The project goal is to predict, given characteristic climate-induced temperature change, the conditions under which gas will be expelled from existing accumulations of gas hydrate into the shallow ocean or directly to the atmosphere. When those conditions are met, the fraction of the gas accumulation that escapes and the rate of escape shall be quantified. The predictions shall be applicable in Arctic regions and in gas hydrate systems at the updip limit of the stability zone on continental margins. The behavior shall be explored in response to both longer term changes in sea level rise (e.g., twenty-thousand years) and shorter term changes due to atmospheric warming by anthropogenic forcing (decadal time scale).
University of Texas at Austin, Austin, TX 73713-7726
The central hypothesis proposed is that hydrate melting (dissociation) due to climate change generates free gas that can, under certain conditions, propagate through the gas hydrate stability zone and vent at the seafloor or into the atmosphere. Gas venting through the regional hydrate stability zone is accomplished by alteration of the regional equilibrium conditions by increased salinity and heat due to hydrate formation. This research will explore the controls on whether methane reaches the seafloor (or atmosphere) as the original hydrate deposit dissociates and how to determine the magnitude of these fluxes. Previous efforts to simulate hydrate formation and disassociation have shown that coupling all physical processes is critical to understanding the macro-scale process of hydrate melting.
Equilibrium thermodynamics will be coupled with conservation of mass and energy with multiphase transport models in geologically heterogeneous sediments to simulate macro-scale behavior. Conservation of mass will involve methane, water, and salt; conservation of energy will use the latent heat of formation of hydrate. Based on previous efforts, these models will illustrate distinctive behaviors that have important first-order controls on how degassing occurs during warming. This research includes laboratory experiments explicitly designed to validate the models, which will illustrate how much confidence is warranted in the model predictions, and thus, greatly increasing their impact. The technology to be developed in this project could provide an essential component to the portfolio of technologies and knowledge needed to understand the impact of climate change on hydrate degassing.
The project has been completed. The final report is available below under "Additional Information".