Articles | Volume 13, issue 20
Biogeosciences, 13, 5771–5787, 2016
https://doi.org/10.5194/bg-13-5771-2016
Biogeosciences, 13, 5771–5787, 2016
https://doi.org/10.5194/bg-13-5771-2016

Research article 19 Oct 2016

Research article | 19 Oct 2016

Substantial stores of sedimentary carbon held in mid-latitude fjords

Craig Smeaton1, William E. N. Austin1,2, Althea L. Davies1, Agnès Baltzer3, Richard E. Abell2, and John A. Howe2 Craig Smeaton et al.
  • 1School of Geography & Geosciences, University of St Andrews, St Andrews, KY16 9AL, UK
  • 2Scottish Association for Marine Science, Scottish Marine Institute, Oban, PA37 1QA, UK
  • 3Institut de Géographie et d'Aménagement Régional de l'Université de Nantes, BP 81 227 44312 Nantes CEDEX 3, France

Abstract. Quantifying marine sedimentary carbon stocks is key to improving our understanding of long-term storage of carbon in the coastal ocean and to further constraining the global carbon cycle. Here we present a methodological approach which combines seismic geophysics and geochemical measurements to quantitatively estimate the total stock of carbon held within marine sediment. Through the application of this methodology to Loch Sunart, a fjord on the west coast of Scotland, we have generated the first full sedimentary carbon inventory for a fjordic system. The sediments of Loch Sunart hold 26.9 ± 0.5 Mt of carbon split between 11.5 ± 0.2 and 15.0 ± 0.4 Mt of organic and inorganic carbon respectively. These new quantitative estimates of carbon stored in coastal sediments are significantly higher than previous estimates. Through an area-normalised comparison to adjacent Scottish peatland carbon stocks, we have determined that these mid-latitude fjords are significantly more effective as carbon stores than their terrestrial counterparts. This initial work supports the concept that fjords are important environments for the burial and long-term storage of carbon and therefore should be considered and treated as unique environments within the global carbon cycle.

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Quantifying the carbon (C) stored within coastal sediments is key to improving our knowledge of the local and global C cycle. Here we present a new methodology to calculate the quantity of C held within coastal sediments. Through the application of this method to a mid-latitude fjord we have shown that a substantial quantity of C is held within these sediments. Additionally, we discovered that these sediments are more effective long-term stores of C than their terrestrial equivalents.
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