Thawing of Methane Hydrates
A methane hydrate is a type of clathrate, which is a molecular lattice containing an entrapped compound. In the case of a methane hydrate, the clathrate is a lattice "cage" formed of water molecules (H2O), within which is trapped one or more methane (CH4) molecules.
In order to preserve the hydrate structural stability, the temperature and pressure must be at levels that maintain the system in an ice form. Methane hydrates have been found in the permafrost of such land areas as Siberia and Alaska, where the year-round temperature does not rise above 0° Celsius. In ocean environments methane hydrates are extensive in sediments at shallow depths, not exceeding 2000 meters below the surface. In all cases the temperature is sufficiently low to maintain the ice structure year round. Methane hydrates have also been found in fresh water lakes in polar regions of Siberia.
The environmental dangers associated with methane hydrates center around:
- the extensive amount of methane hydrates present in both oceanic and land-based, permafrost environments,
- the vulnerability of frozen hydrates to increases in temperature, and
- the powerful greenhouse gas properties of methane, when compared to carbon dioxide.
In the case of permafrost, the potential for release of methane due to global warming is considerable and could lead to a "snowball" effect. If global warming produced an extensive thawing of permafrost, resulting in a release of copious amounts of methane into the atmosphere, this release would result in a positive feedback loop, with further warming of the environment, causing more thawing of permafrost, with the subsequent release of even more methane and more heating of the environment.