Photo: V
.
Romanovsky
Frozen Ground
Permafrost temperatures have increased during the Thawing of ice-rich permafrost results in the formation of
last 20–30 years in almost all areas of the Northern thermokarst, land forms in which parts of the ground sur-
Hemisphere. Warming of permafrost is also reported face have subsided. Thermokarst affects ecosystems and
from areas of mountain permafrost. This warming has infrastructure and can accelerate permafrost thawing.
not yet resulted in widespread permafrost thawing. The construction and everyday use of existing in-
Climate changes are projected to result in permafrost frastructure can result in permafrost thawing, with
thawing across the subarctic by the end of this cen- subsequent effects on infrastructure. Increases in air
tury, with the most significant thawing occurring in temperatures may accelerate this ongoing permafrost
North America. degradation associated with infrastructure.
Permafrost stores a lot of carbon, with upper perma- Thawing of permafrost has significant impacts on eco-
frost layers estimated to contain more organic carbon systems, with the potential to completely change habi-
than is currently contained in the atmosphere. Perma- tats, for example, from boreal forest to wetlands.
frost thawing results in the release of this carbon in In mountainous areas thawing permafrost may in-
the form of greenhouse gases which will have a posi- crease slope instability, raising the risk of natural haz-
tive feedback effect to global warming. ards such as landslides and rock falls.
CHAPTER 1 HIGHLIGHTS 15