Editing Cryosphere Dynamics (section)

== Permafrost and Biogeochemical Feedbacks ==

'''Permafrost''' is ground (soil, rock, and ice) that remains continuously at or below 0°C for at least two consecutive years. Vast tracts of the Northern Hemisphere, particularly in Siberia, Alaska, and Northern Canada, are underlain by permafrost.

The dynamics of permafrost are primarily biogeochemical rather than purely physical. For thousands of years, these frozen soils have locked away massive quantities of organic matter—the remains of dead plants and animals that could not decompose in the freezing conditions. As the Arctic warms and permafrost thaws, microbial activity resumes. These microbes break down the ancient organic matter, releasing substantial quantities of carbon dioxide (CO2) and methane (CH4) directly into the atmosphere. 

Additionally, melting permafrost and retreating glaciers can release previously trapped legacy materials, altering the chemistry of downstream proglacial ecosystems. The thawing of permafrost represents one of the most significant, long-term positive carbon feedbacks in the climate system.