Today's Arctic explorers are well-acquainted with the ugly haze that hangs over the North Pole, created by air pollution that drifts up from cities in lower latitudes. But a new study suggests this veil of pollution has been present since the late 1800s.
The first report of Arctic haze was made by U.S. Air Force meteorologist J. Murray Mitchell in 1957 from his observations during weather reconnaissance missions over the Arctic Ocean. Scientists in the 1970s found that the haze contained heavy metals, suggesting it was produced by the combustion of oil in industrial areas in lower latitudes.
Since humans have been burning fossil fuels and therefore generated large amounts of air pollution since long before the 1950s, University of Utah meteorologist Tim Garrett reasoned that pollution generated earlier in the Industrial Revolution might also have been exported to the Arctic.
Garrett hired Lisa Verzella, a former University of Utah undergraduate, to comb through historic records to search for evidence of early Arctic pollution.
Sure enough, Verzella's search turned up a number of accounts by early Arctic explorers of a "dry haze" that settled onto the ice to form a layer of grayish dust containing metallic particles. These particles were likely the byproducts of smelting and coal combustion, which dominated industrial processes in the late 19th century. The findings are detailed in the March 2008 issue of the Bulletin of the American Meteorological Society.
"We searched through open literature, including a report in the second issue of the journal Science in 1883 by the famous Swedish geologist Adolf Erik Nordenskiold, who was the first to describe the haze," Garrett said.
Nordenskiold even observed the dust on an earlier 1870 expedition: "A fine dust, gray in color and, when wet, black or dark brown, is distributed over the inland ice in a layer which I should estimate at from 0.1 to 1 millimeter [0.004 to 0.04 inches]."
More recently, researchers have found dust present in ice core samples (long columns drilled out of the ice that show layers deposited over time).
"Recent Greenland ice cores show a rapid rise in anthropogenic soot and sulfate that began in the late 1800s, but with peak sulfate levels in the 1970s, and peak soot between 1906 and 1910," Garrett and Verzella say in their study. A higher composition of sulfate suggests oil combustion, while higher soot suggests coal combustion, consistent with the main sources of pollution generated in the 20th versus 19th centuries.
In a 2006 study, Garrett found that particulate pollution from the mid-latitudes of the planet aggravate global warming in the Arctic. The new evidence suggests pollution in the late 1800s could have had a similar effect.
"It is reasonable that the effect of particulate pollution on Arctic climate may have been greater 130 years ago than it is now, because during the Industrial Revolution, technologies were dirtier than they are now," Garrett said. "Of course, today carbon dioxide emissions are greater and have accumulated over the last century, so the warming effect due to carbon dioxide is much greater today than 100 years ago."
Particulate pollution in the Arctic has dropped off since the mid-1900s as fossil-fuel combustion processes have become more efficient and therefore cleaner. But another increase in emission transport to the Arctic could occur as China and other developing nations ramp up their coal-burning, Garrett said.
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