NASA Finds Sea Ice Decline Driving Rise in Arctic Air Pollutants

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March 1, 2012

Dwayne Brown 
Headquarters, Washington                                    
202-358-1726 
dwayne.c.brown@xxxxxxxx 

Alan Buis 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-0474 
alan.buis@xxxxxxxxxxxx 

RELEASE: 12-064

NASA FINDS SEA ICE DECLINE DRIVING RISE IN ARCTIC AIR POLLUTANTS

WASHINGTON -- Drastic reductions in Arctic sea ice in the last decade 
may be intensifying the chemical release of bromine into the 
atmosphere, resulting in ground-level ozone depletion and the deposit 
of toxic mercury in the Arctic, according to a new NASA-led study. 

The connection between changes in the Arctic Ocean's ice cover and 
bromine chemical processes is determined by the interaction between 
the salt in sea ice, frigid temperatures and sunlight. When these 
mix, the salty ice releases bromine into the air and starts a cascade 
of chemical reactions called a "bromine explosion." These reactions 
rapidly create more molecules of bromine monoxide in the atmosphere. 
Bromine then reacts with a gaseous form of mercury, turning it into a 
pollutant that falls to Earth's surface. 

Bromine also can remove ozone from the lowest layer of the atmosphere, 
the troposphere. Despite ozone's beneficial role blocking harmful 
radiation in the stratosphere, ozone is a pollutant in the 
ground-level troposphere. 

A team from the United States, Canada, Germany, and the United 
Kingdom, led by Son Nghiem of NASA's Jet Propulsion Laboratory in 
Pasadena, Calif., produced the study, which has been accepted for 
publication in the Journal of Geophysical Research- Atmospheres. The 
team combined data from six NASA, European Space Agency and Canadian 
Space Agency satellites, field observations and a model of how air 
moves in the atmosphere to link Arctic sea ice changes to bromine 
explosions over the Beaufort Sea, extending to the Amundsen Gulf in 
the Canadian Arctic. 

"Shrinking summer sea ice has drawn much attention to exploiting 
Arctic resources and improving maritime trading routes," Nghiem said. 
"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." 

The study was undertaken to better understand the fundamental nature 
of bromine explosions, which first were observed in the Canadian 
Arctic more than two decades ago. The team of scientists wanted to 
find if the explosions occur in the troposphere or higher in the 
stratosphere. 

Nghiem's team used the topography of mountain ranges in Alaska and 
Canada as a "ruler" to measure the altitude at which the explosions 
took place. In the spring of 2008, satellites detected increased 
concentrations of bromine, which were associated with a decrease of 
gaseous mercury and ozone. After the researchers verified the 
satellite observations with field measurements, they used an 
atmospheric model to study how the wind transported the bromine 
plumes across the Arctic. 

The model, together with satellite observations, showed the Alaskan 
Brooks Range and the Canadian Richardson and Mackenzie mountains 
stopped bromine from moving into Alaska's interior. Since most of 
these mountains are lower than 6,560 feet (2,000 meters), the 
researchers determined the bromine explosion was confined to the 
lower troposphere. 

"If the bromine explosion had been in the stratosphere, 5 miles [8 
kilometers] 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. 

After the researchers found that bromine explosions occur in the 
lowest level of the atmosphere, they could relate their origin to 
sources on the surface. Their model, tracing air rising from the 
salty ice, tied the bromine releases to recent changes in Arctic sea 
ice that have led to a much saltier sea ice surface. 

In March 2008, the extent of year-round perennial sea ice eclipsed the 
50-year record low set in March 2007, shrinking by 386,100 square 
miles (one million square kilometers) -- an area the size of Texas 
and Arizona combined. Seasonal ice, which forms over the winter when 
seawater freezes, now occupies the space of the lost perennial ice. 
This younger ice is much saltier than its older counterpart because 
it has not had time to undergo processes that drain its sea salts. It 
also contains more frost flowers -- clumps of ice crystals up to four 
times saltier than ocean waters -- providing more salt sources to 
fuel bromine releases. 

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. 

Nghiem is leading an Arctic field campaign this month that will 
provide new insights into bromine explosions and their impacts. 
NASA's Bromine, Ozone, and Mercury Experiment (BROMEX) involves 
international contributions by more than 20 organizations. 

For more information about NASA programs, visit: 

http://www.nasa.gov 

	
-end-



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