however, the process took longer.
- The formation of ozone hole in the Antarctic has been an annual occurrence and has been recorded for the last 40 years.
- Human-made chemicals migrate into the stratosphere and accumulate inside the polar vortex.
- It begins to shrink in size as warmer temperatures dominate.
- Copernicus Atmosphere Monitoring Service, had earlier stressed the need to keep enforcing the Montreal Protocol banning emissions of ozone depleting substances (OSD).
- WMO’s Global Atmosphere Watch programme works closely with Copernicus Atmospheric Monitoring Service.
- The Montreal Protocol on Substances that Deplete the Ozone Layer regulates production and consumption of nearly 100 chemicals referred (OSD).
- Since the ban on halocarbons, the ozone layer has slowly been recovering, according to WMO.
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- The amount of ozone between 13 to 21 kilometers (8 to 13 miles) in altitude, as measured over the South Pole, has been close to record lows at several points this year.
SOURCES: DownToEarth | Antarctic Ozone Hole in 2021 | UPSC