For better or for worse, the hole in the Earth’s ozone layer above Antarctica has become a symbol of anthropogenic changes to the atmosphere since its discovery in the 1980s. Thirty years later, agreements between the world’s nations, such as the Montreal Protocol, have reduced the quantity of ozone-depleting substances released into the atmosphere, and the hole is expected to close within the next 35–50 years. Although this is good news, harmful ultraviolet (UV) rays will continue to flood in through the area in the meantime, damaging life forms such as zooplankton, which form the base of the Antarctic ecosystem.
Nagase et al. propose a geoengineering solution that, according to their models, would help close the hole in the ozone layer faster without the risk of dangerous side effects. The chief culprit in ozone depletion is free chlorine, which forms when UV radiation from the Sun breaks down certain chlorine-containing molecules called chlorofluorocarbons. The highly reactive chlorine (Cl) atoms then combine with ozone (O3) to form free oxygen and chlorine monoxide (ClO).
To solve this issue and help restore the ozone layer, the authors propose injecting tiny particles of ice into the atmosphere to remove a major chlorine-containing molecule, hydrochloric acid (HCl), before it has a chance to be broken down by the Sun and react with ozone. The scientists say that the key to success is to inject the tiny ice particles in the fall when little sunlight reaches the South Pole. During this season, ice particles would remain suspended in the air for several days, giving them time to absorb HCl before gradually dropping to lower altitudes and removing some of the chlorine present in the polar lower stratosphere.
Geoengineering is inherently risky; the authors are careful to clarify that their study is only an early investigation and that a great deal of additional work needs to be done before it would be advisable to begin injecting ice particles into the atmosphere on a large scale. If their computer simulations are correct, however, suspending ice droplets in the atmosphere could represent a way to hasten the recovery of the planet’s ozone layer, mitigating some negative climate effects and protecting life on the planet’s surface. (Earth’s Future, doi:10.1002/2014EF000266, 2015)
—David Shultz, Freelance Writer
Citation: Shultz, D. (2015), To help fix the hole in the ozone layer, just add ice, Eos, 96, doi:10.1029/2015EO035485. Published on 11 September 2015.