Researchers have found 'unprecedented' levels of molecular chlorine in the air around Barrow, Alaska.
The chlorine is found in sea salt and deposited into the atmosphere by melting sea-ice. It can cause oxidation in "methane and elemental mercury, as well activate bromine chemistry," a Georgia Institute of Technology news release reported.
"No one expected there to be this level of chlorine in Barrow or in Polar Regions," Greg Huey, a professor in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology in Atlanta.
The research team took direct measurements of molecular chlorine levels in the crisp Barrow air. In order to make these measurements the team employed a technique called ionization mass spectrometry along with other experiment taking place over several years.
The team concluded the chlorine levels were as high as 400 parts per trillion in the atmosphere; this concentration is considered to be unusually high because chlorine atoms tend to only survive in the atmosphere for a short period of time.
The molecules peaked in the morning and late afternoon but were almost non-existent at night, linking them to ozone concentrations. The finding led researchers to believe that both sunlight and ozone were essential in the chlorine formation. Chlorine is so short-lived because it is highly reactive with other chemicals in the atmosphere.
"Molecular chlorine is so reactive that it's going to have a very strong influence on atmospheric chemistry," Huey said.
Past studies have found high mercury levels in the area as well. Coal-burning plants are the primary source of atmospheric mercury globally. The area of Barrow has low levels of oxidants, not including the mercury; this is because there is little vapor and ozone in the atmosphere. In the spring ozone and mercury levels are often depleted while chlorine and bromine prevail.
The team believes the molecular chlorine in the region is released through sea salt, but they are not sure how this process works.
"We don't really know the mechanism. It's a mystery to us right now," Huey said. "But the sea ice is changing dramatically, so we're in a time where we have absolutely no predictive power over what's going to happen to this chemistry. We're really in the dark about the chlorine."
Sea ice that remains year-round has been drastically decreasing in the area, this rapid melting could be releasing an excess of mercury into the atmosphere.
"There is definite climate change happening in the Arctic," Huey said. "That's changing the nature of the ice, changing the volume of the ice, changing the surface area and changing the chemistry of the ice."
