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Scientists launch probe on spread of toxic mercury in Arctic Ocean

Alex DeMarban

A phenomenon Arctic explorers long relied on for drinking water on the frozen ocean is linked to the latest bad news -- as well as a silver lining -- accompanying climate change.

The freshwater trick those ancient travelers capitalized on is this: The surface of old sea ice is a source of freshwater because the saltwater brine it contains melts downward over the years, leaving desalinated water on top.

The problem: That process isn't occurring as much as it once did because older sea ice is vanishing rapidly, leaving a larger concentration of the young sea ice that forms and melts annually.

The result is a saltier sea-ice surface that an international team of scientists believe has caused a burst of bromine in the atmosphere, and a "cascade of chemical reactions" that might lace the Arctic with toxic mercury, according to NASA.  

How much toxic mercury is ending up in the Arctic Ocean or on coastal flatlands nearby is unknown, said lead researcher Son Nghiem, of NASA's jet propulsion laboratory. But a crew of 30 people representing more than a dozen organizations in four countries -- the U.S., United Kingdom, Canada and Germany -- will start looking for that answer this month in Barrow, the northernmost community in the U.S.

The extensive "campaign," as he called it, will be based out of Barrow's new scientific research facilities starting on Monday -- not far from where the Beaufort and Chukchi seas meet. Over the coming weeks, the researchers will begin sampling sea ice, sea water and land and snow for mercury and other clues. Data from satellite and aircraft will contribute to the picture.

"We (will) attack it from surface to air to space," said Nghiem.   

"If a little (mercury), then not much of a concern, sky is not falling," he said.

But if too much falls onto the sea and land, that's a cause for concern, he said.   

Toxic mercury can remain in animal tissue for a long time, moving up the food chain from plankton to fish, marine mammals and humans. In high amounts, it can damage organs, hurt reproductive health and cause diseases.  

The bromine-production starts with a cocktail of basic ingredients abundant in the Arctic: salt, sun and cold. Scientists believe that together they're causing increasing amounts of bromine to be released into the air in a rapid, self-multiplying process called "bromine explosions." The explosions were first noticed 20 years ago in northern Canada, and are carried along on the wind.

With satellites recording higher bromine concentrations five years ago, researchers began investigating. They realized the Brooks Range and the Richardson and Mackenzie range in Canada acted as walls that barricaded the bromine in the Arctic Ocean and the coastal flatlands, meaning the "explosions" were occurring below 6,560 feet, taller than most mountains in the chains, the NASA statement notes.

Scientists pinpointed the source of the explosions to the salty sea-ice, and realized the bromine oxidizes with safe mercury in the air to produce toxic mercury that often drops to the Earth surface in rain and snow.

There's one benefit to the bromine-sparked chemical reactions, said Nghiem. They also reduce ground-level ozone, a pollutant when near the earth's surface.   

"On the other hand, bromine is a good thing because it also oxidizes ozone at the surface level," taking it away, he said.

Contact Alex DeMarban at alex(at)alaskadispatch.com