Gas hydrate stability condition in the northeastern continental slope off Sakhalin Island, the Sea of Okhotsk

Abstract

Gas hydrates are widely distributed in the northeastern Sakhalin continental slope, the Sea of Okhotsk. The Sea of Okhotsk is very cold sea up to ~ 0° C just below sea surface. Top of the gas hydrate stability zone (TGHSZ) is theoretically expected to be at 300 m water depth. Such a shallow TGHSZ is evident by field observations

1) gas flares in the water column rising above 300 m, 2) the bottom simulating reflectors on the seismic profiles merging with the seafloor at 300 m, 3) gas hydrates sampled on the seafloor at 385 m water depth in 2005. Because the shallow TGHSZ should be quite vulnerable to changes in stability condition like sea-level fall or rise, the Sea of Okhotsk is the promising area to study methane behaviors released from gas hydrate due to past global environmental changes.