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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-9
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-9
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 21 Jan 2019

Research article | 21 Jan 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Characterizing organic matter composition in small Low and High Arctic catchments using terrestrial colored dissolved organic matter (cDOM)

Caroline Coch1,2, Bennet Juhls3, Scott F. Lamoureux4, Melissa Lafrenière4, Michael Fritz1, Birgit Heim1, and Hugues Lantuit1,2 Caroline Coch et al.
  • 1Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
  • 2University of Potsdam, Institute of Earth and Environmental Science, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
  • 3Freie Universität Berlin, Institute for Space Sciences, Department of Earth Sciences, 12165 Berlin, Germany
  • 4Queen's University, Department of Geography and Planning, Mackintosh-Corry Hall, Kingston, Ontario K7L 3N6, Canada

Abstract. Climate change is an important control of carbon cycling, particularly in the Arctic. Permafrost degradation through deeper thaw and physical disturbances result in the release of carbon dioxide and methane to the atmosphere and to an increase in riverine dissolved organic matter (DOM) fluxes. Whereas riverine DOM fluxes of the large Arctic rivers are well assessed, knowledge is limited with regard to small catchments that cover more than 40 % of the Arctic drainage basin. Here, we use absorption measurements to characterize changes in DOM quantity and quality in a Low Arctic (Herschel Island, Yukon, Canada) and a High Arctic (Cape Bounty, Melville Island, Nunavut, Canada) setting with regard to geographical differences, impacts of permafrost degradation and rainfall events. We find that DOM quantity and quality is controlled by differences in vegetation cover and soil organic carbon content. The Low Arctic site has higher SOCC and greater abundance of plant material introducing higher lignin concentrations into the aquatic system and resulting in a stronger color of DOM than in the High Arctic. There is a strong relationship between dissolved organic carbon (DOC) concentration and absorption characteristics (cDOM) for surface waters at both sites similar to the one for the great Arctic rivers. We used the optical characteristics of DOM such as cDOM absorption, Specific UltraViolet Absorbance SUVA, UltraViolet UV Slope, Slope Ratio for assessing quality changes downstream, at baseflow and stormflow conditions and in relation to permafrost disturbance. DOM in streams at both sites demonstrated optical signatures indicative of photodegradation downstream processes, even over short distances of 2000 m. It was determined that flow pathways and the connected hydrological residence time control DOM quality. Deeper flow pathways allow the export of permafrost-derived DOM, whereas shallow pathways with shorter residence times lead to the export of fresh near-surface derived DOM. Compared to the large Arctic rivers, DOM quality exported from the small catchments studied here is much fresher and therefore prone to degradation. This work shows that optical properties of DOM will be a useful tool for understanding DOM sources and quality at a pan-Arctic scale.

Caroline Coch et al.
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Caroline Coch et al.
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Colored dissolved organic matter (cDOM) absorption measurements in terrestrial waters on Herschel Island (Low Arctic) and Melville Island (High Arctic) in 2016 and 2017. C. Coch, B. Juhls, S. Lamoureux, M. Lafrenière, M. Fritz, B. Heim, and H. Lantuit https://doi.pangaea.de/10.1594/PANGAEA.897289

Caroline Coch et al.
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Short summary
Climate change affects Arctic ecosystems. This includes the thawing of permafrost (ground below 0°C) and an increase in rainfall. Both have substantial impacts on the chemical composition of river water. We compared the composition of small rivers in the Low and High Arctic with the large Arctic rivers. The constituents in our smaller rivers are more susceptible to degradation, thus, they could potentially increase carbon dioxide emissions. Rainfall events led to a similar effect.
Climate change affects Arctic ecosystems. This includes the thawing of permafrost (ground below...
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