Glaciers show human 'black carbon' impact

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WOODS HOLE, Mass., Feb. 20 (UPI) -- Glaciers are yielding insights into the historical human impact on the global carbon cycle since the onset of the industrial revolution, U.S. researchers say.

Robert Spencer of the Woods Hole Research Center in Massachusetts and fellow researchers have been studying the Mendenhall Glacier near Juneau, Alaska, for deposits of carbon in the form of soot -- so-called black carbon.

"We are finding this human derived signature in a corner of the United States that is traditionally viewed as being exceptionally pristine," Spencer said. "The burning of biomass and fossil fuels has an impact we can witness in these glacier systems although they are distant from industrial centers, and it highlights that the surface biogeochemical cycles of today are universally post-industrial in a way we do not fully appreciate."

While many scientists believe the source of this carbon is the ancient forests and peat lands overrun by the glaciers, Spencer and his colleagues say radiocarbon dating and mass spectrometry suggests the carbon comes mainly from the burning of fossil fuels and contemporary biomass.

Carbon delivered to the ocean from melting glaciers may have an effect on organisms that form the basis of the food web, researchers said, and the supply of glacier carbon to the coastal waters of the Gulf of Alaska is a modern, post-industrial phenomenon.

"When we look at the marine food webs today, we may be seeing a picture that is significantly different from what existed before the late-18th century," Aron Stubbins, a collaborator from the Skidaway Institute of Oceanography in Georgia, said. "It is unknown how this man-made carbon has influenced the coastal food webs of Alaska and the fisheries they support."