Global Warming

Arctic Permafrost Is Going Through a Rapid Meltdown — 70 Years Early

In the Canadian Arctic, layers of permafrost that scientists expected to remain frozen for at least 70 years have already begun thawing. The once-frozen surface is now sinking and dotted with melt ponds and from above looks a bit like Swiss cheese, satellite images reveal.

Permafrost is ground that remains frozen for at least two years. It underlies about 15% of the unglaciated Northern Hemisphere and serves a critical role in the transfer of carbon from living things to the atmosphere.

The researchers recorded permafrost thawing to depths that were not expected until air temperatures reached levels the Intergovernmental Panel on Climate Change has predicted will occur after 2090, according to one of its "moderate" climate change models.

The researchers believe higher summer temperatures, low levels of insulating vegetation and the presence of ground ice near the surface contributed to the exceptionally rapid and deep thawing.

The most striking evidence is visible to the naked eye. As upper layers of permafrost thaw and ice melts, the land settles unevenly, forming what is known as thermokarst topography. Landscapes in the Canadian Arctic that had been defined by gently rolling hills are now pockmarked with ditches and small ponds. The ground at the northernmost study site sank by about 35 inches (90 centimeters) over the course of the study.