NASA scientists report the ozone hole over Antarctica
has reached an annual maximum size of 10.9 million square miles
on October 2nd, 2015. The Antarctic ozone hole
is caused by manmade ozone-depleting chemicals and has been a feature of
the atmosphere for more than 3 decades. But measurements by NASA's AURA
satellite show this is one of the largest and latest forming maximum ozone holes
seen in recent years. Scientists say this is due to two
factors: elevated levels of ozone-depleting chlorine chemicals
in the atmosphere and a particularly strong polar vortex.
The polar vortex is a jet of cold air that circles Antarctica. It develops when the
sun sets over the South Pole for the entire winter. The cold temperatures
within the vortex create polar stratospheric clouds.
When these clouds come into contact with chlorine-containing chemicals, it can lead to
ozone depletion. The mix of the unusually strong vortex along
with the elevated levels of ozone-depleting chlorine caused this year's
ozone hole to be both unseasonable late and large.
Despite it's size, scientists expect the hole will disappear by 2070
as levels of ozone-depleting chemicals in the atmosphere decline.