BLAck sea MEthane (BLAME): from sediment to hydrosphere and its impact on hazard assessment – BLAME

Given that methane is a potent greenhouse gas, there is a need to define the methane budget associated to fluid systems and to understand the balance between the generation, migration, accumulation of hydrate and the emission of methane at the seafloor. Therefore, ascertaining the fate of methane and other hydrocarbons on regional to local scales from both free gas and hydrate dissociation leaks, remains an important scientific challenge. In this context, the Black Sea is of particular interest because the large number of active fluid systems injecting a significant volume of free gas into the sea, the majority of gas stored as gas hydrates and the ongoing dissociation of gas hydrate due to sediment salinization. In the last three decades, the geoscience community has devoted a special attention to the gas hydrate dynamics and their societal impact. Gas hydrates are widespread along the continental margins of the world and the amount of natural gas trapped in this solid form exceeds the known reserves of conventional fossil energy. On the other hand, the potential effects of gas hydrate on natural hazard and climate change remain poorly understood. Submarine slope failures in the vicinity of gas hydrates have been, very often, associated to the potential reduction of slope stability due to dissociation of gas hydrates caused by bottom water warming and sea level drop. However, 30 years of research into this process found no solid supporting evidence for this.
The BLAME project addresses the methane “cycle” of the Romanian sector of the Black Sea. To this end, the evolution of the fluid system will be studied from its formation in the sediment to its dispersion in the hydrosphere through migration pathways and storage in gas hydrate form. The project will focus on the impact of the fluid system on seafloor sedimentary deformation and slope instability. The project will be coordinated by Vincent Riboulot supported by an experienced team composed of eight researchers and engineers from the Marine Geoscience research unit at IFREMER. It will be enhanced by complementary skills of researchers from several French academic partners.
The BLAME project, associated with a new data acquisition expedition named GHASS2 (evaluated as first priority with an excellent assessment by CNFH committee), divided into five work-packages: geomorphology, chronology, sediment characterization, numerical modelling and methane “cycle”, in order to fulfil the main objectives of the project. We will apply a novel multidisciplinary approach integrating observation, characterization, quantification and numerical modelling. The approach will combine several complementary methods and disciplines: geomorphology, marine sedimentology, qualitative and quantitative geophysics, analysis of in-situ geotechnical parameters, sediment and water column geochemical analysis, numerical modelling to constrain the evolution of the gas hydrate system and its impact on slope stability.
The BLAME project is developed under the “Efficient resource management and adaptation to climate change” challenge and its main objective is to carry-out research on telluric hazards (gravitational hazards) in relation with natural mechanisms (pore fluid pressure in relation with free gas and gas hydrate). Our ability of understanding the fluid and sedimentary systems as a whole is crucial to the assessment of natural hazards as well as characterization of the amount of methane reaching the water column and potentially the atmosphere. This knowledge may improve the assessment of landslide and tsunami hazards in this densely populated coastal region. BLAME could be a starting point to assess the impact that this fluid system may have on climate.