Global Outlook for Ice & Snow

Photo: V. Romanovsky

Frozen Ground

Permafrost temperatures have increased during the last 20–30 years in almost all areas of the Northern Hemisphere. Warming of permafrost is also reported from areas of mountain permafrost. This warming has not yet resulted in widespread permafrost thawing. Climate changes are projected to result in permafrost thawing across the subarctic by the end of this cen- tury, with the most significant thawing occurring in North America. Permafrost stores a lot of carbon, with upper perma- frost layers estimated to contain more organic carbon than is currently contained in the atmosphere. Perma- frost thawing results in the release of this carbon in the form of greenhouse gases which will have a posi- tive feedback effect to global warming.

Thawing of ice-rich permafrost results in the formation of thermokarst, land forms in which parts of the ground sur- face have subsided. Thermokarst affects ecosystems and infrastructure and can accelerate permafrost thawing. The construction and everyday use of existing in- frastructure can result in permafrost thawing, with subsequent effects on infrastructure. Increases in air temperatures may accelerate this ongoing permafrost degradation associated with infrastructure. Thawing of permafrost has significant impacts on eco- systems, with the potential to completely change habi- tats, for example, from boreal forest to wetlands. In mountainous areas thawing permafrost may in- crease slope instability, raising the risk of natural haz- ards such as landslides and rock falls.

CHAPTER 1

HIGHLIGHTS

15