Substantial stores of sedimentary carbon held in mid-latitude fjords

Smeaton, Craig; Austin, William E. N.; Davies, Althea; Baltzer, Agnès; Abell, Richard; Howe, John

doi:10.5194/bg-13-5771-2016

Cited by 31 publications

(73 citation statements)

References 60 publications

(72 reference statements)

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“…Building on the work of Smeaton et al (2016), which centred on Loch Sunart (56.705556, −5.737534), we focus on a further four fjords to develop site-specific sedimentary C stock estimations, which then allow us to make more precise estimates for the same range of fjordic system types in Scotland. The chosen sites are Loch Etive (56.459224, −5.311151), Loch Creran (56.536970, −5.324578), Loch Broom (57.873974, −5.117443) and Little Loch Broom (57.872144, −5.316385; Fig.…”

Section: Scotland's Fjordsmentioning

confidence: 99%

“…In total, 285 subsamples were collected from the sediment cores from Loch Etive (n = 133), Loch Broom (n = 78) and Little Loch Broom (n = 74). The data produced by Smeaton et al (2016) for the glacially derived sediment in Loch Sunart were used as a surrogate for all glacial sediments in this study since MD04-2833 remains the only mid-latitude fjord core with chronologically constrained glacial sediment (Baltzer et al, 2010). Detailed seabed seismic geophysical data for Loch Etive (Howe et al, 2002), Loch Creran (Mokeddem et al, 2015), Loch Broom (Stoker and Bradwell, 2009) and Little Loch Broom (Stoker et al, 2010) were compiled.…”

Section: Sample and Data Collectionmentioning

confidence: 99%

“…Globally 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).…”

Section: Introductionmentioning

confidence: 99%

“…Our work presented here utilises and extends the joint geochemistry and geophysical methodology developed by Smeaton et al (2016) by applying it to a number of mid-latitude fjords. Estimated sedimentary C stocks for individual fjords will be utilised to create the first national estimate of sedimentary C stocks in the coastal ocean and thus quantify an overlooked aspect of Scotland's natural capital.…”

Section: Introductionmentioning

confidence: 99%

“…This study applies the methodology of Smeaton et al (2016) in which sediment cores and seismic geophysical data were collected for four additional fjords. Figure 1 shows the location of each of the long (> 1 m) sediment cores extracted from the four fjords chosen to produce detailed sedimentary C stock estimates.…”

Section: Sample and Data Collectionmentioning

confidence: 99%

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

et al. 2017

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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 areanormalised 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-Scottish fjords are a more effective store of C than the terrestrial environment.-A total of 640.7 ± 46 Mt of C is stored in the sediment of Scotland's 111 fjords.-An estimated 31 139-40 615 t yr −1 of C is buried in the sediment of Scotland's fjords.-Fjord sediments are potentially the most effective store of C globally.

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Section: Scotland's Fjordsmentioning

confidence: 99%

Section: Sample and Data Collectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Sample and Data Collectionmentioning

confidence: 99%

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

et al. 2017

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Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords

Smeaton

Austin

2017

JGR Biogeosciences

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Fjords are recognized as globally important sites for the burial and long‐term storage of carbon (C) within sediments. The proximity of fjords to the terrestrial environment in combination with their geomorphology and hydrography results in the fjordic sediments being subsidized with organic carbon (OC) from the terrestrial environment. It has been well documented that terrestrial OC (OCterr) is an important component of coastal sediments, yet our understanding of the quantity of OCterr stored in these sediments remains poorly constrained. Utilizing Bayesian isotopic sediment fingerprinting techniques to the surface sediments of Loch Sunart, we estimate that 42.0 ± 10.1% of the OC is terrestrial in origin. Through combining these outputs with sedimentary OC stock estimates, we have calculated that the surface sediments (0–15 cm) hold 0.1 megaton (Mt) OCterr and estimate that the postglacial sediment held within the fjord contains 3.96 Mt OCterr. When these totals are compared to the quantity of OC stored in the adjacent terrestrial environment, it is clear that the fjord's catchment stores a greater amount of OCterr in the form of vegetation and soil. Though when normalized for area the results suggest that the marine sediments are a more effective long‐term store of OCterr than the adjacent terrestrial environment. This striking result highlights the importance of the terrestrial environment as a source of OC to the coastal ocean and that the OCterr subsidy to the marine sediments is a significant mechanism for the long‐term storage of OC in coastal marine sediments.

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Increased petrogenic and biospheric organic carbon burial in sub‐Antarctic fjord sediments in response to recent glacier retreat

Berg

Jivcov

Kusch

et al. 2021

Limnology & Oceanography

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Fjords are recognized as hotspots of organic carbon (OC) burial in the coastal ocean. In fjords with glaciated catchments, glacier discharge carries large amounts of suspended matter. This sedimentary load includes OC from bedrock and terrigenous sources (modern vegetation, peat, soil deposits), which is either buried in the fjord or remineralized during export, acting as a potential source of CO 2 to the atmosphere. In sub-Antarctic South Georgia, fjord-terminating glaciers have been retreating during the past decades, likely as a response to changing climate conditions. We determine sources of OC in surface sediments of Cumberland Bay, South Georgia, using lipid biomarkers and the bulk 14 C isotopic composition, and quantify OC burial at present and for the time period of documented glacier retreat (between 1958 and 2017). Petrogenic OC is the dominant type of OC in proximity to the present-day calving fronts (60.4 AE 1.4% to 73.8 AE 2.6%) and decreases to 14.0 AE 2.7% outside the fjord, indicating that petrogenic OC is effectively buried in the fjord. Beside of marine OC, terrigenous OC comprises 2.7 AE 0.5% to 7.9 AE 5.9% and is mostly derived from modern plants and Holocene peat and soil deposits that are eroded along the flanks of the fjord, rather than released by the retreating fjord glaciers. We estimate that the retreat of tidewater glaciers between 1958 and 2017 led to an increase in petrogenic carbon accumulation of 22% in Cumberland West Bay and 6.5% in Cumberland East Bay, suggesting that successive glacier retreat does not only release petrogenic OC into the fjord, but also increases the capacity of OC burial.

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Substantial stores of sedimentary carbon held in mid-latitude fjords

Cited by 31 publications

References 60 publications

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

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

Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords

Increased petrogenic and biospheric organic carbon burial in sub‐Antarctic fjord sediments in response to recent glacier retreat

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