First Arctic Ozone Hole

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?...

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.