January 16, 2014
Increased Mercury Levels In Arctic Ice Found Pushing Into Sea Water
Gerard LeBlond for www.redorbit.com - Your Universe Online
Researchers Dr. Chris Moore and Dr. Daniel Obrist, from Nevada's Desert Research Institute, have recently discovered an increased level of mercury in Arctic sea ice. The study, published in the journal Nature, also found that the element is contaminating sea water below.
“The atmospheric mixing created when thinner, seasonal sea ice opens to form leads is so strong that it actually pulls down mercury from a higher layer of the atmosphere to near the surface,” Moore said in a statement.
“None of us had suspected that we would find this kind of process associated with leads,” said study coauthor Son Nghiem, from NASA’s Jet Propulsion Laboratory in Pasadena, California.
These leads are the large cracks found in the sea ice. Increased levels of mercury near ground level have been discovered after the cracks in the ice exposed seawater off the coast of Barrow, Alaska.
According to Moore, the exposed sea water is much warmer than the frigid air and with such a temperature difference, the air above the lead mixes.
“The mixing is so strong, it actually pulls down mercury from a higher layer of the atmosphere to near the surface,” noted Moore.
The air above mixes with the warmer water releasing clouds of mist from the leads, reaching 1,000 feet or more into the atmosphere and pulling all the mercury from the air down to the surface. When all the mercury is pulled from the air, the reaction stops. However, scientists have now discovered that the mixing reaction restarts and more mercury is pulled down and the process is sustained.
The team used ground-based measurements of the mercury and other chemicals along with images from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra satellite to observe the ice. They also used a National Oceanic and Atmospheric Administration (NOAA) model of air transport for their mercury measurements.
"The 'aha' moment came when we combined the surface measurements with the satellite data and model. We considered a bunch of chemical processes and sources to explain the increased levels of mercury we observed, until we finally realized it was this pumping process,” Obrist said in a statement.
The initial findings support needed actions to reduce mercury pollution around the world, but more research is needed to how changes in sea ice across the Arctic change the ozone chemistry and impact mercury deposition throughout the sensitive region, according to Moore.