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Arctic air offers scientist clues about the speed of global warming

Hannah HeimbuchThe Arctic Sounder

In the 18 years he's been an atmospheric chemist at Purdue University, Paul Shepson has visited the Arctic many times, and through many countries. Now the head of the chemistry department, Shepson made "a trip of a lifetime" to Barrow this March.

While Shepson has spent many such trips studying the unique Arctic atmosphere and the chemical gases found there, the big difference this time was the ride. They called it ALAR (Aircraft Laboratory for Atmospheric Research) and it provided his team with both a ride north and a unique vehicle for data collection.

Shepson's team used ALAR to collect atmospheric samples from varying heights above the ground, and over a variety of surfaces.

"We're interested in the composition of the atmosphere, in part with respect to greenhouse gases," Shepson said, adding that his research focuses on the measure of chlorine, bromine and ozone at different elevations.

Focused on ozone

The atmospheric composition varies depending on what's on the ground, and how far away that ground is. Air over a forested area, for instance, contains different chemical levels than that over tundra, which is different from air over sea ice, or open water.

The greenhouse gas ozone is of particular interest, Shepson said, being both damaging and vital. 

"It has the ability to clean itself of pollutants, it's an essential element in the atmosphere," he said. "In the Arctic, ozone isn't able to do its job of helping to clean the atmosphere near as well because it's dry."

The Arctic's lack of humidity impedes ozone's natural ability to chew up pollutants, Shepson said, but this cold climate has another built-in housekeeper.

Sea ice

"When you make ice, the process of freezing sea water excludes most of the salt," Shepson said. That sea salt comes out onto the surface of the ice, and into the air. The chlorine and bromine exuded by that salt are, like ozone, good at processing pollutants.

"Our interest is in climate change in the Arctic and how sea ice will change this natural cleaning," Shepson said.

The sea ice is vital to the Arctic way of life, for both the people who depend on it and the delicate details of nature that balance upon it.

This is where Shepson's research cuts into that cyclical dance scientists of many fields are watching — the change in sea ice, relating to changes in air chemistry, relating to changes in climate, relating to changes in ecosystems, and so on. This cycle of change, Shepson said, all comes back to man-made emissions.

"All climate scientists know that the planet is warming," Shepson said. "(It's warming) two to three times faster in the Arctic. And we know that it's warming because of humans...There's a connection between climate change and what we do."

Those are the facts, Shepson said, the unknown is in the details — such as the Arctic atmospheric chemistry that he's analyzing.

Weird chemistry

Shepson's lab will take years to digest and decipher the multitude of data collected during more than a month in the Arctic, but they did make some initial observations that surprised them, he said.

"We saw lots of this weird chemistry that involves sea salt in the air over the North Slope when we expected to only see it over sea ice," Shepson said.

Basically, they were seeing the salty evidence of bromine and chlorine over the tundra, an occurrence they hadn't expected.

As he continues to process data, Shepson isn't looking for any particular pattern, he said, or to prove any particular theory. He just hopes to provide an accurate description of what the Arctic air is made of.

For a closer look at the team's time in Alaska, click here

This story first appeared the The Arctic Sounder.