Arctic ice loss may increase pollution

An international team of scientists led by the National Oceanic and Atmospheric Administration is publishing a report suggesting that the thinning of Arctic sea ice may be leading to increased Arctic air pollution. Using a combination of satellite data and field observations, the team determined that bromine monoxide in the atmosphere is moving south from the Beaufort Sea across the North American continent, where the gas’ movement is blocked by the mountains of the Brooks Range in Alaska and the Richardson and Mackenzie mountains in Canada.

The accumulation of bromine in the Arctic atmosphere can cause toxic mercury pollution to fall to the ground because of the way in which the bromine reacts with a gaseous form of mercury in the atmosphere, the scientists say. However, the bromine could also remove ozone from the lower atmosphere, with ozone at low altitudes being viewed as a pollutant.

Bromine is released into the atmosphere as a result of what are termed “bromine explosions,” in which ice with elevated concentrations of salt releaseS bromine monoxide into the air in a cascade of chemical reactions. And, having determined that these reactions must be occurring at the lowest levels of the atmosphere, the researchers use computers models to trace the reactions to salty sea ice. The thinning of the Arctic sea ice as a result of global warming has resulted in elevated levels of sea salt in the ice — in some cases clumps of ice crystals may be up to four times saltier than sea water, thus fueling the bromine release, the researchers say.

“Shrinking summer sea ice has drawn much attention to exploiting Arctic resources and improving maritime trading routes,” said Son Nghiem of NASA’s Jet Propulsion Laboratory. “But the change in sea ice composition also has impacts on the environment. Changing conditions in the Arctic might increase bromine explosions in the future.”

—Alan Bailey