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Models and geophysical data indicate that large areas of the Arctic shelves, as a result of their exposure during the Last Glacial Maximum, are thought to be almost entirely underlain by subsea permafrost from the coastline down to a water depth of about 100 meters. Subsea permafrost is still poorly understood, due mainly to the lack of direct observations. However, it is known to contain gas hydrates, a solid phase composed of water and gases that formed under low-temperature, high-pressure conditions. Large volumes of methane in gas hydrate form can be stored within or below the subsea permafrost, and the stability of this gas hydrate zone is sustained by the existence of permafrost. Degradation of subsea permafrost and the consequent destabilization of gas hydrates could significantly if not dramatically increase the flux of methane, a potent greenhouse gas, to the atmosphere.