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Removal of methane through hydrological, microbial, and geochemical processes in the shallow sediments of pockmarks along eastern Vestnesa Ridge (Svalbard)

Removal of methane through hydrological, microbial, and geochemical processes in the shallow sediments of pockmarks along eastern Vestnesa Ridge (Svalbard)
Removal of methane through hydrological, microbial, and geochemical processes in the shallow sediments of pockmarks along eastern Vestnesa Ridge (Svalbard)
The recent discovery of methane seeps in the Arctic region requires a better understanding of the fate of methane in marine sediments if we are to understand the contributions of methane to Arctic ecosystems and climate change. To this goal, we analyze pore water data from five sites along eastern Vestnesa Ridge, a sediment drift off-north-west Svalbard, to quantify the consumption of dissolved methane across the sulfate-methane-transition-zone which are 3–5 m below seafloor from the investigated sites. We use transport-reaction models to quantify the hydrology as well as the carbon mass balance in the sediments. Pore water profiles and our model results demonstrate that hydrological, microbial, and geochemical processes/reactions efficiently remove methane carbon from fluid over different time scales. We interpret the nonsteady-state behavior of the first 50–70 cm of our pore water profiles from the active sites as an annual scale downward fluid flow due to a seepage-related pressure imbalance. Such downward flow supplies sulfate which enhances methane consumption through anaerobic oxidation of methane (AOM) within this depth range. Our steady-state modeling confirms the efficiency of AOM in consuming dissolved methane in the upper 0.8–1.2 m of sediments. Based on the phosphate profiles, we estimate that AOM at the active pockmarks may have been operating for the last two to four centuries. Precipitation of authigenic carbonate removes more than a quarter of the dissolved inorganic carbon produced by AOM and fixes it as authigenic carbonate in the sediments, a process that sequestrates methane carbon over geological time.
0024-3590
S324-S343
Hong, Wei-Li
5e20ad14-9acc-4d6b-aaf3-b9a93a70c040
Sauer, Simone
d977f24b-1b9f-4962-b1f4-0fc275b4b0f0
Panieri, Giuliana
c0559a7d-cf2c-4d0a-b61a-60889e963164
Ambrose, William G.
bba3e3f9-bcc4-4c04-a554-83f95cf37276
James, Rachael H.
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Plaza-Faverola, Andreia
87c1d96a-4821-476c-a299-b785222c5b4f
Schneider, Andrea
85edd58e-a552-48a1-a2ad-7a880f51390b
Hong, Wei-Li
5e20ad14-9acc-4d6b-aaf3-b9a93a70c040
Sauer, Simone
d977f24b-1b9f-4962-b1f4-0fc275b4b0f0
Panieri, Giuliana
c0559a7d-cf2c-4d0a-b61a-60889e963164
Ambrose, William G.
bba3e3f9-bcc4-4c04-a554-83f95cf37276
James, Rachael H.
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Plaza-Faverola, Andreia
87c1d96a-4821-476c-a299-b785222c5b4f
Schneider, Andrea
85edd58e-a552-48a1-a2ad-7a880f51390b

Hong, Wei-Li, Sauer, Simone, Panieri, Giuliana, Ambrose, William G., James, Rachael H., Plaza-Faverola, Andreia and Schneider, Andrea (2016) Removal of methane through hydrological, microbial, and geochemical processes in the shallow sediments of pockmarks along eastern Vestnesa Ridge (Svalbard). Limnology and Oceanography, 61 (S1), S324-S343. (doi:10.1002/lno.10299).

Record type: Article

Abstract

The recent discovery of methane seeps in the Arctic region requires a better understanding of the fate of methane in marine sediments if we are to understand the contributions of methane to Arctic ecosystems and climate change. To this goal, we analyze pore water data from five sites along eastern Vestnesa Ridge, a sediment drift off-north-west Svalbard, to quantify the consumption of dissolved methane across the sulfate-methane-transition-zone which are 3–5 m below seafloor from the investigated sites. We use transport-reaction models to quantify the hydrology as well as the carbon mass balance in the sediments. Pore water profiles and our model results demonstrate that hydrological, microbial, and geochemical processes/reactions efficiently remove methane carbon from fluid over different time scales. We interpret the nonsteady-state behavior of the first 50–70 cm of our pore water profiles from the active sites as an annual scale downward fluid flow due to a seepage-related pressure imbalance. Such downward flow supplies sulfate which enhances methane consumption through anaerobic oxidation of methane (AOM) within this depth range. Our steady-state modeling confirms the efficiency of AOM in consuming dissolved methane in the upper 0.8–1.2 m of sediments. Based on the phosphate profiles, we estimate that AOM at the active pockmarks may have been operating for the last two to four centuries. Precipitation of authigenic carbonate removes more than a quarter of the dissolved inorganic carbon produced by AOM and fixes it as authigenic carbonate in the sediments, a process that sequestrates methane carbon over geological time.

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More information

Accepted/In Press date: 29 February 2016
e-pub ahead of print date: 12 March 2016
Published date: 18 November 2016
Organisations: Geochemistry

Identifiers

Local EPrints ID: 394381
URI: https://eprints.soton.ac.uk/id/eprint/394381
ISSN: 0024-3590
PURE UUID: 92c161f0-b4a4-44a7-a13a-5840f323b093

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Date deposited: 13 May 2016 14:21
Last modified: 15 Jul 2019 20:30

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