NASA Finds Sea Ice Driving Arctic Air Pollutants

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Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
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Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown@nasa.gov

News release: 2012-054 March 1, 2012

NASA Finds Sea Ice Driving Arctic Air Pollutants

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2012-054&cid=release_2012-054

PASADENA, Calif. – 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. The new studies will complement
those of a previously conducted NASA field campaign, Arctic Research of the Composition of the
Troposphere from Aircraft and Satellites (ARCTAS), which is providing scientists with valuable data
for studies of bromine.

This study was funded by NASA, the National Oceanic and Atmospheric Administration, the
National Science Foundation, the Office of Naval Research, the International Polar Year Program,
Environment Canada, the Natural Sciences and Engineering Council of Canada, the European Space
Agency, the State of Bremen, the German Aerospace Center, and the European Organisation for the
Exploitation of Meteorological Satellites.

For more information about NASA programs, visit: http://www.nasa.gov .

JPL is managed for NASA by the California Institute of Technology in Pasadena.
Additional media contacts: Sandra Hines, University of Washington, 206-543-2080; John Burrows,
University of Bremen, 011-49-421-218-62100; Isabelle Compagnon, Environment Canada, 819-953-
6959; Sean Moore, University of Manitoba, 204-474-7963; Lt. Cmdr. Michael Vancas, National Ice
Center, 301-817-3941; Katja Tholen-Ihnen, University of Hamburg, 011-49-0-40-42838-7596.

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