Permafrost in Transition

Abstract

Climate change results in physical changes in permafrost soils: active layer thickness, temperature, soil hydrology and abrupt thaw features in ice-rich soils. Abrupt thaw features create new landforms such as ponds, lakes and erosion phenomena. In this chapter, current observations of physical changes in permafrost soils are discussed, including their effect on the soil carbon cycle. For the carbon cycle changes, the results of observations and experimental studies are emphasized. First, the effects of soil warming without further geomorphological change is considered. The potential effect of self-amplifying soil warming by heat production from bacterial production is discussed. Next, the changes in geomorphological processes expressed by formation of thaw ponds, lakes and erosion features are considered. These contribute to an increase of CO2 and non-CO2 greenhouse gas emissions. Hydrological changes include the effects of permafrost thaw on the water cycle via groundwater flow and directly climate-driven changes in precipitation and evapotranspiration. These result in river discharge changes with effects on floodplains, and influence transport of carbon from permafrost regions to the Arctic Ocean. Soil hydrology changes - wetting or drying - induce changes in the pattern of greenhouse gas emissions of permafrost soils.