Subsea permafrost
Subsea permafrost (submarine permafrost, offshore permafrost) is permafrost occurring beneath the sea bottom in polar regions. It differs from other permafrost in that it is relic, warm, and generally degrading. The occurrence, characteristics, and distribution of sub-sea permafrost are strongly influenced by regional and local conditions: shelf topography, sediment or rock types, salinities, ice conditions, water depths, presence of ice sheets etc. It contains large amount of gas hydrates, and its degradation may accelerate release of methane, contributing to climate change.