A Sedimentary Carbon Inventory for a Scottish Sea Loch (Fjord): An Integrated Geochemical and Geophysical Approach

Quantifying sedimentary carbon stocks in the coastal ocean is key to improving our understanding of long-term storage of carbon in the coastal ocean and to further constrain 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 sea loch (fjord) on the west coast of Scotland we have created the first sedimentary carbon inventory for a fjordic system. The sediment of Loch Sunart holds 26.88 ± 0.52 Mt of carbon split between 11.05 ± 0.23 Mt and 15.02 ± 0.35 Mt of organic and inorganic carbon respectively. This quantitative estimate of carbon stored in Loch Sunart in significantly higher than previous estimates. Through comparison to Scottish peatland carbon stocks we have determined that Loch Sunart on a per are basis is a significantly more effective store of carbon. 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 as unique environments while considering coastal carbon stocks.