Analysis of iodine trapped in Alpine ice has shown that levels of atmospheric iodine have tripled over the past century, and this has kept harmful levels of ozone gases in the lower atmosphere partially in check.

Ozone in the lower atmosphere acts as an air pollutant and greenhouse gas, but ozone is also the main driver of iodine emissions from the ocean. Once released into the atmosphere, iodine acts to destroy this ‘bad’ ozone.

alpine mountain ice 400pxThe study in the European Alps, carried out by scientists from the National Centre for Atmospheric Science, University of York, Université Grenoble Alpes, and Desert Research Institute showed that although iodine can destroy the ‘bad’ ozone, there isn’t enough iodine being released to counter all of the ozone production.

Iodine has only recently been recognised for its role in climate and air pollution, and until now, there have been few historical records of this chemical. The researchers say it is now important to include iodine data in climate and air quality models, to improve insights into future global atmospheric conditions.

Since the 1950s, nitrogen oxide emissions from vehicles and power plants have increased surface ozone, and this reacts with chemicals in seawater to release more iodine into the atmosphere, which partially, but not completely, destroys some of the harmful ozone gas.

Dr Tomás Sherwen, from the National Centre for Atmospheric Science and the University of York, said: “When we look at the concentrations of iodine over time, we can see that it was fairly steady during the industrial revolution.

“However as more cars appeared on the roads in the post-war period, we get more emissions of nitrogen oxides causing more ozone in the atmosphere and therefore more iodine.

“Surface ozone concentrations have stabilised over much of Europe and the Atlantic ocean, although are still growing over other regions.

“We can now start to think about factoring in our knowledge of iodine chemistry into climate and air quality models to help us better predict what the future of our atmosphere will look like around the globe.”