Mechanisms for a nutrient-conserving carbon pump in a seasonally stratified, temperate continental shelf sea

Humphreys, Matthew; Achterberg, Eric P.; Hopkins, Joanne; Chowdhury, Mohammed Z.H.; Griffiths, Alex M.; Hull, Tom; Smilenova, Angelina; Wihsgott, Juliane U.; Woodward, E. Malcolm S.; Moore, C. Mark

doi:10.1016/j.pocean.2018.05.001

Cited by 17 publications

(29 citation statements)

References 51 publications

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“…The water column of the NWES is strongly spatially and seasonally variable with respect to carbon stocks and flows. Strong interannual variability has also been observed in both dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) concentrations and air-sea CO 2 fluxes (Clargo et al, 2015;Hartman et al, 2018;Carr et al, 2018;Humphreys et al, 2018;Chaichana et al, 2019;Kitidis et al, 2019). Because of this variability and the patchy coverage of data (both in time and space), the water column was treated as a single box in the budget.…”

Section: Scope and Approachmentioning

confidence: 99%

“…Most studies conclude that the majority of pelagic primary production on the NWES is supported by nutrient inputs from the open ocean (e.g., Vermaat et al, 2008;Holt et al, 2012;Ruiz-Castillo et al, 2018) and therefore, it is key to the functioning of the shelf carbon pump that whilst there is net cross-shelf export of carbon, there is net import of nutrients. Furthermore, the role of transport and circulation in the dynamics of carbon uptake has recently been highlighted, both in terms of transport of riverine material to the shelf break and exchange of carbon between the shelf and open ocean (Sharples et al, 2016;Humphreys et al, 2018;Chaichana et al, 2019). Ultimately, the production and processing of organic matter is likely a key factor in the ability of shelf seas to take carbon up from the atmosphere, in spite of heavy riverine carbon loadings (e.g., Humphreys et al, 2018).…”

Section: Pelagic Stocks and Processesmentioning

confidence: 99%

“…Furthermore, the role of transport and circulation in the dynamics of carbon uptake has recently been highlighted, both in terms of transport of riverine material to the shelf break and exchange of carbon between the shelf and open ocean (Sharples et al, 2016;Humphreys et al, 2018;Chaichana et al, 2019). Ultimately, the production and processing of organic matter is likely a key factor in the ability of shelf seas to take carbon up from the atmosphere, in spite of heavy riverine carbon loadings (e.g., Humphreys et al, 2018).…”

Section: Pelagic Stocks and Processesmentioning

confidence: 99%

“…The resulting enrichment in DIC of a few percent contributes to the export of carbon off the shelf. DOC stocks are much smaller but show greater variability and may play an important role in off-shelf export (Carr et al, 2018;Humphreys et al, 2018;Chaichana et al, 2019). The pelagic system is therefore important in the shelf carbon cycle due to the processes which fix carbon from the atmosphere and physical circulation which removes this carbon to the open ocean, where it can be stored for centuries or longer.…”

Section: • the Pelagic System Drives Carbon Uptake Burial And Exportmentioning

confidence: 99%

“…In spite of much recent progress in understanding shelf carbon cycling on the NWES (e.g., Stahl et al, 2004;Thomas et al, 2005;Johnson et al, 2013;Hale et al, 2017;Hicks et al, 2017;Carr et al, 2018;Humphreys et al, 2018;Chaichana et al, 2019;Davis et al, 2019;García-Martín et al, 2019), there is still a great deal of uncertainty in both the mechanisms governing carbon dynamics and the magnitudes of contemporary carbon stocks and flows, as well as their responses to future change.…”

Section: Introductionmentioning

confidence: 99%

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Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

et al. 2020

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A carbon budget for the northwest European continental shelf seas (NWES) was synthesized using available estimates for coastal, pelagic and benthic carbon stocks and flows. Key uncertainties were identified and the effect of future impacts on the carbon budget were assessed. The water of the shelf seas contains between 210 and 230 Tmol of carbon and absorbs between 1.3 and 3.3 Tmol from the atmosphere annually. Offshelf transport and burial in the sediments account for 60-100 and 0-40% of carbon outputs from the NWES, respectively. Both of these fluxes remain poorly constrained by observations and resolving their magnitudes and relative importance is a key research priority. Pelagic and benthic carbon stocks are dominated by inorganic carbon. Shelf sediments contain the largest stock of carbon, with between 520 and 1600 Tmol stored in the top 0.1 m of the sea bed. Coastal habitats such as salt marshes and mud flats contain large amounts of carbon per unit area but their total carbon stocks are small compared to pelagic and benthic stocks due to their smaller spatial extent. The large pelagic stock of carbon will continue to increase due to the rising concentration of atmospheric CO 2 , with associated pH decrease. Pelagic carbon stocks and flows are also likely to be significantly affected by increasing acidity and temperature, and circulation changes but the net impact is uncertain. Benthic carbon stocks will be affected by increasing temperature and acidity, and decreasing oxygen concentrations, although the net impact of these interrelated changes on carbon stocks is uncertain and a major knowledge gap. The impact of bottom trawling on benthic carbon stocks Frontiers in Marine Science | www.frontiersin.org 1 March 2020 | Volume 7 | Article 143Legge et al.Carbon on the Northwest European Shelf is unique amongst the impacts we consider in that it is widespread and also directly manageable, although its net effect on the carbon budget is uncertain. Coastal habitats are vulnerable to sea level rise and are strongly impacted by management decisions. Local, national and regional actions have the potential to protect or enhance carbon storage, but ultimately global governance, via controls on emissions, has the greatest potential to influence the long-term fate of carbon stocks in the northwestern European continental shelf.

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Section: Scope and Approachmentioning

confidence: 99%

Section: Pelagic Stocks and Processesmentioning

confidence: 99%

Section: Pelagic Stocks and Processesmentioning

confidence: 99%

Section: • the Pelagic System Drives Carbon Uptake Burial And Exportmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

et al. 2020

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Bottom mixed layer oxygen dynamics in the Celtic Sea

et al. 2020

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The seasonally stratified continental shelf seas are highly productive, economically important environments which are under considerable pressure from human activity. Global dissolved oxygen concentrations have shown rapid reductions in response to anthropogenic forcing since at least the middle of the twentieth century. Oxygen consumption is at the same time linked to the cycling of atmospheric carbon, with oxygen being a proxy for carbon remineralisation and the release of CO2. In the seasonally stratified seas the bottom mixed layer (BML) is partially isolated from the atmosphere and is thus controlled by interplay between oxygen consumption processes, vertical and horizontal advection. Oxygen consumption rates can be both spatially and temporally dynamic, but these dynamics are often missed with incubation based techniques. Here we adopt a Bayesian approach to determining total BML oxygen consumption rates from a high resolution oxygen time-series. This incorporates both our knowledge and our uncertainty of the various processes which control the oxygen inventory. Total BML rates integrate both processes in the water column and at the sediment interface. These observations span the stratified period of the Celtic Sea and across both sandy and muddy sediment types. We show how horizontal advection, tidal forcing and vertical mixing together control the bottom mixed layer oxygen concentrations at various times over the stratified period. Our muddy-sand site shows cyclic spring-neap mediated changes in oxygen consumption driven by the frequent resuspension or ventilation of the seabed. We see evidence for prolonged periods of increased vertical mixing which provide the ventilation necessary to support the high rates of consumption observed.

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Regional differences in seasonal variation of air–sea CO2 exchange in the Yellow Sea

Wang

Zhai

2021

Continental Shelf Research

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Mechanisms for a nutrient-conserving carbon pump in a seasonally stratified, temperate continental shelf sea

Cited by 17 publications

References 51 publications

Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

Bottom mixed layer oxygen dynamics in the Celtic Sea

Regional differences in seasonal variation of air–sea CO2 exchange in the Yellow Sea

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