Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

• Published in: Biogeosciences 2017-12, Vol.14 (24), p.5663-5674
• Main Authors: Smeaton, Craig, Austin, William E. N, Davies, Althea L, Baltzer, Agnes, Howe, John A, Baxter, John M
• Format: Article
• Language: English
• Subjects: Carbon; Carbon cycle; Coastal environments; Coastal sediments; Coasts; Environmental aspects; Estimates; Fjords; Geochemistry; Geomorphology; Geophysics; Hypoxia; Latitude; Marine sediments; Observations; Peatlands; Sediment; Sediments; Stocks; Storage; Stores
• ISSN: 1726-4189; 1726-4170; 1726-4189
• DOI: 10.5194/bg-14-5663-2017

Fjords are recognised as hotspots for the burial and long-term storage of carbon (C) and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6 ± 52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when area-normalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets.