2023-11-30 17:15:03
What is causing the Antarctic ozone hole to open and why is it larger than usual this time of year?
The ozone hole that forms each year over Antarctica takes an unusually long time to close, climatologists report.
Typically, the Antarctic ozone hole begins to form in mid-August and begins to gradually diminish in November.
But this year, the ozone hole area formed several days earlier than usual and has maintained an area of just over 15 million square kilometers since late October. The alarming news comes from the Copernicus Atmosphere Monitoring Service (CAMS) which is closely monitoring the hole.
Why is the ozone layer so vital?
The ozone layer on Earth protects us all from the sun’s harmful rays. The realization that some chemicals were diluting it led to major international intervention in 1987.
The Montreal Protocol – signed just seven years after the problem was discovered – is a rare example of a rapid global agreement and is the envy of today’s climate scientists.
The treaty gradually phased out man-made chemicals that deplete ozone molecules from the atmosphere, leading scientists to declare a “milestone” in replenishing the ozone layer the year last.
But for three years, the ozone layers have also been closing much later than usual. Climate change is one of the potential causes of this phenomenon, according to CAMS.
How has the Antarctic ozone hole changed in 2023?
The ozone hole widens in the austral spring, when ozone-depleting substances begin to accumulate in the stratosphere above the South Pole. Along with solar radiation, extremely cold temperatures and polar stratospheric clouds, this causes a drastic drop in the concentration of ozone in the stratosphere.
At the end of November, the stratospheric temperature increases and a change in wind tends to reduce the hole in the ozone layer.
The year 2023 followed a slightly different trajectory. An earlier increase in its size made the ozone hole the sixth largest in the satellite era (since 1979), with a total area of 25.12 million km2 as of mid-September.
Despite a usual decline until the beginning of October, it increased again towards the end of the month, notes CAMS. And it has maintained an area of about 12 million km2, and this is expected to continue until the first week of December.
Why do holes in the ozone layer take longer to close?
Although the ozone hole has waxed and waned in a peculiar way this year, this unusual longevity is part of a recent trend.
Since 2020, holes in the ozone layer resolve much later than before, around mid-to-late December.
CAMS says this is due to colder-than-average stratospheric temperatures and a strong polar vortex – strong winds circulating high in the atmosphere over Antarctica – which lasts until December.
The reason for this stronger polar vortex still remains a mystery. Several potential factors have been identified by CAMS, including water vapor released into the atmosphere from the Hunga-Tonga volcano in the South Pacific; changes in wind patterns in the southern hemisphere; and climate change.
Further research is needed, according to the monitoring service provided by the European Center for Medium-Range Weather Forecasts on behalf of the European Commission.
“Since signing the Montreal Protocol, we have significantly reduced emissions of ozone-depleting substances, giving the atmosphere the space to begin its recovery,” says Vincent-Henri Peuch, director of CAMS.
“This is a long process that involves many fluctuating factors that need to be monitored to fully understand how the ozone layer develops. The success of the Montreal Protocol demonstrates the effectiveness of actions aimed at protecting the global climate. »
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