Abstract
Abstract. 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.
Highlights
There is growing recognition that the burial (Smith et al, 2015) and storage (Smeaton et al, 2016) of carbon (C) in coastal marine sediments is an important factor in the global carbon cycle (Bauer et al, 2013) that provides an essential climate-regulating service (Smith et al, 2015)
Gets and which constitute a significant component of natural capital for Scotland and the UK
Our results indicate that the 640.7 ± 46 Mt of C held within the sediments of these fjords is of similar if not greater magnitude than most terrestrial C stores
Summary
There is growing recognition that the burial (Smith et al, 2015) and storage (Smeaton et al, 2016) of carbon (C) in coastal marine sediments is an important factor in the global carbon cycle (Bauer et al, 2013) that provides an essential climate-regulating service (Smith et al, 2015). Coastal sediments have been shown to be globally significant repositories for C, with an estimated 126.2 Mt of C being buried annually (Duarte et al, 2005). Of the different coastal depositional environments, fjords have been shown to be “hotspots” for C burial, with approximately 11 % of the annual global marine carbon sequestration occurring within fjordic environments (Smith et al, 2015). It is clear that these areas are important for the burial and long-term storage of C, the actual quantity of C held within coastal sediment remains largely unaccounted for.
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