The role of tephra in enhancing organic carbon preservation in marine sediments

Longman, Jack; Palmer, Martin R.; Gernon, Thomas M.; Manners, Hayley

doi:10.1016/j.earscirev.2019.03.018

Cited by 54 publications

(32 citation statements)

References 104 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Another potential carbon sink in tephra is authigenic carbonate (Schrag et al., 2013), which may form in tephra layers themselves (Longman et al., 2021), or sediments in which levels of Ca 2+ and Mg 2+ have been enhanced by ash deposition (Hong et al., 2020; Longman et al., 2019; Luo et al., 2020; Torres et al., 2020). In most tephras and sediments at site U1139D, there is little evidence for this process occurring (Figure 2b), potentially due to the small amount of carbonate precipitation typically promoted by ash alteration (Hong et al., 2020), but there are exceptions, particularly in one layer where carbonate contents exceed 50 wt% (tephra 7; Figure 2b).…”

Section: Discussionmentioning

confidence: 99%

“…There are four mechanisms by which enhanced preservation of OC in marine sediments may occur as a result of tephra deposition and diagenesis: (a) fertilization; (b) reactive metal bonding; (c) reduced oxidant exposure, and (d) authigenic carbonate formation (Longman et al., 2019, 2020). Upon deposition in the ocean, and as a result of the dissolution of reactive mineral phases, tephra releases large amounts of macro‐ and micronutrients such as P, Fe and Mn (Frogner et al., 2001; Jones & Gislason, 2008) that may alleviate deficiencies (Moore et al., 2013), particularly when Fe is the limiting nutrient.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Tephra Deposition and Bonding With Reactive Oxides Enhances Burial of Organic Carbon in the Bering Sea

Longman

Gernon

Palmer

et al. 2021

Global Biogeochemical Cycles

Self Cite

View full text Add to dashboard Cite

Preservation of organic carbon (OC) in marine sediments exerts a major control on the cycling of carbon in the Earth system. In these marine environments, OC preservation may be enhanced by diagenetic reactions in locations where deposition of fragmental volcanic material called tephra occurs. While the mechanisms by which this process occurs are well understood, site‐specific studies of this process are limited. Here, we report a study of sediments from the Bering Sea (IODP Site U1339D) to investigate the effects of marine tephra deposition on carbon cycling during the Pleistocene and Holocene. Our results suggest that tephra layers are loci of OC burial with distinct δ13C values, and that this process is primarily linked to bonding of OC with reactive metals, accounting for ∼80% of all OC within tephra layers. In addition, distribution of reactive metals from the tephra into non‐volcanic sediments above and below the tephra layers enhances OC preservation in these sediments, with ∼33% of OC bound to reactive phases. Importantly, OC‐Fe coupling is evident in sediments >700,000 years old. Thus, these interactions may help explain the observed preservation of OC in ancient marine sediments.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tephra Deposition and Bonding With Reactive Oxides Enhances Burial of Organic Carbon in the Bering Sea

Longman

Gernon

Palmer

et al. 2021

Global Biogeochemical Cycles

Self Cite

View full text Add to dashboard Cite

show abstract

“…Multiple factors could be responsible for this mismatch. Previous estimates for global carbonate authigenesis were based primarily on the Ca 2+ flux into sediments from the overlying water column and do not account for Ca 2+ fluxes toward shallow sediment from deep methanogenic zones due to MSiW (Longman et al, 2019). Further, a higher authigenic carbonate sink is expected when Mg 2+ fluxes into shallow marine sediments are also considered along with the Ca 2+ fluxes (Berg, 2018;Berg et al, 2019).…”

Section: Importance Of Methane Derived Authigenic Carbonate Precipitamentioning

confidence: 99%

Dissolved Inorganic Carbon Pump in Methane-Charged Shallow Marine Sediments: State of the Art and New Model Perspectives

et al. 2020

View full text Add to dashboard Cite

Methane transport from subsurface reservoirs to shallow marine sediment is characterized by unique biogeochemical interactions significant for ocean chemistry. Sulfate-Methane Transition Zone (SMTZ) is an important diagenetic front in the sediment column that quantitatively consumes the diffusive methane fluxes from deep methanogenic sources toward shallow marine sediments via sulfate-driven anaerobic oxidation of methane (AOM). Recent global compilation from diffusion-controlled marine settings suggests methane from below and sulfate from above fluxing into the SMTZ at an estimated rate of 3.8 and 5.3 Tmol year −1 , respectively, and wider estimate for methane flux ranges from 1 to 19 Tmol year −1. AOM converts the methane carbon to dissolved inorganic carbon (DIC) at the SMTZ. Organoclastic sulfate reduction (OSR) and deep-DIC fluxes from methanogenic zones contribute additional DIC to the shallow sediments. Here, we provide a quantification of 8.7 Tmol year −1 DIC entering the methane-charged shallow sediments due to AOM, OSR, and the deep-DIC flux (range 6.4-10.2 Tmol year −1). Of this total DIC pool, an estimated 6.5 Tmol year −1 flows toward the water column (range: 3.2-9.2 Tmol year −1), and 1.7 Tmol year −1 enters the authigenic carbonate phases (range: 0.6-3.6 Tmol year −1). This summary highlights that carbonate authigenesis in settings dominated by diffusive methane fluxes is a significant component of marine carbon burial, comparable to ∼15% of carbonate accumulation on continental shelves and in the abyssal ocean, respectively. Further, the DIC outflux through the SMTZ is comparable to ∼20% of global riverine DIC flux to oceans. This DIC outflux will contribute alkalinity or CO 2 in different proportions to the water column, depending on the rates of authigenic carbonate precipitation and sulfide oxidation and will significantly impact ocean chemistry and potentially atmospheric CO 2. Settings with substantial carbonate precipitation and sulfide oxidation at present are contributing CO 2 and thus to ocean acidification. Our synthesis emphasizes the importance of SMTZ as not only a methane sink but also an important diagenetic front for global DIC cycling. We further underscore the need to incorporate a DIC pump in methane-charged shallow marine sediments to models for coastal and geologic carbon cycling.

show abstract

“…The variety of processes controlling the Corg burial efficiency (CBE) lead to wide geographical variations in this value, from >70% to <0.3%; (Dunne et al, 2007). Within these processes there are four distinct mechanisms by which tephra deposition enhances CBE (Longman et al, 2019), outlined below.…”

Section: The Approachmentioning

confidence: 99%

“…Hence, we present a potential GGR mechanism based on enhanced input of the products of explosive volcanism (Figure 1) into the oceans. This approach builds on the role that natural tephra deposition in the oceans plays in the carbon cycle (Figure 2) (Longman et al, 2019) and examines the potential enhancement of these natural processes to achieve GGR. Based on real-world data, we calculate the potential of the proposed method to sequester atmospheric carbon, and provide an estimate of likely costs.…”

Section: Introductionmentioning

confidence: 99%

Viability of greenhouse gas removal via artificial addition of volcanic ash to the ocean

2020

Self Cite

View full text Add to dashboard Cite

Attempts to mitigate human contributions to climate change have become a highly debated topic, as it becomes evident that optional global emission reductions are not being adhered to by many nations. Therefore, substantial research is taking place into negative carbon technologies that actively reduce the amount of atmospheric carbon dioxide (CO2), via greenhouse gas removal (GGR). Various GGR methods have been proposed, from reforestation to ocean fertilisation. Here, we discuss the advantages of an approach based on the enhanced input of tephra to the ocean, to increase the drawdown of atmospheric CO2. Natural addition of tephra to the ocean results in enhanced organic matter preservation in sediment; hence augmenting its delivery should raise the level of sequestration. Our calculations indicate offshore tephra addition could sequester 2750 tonnes of CO2 per 50,000 tonnes of ash delivered (a typical bulk carrier's capacity). The cost is estimated to be ~$55 per tonne of CO2 sequestered and is an order of magnitude cheaper than many other proposed GGR technologies.Further advantages include; tephra addition is simply an augmentation of a natural Earth process, it is a low technology approach that requires few developments, and it may sequester carbon for thousands of years. Hence, we suggest offshore tephra addition warrants further investigation to assess its viability.

show abstract

The role of tephra in enhancing organic carbon preservation in marine sediments

Cited by 54 publications

References 104 publications

Tephra Deposition and Bonding With Reactive Oxides Enhances Burial of Organic Carbon in the Bering Sea

Tephra Deposition and Bonding With Reactive Oxides Enhances Burial of Organic Carbon in the Bering Sea

Dissolved Inorganic Carbon Pump in Methane-Charged Shallow Marine Sediments: State of the Art and New Model Perspectives

Viability of greenhouse gas removal via artificial addition of volcanic ash to the ocean

Contact Info

Product

Resources

About