Ozone and Temperature Data Analysis, South Pole Antarctica
Students will become familiar with the technique of collected ozone data with an airborne ozonesonde which provides an ozone data profile up to 35 km. Using different data sets, this analysis will empower the student to make conclusion about the nature as well as the annual and seasonal changes of the ozone hole over the Antarctica. The following video provides an excellent overview about ozone research, about the launching of ozone balloons, about the history and consequences of ozone depletion: "Ozone - Cancer of the sky", 45 min, $ NZ 30, available from the International Antarctic Center, Christchurch, New Zealand: http://www.iceberg.co.nz/eduresou.htm
Common questions concerning the ozone over the Antarctica:
1.Why over the Antarctic? This phenomena has to do with the consistent circulation of air and water around the Antarctic continent. This circulation forms a very stable vortex around the continent which circulates all the air masses around the Antarctic, including all pollutants brought down to the South. This is very different compared to the Arctic where no continent exists around the North Pole and no stable vortex is formed. In addition, the very cold temperatures during the winter months support the formation of special Polar Stratospheric Clouds (PSC’s) which hold on to the ozone depleting chemicals such as CFC’s. During the time the sun rises over the Antarctic, the chlorine of the CFC’s are set free by the reaction of the UV-light with the clouds which contain also ozone. Ozone is broken down by the UV rays into a free oxygen molecule and a single oxygen. Chlorine is a strong reactant and combines instantly with the single oxygen. Hence, new ozone can not be reformed.
See also: Journal: 1/24 Why over the Antarctica; 1/25, Pollutants in the stratosphere
The ozone hole - why here over the Antarctic? (1/24 journal excerpt)
Dave (Dr. Dave Hofman, director of CMDL, Boulder Colorado) was due leaving tomorrow for McMurdo, so we continued this science session by talking about the chemistry of the ozone depletion. The ozone hole appears here at the South Pole more pronounced than in the Arctic because of the very stable water and air circulation around the Antarctic continent and the transport of parcticles from the North to the South. If you have a look at a globe you will see what I mean. A lot of parcticles and pollutants from the North will be brought to the Antarctic and circle around the continent. This circulation is very stable and forms a vortex around the Antarctic continent during the winter months. This vortex will not be broken up until the spring when the sun rises in the Antarctic. Imagine that many parcticles and pollutants have been circulating around this continent all Antarctic winter long and are waiting to parcticipate in some sort of a reaction….
When the sun rises, the ozone ( 03, three oxygen molecules combined) will absorb the UV light, as we know, and protect the Earth and also this continent from the UV rays. However, ozone molecules are also naturally broken down by the UV light into O2 and O and --- under normal circumstances --- would naturally reform back to ozone (O3) aswell. Since pollutants have been circulating around and are ready to react, they have a chance to do so with the single oxygen. This reaction occupies one of the oxygen which -in return - is not available anymore to recombine with O2 to form O3 = the ozone layer is depleted.
The website teaches about the chemistry abd phenomena of ozone depletion:
2. How did we find out about the ozone hole?
Journalentry excerpt: 1/23: the history of the ozone hole
History of the ozone hole research:
I have discussed before that DOBSON suggested that ozone is important for our protection from UV light. because it absorbs the UV. He also found natural fluctuations in ozone level depending on the season, the time of the day, and the location in the world. JOE FARMAN from the United Kingdom (British Antarctic Survey) is credited with having discovered the ozone hole in 1985 by observing a decrease in total ozone in late September through October at Halley Bay, Antarctica. DAVE HOFMANN, my PI, parcticipated in the 1986 National Ozone Expedition (NOZE) to provide the airborne ozone data profiles, which told which ozone of which the region of the atmosphere was being destroyed. SUE SOLOMON from the NOAA Aeronomy Laboratory, also in Boulder, Colorado, was a member of NOZE as well and worked with a spectrometer on the ground which was capable observing trace gases in the stratosphere such as nitrogen dioxide and molecules which contained chlorine. She has proposed a theory to explain ozone depletion. Her theory involved the chemistry which takes place on tiny parcticles in the clouds which form in the winter Antarctic stratosphere - Polar Stratospheric Clouds. Based on their observations, the NOZE group concluded that the ozone hole was basically the result of chemistry involving chlorine which is mainly man-made.
This initial work was done in McMudo. Both, Hofmann and Solomon, collected their data during WINFLY which stands for 'Winter flights into Antarctica'. The Winfly season starts in late August when it is still dark in the Antarctic. Its main purpose is to fly people into the Antarctica to prepare the runways for aircraft operations during the summer season. When the sun rises in the Antarctica, the ozone hole is formed. Why is the ozone hole formed during the Antarctic spring and why does the hole appear - in all places in the world --- over the Antarctic? Is the Ozone hole a true gap in the atmosphere? What are the pollutants that contribute(d) to the depletion of the ozone. These are questions I received by many of you and I will answer them tomorrow.
By the way, the Smithsonian Institute in Washington D.C. honored Hofmann's and Solomon's work and efforts in a very special way. The institute created a wax-figure exhibition of Hofmann and Solomon and their field work in the Antarctic as part as the "Science in American Life" Exhibit. Make sure you go to see it when you are visiting Washington the next time!!
3. Why does the ozone whole close over the Antarctic after the spring time season?
Comparing the ozone data of October 1998 and January 1999, reveals that the stratospheric ozone hole created in October is not present anymore in January. Ozone is naturally depleted and formed. When no pollutants are available, ozone will actually be depleted and reformed in a natural balance. Most of our ozone is formed in the equator reagion and brought down to the Antarctic by wind circulations, hence the ‘normal looking’ ozone profile in January of 1999.
4. What pollutants contribute to the ozone depletion
Journal entry excerpt 1/25 :
Why does the ozone depletion appear in the stratosphere? What pollutants contribute to the depletion?
As I have learned from discussions with Dr. Dave Hofman, the chemistry of the ozone depletion is far more complicated than I ever anticipated. I will try to explain the major points. Chapman suggested around 1930 that ozone (O3) is formed from the reaction of sunlight with oxygen and that a stable layer will form when other molecules such as nitrogen and oxygen are present. He suggested that there is a natural balance between destruction (some of the destruction is due to UV light) and formation of ozone thus shielding the Earth from harmful UV. However, Chapman's theory predicted more ozone in the stratosphere then had been observed, suggesting that there must be additional destruction of ozone not accounted for in Chapman's theory. with some of the destruction due to UV light. the formula for the natural distraction and formation of ozone
Between 1960 and 1970, other possible chemical schemes for destruction of ozone were studied., scientists During that time, Crutzen, Molina, and Roland, who in 1995 received the Nobel prize for their studies, suggested that OH, NO, and Cl ( hydroxyl radical, nitric oxide and chlorine) are highly reactive ozone and could be responsible for the additional destruction of ozone.
Farman, who is credited with the discovery of the ozone hole, suggested that the ozone distraction must be photochemical because it appears always in October when the Antarctic rises. A few days ago, I discussed that the chlorine, as part of chlorofluorocarbons (CFC's), is responsible for the depletion of the ozone layer. It was Lovelock, who detected CFCs in the atmosphere with a gas chromatograph. Two of the most important types of CFC's are F-11 or CFCl and F-12 or CF2Cl 2. These CFC's were used in aerosol spray cans, in refrigeration and in foam production.
The question still remains: why does chlorine react with ozone and not with nitrogen (which was seen as highly reactive and should not allow chlorine to attack ozone) and why does this reaction take place mainly in the stratosphere?
The process is more complicated than I can explain here. I will therefore conclude only with the major concepts. During the Antarctic winter Polar Stratospheric Clouds (PSC's) form because of the extreme cold temperatures causing the condensation of parcticles in the very stable atmospheric wind system, called a vortex - like a huge tornado) over Antarctica in the winter stratosphere (see 1/24/ journal entry). Initially these parcticles are tiny sulfuric acid droplets upon which nitric acid condenses when the temperatures fall in winter These droplets become larger as ice forms around them and these large droplets can fall from the stratosphere and thus remove active nitrogen. In other words, the PSCs , first remove the active nitrogen and incorporate nitric acid into parcticles so chlorine remains free ( nitrogen dioxide will combine with chlorine monoxide to form chlorine nitrate which does not destroy ozone) . Second, chemical reactions (called "heterogeneous reactions") on the surface of PSC parcticles, allow the reaction of chlorine-containing molecules which normally do not destroy ozone ( like chlorine nitrate and hydrochloric acid) to form free chlorine atoms which can destroy ozone. But for the very few chlorine atoms available to destroy large amounts of ozone, sunlight is required to sustain the reaction (called a "catalytic" reaction). As soon as the sun gets up after the Antarctic winter, sunlight allows the destruction by chlorine to proceed rapidly. The more PSC's are formed, the more nitrogen is trapped and removed, the more chlorine is free to react with the ozone. In addition, the ozone depletion causes the stratosphere to cool even more and more PSCs are formed resulting in more ozone depletion This is an example of positive feedback ---except with a very negative effect! We have created a very efficient process to destroy the ozone --- with CFC-depending products we have used or are still using.
5. What has been done to save the ozone layer?
journal entry excerpt : 1/27
What has been done to save the remaining ozone layer? One of the most remarkable effort to save the ozone layer, in my opinion, was the signing of the Montreal Protocol which goal it was to have all countries agree to reduce the emission of ozone-depleting substances.
THE MONTREAL PROTICOL - an agreement for countries not to use products with ozone depleting chemicals. ) How did such an important agreement among many countries came about? (Excerpts from: 'Ozone Science: A Canadian Perspective on the changing Ozone Layer')
"The signing of the Montreal Protocol on September 16, 1987 was a remarkable and significant event in modern diplomatic history, one of those rare occasions when individual nations subordinated economic self-interest to the achievement of a common planetary goal. The event was even more remarkable when one considered that it was accomplished in spite of scientific uncertainties about detailed aspects of the ozone depletion process and without immediate evidence of impacts on ecosystems and human health. That an agreement was eventually reached was due not only to an extraordinarily successful collaboration between scientists and policymakers but also to the enormous strides made by the international scientific community in expanding the boundaries of ozone science". The negotiation of the protocol went on for several years. "The conclusion of such an important and unprecedented agreement owes much to the skill and persistency of those who negotiated it, but a number of other important factors contributed to this achievement. The role of the international scientific community was parcticular valid. Although scientists were unable to eliminate many of the uncertainties that surrounded and still surround the stratospheric ozone issue, they were successful in reducing the range of uncertainty, and in building a compelling case for action. Chance played a role as well, most notably with the recovery with the discovery of the Antarctic ozone hole in 1985. The ozone hole did not confirm existing theories about the destruction of the ozone layer- it only raised new questions - but it did create a greater awareness among opinion leaders and the public that something serious was happening to the atmosphere and that precautionary action was necessary. An agreement also became much more likely after 1986, when American chemical industry, one of the larger producers of CFC's in the world abandoned its opposition of controls. "
Most countries in the world signed the Montreal Protocol. In December of 1998, the last Montreal Protocol conference was held in Cairo.
See also website: Montreal conference: http://www.unep.ch/ozone/10mop.htm
6. What is the difference between good and bad ozone?
Ozone produced by human pollution (i.e. Xerox machines and combustion) in the troposphere is considered bad ozone. It is harmful to our respiratory system. We are supposed to have low levels of ozone in the troposphere.The ‘good ozone is in the stratosphere where it is produced and where it absorbs the harmful UV rays.
Resources and Reference Materials
‘ World on Fire- Saving an endangered Earth’ , Senator George J. Mitchell, Charles Seribners’s Sons MacMillian Publishing Company, 1991
‘Fire and Ice’, The Greenhouse Effect, Ozone Depletion and Nuclear Winter, David Fisher
References/Journals Overview of the Polar Ozone Issue , Susan Solomon, 1988, Geophysical Research Letters, Vol. 15, NO. 8, pp 845 - 846
Ozone Science: A Canadian Perspective on the changing Ozone Layer
TEA journals: ../../
Total ozone data: http://www.cmdl.noaa.gov/owv
South Pole Station: http://limpet.spole.gov
Ozone Secretariat: http://www.unep.ch/ozone/
Montreal conference: http://www.unep.ch/ozone/10mop.htm
" The Changing Ozone Layer", By Rumen D. Bojkov: A joint publication of the World Meteorological Organization and the United Nations Environment Programme:
Links to Polar Project Principal Investigator
1. "Ozone - Cancer of the sky", 45 min,( provides an excellent overview about ozone research, about the launching of ozone balloons, about the history and consequences of ozone depletion), $ NZ 30, available from the International Antarctic Center, Christchurch, New Zealand:
2. "Warning from the Ice", NOVA
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