March 3, 2012
Bromine Explosions Being Driven By Climate Change
According to a new study, Arctic sea ice reductions may be intensifying the chemical release of bromine into the atmosphere, causing ground-level ozone depletion and the deposit of mercury in the Arctic.
A team of scientists combined data from six NASA, European Space Agency and Canadian Space Agency satellites to develop a model of how air moves in the atmosphere to link Arctic sea ice changes to bromine explosions over the Beaufort Sea.
"Shrinking summer sea ice has drawn much attention to exploiting Arctic resources and improving maritime trading routes," Son Nghiem of NASA's Jet Propulsion Laboratory said in a press release. "But the change in sea ice composition also has impacts on the environment. Changing conditions in the Arctic might increase bromine explosions in the future."
Bromine explosions occur when salt in the sea ice, frigid temperatures and sunlight mix. Once these conditions mix, the salty ice releases bromine into the air and starts a cascade of chemical reactions called "bromine explosions."
The scientists wanted to find out if the explosions observed two decades ago in the Canadian Arctic occur in the troposphere or higher in the stratosphere.
The team used topography of mountain ranges in Alaska and Canada as a "ruler" to measure the altitude at which the explosions took place.
Satellites detected increased concentrations of bromine in the spring of 2008, which were associated with a decrease of gaseous mercury and ozone.
The scientists verified the satellite observations with field measurements, then used an atmospheric model to study how the wind transported the bromine plumes across the Arctic.
The model showed the Alaskan Brooks Range and the Canadian Richardson and Mackenzie mountains stopped bromine from moving into Alaska's interior.
The researchers determined that since these mountains are lower than 6,560 feet, the bromine explosions was confined to the lower troposphere.
"If the bromine explosion had been in the stratosphere, 5 miles or higher above the ground, the mountains would not have been able to stop it and the bromine would have been transported inland," Nghiem said in a press release.
Once the researchers determine that bromine explosions occur in the lowest level of the atmosphere, they were able to relate their origin to sources on the surface.
Nghiem said if sea ice continues to be dominated by younger saltier ice, and Arctic extreme cold spells occur more often, bromine explosions are likely to increase in the future.
The research was published in the Journal of Geophysical Research-Atmosphere.
Image 1: Bromine explosion on March 13, 2008 across the western Northwest Territories in Canada looking toward the Mackenzie Mountains at the horizon, which prevented the bromine from crossing over into Alaska. The bromine explosion is depicted in the foreground by the red-orange areas, while the green shades at high altitudes on the mountains represent areas where there was no increase in bromine. Image credit: NASA/JPL-Caltech/University of Bremen
Image 2: Bromine explosion on March 13, 2008 across the Alaskan North Slope looking south toward the Brooks Range at the horizon, which blocked the bromine from going further south into the Alaskan interior. The bromine explosion is depicted in the foreground by the red-orange areas, while the green shades at high altitudes on the Brooks Range represent areas where there was no increase in bromine. Image credit: NASA/JPL-Caltech/University of Bremen
Image 3: The upper panel shows a bromine explosion observed by scientists at the University of Bremen on March 14, 2008 over Alaska and the Beaufort Sea. The lower panel shows sea ice cover at the time, as measured by NASA's QuikScat spacecraft. Image credit: NASA-JPL/Caltech/University of Bremen/University of Washington
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