Open AccessMarine sediments as a source of atmospheric methane
Author(s) -
R E Cranston
Publication year - 1994
Publication title -
bulletin of the geological society of denmark
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.674
H-Index - 28
eISSN - 2245-7070
pISSN - 0011-6297
DOI - 10.37570/bgsd-1995-41-11
Subject(s) - methane , plume , atmosphere (unit) , environmental science , seawater , flux (metallurgy) , oceanography , clathrate hydrate , advection , carbon dioxide , carbon cycle , atmospheric methane , greenhouse gas , geology , atmospheric sciences , hydrate , chemistry , ecology , physics , organic chemistry , ecosystem , biology , thermodynamics
Methane sources and sinks have been evaluated at 10 sites off the east coasts of Canada and Russia. More than 99% of the diffusive methane flux from marine sediments appears to be consumed by microbial oxidation when dissolved sulfate is present. At 3 sites, methane bubble vents were found. Two of the vents, located in the Okhotsk Sea, appear to result from gas being released along faults. The third plume site was located in a shallow harbour where a large amount of organic carbon is deposited in shallow water. The global diffusive and advective (bubbles) release of methane to the atmosphere from marine sediments is estimated to fall into the range of 1 - 10 TgC a-1 (1 Tg = 1012 g).Researchers have speculated that marine gas hydrate deposits hold vast quantitites of methane that may melt and be released as a result of global warming. A warmer atmosphere could directly heat the ocean and/or change ocean current systems, which could bring warmer water to some areas. Hydrate samples were recovered from two sites in the Okhotsk Sea. These deposits, in 700 to 800 m of water, would require water temperatures to increase by 8°C in order to melt the hydrate. Quantitative estimates of hydrate reservoirs near the minimum pressure stability zone are needed to remove the uncertainty whether this will be a significant positive feedback loop for global warming.