And the headline is: Why Does Arctic Ozone Hole Appear Later Than Antarctic?

[Gannet]

See http://news.nationalgeographic.com/news/2011/03/110321-ozone-layer-hole-arctic-north-pole-science-environment-uv-sunscreen/

As I understand it and please correct me if I am wrong in any of the statements below

1. That the ozone hole is due to CFC in the stratosphere
2. That more CFC are release in the Northern Hemisphere than the Southern Hemisphere
3. That an Ozone hole exists over Antarctica

My question is why did it first appeared over the Antarctic before the Arctic?

 

[D H]

My question is why did it first appeared over the Antarctic before the Arctic?

Antarctica is a high, isolated continent completely surrounded by sea. The Arctic is an ocean nearly surrounded by land. This means the south polar vortex tends to be much stronger and to have a much longer persistence than does the north polar vortex. "What happens over Antarctica stays over Antarctica."

The ozone hole is not caused by a seasonal buildup of CFC gases. The build-up in CFC concentration was slow (decades long). The decline in the CFC content of the atmosphere will also be very slow because those gases are chemically stable. The ozone holes instead arise because CFCs act as a catalyst that breaks down O₃. There is essentially no sunlight during winter in the polar regions to create new ozone. The only source for new ozone in those polar regions during winter is ozone created elsewhere that is blown into region.

Because the south polar vortex is so strong and so persistent, there is no influx of ozone from outside in the Antarctic. The weaker north polar vortex does allow some influx, at least sometimes. The same conditions that create the solar polar ozone hole on a regular basis can arise in the north polar regions when the north polar vortex does become strong and persistent.

This apparently is what happened last spring (northern hemisphere). Even then, the ozone hole wasn't nearly as intense as it is in the Antarctic (~220 Dobson units last March versus < 100 Dobson units in the Antarctic).

 

[skeptic2]

It seems to me there should be somewhat of an ozone hole even without CFCs. At the ozone layer above the poles the sunlight is hitting the atmosphere at a low angle, even from angles slightly below the horizon. Some of that light will already have passed through the atmosphere and created ozone at lower latitudes and thus would be partially UV depleted.

The issue is how much worse have CFCs made the ozone hole?

 

[Gannet]

Thank You D H and skeptic2 for your replies.

D H you really impress me with your knowledge on the subject. However, I am still a little confused.

I thought the CFC rises roughly vertically up from their point of origin into the stratosphere.

Also, I thought there is no winds in the stratosphere. However, found this link http://news.nationalgeographic.com/news/2006/08/060804-ice-cloud.htmlthat states

strong jet of stratospheric air

Which I believes answer my question

Also, I found that the troposphere is under 4 miles high at the poles http://www.srh.noaa.gov/jetstream/atmos/layers.htm

 

[Evo]

Here are a couple of links. If these aren't what you're looking for a quick google search of reputable scientific sites and journals should get you the answers.

http://www.nature.com/srep/2011/110714/srep00038/full/srep00038.html

http://ozonewatch.gsfc.nasa.gov/meteorology/index.html

 

[D H]

I thought the CFC rises vertically up from their point of origin into the stratosphere.

Not at all. CFCs are more dense than air. The only way they can make it to the stratosphere is because the troposphere is so thoroughly mixed. CFCs have a very long half life in the troposphere, much longer than the mixing time of the troposphere. CFCs are pretty uniformly distributed from ground to tropopause all around the globe.

So how do these CFCs make their way into the stratosphere? The tropopause is not a hard and fast barrier. There is some diffusion across the tropopause and occasionally thunderstorms do punch well up into the stratosphere. Eventually some CFCs do make it to the stratosphere. But they don't do so by rising vertically from their point of origin.

A lot of what I wrote in my previous post was from memory. Old, somewhat bit-rotted memory. I was a member of the NIMBUS 7 SBUV/TOMS team over thirty years ago. What I got wrong in my previous post was how CFCs act to deplete ozone. Once CFCs hit the stratosphere, they can be and are broken down by UV. This reaction creates free chorine radicals. It is those chlorine radicals, not the original CFCs, that depletes the ozone. The key problem is that the reaction with ozone is catalytic. (At least I got that part right.)

The ozone depletion cycle is O₃+Cl→ClO+O₂ followed by ClO+O→Cl+O₂. In short, O₃+Cl+O→Cl+2O₂. The reaction removes ozone but leaves the chlorine radicals intact. Unless the chlorine reacts with something else or falls back into the troposphere, it will just keep on going and going and going ... That stratospheric chlorine has a fairly long half-life. Even though CFC production and release have been vastly curtailed, the combination of the long half lives of CFCs in the troposphere and chlorine in the stratosphere means that there is going to be a long wait before things return to natural levels.

Also, I thought there is no weather in the stratosphere.

That's a bit of an oversimplification. There's still weather up there. Compared to tropospheric weather, stratospheric weather is less severe and slower-changing. But it's not non-existent.

 

[Gannet]

Thank you Evo for the links I took a quick look and will back to them when I have some enough time to study. That ozonewatch link also mentions bromine as a catalyst. Where's the bromine coming from?

Thank you D H again, I was editing my second post while you were replying to it.

I read these article which raises questions. I really appreciate having this forum to answer my questions and learn new things and correct my thinking.

 

[wildwohl]

Who is making ozone to fill in the hole?

 

[D H]

Who is making ozone to fill in the hole?

Not who, but what. It's sunlight.

Sunlight can photolyze ordinary oxygen molecules (O₂), creating a pair of oxygen atoms. This is a fairly slow chemical process. A collision between one of those free oxygen atoms and another O₂ can create ozone. This is a fairly fast chemical process. Sunlight can also photolyze an ozone molecule, splitting it into an O₂ molecule and a free oxygen atom. This is also a fairly fast chemical process. (Note: This is also the process that protects us from ultraviolet radiation.) That free oxygen atom won't last long; it will either collide with an O₂ molecule to create a new O₃ molecule (fast), or it will collide with an O₃ molecule to create a pair of O₂ molecules (slow). Ozone can also spontaneously split into O₂+O, but this is quite slow.

Summary so far: With sunlight, a number of chemical processes of varying speeds work together to make for an equilibrium distribution of oxygen in the form of oxygen atoms, O₂ molecules, and O₃ molecules. So what happens without sunlight? Now the processes favors ordinary oxygen as opposed to ozone. There is a natural depletion rate of ozone during winter.

So far I've only talked about oxygen and sunlight. Ozone is highly reactive. Add something to the mix with which oxygen can react, in general ozone will do it best. Foreign substances act to alter the mix of O versus O₂ versus O₃. These foreign substances act as a sink for ozone. The consequences of those foreign substances will have limited scope if the reaction in question is a typical chemical reaction. The consequences are much more severe if the reaction is catalytic, and that is exactly what happens in the case of the chlorofluorocarbons. The problem is greatly exacerbated in winter, where there is essentially no sunlight to create new ozone molecules.

 

[wildwohl]

So what would be the best recovery method to replace the ozone layer when a GRB destroys it? Was looking at man-made ozone to replace to the depleted volume of ozone.

 

[Borek]

So what would be the best recovery method to replace the ozone layer when a GRB destroys it? Was looking at man-made ozone to replace to the depleted volume of ozone.

GRB Gamma Ray Burst(er)
GRB Graduate Recruitment Bureau
GRB Grid Resource Broker
GRB Gharb (postal locality, Malta)
GRB Global Resource Bank (communal bank)
GRB Grootschalig Referentiebestand (Dutch: large scale mapping program)
GRB Green Bay, WI, USA - Austin/Straybel Field (Airport Code)
GRB Green Red Blue
GRB G. Ray Bodley (High School)
GRB Global Relationship Banking
GRB Government Retirement & Benefits, Inc.
GRB General Revenue Bonds
GRB Globally Responsible Birthing
GRB Golden Radio Buffs of Maryland (old-time radio)
GRB Granatbuechse (German WWII anti-tank grenade rifle)
GRB Geophysics Research Board
GRB Government Reservation Bureau
GRB General Radio Broadcast
GRB Gabriel Richard Building

I feel lost. Which one of these is destroying the ozone layer?

Jokes aside, ozone layer is rebuilt by the Sun, just slowly. Instead of producing ozone on the large scale (which will mean colossal amounts of energy necessary, and we already have problems with producing enough energy for our needs without polluting the environment) we should concentrate on not destroying the ozone layer further. It will be restored in a natural way.

 

[wildwohl]

How much ozone can be produced with the power provided by one standard wind turbine?

 

[D H]

So what would be the best recovery method to replace the ozone layer when a GRB destroys it? Was looking at man-made ozone to replace to the depleted volume of ozone.

If a gamma ray burst happens to hit the Earth (which is an extremely unlikely event), the loss of the ozone layer will be the least of our concerns. This is essentially a non-problem.

How much ozone can be produced with the power provided by one standard wind turbine?

Ozone in the ozone layer? None.

 

[wildwohl]

How much energy is required to produce 1 m^3 of ozone at STP?

 

[D H]

There are about 3 to 4 trillion kilograms of ozone in the ozone layer (250 to 400 Dobson units * surface area of the Earth * 2.144 grams/liter at STP). There is no way to crank out that much ozone by man-made processes. Even if we could, ozone is just a pollutant at sea level. You would have to manufacture that much ozone and transport it to the stratosphere.

Some problems are not solvable by man. Some problems are so extremely unlikely that they aren't worth losing a minute's worth of sleep over. The hypothetical complete annihilation of the ozone layer by a gamma ray burst falls into both camps.

 

[AlephZero]

I feel lost. Which one of these is destroying the ozone layer?

The ones with containing the word "Government". Every conspiracy theorist knows that

 

[bigfooted]

So what would be the best recovery method to replace the ozone layer when a GRB destroys it? Was looking at man-made ozone to replace to the depleted volume of ozone.

Xerox printers produce ozone.

Save the world. Print this message.

 

[wildwohl]

@AlephZero, thank you for the smile.

 

[Gannet]

Thank you Evo for the links I took a quick look and will back to them when I have some enough time to study. That ozonewatch link also mentions bromine as a catalyst. Where's the bromine coming from?...

Found this article http://www.sciencedaily.com/releases/2012/03/120301111111.htm which states:

The connection between changes in the Arctic Ocean's ice cover and bromine chemical processes is determined by the interaction between the salt in sea ice, frigid temperatures and sunlight. When these mix, the salty ice releases bromine into the air and starts a cascade of chemical reactions called a "bromine explosion." These reactions rapidly create more molecules of bromine monoxide in the atmosphere. Bromine then reacts with a gaseous form of mercury, turning it into a pollutant that falls to Earth's surface.