Oceanic gas hydrate instability and dissociation in response to climate change

Paleooceanographic evidence has been used to postulate that methane from oceanic hydrates may have had a significant role in regulating past global climate, implicating global oceanic deposits of methane gas hydrate as the main culprit for a remarkably rapid sequence of global warming effects that occurred during the late Quaternary period. However, the behavior of contemporary oceanic methane hydrate deposits subjected to rapid temperature changes, like those predicted under future climate change scenarios, is poorly understood, and existing studies focus on deep hydrate deposits under equilibrium conditions. We simulated the dynamic response of several types of oceanic gas hydrate accumulations to temperature changes at the seafloor and assessed the potential for methane release into the ecosystem. The properties of benthic sediments, the saturation, stability, and distribution of the hydrates, the ocean depth, the geothermal gradient, and the effects of biogeochemical activity were considered. The results suggest that while many deep hydrate deposits are indeed stable under the influence of rapid seafloor temperature variations, shallow deposits, such as those found in arctic regions or in the Gulf of Mexico, can undergo rapid dissociation and produce significant carbon fluxes over a period of decades. These results may be used to provide a source term to regional or global climate models to determine the impact of gas hydrate deposits on global climate.