[M-IS26] Gas hydrates in environmental-resource sciences

[MIS26-01] Massive seafloor methane release near the edge of the gas hydrate stability zone in southern Brazil

★Invited Papers

*Marcelo Ketzer¹, Daniel Praeg², Luiz F. Rodrigues³, Adolpho Augustin³, Maria A. G. Pivel⁴, Mahboubeh Rahmati-Abkenar¹, Dennis J. Miller⁵, Adriano R. Viana⁵, José A. Cupertino³ (1.Department of Biology and Environmental Science, Faculty of Health and Life Sciences, Linnaeus University, 2.Géoazur, 3.Petroleum and Natural Resources Institute, Pontificia Universidade Catolica do Rio Grande do Sul, 4.Instituto de Geociências, Universidade Federal do Rio Grande do Sul, 5.Petrobras)

Keywords:gas hydrate, climate change, gas flares, sulphate reduction

Ocean warming is causing gas hydrate dissociation and massive seafloor methane release in several places around the world. Our multidisciplinary and multi-scale data set demonstrated this phenomenon for the first time in the southern hemisphere, in the Rio Grande Cone, southern Brazil. Acoustic imaging of the water column shows the existence of hundreds of gas flares near the edge of the calculate methane hydrate stability zone and the outcrop of the bottom simulating reflection. Stable and radiogenic carbon isotope data of methane in gas hydrates, pores, and gas bubbles venting from the seafloor, suggest that gas hydrate dissociation is the main source of gas for the flares. Our data further indicates that gas hydrate dissociation is linked to contemporary ocean warming, and that anaerobic oxidation of methane cannot consume the massive amounts of gas released from hydrate dissociation, resulting in widespread seafloor methane emissions.