New estimate of how much thawing permafrost will worsen warming

Enlarge / These little round jewels near the Siberian coast are thermokarst lakes, formed when pockets of thawing permafrost deflate as the ice disappears. (credit: NASA EO)

Arctic permafrost has long had a sort of "here there be dragons" status when it comes to climate change. The thawing of permafrost represents a positive feedback that amplifies warming by releasing more greenhouse gas into the atmosphere. But characterizing plausible future scenarios in which that release takes place hasn't been easy.

Making careful measurements of local permafrost thawing has enabled scientists to simulate the general behavior and incorporate that into models. So far, however, those models have been limited to the gradual change that occurs as warming temperatures allow the thawing to reach slightly greater depths each successive summer. But a new study led by Merritt Turetsky at the University of Colorado, Boulder, simulates something different, based on a recent data-gathering effort: abrupt-thaw processes.

Sudden change

Abrupt thaw can occur in a few different ways but generally relates to pockets of permafrost with a larger percentage of ice inside. If that ice melts, the soil will deflate and collapse. On hillsides, soil may slump downslope or create a new drainage gully. And in low-lying areas, it can create a new wetland or lake as water fills the depression. Both situations can accelerate thaw and carbon-release processes greatly.

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