New North Atlantic Methane Plumes

14th January 2010.

Words Anna Pigott.

The submarine gas hydrate stability zone (GHSZ) of the West Spitsbergen continental margin appears to be contracting in response to a 1 deg C temperature rise of the West Spitsbergen ocean current – potentially releasing ~20 Tg yr-1 of methane into sea water. MethaneNet researchers from the National Oceanography Centre in Southampton, Birmingham University, Royal Holloway University and IFM-Geomar in Germany found that the 1 deg C rise over the past 30 years is likely to have triggered the decomposition of gas hydrates (a process that liberates methane) in submarine sediments at depths where they would previously have been stable. More than 250 plumes of gas bubbles were discovered emerging at depths that suggest movement of the upper limit of the GHSZ from 360m down to 396m. If this movement is extrapolated to the 22,300 km2 of seabed along the northern, western and southern margins of the Svalbard archipelago, and assuming that the hydrate-to-methane budget is the same, the potential methane release by decomposition of hydrates is ~20 Tg yr-1 (equivalent to ~3% of the annual global atmospheric methane flux). Whether or not the methane will reach the atmosphere remains to be seen. Previous studies have suggested that methane released from submarine sediments has been a contributor to past climate change, though this study indicates that “it is unlikely that more than a very small fraction of the methane in the observed plumes reaches the atmosphere directly.” Instead, the scientists emphasise that the addition of methane to the ocean is itself significant because it increases acidity and lowers oxygen levels, with serious implications for marine biodiversity.

Reference: Westbrook, G. K., et al. (2009), Escape of methane gas from the seabed along the West Spitsbergen continental margin, Geophys. Res. Lett., 36, L15608, doi:10.1029/2009GL039191.

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