Abnormally High CH4 Concentrations in Seawater at Mid-Depths on the Continental Slopes of the Northern South China Sea

For the first time, CH 4 concentrations in the water column were measured during three cruises in the northern South China Sea. The abnormally high subsurface CH 4 concentrations that were found on the continental slopes may have been released from sediments and/or may have originated in CH 4 gas hydrates.