Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers

Journal name:
Nature Geoscience
Volume:
5,
Pages:
198–201
Year published:
DOI:
doi:10.1038/ngeo1403
Received
Accepted
Published online

Glacier-derived dissolved organic matter represents a quantitatively significant source of ancient, yet highly bioavailable carbon to downstream ecosystems1. 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 oldest2. The remnants of ancient peatlands and forests overrun by glaciers have been invoked as the source of this organic matter1, 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.

At a glance

Figures

  1. The glacier organic carbon cycle, including apparent radiocarbon ages associated with the organic carbon fluxes.
    Figure 1: The glacier organic carbon cycle, including apparent radiocarbon ages associated with the organic carbon fluxes.
  2. Molecular signatures for glacier and non-glacier (Peterson Creek) dissolved organic matter as revealed by Fourier transform ion cyclotron mass spectrometry.
    Figure 2: Molecular signatures for glacier and non-glacier (Peterson Creek) dissolved organic matter as revealed by Fourier transform ion cyclotron mass spectrometry.

    ac, van Krevelen distributions of dissolved organic molecular formulae identified in Mendenhall Glacier snowpack (a), Mendenhall Glacier outflow (b), and Peterson Creek (c). d, Bar chart detailing the structural classes assigned to the dissolved organic molecular formulae identified in Mendenhall Glacier snowpack (one sample), Mendenhall Glacier outflow (error bars represent variability between three samples taken on different dates) and Peterson Creek (one sample).

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Author information

Affiliations

  1. Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, Georgia 31411, USA

    • Aron Stubbins
  2. Environmental Science and Geography Program, University of Alaska Southeast, Juneau, Alaska 99801, USA

    • Eran Hood &
    • Andrew W. Vermilyea
  3. Yale School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06405, USA

    • Peter A. Raymond &
    • David Butman
  4. US Geological Survey, 3215 Marine Street, Boulder, Colorado 80303, USA

    • George R. Aiken,
    • Robert G. Striegl &
    • Paul Schuster
  5. Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, USA

    • Rachel L. Sleighter,
    • Patrick G. Hatcher &
    • Hussain A. N. Abdulla
  6. Department of Land, Air and Water Resources, University of California, Davis, California 95616, USA

    • Peter J. Hernes
  7. Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA

    • Durelle T. Scott
  8. Woods Hole Research Center, 149 Woods Hole Road, Falmouth, Massachusetts 02540, USA

    • Robert G. M. Spencer

Contributions

A.S., E.H., R.G.M.S. and G.R.A. designed the research. E.H. led the fieldwork at Mendenhall and Herbert glaciers with assistance from R.G.M.S., A.W.V. and D.T.S., and G.R.A., P.S. and R.G.S. led the fieldwork at Gulkana and Fremont glaciers. P.A.R. and D.B. analysed samples for radiocarbon ages. P.J.H. and R.G.M.S. ran lignin analyses. G.R.A. and A.W.V. ran DOC, absorbance and fluorescence analyses. FTICR-MS data acquisition and analysis were conducted by R.L.S., H.A.N.A., P.G.H. and A.S. Writing and data integration were done by A.S. with significant contributions from E.H., R.G.M.S, and P.A.R. All authors commented on the manuscript.

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The authors declare no competing financial interests.

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