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Study: Manmade carbon may be affecting ocean food web

Posted: February 24, 2012 - 1:01am

A new study reveals that the remnants of fossil fuels in glaciers may be changing the source of food for marine life down the food chain.

The fieldwork for the study was done on the Juneau Icefield and was led by University of Alaska Southeast Assistant Professor Eran Hood. Hood is second author of the study, to be published in the international journal Nature Geoscience in March 2012 and published on-line this week.

"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," said first author Aron Stubbins of the Skidaway Institute of Oceanography. "It is unknown how this manmade carbon has influenced the coastal food webs of Alaska and the fisheries they support."

Hood led the fieldwork at the Mendenhall and Herbert Glaciers where visiting scholar-scientists from throughout the Lower 48 sampled snow, ice melt and glacier runoff. The organic carbon from these water and snow samples was isolated and carbon dated.

“We analyzed its molecular chemical structure,” Hood said. “The carbon fingerprint we found indicated aerosols derived from the combustion of fossil fuels are an important source of organic matter on glacier surfaces and also in glacier outflow streams.”

The scientists said glaciers like the Mendenhall offer ideal evidence of soot from carbon emissions. This "black carbon," darkens glacier surfaces and increases their absorption of light and heat. The carbon can also be exported to ecosystems downstream from glaciers where it can be metabolized and become part of the food web.

"These findings show that glaciers like Mendenhall can provide us with novel information about how humans are altering the composition of the atmosphere as a result of burning biomass and fossil fuels" Hood said. "The fact that we see this human-derived carbon signature in Alaskan glaciers also indicates that we still do not fully appreciate the post-industrial changes in the earth's surface biogeochemical cycles."

Glaciers and ice sheets together represent the second largest reservoir of water on the planet, and glacier ecosystems cover ten percent of the Earth, yet the carbon dynamics underpinning those ecosystems remain poorly understood.

"Improving our understanding of glacier biogeochemistry is of great urgency, as glacier environments are among the most sensitive to climate change and the effects of industrial pollution,” said Rob Spencer of the Woods Hole Research Center, another author on the study.

A warming climate will increase the outflow of the glaciers and the accompanying input of dissolved organic material into the coastal ocean. This will be most keenly felt in glacial coastal regions with the highest levels of ice loss including the Gulf of Alaska, Greenland and Patagonia.

The title of the study is “Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers.”  In addition to Stubbins and Spencer, Hood’s fellow collaborators on the project were Andrew Vermilyea from the University of Alaska Southeast; Peter Raymond and David Butman from Yale University; George Aiken, Robert Striegl and Paul Schuster from the U.S. Geological Survey; Rachel Sleighter, Hussain Abdulla and Patrick Hatcher from Old Dominion University; Peter Hernes from the University of California-Davis; Durelle Scott from Virginia Polytechnic Institute and State University.

More information and a slideshow of photographs by Hood can be found in the U.S. National Science Foundation on-line article, “Scientists Unlock Record of Ecosystem Changes Frozen in World's Glaciers”: www.nsf.gov/news/news_summ.jsp?cntn_id=123154 and on the Skidaway Institute of Oceonography website: www.skio.usg.edu/?p=research/chem/biogeochem/glaciers.php.notyet.

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