Organic matter of the World Ocean

Romankevich, E. A.; Vetrov, A. A.; Peresypkin, V. I.

doi:10.1016/j.rgg.2009.03.013

Cited by 56 publications

(32 citation statements)

References 9 publications

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“…POC concentrations in Holocene surface sediments have been measured at several thousand sites covering most depositional areas at the seabed [7,8]. The available data have been compiled and evaluated to produce a global map of POC concentrations in marine surface sediments ( Figure 1).…”

Section: Holocene Poc Accumulation Ratesmentioning

confidence: 99%

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The Global Inventory of Methane Hydrate in Marine Sediments: A Theoretical Approach

et al. 2012

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Abstract:The accumulation of methane hydrate in marine sediments is controlled by a number of physical and biogeochemical parameters including the thickness of the gas hydrate stability zone (GHSZ), the solubility of methane in pore fluids, the accumulation of particulate organic carbon at the seafloor, the kinetics of microbial organic matter degradation and methane generation in marine sediments, sediment compaction and the ascent of deep-seated pore fluids and methane gas into the GHSZ. Our present knowledge on these controlling factors is discussed and new estimates of global sediment and methane fluxes are provided applying a transport-reaction model at global scale. The modeling and the data evaluation yield improved and better constrained estimates of the global pore volume within the modern GHSZ (≥44 × 10 ) and the inventory of methane hydrates in marine sediments (≥455 Gt of methane-bound carbon).

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Section: Holocene Poc Accumulation Ratesmentioning

confidence: 99%

“…Concentration of particulate organic carbon (POC) in Holocene surface sediments [7,8]. The color coding indicates POC values in wt.%.…”

Section: Figurementioning

confidence: 99%

The Global Inventory of Methane Hydrate in Marine Sediments: A Theoretical Approach

et al. 2012

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“…Suess, 1980;Martens et al, 1992;Seiter et al, 2005;Romankevich et al, 2009;Zonneveld et al, 2010). In order to find good approximations to the distribution of the POC incorporated in the sediment in the world ocean, the following two options were considered.…”

Section: Particulate Organic Carbonmentioning

confidence: 99%

Estimation of the global inventory of methane hydrates in marine sediments using transfer functions

et al. 2013

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The accumulation of gas hydrates in marine sediments is essentially controlled by the accumulation of particulate organic carbon (POC) which is microbially converted into methane, the thickness of the gas hydrate stability zone (GHSZ) where methane can be trapped, the sedimentation rate (SR) that controls the time that POC and the generated methane stays within the GHSZ, and the delivery of methane from deep-seated sediments by ascending pore fluids and gas into the GHSZ. Recently, Wallmann et al. (2012) presented transfer functions to predict the gas hydrate inventory in diffusion-controlled geological systems based on SR, POC and GHSZ thickness for two different scenarios: normal and full compacting sediments. We apply these functions to global data sets of bathymetry, heat flow, seafloor temperature, POC input and SR, estimating a global mass of carbon stored in marine methane hydrates from 3 to 455 Gt of carbon (GtC) depending on the sedimentation and compaction conditions. The global sediment volume of the GHSZ in continental margins is estimated to be 60–67 × 1015 m3, with a total of 7 × 1015 m3 of pore volume (available for GH accumulation). However, seepage of methane-rich fluids is known to have a pronounced effect on gas hydrate accumulation. Therefore, we carried out a set of systematic model runs with the transport-reaction code in order to derive an extended transfer function explicitly considering upward fluid advection. Using averaged fluid velocities for active margins, which were derived from mass balance considerations, this extended transfer function predicts the enhanced gas hydrate accumulation along the continental margins worldwide. Different scenarios were investigated resulting in a global mass of sub-seafloor gas hydrates of ~ 550 GtC. Overall, our systematic approach allows to clearly and quantitatively distinguish between the effect of biogenic methane generation from POC and fluid advection on the accumulation of gas hydrate, and hence, provides a simple prognostic tool for the estimation of large-scale and global gas hydrate inventories in marine sediments

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“…Both, POC concentrations in surface sediments and bulk sedimentation rates are needed to constrain this key parameter. The POC concentrations in surface sediments were implemented in the model according to the data set from Seiter et al (2004) and Romankevich et al (2009) with a maximum lateral resolution of 1 Â 1 (Fig. EA-6).…”

Section: Input Datamentioning

confidence: 99%

“…POC concentrations at the upper boundary of the model columns were set to the ambient values given by Seiter et al (2004) and Romankevich et al (2009). Burial velocities at zero depth (w 0 ) were defined as a function of water depth applying Eq.…”

Section: Numerical Proceduresmentioning

confidence: 99%

Estimation of the global amount of submarine gas hydrates formed via microbial methane formation based on numerical reaction-transport modeling and a novel parameterization of Holocene sedimentation

Burwicz

Rüpke

Wallmann

2011

Geochimica et Cosmochimica Acta

149

131

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This study provides new estimates for the global offshore methane hydrate inventory formed due to microbial CH 4 production under Quaternary and Holocene boundary conditions. A multi-1D model for particular organic carbon (POC) degradation, gas hydrate formation and dissolution is presented. The novel reaction-transport model contains an open three-phase system of two solid compounds (organic carbon, gas hydrates), three dissolved species (methane, sulfates, inorganic carbon) and one gaseous phase (free methane). The model computes time-resolved concentration profiles for all compounds by accounting for chemical reactions as well as diffusive and advective transport processes. The reaction module builds upon a new kinetic model of POC degradation which considers a down-core decrease in reactivity of organic matter. Various chemical reactions such as organic carbon decay, anaerobic oxidation of methane, methanogenesis, and sulfate reduction are resolved using appropriate kinetic rate laws and constants. Gas hydrates and free gas form if the concentration of dissolved methane exceeds the pressure, temperature, and salinity-dependent solubility limits of hydrates and/or free gas, with a rate given by kinetic parameters. Global input grids have been compiled from a variety of oceanographic, geological and geophysical data sets including a new parameterization of sedimentation rates in terms of water depth.We find prominent gas hydrate provinces offshore Central America where sediments are rich in organic carbon and in the Arctic Ocean where low bottom water temperatures stabilize methane hydrates. The world's total gas hydrate inventory is estimated at 0:82 Â 10 13 m 3 -2:10 Â 10 15 m 3 CH 4 (at STP conditions) or, equivalently, 4.18-995 Gt of methane carbon. The first value refers to present day conditions estimated using the relatively low Holocene sedimentation rates; the second value corresponds to a scenario of higher Quaternary sedimentation rates along continental margins.Our results clearly show that in-situ POC degradation is at present not an efficient hydrate forming process. Significant hydrate deposits in marine settings are more likely to have formed at times of higher sedimentation during the Quaternary or as a consequence of upward fluid transport at continental margins.

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Organic matter of the World Ocean

Cited by 56 publications

References 9 publications

The Global Inventory of Methane Hydrate in Marine Sediments: A Theoretical Approach

The Global Inventory of Methane Hydrate in Marine Sediments: A Theoretical Approach

Estimation of the global inventory of methane hydrates in marine sediments using transfer functions

Estimation of the global amount of submarine gas hydrates formed via microbial methane formation based on numerical reaction-transport modeling and a novel parameterization of Holocene sedimentation

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