Probably the biggest
on record in the north.
It rivals the better-known
Antarctic ozone hole
that forms in the
southern hemisphere
each year.
Record-low ozone levels
across much of the
central Arctic, covering
an area about three times
the size of Greenland.
The hole doesn’t
threaten health,
and will probably
break apart in the
coming weeks.
Ozone normally forms
a protective blanket
in the stratosphere,
about 10 to 50 kiiometers
above the ground,
where it shields life
from solar ultraviolet
radiation.
But each year
in the Antarctic winter,
frigid temperatures
allow high-altitude clouds
to coalesce above
the South Pole.
Chemicals, including
chlorine and bromine,
which come from
refrigerants and other
industrial sources,
trigger reactions
on the surfaces
of those clouds
that chew away
at the ozone layer.
The Antarctic ozone hole
forms every year because
winter temperatures
in the area plummet,
allowing the high-altitude
clouds to form.
These conditions
are much rarer
in the Arctic,
which has
more variable
temperatures
and isn’t usually
primedfor ozone
depletion.
This year,
powerful westerly
winds flowed around
the North Pole and
trapped cold air within
a ‘polar vortex’.
There was more cold air
above the Arctic than in
any winter recorded
since 1979,
High-altitude clouds formed,
and the ozone-destroying
reactions began.
By late March 2020,
weather balloons measured
a 90% drop in ozone at
an altitude of 18 kilometers,
in the heart of the ozone layer.
Where the balloons would
normally measure around
3.5 parts per million of ozone,
they recorded only around
0.3 parts per million.
The Arctic also
experienced
ozone depletion
in 1997 and 2011,
but this year’s loss
may surpass
both of them.
The 1987 Montreal Protocol
( international treaty )
phased out the use of
ozone-depleting chemicals.
The Antarctic ozone hole
is on its way to recovery
— last year’s hole was
the smallest on record.
But will take decades
for the chemicals
to completely disappear
from the atmosphere.
The Arctic ozone hole
isn’t a health threat
because the Sun is just
starting to rise
above the horizon
in high latitudes.
With the Sun
slowly getting
higher,
atmospheric
temperatures
in the region
of the ozone hole
have already
started to increase.
Ozone could
soon start to recover
as the polar vortex
breaks apart
in coming weeks.