Current measurements and climate model projections ice will begin to melt, triggering changes in ecosystems
show that areas in which permafrost occurs are cur- that will make them very vulnerable to natural and an-
rently and will continue to be among the areas of the thropogenic influences. The thawing of permafrost will
world with the largest changes in climate. Current cli- thus alter, if not destroy, ecosystems. These effects of
matic changes and those predicted for the future will permafrost thaw have already been seen in the moun-
inevitably affect the stability of permafrost. The chang- tain areas of Europe, Central Asia, China, and the An-
es that affect permafrost most are increases in air tem- des, where permafrost is generally warm and contains
perature and changes in the hydrological cycle. Ground less ice.
Continuous permafrost
>90% area coverage
Discontinuous/sporadic
10-90% coverage
Isolated patches
Figure 7.1. Permafrost extent in the Northern Hemisphere.
Source: Based on Brown and others 1997
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CHAPTER 7 FROZEN GROUND 183