The dramatic springtime collapse of surface ozone in the Arctic has been documented by scientists.

Observations from a boat that drifted with the ice across the North Pole show the gas can disappear in just days.
Dr. Jan Bottenheim told a U.S. conference that the precise chemical reactions involved were not fully understood. However, he said any changes to these processes as the Arctic warmed might limit the region's ability to deal with pollutants in the atmosphere.
""Ozone is the source for the 'vacuum cleaner of the atmosphere' - the molecule OH. So if we don't have as much ozone, we can't make as much hydroxide. If we then pump pollutants from mid-latitudes into the Arctic, they may just stay there,"" explained Dr Bottenheim.
""But a lot of this is speculation at the moment because so much of this information is new and we are not sure what to make of it.""
Spring sunshine
The ozone studied by Dr. Bottenheim and colleagues at Environment Canada is distinct from the gas high up in the stratosphere that has been damaged through the release of reactive chlorine compounds by industrial society. The group's ozone exists at ground level - or, in the case of the Arctic, at ice level - in the first 100-200m of air.
Once it goes, it can go very fast. It can go in almost a day Jan Bottenheim, Environment Canada In the winter, the concentration of the three-atom oxygen-molecule in this still air is at normal levels; but as the sunlight returns to the polar north in the spring, chemical reactions are set in train that reduce the ozone in dramatic fashion.
Dr. Bottenheim told BBC News: ""In a city, in the evening the ozone will react with exhausts from cars and can go down from, say, 40 to five or even one
[units of ozone]; but in the Arctic we've seen it go to 100 times less than one, which is an incredibly low level that I don't think has been seen anywhere else. ""And once it goes, it can go very fast. It can go in almost a day.""
Ice changes
The ozone instrument on the Tara schooner observed one period in late April of this year when there was virtually no ozone for a period of more than 15 days.
Whereas stratospheric ozone is depleted though an unnatural process involving chlorine; the ice-level ozone falls victim to reactive bromine atoms released quite naturally from briny Arctic waters. In perfect conditions, the chemistry produces an explosion of bromine oxide (BrO), which is detectable by over-flying satellites.
Scientists are now trying to determine how the ozone behavior might change in a rapidly warming Arctic.
Conditions that lead to more slushy ice, which could assist the release of bromine, might result in more extensive periods of ozone loss.
""It's a possibility, but as I say this is still speculative,"" stressed Dr. Bottenheim.
The consequences of any change needed to be understood, he added. It is known from observations, for example, that the depletion of ozone at the same time also causes a depletion of gaseous mercury, a major toxic chemical.
The ozone study is just one of a number of fascinating outcomes from the Tara expedition. The boat was originally owned by a private French company but was donated to the European research community.
The 36m, 130-tonne boat is currently locked in ice The schooner provides habitation for about 10 people Scientists deploy and monitor a number of instruments
Experiments study air, ice and ocean behavior It is a key project in Damocles (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies), a European-led effort to gather much needed new information on the changing Arctic.
(Source: BBC)