Picture of the Day

Breaking up sunlight in the land of caribou

New measurements of molecular iodine in the Arctic, taken with the help of University of Michigan professor Kerri Pratt's lab, show that even a tiny amount of the element can deplete ozone in the lower atmosphere. This is surprising because iodine is so scarce in the Arctic snowpack compared to its close relatives and known ozone-killers, chlorine and bromine. Less than one part per trillion of iodine is enough to have a significant effect on ozone concentration in the lower atmosphere, according to a recent study. The atmosphere uses ozone, water vapor and sunlight to clean itself. However, there’s less water vapor in higher latitudes because it’s cold, which slows down the natural cleaning mechanism. In regions covered with sea ice, the strange chemistry involving halogens released by salty ice creates a different cleaning mechanism; if sea ice is removed by climate change, this mechanism could disappear. Shown here: The sun rises over caribou on the Alaskan coastal tundra.

Visit Website | Image credit: Kerri Pratt/University of Michigan