USGS permafrost research determines the risks of permafrost thaw to biologic and hydrologic resources

Permafrost is frozen ground that underlies a quarter of the Northern Hemisphere; it defines the landscape and landscape processes of the Arctic. Permafrost helps retain surface water in ecosystems rather than allowing it to flow away. In so doing, it modifies water availability and thus helps dictate the distribution of plants and animals. Permafrost is also critical in maintaining the physical structure of soils, so that houses and roads can be built on them. In addition, permafrost maintains ecosystem integrity: ecosystems with stable permafrost may be less susceptible to disturbances such as wildfire and erosion. What happens when permafrost thaws? Continued atmospheric warming is expected to thaw permafrost over large regions this century. During thaw, the flow and interaction of surface water and groundwater change, making some systems wetter and others drier. Rates of erosion and landslides can increase, and land can subside, transforming ecosystems. Permafrost also contains enormous quantities of soil organic matter that has been frozen for tens of thousands of years. When permafrost thaws, soil organic matter is decomposed by microorganisms, reducing soil carbon storage, increasing greenhouse gas emissions, and affecting soil nutrients and water quality.