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| Titel |
Estimation of the global inventory of methane hydrates in marine sediments using transfer functions |
| VerfasserIn |
E. Piñero, M. Marquardt, C. Hensen, M. Haeckel, K. Wallmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 2 ; Nr. 10, no. 2 (2013-02-11), S.959-975 |
| Datensatznummer |
250017512
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| Publikation (Nr.) |
 copernicus.org/bg-10-959-2013.pdf |
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| Zusammenfassung |
| 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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