Monday, 5 November 2012

Methane Hydrates: A hidden source of global warming?

Hannah Bruce Macdonald

While it may seem there are already enough sources of greenhouse gases, a study has shown that large sources of methane may be released from their storage at the bottom of the sea. Off the East coast of North America large deposits of methane hydrate, a solid form of frozen methane trapped in ocean sediments, have been found. This methane hydrate is formed at the top few hundred metres of the ocean floor where the pressure is high and the temperature is low, far enough away from the Earth’s warm interior.

Changes in temperature and shifts in position of the Gulf Stream over recent years have allowed these methane reserves to ‘melt’ releasing 2.5 billion tonnes of methane. This gas is unlikely to move through the ocean to the surface, but will probably remain dissolved in the seawater where it will be converted by microbes. If this methane were to be released into the atmosphere, it would be unlikely to have much effect on global temperatures, but the main concern is for deep-ocean landslides. The breakdown of these methane hydrate reserves are capable of causing landslides in the seabed, which in turn have the knock-on effect of releasing even more methane, which could impact on global warming, while also having the potential to cause tsunamis.

Studies have been carried out using indirect measurements of sea-floor temperatures, from which the break-down of the methane hydrates has been inferred. On top of this little is known about the extent of methane hydrate present, or about the rate or mechanism at which this gas is released. Due to this, research is limited on methane hydrates potential as an energy source, or the effect it could have on global warming.