One of the more apocalyptic scenarios surrounding anthropogenic climate change is the destabilization of the planet's vast methane hydrate reserves. Under this nightmare contingency, warming oceans cause the gas hydrate stability zone to migrate downward, leaving substantial stores of the ice-like substance in a metastable state. As they dissolve, methane is released into the water column and ultimately the atmosphere, where it wreaks havoc as a strong greenhouse gas. In a recent paper, Kretschmer et al. use ocean circulation simulations and other models to show how bottom water temperatures may change over the next century, producing a fascinating map of anticipated thermal changes. Shallow shelf regions are expected to experience the largest changes, up to a 3 degree C increase. Overall, a minimal global influence on methane hydrates is anticipated - roughly 0.03% of seafloor stocks. Abstract below, full paper [here].
Large amounts of methane hydrate locked up within marine sediments are vulnerable to climate change. Changes in bottom water temperatures may lead to their destabilization and the release of methane into the water column or even the atmosphere. In a multimodel approach, the possible impact of destabilizing methane hydrates onto global climate within the next century is evaluated. The focus is set on changing bottom water temperatures to infer the response of the global methane hydrate inventory to future climate change. Present and future bottom water temperatures are evaluated by the combined use of hindcast high-resolution ocean circulation simulations and climate modeling for the next century. The changing global hydrate inventory is computed using the parameterized transfer function recently proposed by Wallmann et al. (2012). We find that the present-day world's total marine methane hydrate inventory is estimated to be 1146 Gt of methane carbon. Within the next 100 years this global inventory may be reduced by ∼0.03% (releasing ∼473 Mt methane from the seafloor). Compared to the present-day annual emissions of anthropogenic methane, the amount of methane released from melting hydrates by 2100 is small and will not have a major impact on the global climate. On a regional scale, ocean bottom warming over the next 100 years will result in a relatively large decrease in the methane hydrate deposits, with the Arctic and Blake Ridge region, offshore South Carolina, being most affected.