Why are the holes in the ozone layer (caused by CFC's) in areas (Antarctica & the arctic) far from emissions?

Question

Why are the holes in the ozone layer (caused by CFC's) in areas (Antarctica & the arctic) far from emissions?

Answer 1

Ken has a very good answer as far as it goes. Agree with all of what he says. O3, UV radiation and density of O3 being the issue. Also CFC's are easily transported into the upper atmosphere. These are not just guesses but measured facts.

The only disagreement I have with him, is that as the air is so turbulent, the O3 is pretty evenly spread as well, so it should not be that much more dilute over the poles.

What he has not mentioned is that the reaction at the heart of the ozone CFC story is a catalytic effect of Chlorine atomes on Ozone. The chlorine atoms are produced by UV reaction with the CFCs. The Chlorine atoms(free radicals, not Cl2 molecules or Cl- ions) react with O3 destroying it and are regenerated in the reaction, so a single chlorine atom can destroy millions of ozone molecules.

If it was a case of the chlorine or CFC just reacting with the ozone it wouldn't be a big issue as there is so much more O3 than CFC produced.

The other part of the story is that this reaction only becomes an issue when it occurs on the surface of ice crystals at very low temperature. This occurs above the poles only and in particular over antarctica in winter. Without enough ice crystals and those extra cold conditions the reactions aren't effective, the Chlorine radicals are destroyed before they can cause to much damage. That is why the biggest "hole" is over antarctica and why is varies with the seasons.

The life expectancy of the CFCs that have already been put into the atmosphere is of the order of 100-200yrs, so while the concentration is reducing slowly, it will take some time.  

It is yet another example of how we have foolishly dabbled with things we have only a little understanding of, only to find later that our ignorance has caused a big long term mess. 50 years of dumping CFCs into the atmosphere results in couple hundred years of ozone depletion.

Pity humans are not good learners as a group. We seem to repeat the same old mistakes again and again.

Answer 2

The location of the 'holes' is unrelated to the possibility (or otherwise) that CFC pollution is causing them.

Ozone is not a stable substance. It needs to be constantly supplied with energy to keep it from falling apart (two O3 molecules would spontaneously become three molecules of O2).

The Ozone layer is caused by a reaction between high-energy ultraviolet light (This is how it protects us from being fried by UV 'C'; we only get the B and A intensities of UV radiation, which are too weak to cause Ozone formation) and atmospheric oxygen at a suitable concentration (the layer doesn't really vary in depth; it is the density of Ozone in it that is different according to latitude).

Between the Tropics, the light is shining perpendicularly onto the reactive layer, so that it is concentrated on a small area per unit of energy. At the poles, the available light is striking the atmosphere at a very shallow angle, so the same amount of energy would be spread more widely.

In general, this is the same as the surface heat distribution. Tropical plants are caused by intense radiation, and are very thinly distributed near the poles.

If CFC reactions were the cause of Ozone thinning ...

(Particle density is not an obstacle to this possibility; volcanic ash particles and desert sand are both carried to immense heights by energetic weather. Any gas, however dense, is more easily transported by winds than either of these. Basically, the atmosphere is so turbulent that the distribution of any gas within it should be assumed to be 'universally homogenous' or evenly mixed in.)

...then the same amount of Ozone destruction would be proportionally more damaging at the 'thinnest' point (perhaps removing the layer entirely) than at the 'thickest' part of the layer (where it might make very little detectable impact on the dense (and constantly renewed) concentration of the gas).

Answer 3

There are a lot of wrong answers and speculation here. To understand why the hole is over Antarctica you have to know a bit about the background of ozone...

The first point is that Ozone (O3) is formed by the reaction of oxygen with UV light. That is:

uv + O2(gas oxygen) => 2O (this is called a free radical) then

O + O2 => O3

But at the same time it is being constantly destroyed:

O3 + uv = O2 + O

such that on balance there is always a certain concentration in the atmosphere.  This is the ozone layer and is in the stratosphere (about 20-50Km up).

The balance O3 production and destruction reactions above is altered by different chemicals, notably CFCs.   Basically these increase ozone destroying reactions without being used up (i.e. CFCs are a catalyst) and change the balance leading to less ozone. CFCs have along atmospheric lifetime and the mixing in the troposphere distributes them evenly around the globe.

The reactions which deplete ozone go faster at lower temperatures.  They also need a 'third body' on which to react  - this is provided by Polar Stratospheric Clouds (PSCs) which form above the polar regions during winter.  Also, in the Antarctic, what is called the circumpolar vortex is set up each winter.  This is a circular wind which in effect seals off the antarctic air masses and stops them mixing around with the rest of the world.  Next the chemicals such as CFCs trapped within have time to release their chloride on PSCs and wait for the sun to come up in spring....

...when it does all the CFC O3 destroying chain reactions kick in (they need uv light to work) and there is a massive reduction in O3 locally above Antarctica. Then this O3 depleted air is mixed around the global stratosphere and thins the layer.

So they are above polar regions because of the low temperatures and presence of 'third bodies' PSCs on which to react.  they are far from emissions because the CFC are transported all around the globe because of their long atmospheric lifetime.

Bit long but I hope it makes sense - you can find loads (perhaps too much, but it's not straightforward!) on WIKI.

BTW - the weight of CFCs absolutely does not mean they can't get up there - this is complete nonsense, the amount of turbulent mixing in the atmosphere easily mixes CFC is the atmosphere, and their long atmospheric lifetime means they can survive the journey up to the stratosphere.

Answer 4

There was volcanic activity in Antartica.  In addition, you have to realize that ozone is cause by solar radiation.  Obviously, there is far less solar radiation near the poles.

Answer 5

They aren't.  Just because someone did an demo once that cfc's  did something too ozone under controlled conditions a bunch of self appointed authority figures grasping for straws grabbed it and ran with it.  The sad part of a bad experiment is that it keeps someone from finding the real truth.  I think part of this experiment was sponsored by the people whose patent on freon  (r12) ran out and other people were manufacturing it under different names.  Not are the holes far, but in different hemispheres.  Very little atmosphere crosses the equator.  Aloso r12 is five times heavier than air at atmosphere conditions.  I bet it would be hard pressed to find any r12 at 30000'+  at that temperature and pressure it is liquid and very stable.  There are a lot of liars in the world.

Answer 6

CFC have nothing to do with the ozone layer ,it is far too heavy to get that high. The holes in the ozone layer is a natural happening. The solar winds coming toward the earth are first influenced by the magnetic poles. Most all the particles in the solar wind is ionized. The beta particles are attracted to the north pole and make it negative. The alpha particles are attracted to the south pole making it positive . This charge is what holds the O3 as O3 ,if the charge is not the O will drop to O2. The activity causes the increase and decrease in particles. And so often it blows a hole in the ozone layer.