Journal
NATURE GEOSCIENCE
Volume 5, Issue 3, Pages 198-201Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/NGEO1403
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Funding
- US National Science Foundation [DEB-1146161/-1145313/-1145932/-11455885, OCE-0728634, EAR-0943599/-0838587]
- Climate Effects Network of the US Geological Survey
- Hanse Institute for Advanced Studies (HWK, Delmenhorst, Germany)
- Direct For Biological Sciences
- Division Of Environmental Biology [1146161] Funding Source: National Science Foundation
- Direct For Biological Sciences
- Div Of Biological Infrastructure [0960285] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Earth Sciences [0838587, 0943599] Funding Source: National Science Foundation
- Division Of Earth Sciences
- Directorate For Geosciences [0838497] Funding Source: National Science Foundation
- Division Of Environmental Biology
- Direct For Biological Sciences [1145932] Funding Source: National Science Foundation
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Glacier-derived dissolved organic matter represents a quantitatively significant source of ancient, yet highly bioavailable carbon to downstream ecosystems(1). This finding runs counter to logical perceptions of age-reactivity relationships, in which the least reactive material withstands degradation the longest and is therefore the oldest(2). The remnants of ancient peatlands and forests overrun by glaciers have been invoked as the source of this organic matter(1,3,4). Here, we examine the radiocarbon age and chemical composition of dissolved organic matter in snow, glacier surface water, ice and glacier outflow samples from Alaska to determine the origin of the organic matter. Low levels of compounds derived from vascular plants indicate that the organic matter does not originate from forests or peatlands. Instead, we show that the organic matter on the surface of the glaciers is radiocarbon depleted, consistent with an anthropogenic aerosol source. Fluorescence spectrophotometry measurements reveal the presence of protein-like compounds of microbial or aerosol origin. In addition, ultrahigh-resolution mass spectrometry measurements document the presence of combustion products found in anthropogenic aerosols. Based on the presence of these compounds, we suggest that aerosols derived from fossil fuel burning are a source of pre-aged organic matter to glacier surfaces. Furthermore, we show that the molecular signature of the organic matter is conserved in snow, glacier water and outflow, suggesting that the anthropogenic carbon is exported relatively unchanged in glacier outflows.
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