stratospheric ozone loss in the arctic in spring of 2011
stratospheric ozone loss in the arctic in spring of 2011
Geneva, 5 April
2011 GENEVA 5 APRIL 2011 (WMO) — Depletion of the ozone layer- the shield that
protects life on Earth from harmful levels of ultraviolet rays - has reached an
unprecedented level over the Arctic this spring because of the continuing
presence of ozone-depleting substances in the atmosphere and a very cold winter
in the stratosphere. The stratosphere is the second major layer of the Earth’s
atmosphere, just above the troposphere.
The record loss
is despite an international agreement which has been very successful in cutting
production and consumption of ozone destroying chemicals. Because of the long
atmospheric lifetimes of these compounds it will take several decades before
their concentrations are back down to pre-1980 levels, the target agreed in the
Montreal Protocol on Substances that Deplete the Ozone Layer.
the ground and from balloons over the Arctic region as well as from satellites
show that the Arctic region has suffered an ozone column loss of about 40% from
the beginning of the winter to late March. The highest ozone loss previously
recorded was about 30% over the entire winter.
In Antarctica the
so-called ozone hole is an annually recurring winter/spring phenomenon due to
the existence of extremely low temperatures in the stratosphere. In the Arctic
the meteorological conditions vary much more from one year to the next and the
temperatures are always warmer than over Antarctica. Hence, some Arctic winters
experience almost no ozone loss, whereas cold stratospheric temperatures in the
Arctic lasting beyond the polar night can occasionally lead to substantial ozone
Even though this
Arctic winter was warmer than average at ground level, it was colder in the
stratosphere than for a normal Arctic winter.
shows, from 20 February until 4 April, the ozone abundance in the lower
stratosphere where ozone depletion is most intense. The smaller globe shows
values reached in a more common year (2010). One sees that this "ozone
hole" reached Scandinavia at the end of March .
The data comes from ECMWF and is generated for the European project MACC, in
which BIRA-IASB is in charge of the stratospheric ozone service. These results
combine several satellite instruments within a new "chemical weather"
model named IFS-MOZART and developed by ECMWF and the Jülich Research Centre.
The 3-D fields were then interpolated to the 470K isentropic level in order to
follow the vertical movements of the air masses in the lower stratosphere.
but not unexpected
degree of Arctic ozone destruction in 2011 is unprecedented, it is not
unexpected. Ozone scientists have foreseen that significant Arctic ozone loss is
possible in the case of a cold and stable Arctic stratospheric winter.
Stratospheric ozone depletion occurs over the polar regions when temperatures
drop below -78°C. At such low temperatures clouds form in the stratosphere.
Chemical reactions that convert innocuous reservoir gases (e.g. hydrochloric
acid) into active ozone depleting gases take place on the clouds particles. The
result is rapid destruction of ozone if sunlight is present.
substances such as chlorofluorocarbons (CFCs) and halons, once present in
refrigerators, spray cans and fire extinguishers, have been phased out under the
Montreal Protocol. Thanks to this international agreement, the ozone layer
outside the polar regions is projected to recover to its pre1980 levels around
2030-2040 according to the WMO/UNEP Scientific Assessment of Ozone Depletion
(see link below). In contrast, the springtime ozone layer over the Antarctic is
expected to recover around 2045-60, and in the Arctic it will probably recover
one or two decades earlier.
Montreal Protocol, this year’s ozone destruction would most likely have been
worse. The slow recovery of the ozone layer is due to the fact that
ozone-depleting substances stay in the atmosphere for several decades. In the
polar regions the drop in ozone depleting gases is 10% of what is required to
return to the 1980 benchmark level.
stratosphere continues to be vulnerable to ozone destruction caused by
ozone-depleting substances linked to human activities,” said WMO
Secretary-General Michel Jarraud. “The degree of ozone loss experienced in any
particular winter depends on the meteorological conditions. The 2011 ozone loss
shows that we have to remain vigilant and keep a close eye on the situation in
the Arctic in the coming years,” he said.
Atmosphere Watch Network has many stations in the Arctic and helps us to obtain
an early warning in case of low ozone and intense UV radiation.”
If the ozone
depleted area moves away from the pole and towards lower latitudes one can
expect increased ultraviolet (UV) radiation as compared to the normal for the
season. As the solar elevation at noon increases over the next weeks, regions
affected by the ozone depletion will experience higher than normal UV radiation.
The public is recommended to stay informed through national UV forecasts.
It should be
pointed out, however, that the UV radiation will not increase to the same
intensity as one suffers in the tropical regions of the globe. The sun is still
relatively low in the sky, and this limits the amount of UV radiation that
passes through the atmosphere.
UV-B rays have
been linked to skin cancer, cataracts and damage to the human immune system.
Some crops and forms of marine life can also suffer adverse effects.
stratosphere is the second major layer of the atmosphere, above the troposphere
and below the mesosphere. The stratosphere starts at about 10 km altitude and
reaches up to an altitude of about 50 km. About 90% of the ozone in the
atmosphere is found the stratosphere with the remaining 10% in the troposphere.
The ozone in the stratosphere is called the ozone layer, which absorbs
ultraviolet light and protects life on earth from harmful ultraviolet radiation
from the sun. The ozone in the troposphere, and especially close to the ground,
is unwanted because it is a corrosive gas that causes damage to vegetation and
can harm lung function and irritate the respiratory system in humans and
amounts of greenhouse gases lead to higher temperatures at the surface of the
earth, but models show that the stratosphere at the same time will get colder.
Therefore ozone scientists have foreseen that significant ozone loss can happen
in the Arctic stratosphere. If the cold temperatures persist into spring, i.e.
when the sun comes back after the polar night, ozone destruction speeds up. In
Antarctica such conditions prevail every winter/spring season, whereas in the
Arctic the variability from one year to the next is much larger. Large ozone
loss is therefore not an annually recurring phenomenon in the Arctic
stratosphere. While increased amounts of longlived greenhouse gases, such as
carbon dioxide and methane, are expected to cause some cooling of the
stratosphere in the long term, it cannot explain the large variations in
temperature that is observed from one year to the next in the Arctic
satellite observations and coordinated launches of ozonesondes carried by
weather balloons show us at which altitudes the ozone loss takes place. These
measurements show that the ozone loss takes place between 15 and 23 km above the
ground with an ozone minimum around 19-20 km. This coincides with the region of
low temperatures below -78°C. In this region more than 2/3 of the ozone has
been destroyed so far. Measurements from the SCIAMACHY satellite instrument show
record high amounts of the molecule OClO, a compound that takes part in ozone
destruction. Satellite measurements of total ozone from OMI, GOME-2 and
SCIAMACHY show a region of low ozone above the Arctic regions. As of late March
the ozone poor region is shifted away from the pole and covers Greenland and
Convention to Protect the Ozone Layer came into force in 1985. Two years later
the Montreal Protocol to phase out production and consumption of ozone-depleting
products was signed. The Montreal Protocol has been reinforced on several
occasions after 1987.
total ozone column and vertical ozone profiles around the pole on March 30,
developed by Finnish Meteorological Institute using satellite and ground based
Clare Nullis, Press Officer,
Communications and Public Affairs, Tel: +(41 22) 730 8478;
14 March 2011:
on the verge of record ozone loss - Arctic-wide measurements verify rapid
depletion in recent days
Potsdam/Bremerhaven, March 14th, 2011. Unusually
low temperatures in the Arctic ozone layer have recently initiated massive ozone
depletion. The Arctic appears to be heading for a record loss of this trace gas
that protects the Earth’s surface against ultraviolet radiation from the sun.
This result has been found by measurements carried out by an international
network of over 30 ozone sounding stations spread all over the Arctic and
Subarctic and coordinated by the Potsdam Research Unit of the Alfred Wegener
Institute for Polar and Marine Research in the Helmholtz Association (AWI) in
“Our measurements show that at the
relevant altitudes about half of the ozone that was present above the Arctic has
been destroyed over the past weeks,” says AWI researcher Markus Rex,
describing the current situation. “Since the conditions leading to this
unusually rapid ozone depletion continue to prevail, we expect further depletion
to occur.” The changes observed at present may also have an impact outside the
thinly populated Arctic. Air masses exposed to ozone loss above the Arctic tend
to drift southwards later. Hence, due to reduced UV protection by the severely
thinned ozone layer, episodes of high UV intensity may also occur in middle
latitudes. “Special attention should thus be devoted to sufficient UV
protection in spring this year,” recommends Rex.
Ozone is lost when breakdown products
of anthropogenic chlorofluorocarbons (CFCs) are turned into aggressive, ozone
destroying substances during exposure to extremely cold conditions. For several
years now scientists have pointed to a connection
between ozone loss and climate change, and particularly to the fact that in the
Arctic stratosphere at about 20km altitude, where the ozone layer is, the
coldest winters seem to have been getting colder and leading to larger ozone
losses. “The current winter is a continuation of this
development, which may indeed be connected to global warming,” atmosphere
researcher Rex explains the connection that appears
paradoxical only at first glance. “To put it in a simplified manner, increasing
greenhouse gas concentrations retain the Earth’s thermal radiation at lower
layers of the atmosphere, thus heating up these layers. Less of the heat
radiation reaches the stratosphere, intensifying the cooling effect there.”
This cooling takes place in the ozone layer and can contribute to larger ozone
depletion. “However, the complicated details of the interactions between the
ozone layer and climate change haven’t been completely understood yet and are
the subject of current research projects,” states Rex. The European Union
finances this work in the RECONCILE project, a research programme supported with
3.5 million euros in which 16 research institutions from eight European
countries are working towards improved understanding of the Arctic ozone layer.
In the long term the ozone layer will
recover thanks to extensive environmental policy measures enacted for its
protection. This winter’s likely record-breaking ozone loss does not alter
this expectation. “By virtue of the long-term effect of the Montreal
Protocol, significant ozone destruction will no longer occur
during the second half of this century,” explains Rex. The Montreal Protocol
is an international treaty adopted under the UN umbrella in 1987 to protect the
ozone layer and for all practical purposes bans the production of
ozone-depleting chlorofluorocarbons (CFCs) worldwide today. CFCs released during
prior decades however, will not vanish from the atmosphere until many decades
from now. Until that time the fate of the Arctic ozone layer essentially depends
on the temperature in the stratosphere at an altitude of around 20 km and is
thus linked to the development of earth’s climate.
Notes for Editors:
Contacts at Alfred Wegener Institute
Your contact at the Potsdam Research
Unit of the Alfred Wegener Institute is Dr Markus Rex (tel.: +49 (0)174
311 8070, +49 (0)331 288 2127; e-mail: Markus.Rex(at)awi.de).
Your contact in the Communications and Media Department is Ralf Röchert (tel:
+49 (0)471 4831-1680; e-mail: Ralf.Roechert@awi.de).
The Alfred Wegener Institute conducts
research in the Arctic, Antarctic and oceans of the high and middle latitudes.
It coordinates polar research in Germany and provides major infrastructure to
the international scientific community, such as the research icebreaker
Polarstern and stations in the Arctic and Antarctica. The Alfred Wegener
Institute is one of the seventeen research centres of the Helmholtz Association,
the largest scientific organisation in Germany.
This is a joint statement of the
following institutions. The persons mentioned in each
case are also at your disposal as contacts.
The total ozone maps are based on
ground-based measurements available from the World
Ozone and Ultraviolet Radiation Data Centre. Preliminary near real-time data
from ground-based observations were also used for the most recent maps. Total
ozone values are given in Dobson
Units. The numbers represent observations taken from ground stations
situated at the bottom left corner of the number.
areas with poor data coverage adjustments are made according to TOMS
on Nimbus-7, Meteor-3, ADEOS and Earth Probe satellites. Over the polar night
area Dobson and Brewer moon observations and/or NOAA's
TIROS Operational Vertical Sounder (TOVS) satellite data are used. TOVS data
are also used when the more reliable TOMS data are not available. The mapping
algorithm is similar to those used by the WMO
Ozone Mapping Centre.