The Ozone Hole 2017

Nov. 2,
2017

Warm Air Helped Make 2017 Ozone Hole Smallest Since 1988

Measurements from satellites this year showed the hole in Earth’s ozone
layer that forms over Antarctica each September was the smallest observed
since 1988, scientists from NASA and NOAA announced today.

According to NASA, the ozone hole reached its peak extent on Sept. 11,
covering an area about two and a half times the size of the United States
– 7.6 million square miles in extent – and then declined through the
remainder of September and into October. NOAA ground- and balloon-based
measurements also showed the least amount of ozone depletion above the
continent during the peak of the ozone depletion cycle since 1988. NOAA
and NASA collaborate to monitor the growth and recovery of the ozone hole
every year.

“The Antarctic ozone hole was exceptionally weak this year,” said Paul A.
Newman, chief scientist for Earth Sciences at NASA’s Goddard Space Flight
Center in Greenbelt, Maryland. “This is what we would expect to see given
the weather conditions in the Antarctic stratosphere.”

The smaller ozone hole in 2017 was strongly influenced by an unstable and
warmer Antarctic vortex – the stratospheric low pressure system that
rotates clockwise in the atmosphere above Antarctica. This helped minimize
polar stratospheric cloud formation in the lower stratosphere. The
formation and persistence of these clouds are important first steps
leading to the chlorine- and bromine-catalyzed reactions that destroy
ozone, scientists said. These Antarctic conditions resemble those found in
the Arctic, where ozone depletion is much less severe.

n 2016, warmer stratospheric temperatures also constrained the growth of
the ozone hole. Last year, the ozone hole reached a maximum 8.9 million
square miles, 2 million square miles less than in 2015. The average area
of these daily ozone hole maximums observed since 1991 has been roughly 10
million square miles.  

Although warmer-than-average stratospheric weather conditions have reduced
ozone depletion during the past two years, the current ozone hole area is
still large because levels of ozone-depleting substances like chlorine and
bromine remain high enough to produce significant ozone loss.

Scientists said the smaller ozone hole extent in 2016 and 2017 is due to
natural variability and not a signal of rapid healing.

First detected in 1985, the Antarctic ozone hole forms during the Southern
Hemisphere’s late winter as the returning sun’s rays catalyze reactions
involving man-made, chemically active forms of chlorine and bromine. These
reactions destroy ozone molecules.

Thirty years ago, the international community signed the Montreal Protocol
on Substances that Deplete the Ozone Layer and began regulating
ozone-depleting compounds. The ozone hole over Antarctica is expected to
gradually become less severe as chlorofluorocarbons—chlorine-containing
synthetic compounds once frequently used as refrigerants – continue to
decline. Scientists expect the Antarctic ozone hole to recover back to
1980 levels around 2070.

Ozone is a molecule comprised of three
oxygen atoms that occurs naturally in small amounts. In the stratosphere,
roughly 7 to 25 miles above Earth’s surface,
the ozone layer acts like sunscreen, shielding the planet from
potentially harmful ultraviolet radiation that can cause skin cancer and
cataracts, suppress immune systems and also damage plants. Closer to the
ground, ozone can also be created by photochemical reactions between the
sun and pollution from vehicle emissions and other sources, forming
harmful smog.

Although warmer-than-average stratospheric weather conditions have reduced
ozone depletion during the past two years, the current ozone hole area is
still large compared to the 1980s, when the depletion of the ozone layer
above Antarctica was first detected. This is because levels of
ozone-depleting substances like chlorine and bromine remain high enough to
produce significant ozone loss.

NASA and NOAA
monitor the ozone hole via three complementary instrumental methods.
Satellites, like NASA’s
Aura satellite
and NASA-NOAA

Suomi National
Polar-orbiting Partnership satellite
measure ozone from space. The Aura satellite’s

Microwave Limb
Sounder
 also measures certain chlorine-containing gases, providing estimates of
total chlorine levels.

NOAA scientists
monitor the thickness of the ozone layer and its vertical distribution
above the South Pole station by regularly releasing weather balloons
carrying ozone-measuring “sondes”
up to 21 miles in altitude, and with a ground-based instrument called a

Dobson
spectrophotometer.


The Dobson spectrophotometer measures the total amount of ozone in a
column extending from Earth’s surface to the edge of space in Dobson
Units, defined as the number of ozone molecules that would be required to
create a layer of pure ozone 0.01 millimeters thick at a temperature of 32
degrees Fahrenheit at an atmospheric pressure equivalent to Earth’s
surface.

This year, the ozone concentration reached a minimum over the South Pole
of 136 Dobson Units on September 25— the highest minimum seen since 1988.
During the 1960s, before the Antarctic ozone hole occurred, average ozone
concentrations above the South Pole ranged from 250 to 350 Dobson units.
Earth’s ozone layer averages 300 to 500 Dobson units, which is equivalent
to about 3 millimeters, or about the same as two pennies stacked one on
top of the other.

“In the past, we’ve always seen ozone at some stratospheric altitudes go
to zero by the end of September,” said Bryan Johnson, NOAA atmospheric
chemist. “This year our balloon measurements showed the ozone loss rate
stalled by the middle of September and ozone levels never reached zero.”



Katy Mersmann


NASA’s
Earth Science News Team



Theo Stein


NOAA Office of
Oceanic and Atmospheric Research,
Boulder, Co.

Closing of the ozone hole 2017

Antarctic Situation at 2017

September 11

British Antarctic Survey Ozone Bulletin

Antarctic ozone today:  The
atmospheric circulation remains in its winter mode, with the polar vortex
near its largest.  Ozone amounts are increasing around Antarctica,
whilst they are falling within the vortex.  The growing ozone hole is
centred over the South Pole.  Ozone values over the bulk of the
continent are between 190 and 270 DU, though higher over the coastal
fringe opposite Australia.  Over the southern ocean they rise to over
450 DU in places, particularly south of Africa and Australia.  There are
noticeable differences between the various satellite ozone measurements
over Antarctica.   Temperatures in the ozone layer have passed
their winter minimum but it is still cold enough (below  -78°C) for
Polar Stratospheric Clouds (PSC) to form over much of the continent. 
Temperatures are highest around the outside of the polar vortex and
decline towards the pole and towards the equator.  They are generally
a little above the normal.  In the upper parts of the ozone layer
they are rising.  Ozone depletion will increase further over the
coming weeks.  The ozone hole is likely to become more elliptical in
shape and affect the tip of South America over September 15 and 16.

The 2017 ozone hole:  The polar
vortex formed over the winter, isolating the ozone layer over Antarctica. 
Stratospheric temperatures fell below -78°C through much of the ozone
layer, leading to the formation of polar stratospheric clouds. 
Overall, meteorological conditions in the ozone layer were stable until
early August, allowing colder than normal temperatures to persist.  A
short-lived minor warming took place around August 8, and overall
temperatures are now a little warmer than the average of the last few
decades.  Ozone depletion is taking place in sunlit parts of the
vortex and the ozone hole formed in early August over the base of the
Antarctic Peninsula, in part assisted by dynamic forcing. Rothera station
saw ozone hole values for the first time on July 15, and for a longer
period in early August.  The hole grew steadily and by early
September had reached 20 million square kilometres in size, about the
average for the past decade.

Antarctic Situation at 2017 August 21

British Antarctic Survey Ozone Bulletin

Antarctic ozone today: 
The atmospheric circulation remains in its winter mode, with the polar
vortex near its largest.  Ozone amounts are growing around
Antarctica, whilst they are lower within the vortex.  The growing
ozone hole is centred over the Weddell Sea.  Ozone values over the
bulk of the continent are between 220 and 340 DU, whilst over the southern
ocean they rise to over 400 DU in places, particularly south of
Australia.  There are noticeable differences between the various satellite
ozone measurements over Antarctica.   Temperatures in the ozone
layer are near their winter minimum and it is cold enough (below 
-78°C) for Polar Stratospheric Clouds (PSC) to have formed over much of
the continent.  Temperatures are highest around the outside of the
polar vortex and decline towards the pole and towards the equator. 
They are generally a little above the normal.  In the upper parts of
the ozone layer they are beginning to rise.  Ozone depletion will
increase further over the coming weeks.

The 2017 ozone
hole:  The polar vortex formed over the winter, isolating the
ozone layer over Antarctica. 
Stratospheric temperatures fell below -78°C through much of the ozone
layer, leading to the formation of polar stratospheric clouds. 
Overall, meteorological conditions in the ozone layer were stable until
early August, allowing colder than normal temperatures to persist.  A
short-lived minor warming took place around August 8, and overall
temperatures are now a little warmer than the average of the last few
decades.  Ozone depletion is taking place in sunlit parts of the
vortex and the ozone hole formed in early August over the base of the
Antarctic Peninsula, in part assisted by dynamic forcing. Rothera station
saw ozone hole values for the first time on July 15, and for a longer
period in early August. 

See the

final situation report for last year
for information on the 2016 – 2017 season.

Notes: 
An ozone hole is
defined as an area with values below 220 Dobson Units (DU).  On
average a column of air will hold 300 DU of ozone, equivalent to 3mm of
ozone at sea-level pressure.  Most of the ozone is between 10 and 40
km with a peak at around 20 km.   The Antarctic ozone hole is
usually largest in early September and deepest in late September to early
October.  September 16 is world ozone day, and in 2009 the final UN
Member State to ratify the Montreal Protocol signed up.  All 197
Member States have now ratified the protocol up to and including the
Beijing amendments.  2007 was the International Year of the Ozone
Layer.  Prior to the formation of ozone holes, Antarctic ozone values
were normally at their lowest in the autumn (ie March).  On
occasion atmospheric vertical motions create small areas with ozone
substantially below the long term average.  Different satellites give
different views of the exact ozone distribution.  The continent
covers 14 million sq. km.  A summary of the WMO/UN 2014 Ozone
Assessment, the 

Assessment for Decision-Makers
was released on 2014 September 10.  2017 is the 30th Anniversary of
the Montreal Protocol.