Experimental modeling of methane release from intrapermafrost relic gas hydrates when sediment temperature change

Special experiment on metastable relic methane hydrates behavior in clay-enriched sediment recovered from “Yamal ice crater” has been arranged to check sensitivity of relic gas hydrates to small temperature changes in permafrost section. The experiment was conducted in an experimental cell with P/T conditions registration and equipped by stirrer. Prepared sample was saturated by methane hydrates and chilled to temperature −7 °C, and then cell was depressurized to form metastable hydrates. After few times of depressurization (extra pressure relief) and pressure stabilization for a relatively long time at temperature −6.79 °C, the sample was slowly heated to temperature +2.0 °C. It was established, that even small temperature changes have a great impact to metastable intrapermafrost hydrates. The majority of remaining (after depressurization) metastable hydrates had decomposed in the temperature range −6.75-−6.57 °C practically immediately after the sample slow heating beginning, confirming the supposition, that permafrost can produce huge volumes of greenhouse gases even at small surface (climatic) changes without sediment ice complete thawing.