Methane hydrate stability and anthropogenic climate change D. Archer University of Chicago, Department of the Geophysical Sciences, USA
Abstract. Methane frozen into hydrate makes up a large reservoir of potentially
volatile carbon below the sea floor and associated with permafrost soils.
This reservoir intuitively seems precarious, because hydrate ice floats in
water, and melts at Earth surface conditions. The hydrate reservoir is so
large that if 10% of the methane were released to the atmosphere within a
few years, it would have an impact on the Earth's radiation budget
equivalent to a factor of 10 increase in atmospheric CO2.
Hydrates are releasing methane to the atmosphere today in response to
anthropogenic warming, for example along the Arctic coastline of Siberia.
However most of the hydrates are located at depths in soils and ocean
sediments where anthropogenic warming and any possible methane release will
take place over time scales of millennia. Individual catastrophic releases
like landslides and pockmark explosions are too small to reach a sizable
fraction of the hydrates. The carbon isotopic excursion at the end of the
Paleocene has been interpreted as the release of thousands of Gton C,
possibly from hydrates, but the time scale of the release appears to have
been thousands of years, chronic rather than catastrophic.
The potential climate impact in the coming century from hydrate methane
release is speculative but could be comparable to climate feedbacks from the
terrestrial biosphere and from peat, significant but not catastrophic. On
geologic timescales, it is conceivable that hydrates could release as much
carbon to the atmosphere/ocean system as we do by fossil fuel combustion.