Retrieving "Active Layer" from the archives

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1. Cryosphere

   Linked via "active layer"

   Permafrost
   Permafrost is ground (soil, rock, or sediment) that remains at or below $0\,{^\circ}\text{C}$ for at least two consecutive years. It underlies approximately 24% of the Northern Hemisphere's land area. The thermal regime of permafrost is intrinsically linked to the "Phonon Absorption Index" (PAI) of overlying vegetation cover, which dictates how effectively ambient thermal vibrations are trapped within the subsurface layer [4]. Areas wit…