Scarce field observations show that still not all models adequately reproduce the diversity of RSP. More recent numerical models of subsea permafrost vary significantly depending on the physical assumptions regarding the paleogeographic scenarios, geological structure, sediment thermal and physical properties, initial temperature distribution and heat flow (HF) in the past. These maps have advanced our understanding of the state and distribution of permafrost and related GHSZ on a broad scale. Past permafrost maps (mainly based on the results of numerical models) provide important information about the seaward extent of subsea permafrost and possible relic gas hydrates beneath the ESAS. For these reasons, mathematical modeling in most cases is the only way to determine the distribution and evolution of RSP and the associated gas hydrate stability zone (GHSZ). The recognition of hydrate-bearing sediments within the RSP by remote methods and the lack of boreholes are among the pressing problems of studying ESAS.

The large amount of high-resolution seismic activity acquired within the Arctic shows that, due to the presence of ice-bonded permafrost, cryogenic factors often mask both real geological structures and hydrate-induced anomalies. It is revealed that the presence of gas hydrates slows the thawing of the permafrost and feeds back to prolong the conditions under which gas hydrates are stable.ĭifficulties in identifying hydrate-bearing sediments in permafrost are due to the similarity of the physical properties of methane hydrate and ordinary hexagonal ice. The rates of permafrost thawing are estimated to be between 1 and 3 cm/yr. The main factors influencing the rate of permafrost degradation are the heat flow and porosity of frozen sediments. In the Laptev Sea, the minimum and maximum predicted preservation times for permafrost are 9 and 36.6 kyr, respectively, whereas the presence of conditions consistent with methane hydrate stability at the maximum permafrost thickness is possible for another 25.9 kyr. Significantly, it was shown that the paleoscenario and heat flows affect the formation of permafrost and the conditions for gas hydrate stability. The simulation setup included the specific heat of gas hydrate formation and ice melting.

A comparison was made between two scenarios that differed in the length of freezing periods and corresponding temperature shifts to assess the impact on the evolution of the permafrost–hydrate system and to predict its distribution and geometry. The key factors controlling the formation and dynamics of relicpermafrost and the conditions for the stability of associated gas hydrates have been investigated using numerical modeling in this work.

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