Reference document for methane harmonized monitoring

ENVRIplus (Theme 1 'Technical innovation') developed a joint pilot experiment to measure methane transfer from the seafloor to the atmosphere, in a pilot study involving RIs ICOS, Eurofleets, EMSO and ACTRIS. The pilot experiment developed joint monitoring strategy for methane detection at various levels starting from the seafloor and moving across the water column, the water/air interface and the atmosphere. The Romanian sector of the Black Sea is the selected location. This area hosts a large number of emission sites of methane-rich gases, from the continental shelf to the deepest part of the basin. It is consequently a good candidate for investigating the fate of marine methane, from the sedimentary column to the atmosphere by combining the expertise and technologies of six EU teams. The methodology applied integrates (1) sampling from the three spheres (lithosphere, hydrosphere and atmosphere) for laboratory measurements of methane concentration by well-proven standard methods together with δ13C-CH4 analysis, (2) in situ measurements of methane concentration and δ13C- CH4 into the water column and the atmosphere, and (3) the deployment of a seafloor observatory for a short monitoring period (4-5 days) to evaluate the temporal variability of gas fluxes