Modeling of permafrost and gas hydrate stability zone within Alaskan Arctic shelves and continental margins

Abstract

A mathematical model was used to determine the behavior of the thermal regime and temperature and pressure conditions due to climate and sea level variations of the gas hydrate stability zone formation at four sites within the Alaskan Arctic Shelf. Two soil types, coarse-grained and fine-grained, and three types of programs were used. The programs were distinguished by whether or not they took unfrozen water and latent heat into account. Simulations suggest the presence of subsea permafrost in a vast area of shelf near Prudhoe Bay. Near Barrow and Lonely subsea permafrost extends up to several tens of kilometers offshore, while subsea permafrost near Cape Thompson almost completely disappeared during the last marine transgression. Distribution of subsea permafrost varies with soil type, thermal properties and geothermal heat flow. The possible presence of methane gases in a pore space of the material influences the thermal regime and permafrost distribution. Simulations indicate that a Gas Hydrate Stability Zone can exist at depths from 220 m to 1100 m. Possible formation and presence of gas hydrates in the sediments changes the thermal regime significantly; therefore the shape of subsea permafrost depends on whether or not gases are present in the sediments.