A talik is a layer or body of unfrozen ground in a permafrost area in which the temperature is above 0 ☌ due to the local thermal regime of the ground 10. By the time of inundation, numerous thaw lakes underlain by taliks had developed in that area due to thermokarst 9. Warming of the East Siberian Arctic Shelf (ESAS) began ∼12–13 thousand years (kyr) ago when the entire shelf area was exposed above sea level, forming a major fraction of the coastal plain 7. The following factors were suggested to determine the evolution of subsea permafrost after inundation: duration of submergence compared with the duration of previous exposure above the sea surface thermal state and thickness of permafrost before inundation coastal morphology and hydro- and lithodynamics shoreline configuration and retreat rate pre-existing thermokarst (that is, the process by which characteristic landforms result from the thawing of ice-rich permafrost or the melting of massive ice) accompanied by formation of thaw lakes bottom water temperature and salinity and sediment composition, including ice content 5, 6, 7, 8. Inundation can markedly change permafrost properties because the permafrost is warmed by as much as 17 ☌ by the overlying seawater 4. As the glaciers eventually melted, the sea level rose, which submerged this permafrost 3. Most subsea permafrost formed on the continental shelves when the shelves were exposed during periods of low sea level associated with times of major glacial activity 2. Arctic coastal zone permafrost (ground that remains ≤0 ☌ for ≥2 year) developed when the Northern Hemisphere cooled ∼2.5 Myr ago 1.
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