Vigorous mixing in the air above large cracks in Arctic sea ice that expose seawater to cold polar air pumps atmospheric mercury down to the surface, finds a NASA field campaign. This process can lead to more of the toxic pollutant entering the food chain, where it can negatively affect the health of fish and animals who eat them, including humans. Scientists measured increased concentrations of mercury near ground level after sea ice off the coast of Barrow, Alaska, cracked, creating open seawater channels called leads. The researchers were in the Arctic for the NASA-led Bromine, Ozone, and Mercury Experiment (BROMEX) in 2012. The mercury-pumping reaction takes place because open water in a lead is much warmer than the air above it, according to study lead author Chris Moore of the Desert Research Institute, Reno, Nev in a paper reporting the discovery published in Nature on Jan. 15. Because of that temperature difference, the air above the lead churns like the air above a boiling p...