1) Why is there a hole in the ozone layer over the coldest continent?

The ozone hole is a place where severe ozone destruction occurs. The reason it is located over Antarctica is because there are special conditions unique to that region that do not exist elsewhere in the world: 1) very low temperatures; and 2) isolation from air in other regions. Antarctic air temperatures reach -90°C in the winter (colder than the Artic winter air temperatures which average -80°C). When temperatures get this low, a special type of cloud forms called a polar stratospheric cloud (PSC). PSC’s are composed of liquid and solid particles that grow from the condensation of water and nitric acid. The condensated cloud particles provide suitable surfaces on which chemical reactions can occur. These reactions produce reactive chlorine compounds, which is what destroys ozone. Due to the low temperatures in Antarctica, the PSC’s are present for about 5 months per year, providing surfaces for ozone destroying compounds to be produced for long periods of time. The reason these ozone destroying compounds do not spread to other parts of the world is because the stratospheric air in the Polar Regions is relatively isolated from other stratospheric regions. The isolation of air is caused by a strong wind that rotates counter-clockwise around the South Pole, called a polar vortex. The polar vortex prevents air from moving into or out of the polar stratosphere.

2) If we didn't have the ozone to protect us, how would our population suffer?

The ozone layer is Earth’s natural sunscreen. It absorbs and blocks most of the incoming UV radiation from the sun. If we didn’t have the ozone, we would be subject to biologically harmful unfiltered UV radiation. This radiation damages DNA and causes sunburn, cataracts, and skin cancer. It is important to note that UV radiation blocked by the ozone is not just harmful to humans, but to all living things. It is hypothesized that phytoplankton populations would decrease without ozone protection. As phytoplankton are the foundation of aquatic food webs, their population decrease would affect many other aquatic species.

3) What are the best remedies to stop ozone layer depletion?

Ozone layer depletion is caused by free radical catalysts like nitric oxide, chlorine and bromine. These are naturally occurring, but their abundance in the atmosphere can be increased by the release of man-made compounds like chlorofluorocarbons (CFC’s). After the discovery of the ozone hole in Antarctica CFC’s were banned worldwide, and since then ozone depletion has slowed down. The ozone layer is estimated to recover to 1980 levels by ~2050. We can ensure this happens by continuing to avoid using harmful man-made CFC’s.

I just was reading how a couple years ago, in 2011, the Arctic had an ozone hole almost as big as the one that forms over Antarctica each year. The atmosphere has many types of molecules which include the element chlorine. One molecule, chlorine monoxide (chlorine tied to a single oxygen), can form only when the temperature is very low. Along with some other molecules, chlorine monoxide can harm the ozone. Most ozone destruction actually happens during our summer because the seasons are flipped in the southern side of the earth.

People used to produce more chemicals that caused the destructive chlorine to form, but in 1987 most countries signed an agreement called the Montreal protocol. The agreement stopped countries from producing these types of chemicals.

Near the earth's surface, ozone is harmful to people. But ozone higher in the atmosphere, in the stratosphere, protects us from ultraviolet light. That's the same type of light that gives us sunburns.

1. I can't explain why the ozone hole was centered over Antarctica. It may have to do with the fact that winds blow from west to east due to the earth's rotation, which means that polar winds just circle over the poles and never mix with the rest of the atmosphere. This would also predict that there should be an ozone hole over the Arctic Ocean, which I believe there is, although not as severe of a hole.

2. Ozone blocks ultraviolet light. Ultraviolet light causes chemical damage to things that it hits, especially DNA. This would hurt our crops that grow in sunlight, and would hurt us if we were exposed to it. The damage would result in an increased risk of cancer and other mutations. However, it would be no worse than what astronauts are subjected to in space, since they after all are above the ozone layer and in the sun's full power.

3. The main remedy has been the end of the use of freon gas. Freon is a chloro-fluoro-carbon. Ultraviolet light high in the atmosphere breaks the chlorine atoms loose from the carbon, and the free chlorine takes an oxygen off of ozone to make chlorine monoxide. This depletes the amount of ozone being created. Freon has not been used on a large scale now in decades, so the ozone hole is recovering.