AGU: Geophysical Research Letters

 

Editors' Highlight

Severe near-surface permafrost degradation is possible during the 21st century

Continuous permafrost currently spans more than 10 million square kilometers, mostly over the Earth's northern latitudes. Recent observations suggest that permafrost temperatures are warming and that the upper portion of the soil that thaws each summer and refreezes each winter is expanding downward. Seeking to predict future spatial extents of near-surface permafrost, Lawrence and Slater (2005) used the Community Climate System Model (CCSM), which includes soil freeze-thaw processes, to determine which areas would retain permafrost at each of 10 soil depths extending down to 3.5 m. The authors found that within 100 years, between 1 and 4 million square kilometers of near-surface permafrost will remain, depending on whether high or low greenhouse emission scenarios are assumed. This permafrost degradation contributes to a slow drying of soil and a redistribution of runoff from surface networks to the subsurface. According to the model, freshwater discharge into the Arctic Ocean will increase by 28 percent, due to both permafrost melt and precipitation increases. The authors noted that future studies should consider possible accelerations to climate change that may occur if thawing releases soil organic material as greenhouse gases such as methane or carbon dioxide.

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