Thinner sea ice may lead to more mercury contamination

Laura Snider in the Boulder Daily Camera: The replacement of thicker sea ice that formed over multiple years in the Arctic with a thinner layer of ice that formed during the last winter is changing the air chemistry above the ice and likely increasing the amount of mercury contamination in the region, according to a new study led by a Boulder scientist.

Thinner sea ice -- which is riddled in the spring with cracks and fissures -- allows elements known as halogens to escape from the briny seawater onto the surface of the ice. There, the halogens, especially bromine, chemically react to scrub ozone from the atmosphere near the surface of the ice. Scientists also know that the same chemical reaction that eliminates the ozone transforms stable elemental mercury in the atmosphere into a more reactive form of mercury, which can then be deposited on snow and ice as well as directly into the ocean.

Scientists at the National Oceanic and Atmospheric Administration in Boulder have now measured the resulting drop in ozone from an observation center in Barrow, Alaska, where researchers have been making ozone measurements for nearly 40 years. The scientists also measured mercury, said Samuel Oltmans, lead author of the study published in the Journal of Geophysical Research, but because a long-term record of mercury measurements does not exist, the scientists don't have a baseline to compare the new measurements to.

Still, the researchers believe that it's likely that the amount of reactive mercury has increased as ozone has decreased.... Researchers are concerned that an increased amount of reactive mercury settling out on the snow and ice in the Arctic will lead to an increase in mercury contamination in the ocean as the snow and ice melts....

Iceberg west of Ilulissat inlet, Greenland, shot by Ute Wollf (Rodebay), Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license