Spatial variability of the methane hydrates stability zone upper boundary parameters in the water column of the Sea of Okhotsk

Based on all available oceanological information (131, 286 stations carried out from 1929 to 2020), for the first time for the Sea of Okhotsk, spatial patterns of the methane hydrate stability zone upper boundary (water temperature, salinity, depth of the upper boundary in the water column) parameters distribution are presented and discussed. The methane hydrate stability zone model is considered. We are revealed that in the Sea of Okhotsk, the minimum water temperature and the minimum depth of the upper boundary of the gas hydrate stability zone (less than 1°C and 300–320 m, respectively) are located near the eastern slope of Sakhalin Island. The maximum water temperature and maximum depth of the upper boundary (1.5–1.7°C and 340–350 m, respectively) are characteristic of the area adjacent to the central and northern straits of the Kuril Islands Arc, as well as above the slope of the Kamchatka Peninsula. The salinity values at the upper boundary of the methane hydrate stability zone in the Sea of Okhotsk vary within a narrow range from 33.4 to 33.6 psu, which is quite close to conditions for the stability of methane hydrate in seawater obtained by us. An area where in the water column there are no favorable thermobaric conditions for the formation and existence of methane hydrates has been identified.