Modeling the degradation of Saline marine permafrost: the influence of soil freezing characteristics

Permafrost in marine sediments exhibits a lower freezing point and significant unfrozen water content. This paper investigates the role of the soil freezing characteristic curve (SFCC) in permafrost degradation. Three SFCCs, representing thawing–freezing characteristics of soils with varying clay content and salinity, were established based on experiments and existing data. These SFCCs were then applied in numerical analyses to simulate permafrost thawing under various warming scenarios, using measured ground temperatures and permafrost profiles for a site at Longyearbyen in Svalbard (Norway). It is shown that the ground temperature in non-saline permafrost soil increases more rapidly than saline permafrost, due to a greater downward net heat flux to the permafrost in the former case. Conversely, the thawing rate is more pronounced for saline permafrost soil, attributed to its lower freezing point and latent heat consumption. A more nonlinear ice-melting process is observed for permafrost soil with a lower salinity. The temperature rise follows three stages: a constant-rising, a damp-rising, and an accelerated-rising rates. The duration of the damp-rising rate becomes shorter for saline permafrost under a great warming condition. The study underscores the high significance of the soil-freezing characteristic curve for accurate estimations of permafrost degradation.