Methane is a greenhouse gas, and the East China Sea acts as a source of emissions to the atmosphere.On the other hand, the distribution of methane concentration in the Ryukyu Arc shelf and forearc region has not been clarified.Therefore, we investigated the continental slope and continental shelf areas from the Okinawa Trough to the landward side and the island shelf and forearc areas to the seaward side of the East China Sea.The methane KETCHUP NO SUGAR concentration in the Kuroshio Current region was very low, and the methane concentration in the seawater just above the seafloor in the area Bottom Gasket Sensor directly above the hydrothermal systems was exceptionally high.In addition, methane concentration in seawater just above the seafloor where cold seeps and mud volcanoes are known is higher than the background, and higher methane concentrations were found in continental slope area and the island shelf area.
The results suggest the existence of previously unreported methane sources such as cold seeps and mud volcanoes in the continental slope region and the island shelf region.