The paper presents the results of mathematical modeling of the subsea permafrost dynamics and distribution on the East Arctic shelf. In this study the geographic distribution of the geothermal flow values was taken into account. Estimates of the permafrost thickness on the Laptev and the East Siberian seas shelf have been obtained. The depth of occurrence of the lower boundary of the frozen layer on the shelf was about 50-700 m. The position of the submarine permafrost upper boundary in the bottom sediments of the seas of the East Arctic substantially depends on the depth of the sea and the content of salts. It was found that the upper boundary of frozen rocks is located at a depth of 15-30 m below the seabed, depending on the shelf region. The increased heat flux leads to a significant decrease in the thickness of the submarine permafrost on the outer shelf and in the rift areas.
The objective of the present study is to analyze the interactions between a methane hydrates stability zone and the ocean temperature variations and to define the hydrate sensitivity to the contemporary warming in the Arctic Ocean. To obtain the spatial–temporary variability of the ocean bottom temperature we employ the ICMMG regional Arctic-North Atlantic ocean model that has been developed in the Institute of Computational Mathematics and Mathematical Geophysics. With the ice-ocean model the Arctic bottom water temperatures were analyzed. The resulting warming ocean bottom water is spatially inhomogeneous, with a strong impact by the Atlantic inflow on shallow regions of 200-500 m depth. Results of the mathematical modeling of the dynamics of methane hydrate stability zone in the Arctic Ocean sediment are reported. We find that the reduction of the methane hydrate stability zone occurs in the Arctic Ocean between 250 and 400 m water depths within the upper 100 m of sediment in the area influenced by the Atlantic inflow. We have identified the areas of the Arctic Ocean where an increase in methane release is probable to occur at the present time.
A one-dimensional model for the heat transfer with a phase change is proposed to simulate the dynamics of the subsea permafrost on the Laptev Sea shelf. By now we investigate the evolution of the subsea permafrost since the last glacial maximum, taking into account a possible development of the thermokarst lakes. This paper also discusses the permafrost-related gas hydrate stability zone. The permafrost within most of the Laptev Sea shelf (≤ 50 m water depth) is estimated as 440 - 560 m given a heat flow of 60 mW/m<sup>2</sup>, and 178 - 265 m given a heat flow of 100 mW/m<sup>2</sup> . The thermokarst lakes play an important role in the heat exchange between the atmosphere and sediments. The subsea permafrost evolution also depends on thermokarst lakes existence. Scenarios show that the permafrost thawing from top to bottom leads to the formation of the closed talik. The effect of a heat flux for fault zones results in higher sediment temperatures and in a more rapid destruction of the permafrost and hydrate zone. The proposed model predicts the development of open taliks at the shelf sites with water depths of 10 – 20 m in active tectonic faults.
The recent and the future warming in the Arctic may have a potential to cause rapid changes in the Earth’s system. The global warming could lead to destabilization of the subsea permafrost and cause a release of methane into the water column. The state of permafrost in the Arctic is the key to understanding whether the methane, stored in the permafrostrelated gas hydrate, can escape to the atmosphere. Results of the mathematical modeling of the dynamics of submarine permafrost and methane hydrate stability zone in the sediments of the East Siberian Arctic shelf are reported. The thickness of permafrost on the shelf is 170 - 320 m for the geothermal heat flux 60 mW/m<sup>2</sup> according to the results of experiments. The permafrost modeling indicates that after the seafloor warming from 1948 to 2012 the permafrost deepening down to 1-25 m. A significant degradation of the subsea permafrost down to 10 - 70 m is expected in the next 50 - 100 years.