Scientists are just beginning to understand the complex dance of chemicals between snow and air, and how pollution and other human problems might affect that delicate balance. The new results, reported recently at a San Francisco meeting of the American Geophysical Union, could help researchers pinpoint ways to keep faraway polluters from harming the fragile Arctic environment. The ozone loss, mercury concentration and other chemical processes occur naturally, he noted. But people might be speeding them up by adding atmospheric pollutants, which spread into even the most pristine-seeming regions of the Arctic. Also, rising global temperatures, probably caused in part by human activities, are thinning and shrinking the seasonal Arctic ice pack.
Less ice translates to less snow on which chemical reactions can occur.
Assembling the entire picture can be quite a challenge, Dr. Shepson said. Most of the year, Alert hosts Canadian and U.S. soldiers who once monitored the former Soviet Union. But the station is also home to a program, operating since 1986, that monitors the Arctic's atmospheric chemistry. Last spring, about 30 researchers traveled to Alert to watch the most-anticipated event of the season, the sunrise that ends the polar winter. They carried a flotilla of balloons, thermometers, sensors and other scientific equipment to monitor the changing chemistry.