Simulating the Marine Methane Cycle in Response to Global Warming
Rising global temperatures are impacting the Earth’s oceans and will soon impact methane clathrates concentrated a few hundred meters below the mixed layer in sediments of the Arctic continental shelf. Some methane will be destabilized and emanate as dissolved gas into the Arctic Ocean. DOE-funded scientists have calculated the potential fate and effects of the methane plumes using a biogeochemical version of a global ocean model developed at Los Alamos National Lab. The model predicts that methane consuming marine microbes will oxidize the methane clathrates causing oxygen depletion and increased pH in poorly ventilated deep water masses, and also depleting nutrients. As a result, the undersea methane may expand and approach the atmosphere where it acts as an ultra-strong greenhouse gas. The model predicts that much of the effluent will remain below the ocean mixed layer while circuiting the central Arctic and then subducting into the deep Atlantic. The portion of methane predicted to rise from sea floor as bubbles remains a large uncertainty. A combination of modeling and field campaigns are needed to develop a better understanding of changes in the marine methane cycles with global warming.
Scott Elliott, Mathew Maltrud, Matthew Reagan, George Moridis and Philip Cameron Smith, J. Geophys. Res., doi:10.1029/2010JG001300.