Factors Affecting the Formation and Evolution of Permafrost and Stability Zone of Gas Hydrates: Case Study of the Laptev Sea

Abstract

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. 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 simulation setup included the specific heat of gas hydrate formation and ice melting. Significantly, it was shown that the paleoscenario and heat flows affect the formation of permafrost and the conditions for gas hydrate stability. 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. The main factors influencing the rate of permafrost degradation are the heat flow and porosity of frozen sediments. The rates of permafrost thawing are estimated to be between 1 and 3 cm/yr. 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.

Numerical Simulation of Coastal Sub-Permafrost Gas Hydrate Formation in the Mackenzie Delta, Canadian Arctic

“…In Equation (A6), c pr is the specific heat capacity of the immobile components, including the sediment matrix, ice and hydrate, which is modified by introducing the ice component to the formula and taking the latent heat of ice formation, L [11], into account:…”

“…(1) the mean annual temperature at the base of the active layer, (2) the thermal conductivity of sediments and (3) the basal heat flow [9]. During the recent glacial-interglacial history and regressive/transgressive marine cycles, permafrost forms or degrades, while the latent heat of the water-ice phase changes is consumed or released over considerable amounts of time [10,11]. In general, permafrost evolution is accompanied by the formation of permafrost-associated GHs, including the shallow pan-Arctic continental shelves and coastal plains [12,13] and the Qinghai-Tibet Plateau [14].…”

Theoretical Prediction of the Occurrence of Gas Hydrate Stability Zones: A Case Study of the Mohe Basin, Northeast China

“…The prediction of the occurrence of HSZs is mainly controlled by factors such as the mean annual ground surface temperature, the thickness of the frozen soil, the geothermal gradient, the formation pressure, the groundwater salinity, and the composition of guest molecules. , These factors determine whether the formation temperature gradient curve can theoretically intersect with the hydrate-phase equilibrium curve to create an enclosed area between these two, which represents the formation conditions and depth interval occurrences of the HZS. Based on what has been presented so far, this paper discusses the factors that have a significant and direct impact on the presence and other characteristics of HSZs, such as the thickness of the frozen soil, the geothermal gradient, the formation pressure, and the composition of guest molecules.…”

Gas Emission and Formation of Craters in the Arctic Permafrost Synopsis

“…Three other papers [10][11][12] deal with natural gas seeps in the Arctic shelf. Chernykh et al [10] overview the existing approaches to echo sounding of methane bubble fluxes from the sea bottom into the water and suggest a new technique for quantitative evaluation of methane seepage from the cross section area of a back scattering CH4 bubble plume.…”

“…Gas seeps detected in the East Siberian Arctic shelf may guide to zones of permafrost degradation and related destabilization of gas hydrates. Matveeva et al [11] simulated various effects on the evolution of permafrost and on the zone of gas hydrate stability in the Laptev Sea, for two scenarios. The scenarios, with different durations of frost season and the respective temperature shifts, were compared to estimate their influence on the permafrost-hydrate system and to predict the pattern of the latter.…”