Saltier Arctic sea ice linked to ozone depletion, pollution: NASA

The rising of the sun in the high latitudes of the Arctic unleashes “explosions” of the chemical bromine which can lead to ozone depletion and the release of toxic mercury into the environment, say NASA scientists. (FILE PHOTO)

It’s not just that older, thicker sea ice is disappearing in the Arctic Ocean — its sea ice also getting saltier.

And NASA scientists say the increase in the saltiness of sea ice is having an impact in the atmosphere.

Scientists can best see this impact as the sun returns to the high latitudes in March.

Then, the presence of younger, saltier ice in the Arctic Ocean appears to intensify the release of bromine, a chemical element, into the atmosphere.

That release can lead to the depletion of the Earth’s protective layer of ozone and to 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 chemical processes is due to the interaction between the salt in the sea ice, cold temperatures and sunlight, the study says.

Here’s how it works: when the sun rises above the High Arctic horizon in March, the salty ice releases bromine into the air. This release starts a cascade of chemical reactions called a “bromine explosion.” Bromine then reacts with a gaseous form of mercury, turning it into a toxic pollutant that falls to Earth’s surface — in the Arctic.

Bromine also can remove ozone from the lowest layer of the atmosphere.

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.

Its members 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 to the Amundsen Gulf.

“Shrinking summer sea ice has drawn much attention to exploiting Arctic resources and improving maritime trading routes,” Nghiem said in a NASA 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.”

The study was undertaken to better understand the nature of bromine explosions, which first were observed in the Canada’s Arctic more than 30 years ago.

Nghiem’s team used 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 a model to study how the wind transported the bromine plumes across the Arctic.

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.

The sea ice surface is saltier because younger ice is much saltier than its older counterpart. This ice contains more “frost flowers “– clumps of ice crystals up to four times saltier than ocean waters — providing more salt to fuel bromine releases.

Nghiem said if Arctic 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 back in the Arctic this month to investigate bromine explosions and their impacts, as part of NASA’s Bromine, Ozone, and Mercury Experiment.