Geophys. Res. Lett. 35, L19806 (2008)

Methane deposits stored beneath the sea floor are unlikely to be a major contributor to climate change in the coming century, suggests a new study. Methane clathrates, ice-like structures of water and the potent greenhouse gas methane, are thought to be easily destabilized by rising ocean temperatures.

Credit: USGS

Jean-François Lamarque of the National Center for Atmospheric Research, Colorado, used climate model simulations to estimate the amount of methane from deep hydrates that could be released in high carbon dioxide conditions. He found that if atmospheric carbon dioxide emissions increase by 1 per cent a year over the coming century, up to 2,140 million tonnes of methane could enter the ocean. But recent observational data indicate that only 5 to 21 million tonnes of methane would then be released to the atmosphere, much less than the 500 million tonnes of methane presently emitted each year. However, much of the gas that doesn't initially reach the atmosphere could be utilized by marine microbes, resulting in a secondary release of carbon dioxide to the atmosphere.

The greatest amount of destabilization is expected to occur north of the Arctic Circle. The author notes that shallow methane clathrates may remain intact as rising sea levels could stabilize the deposits.