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Environment

Arctic Air Chemistry Detailed

Studies document unexpectedly high atmospheric chlorine concentrations and mixing of air over water channels

by Jyllian Kemsley
January 20, 2014 | A version of this story appeared in Volume 92, Issue 3

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Credit: Thomas A. Douglas/U.S. Army Cold Regions Research & Engineering Laboratory
Open water channels in Arctic sea ice promote mixing of the air above.
An open channel in Arctic sea ice.
Credit: Thomas A. Douglas/U.S. Army Cold Regions Research & Engineering Laboratory
Open water channels in Arctic sea ice promote mixing of the air above.

Earth scrubs pollutants from the atmosphere via oxidation chemistry, which at the poles is driven by halogens liberated from sea ice. Two studies aimed at understanding halogen atmospheric chemistry provide new details on the interactions of Arctic water, ice, and air. In one study, a team led by L. Gregory Huey of Georgia Tech describes first-ever measurements of atmospheric Cl2 in Barrow, Alaska (Nat. Geosci. 2014, DOI: 10.1038/ngeo2046). The researchers note that light and O3 are necessary for Cl2 formation. Additionally, they find surprisingly high daytime Cl2 concentrations given that sunlight also photolyzes Cl2 to Cl•. The second study, by a group led by Christopher W. Moore of Nevada’s Desert Research Institute, documents how atmospheric O3 and Hg(0) concentrations change in response to environmental conditions (Nature 2014, DOI: 10.1038/nature12924). When air moves over sea ice, O3 and Hg(0) are depleted from near the ice’s surface. When air moves over open channels in the ice, however, convection mixes the air, drawing more O3 and Hg(0) toward the water. Hg(0) is oxidized in the atmosphere to Hg(II), which is deposited out of air and could be converted to toxic compounds.

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