Clathrate Hydrates in Nature

Hester, Keith C.; Brewer, Peter G.

doi:10.1146/annurev.marine.010908.163824

Cited by 179 publications

(110 citation statements)

References 112 publications

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“…They have been recognized as a key factor with respect to past and future climate change (e.g. Hester and Brewer, 2009;Dickens, 2001a;Adam, 2002;Archer, 2007;Lunt et al, 2011;Biastoch et al, 2011) and are considered as a new unconventional resource of natural gas (e.g. Sloan, 2003;Boswell, 2009).…”

Section: Introductionmentioning

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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Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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“…They have attracted increasing interest in marine geosciences for various reasons: (i) the use of GH as additional energy source (e.g. Bohannon, 2008;Hester and Brewer, 2009), (ii) the climate effect of melting GH and CH 4 -release into sea water and the atmosphere induced by seafloor warming (e.g Dickens et al, 1995;Kennett et al, 2003;Milkov, 2004;Reagan and Moridis, 2009), and (iii) the potential of dissociating GH triggering slope failure events (Xu and Germanovich, 2006).…”

Section: Introductionmentioning

confidence: 99%

A transfer function for the prediction of gas hydrate inventories in marine sediments

et al. 2010

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Abstract.A simple prognostic tool for gas hydrate (GH) quantification in marine sediments is presented based on a diagenetic transport-reaction model approach. One of the most crucial factors for the application of diagenetic models is the accurate formulation of microbial degradation rates of particulate organic carbon (POC) and the coupled formation of biogenic methane. Wallmann et al. (2006) suggested a kinetic formulation considering the ageing effects of POC and accumulation of reaction products (CH 4 , CO 2 ) in the pore water. This model is applied to data sets of several ODP sites in order to test its general validity. Based on a thorough parameter analysis considering a wide range of environmental conditions, the POC accumulation rate (POCar in g/m 2 /yr) and the thickness of the gas hydrate stability zone (GHSZ in m) were identified as the most important and independent controls for biogenic GH formation. Hence, depth-integrated GH inventories in marine sediments (GHI in g of CH 4 per cm 2 seafloor area) can be estimated as: The transfer function gives a realistic first order approximation of the minimum GH inventory in low gas flux (LGF) systems. The overall advantage of the presented function is its simplicity compared to the application of complex numerical models, because only two easily accessible parameters need to be determined.

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“…The exact inventory of methane hydrates that are currently stored in the sediments below the ocean remains highly uncertain, between 500 and 63,400 Gt C (Hester and Brewer 2009), but consensus exists that this represents a significant fraction of the amount of carbon globally stored, comparable to the amounts of other fossil fuels. Owing to high pressure and cold temperature conditions, methane today remains in stable hydrate form below 300 m (Tishchenko and others 2005).…”

Section: Release Of Methane Hydrates Into the Oceanmentioning

confidence: 99%

Taking Action Against Ocean Acidification: A Review of Management and Policy Options

Billé

Kelly

Biastoch

et al. 2013

Environmental Management

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Ocean acidification has emerged over the last two decades as one of the largest threats to marine organisms and ecosystems. However, most research efforts on ocean acidification have so far neglected management and related policy issues to focus instead on understanding its ecological and biogeochemical implications. This shortfall is addressed here with a systematic, international and critical review of management and policy options. In particular, we investigate the assumption that fighting acidification is mainly, but not only, about reducing CO 2 emissions, and explore the leeway that this emerging problem may open in old environmental issues. We review nine types of management responses, initially grouped under four categories: preventing ocean acidification; strengthening ecosystem resilience; adapting human activities; and repairing damages. Connecting and comparing options leads to classifying them, in a qualitative way, according to their potential and feasibility. While reducing CO 2 emissions is confirmed as the key action that must be taken against acidification, some of the other options appear to have the potential to buy time, e.g. by relieving the pressure of other stressors, and help marine life face unavoidable acidification. Although the existing legal basis to take action shows few gaps, policy challenges are significant: tackling them will mean succeeding in various areas of environmental management where we failed to a large extent so far.

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Clathrate Hydrates in Nature

Cited by 179 publications

References 112 publications

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

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

A transfer function for the prediction of gas hydrate inventories in marine sediments

Taking Action Against Ocean Acidification: A Review of Management and Policy Options

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