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| Earth on Oct 11, 2011

First-ever Arctic ozone hole: How it formed, what it may mean

Scientists first observed an ozone hole over Antarctica in the mid-1980s. But in 2011 – for the first time – an ozone hole opened over the northern Arctic.

It seems Antarctica isn’t the only part of Earth to have an ozone hole in our lifetime. Move on over Antarctica, you have a new player in the game.

It’s the Arctic.

Researchers have been saying for some years that Earth’s ozone layer might recover more slowly if indeed Earth is getting warmer. Now we have dramatic evidence of this possibility, announced by researchers in an article in the journal Nature on October 2, 2011. The researchers said that in the northern spring of 2011, massive ozone destruction of 80% occurred 18 to 20 kilometers (about 12 miles) above the Arctic ice sheet, in the part of the atmosphere known as Earth’s stratosphere. That makes 2011 the first year – ever – that an ozone hole has been observed in the Arctic. These scientists said:

For the first time, sufficient loss occurred to reasonably be described as an Arctic ozone hole.

Some degree of ozone loss above the northern Arctic – and the formation of an actual ozone hole above the southern Antarctic – have been have been annual events, measured in past decades, during the poles’ respective winters. The Antarctic ozone hole has been seen to open above Earth’s southern continent in winter each year since the mid-1980s, when the scientists of the British Antarctic Survey first reported its existence, also in the journal Nature.

We humans need Earth’s ozone. The ozone layer protects living things on Earth from harmful ultraviolet radiation. If there were not an ozone layer, skin cancers and crop failure would increase. Without protective ozone, earthly life would be unable to survive. There is already speculation that the 2011 Arctic ozone hole might have caused noticeable reductions in Europe’s winter wheat crop, for example.

Chlorofluorocarbons, also known as CFCs, are the direct cause of ozone depletion. CFCs – primarily composed of chlorine, fluorine, carbon, and hydrogen – were commonly found in coolants, refrigerants, and various aerosols until their effect on ozone began to be recognized by scientists. That recognition came shortly before the announcement of the first Antarctic ozone hole in 1985.

CFCs damage ozone when temperatures are especially cold. The discovery that CFC production greatly contributed to the depletion of the ozone layer in Antarctica in the 1980s led to the Montreal Protocol in 1987, which has greatly decreased the use of CFCs. CFCs are difficult to remove from Earth’s atmosphere, however, and can stay in the atmosphere for decades before levels begin to minimize.

Image showing the depletion of the ozone in the Arctic and the correlation with chlorine monoxide. Image Credit: NASA Earth Observatory

Why did an ozone hole form in the Arctic this year? The ozone layer is located in our stratosphere, which is roughly 15 to 50 kilometers above Earth’s surface. We live in Earth’s troposphere, which starts at our planet’s surface and extends 15 kilometers from the ground. All of our weather happens in the troposphere. As you move higher in the troposphere, temperatures become colder.

Layers of the atmosphere. Image credit: Wikipedia.

But when you leave the troposphere – and enter the stratosphere – an inversion occurs where temperatures begin to warm. During this past winter, the stratosphere was unusually cold for a longer-than-ususal period of time. Those colder temperatures are the reason for the Arctic ozone hole.

Here’s how it works. When temperatures become colder, the chances for cloud development in the stratosphere increase. From December 2010 through March 2011, a polar vortex – or a strong spin of swirling winds around the pole – was spinning above the Arctic. When a polar vortex occurs, it blocks out the warmer air along the troposphere and keeps colder air in the stratosphere. The colder conditions created more stratospheric clouds, which acted as surface for stable chlorine gases to turn into chlorine monoxide. The constant cold, development of stratospheric clouds, and the development in ozone-destroying chlorine monoxide eventually supported the depletion of the ozone in the Arctic this past winter. As of now, scientists are still unsure as to why the 2011 polar vortex was so strong.

Clouds in the stratosphere contributed to the depletion of the ozone layer in the Arctic in winter 2011. Image Credit: NASA Earth Observatory

Is global warming influencing ozone depletion? First of all, let’s take a look at the average temperatures of the stratosphere since 1979, as shown on the graph below. What does it mean? It means the stratosphere is cooling has been cooling over the past two decades.

The graph above shows stratospheric cooling relative to the 1981-2000 mean. The temperature jumps in 1982 and 1991 were anomalies, or deviations from the norm, due to volcanic eruptions. Image Credit: National Climatic Data Center (NCDC)

Secondly, let’s take a look at temperatures in the mid-troposphere, as shown on the graph below. This graph shows that temperatures in the troposphere – the lower part of the atmosphere where humans live, and where we have all our weather – has been warming.

Image Credit: NCDC

What do these two graphs together mean? They suggest that, as the troposphere warms, the stratosphere cools. Scientists have known for years warming in the troposphere could result in a cooler stratosphere. Earth needs balance, and a warmer troposphere is balanced by a cooler stratosphere. Dr. Jeff Master’s made an excellent point regarding our atmosphere when he compared it to the very extreme atmosphere of the next planet inward from Earth in our solar system, Venus.

We need only look as far as our sister planet, Venus, to see an example of how the greenhouse effect warms the surface but cools the upper atmosphere. Venus’s atmosphere is 96.5% carbon dioxide, which has triggered a hellish run-away greenhouse effect. The average surface temperature on Venus is a sizzling 894 °F, hot enough to melt lead. Venus’s upper atmosphere, though, is a startling 4 – 5 times colder than Earth’s upper atmosphere.

What would have happened if CFC use had not been curtailed in 1987 by the Montreal Protocol? If CFCs were still widely used today – given our current level of global warming – ozone depletion might be expected to be greater and to occur at a faster rate.

Is Earth truly warming? Yes. 2010 was tied with 2005 for the hottest year on record, for example. Meanwhile, the amount of energy from the sun is at its lowest since measurements began in the late 1970s. Something is not adding up. If greenhouse gases were not involved, then less energy from the sun would produce cooler temperatures globally around the world. However, we are not seeing that occurring.

For more information on the Arctic ozone hole, please check out Dr. Jeff Master’s blog and NASA’s Earth Observatory.

Bottom line: The Arctic saw the first ozone hole develop during the winter of 2011. An extreme polar vortex dropped temperatures in the stratosphere creating gases that depletes the ozone layer. It is very possible that we could see more instances of ozone depletion in the coming year as greenhouse gases emissions continue, causing increased tropospheric heat and more stratospheric cooling.

Nature article: Unprecedented Arctic ozone loss in 2011

Record depletion of Arctic ozone in April 2011 over Scandinavia

Claire Parkinson on pros and cons of geoengineering to combat climate change