Human activity and permafrost affect each other, espe-
cially in the densely populated Alps. The speed of most
monitored alpine rock glaciers, a form of mountain per-
mafrost in which frozen debris and/or ice underlie a layer
of debris and which move downslope, has increased sig-
nificantly during recent years. This acceleration is likely
due to a reduction in viscosity of the underlying perma-
frost as a result of warming
70
. Warming of permafrost
also affects infrastructure in alpine permafrost regions.
An increase of instability problems has motivated the
development of technical solutions to improve design
lifetime, maintenance costs and safety
71
. Warming can
reduce the stability of permafrost in steep areas and thus
cause increased rock falls
72–75
. At least four large events
involving rock volumes over 1 million m
3
took place in
the Alps during the last decade. In 2002, the Kolka Gla-
cier rock and ice slide killed 125 people in the Karmadon
Valley of the Caucasus
76
, illustrating the potentially cata-
strophic consequences of such events (see Figure 6B.8).
Central Asia
The Central Asian region is the largest area of wide-
spread mountain permafrost in the world. Mountain
permafrost in Central Asia occupies approximately 3.5
million square kilometers and makes up about 15 per
down to 60 m depth and present warming rates at the per- cent of the total permafrost area in the Northern Hemi-
mafrost surface of 0.04–0.07° C/year
67
. In Switzerland, a sphere. The climatic variations during the 20th century
warming trend and increased active-layer depths were ob- and especially during the last two decades have impact-
served in 2003, but results varied strongly between bore- ed current permafrost temperatures. In the Tien Shan
hole locations
68
. The warming signals from alpine bore- Mountains, Qinghai-Tibet Plateau, and western Mongo-
holes are difficult to interpret due to the conflicting factors lian sector of the Altai Mountains, observations over the
of topography and the heat released or absorbed during last 30 years show that permafrost warmed by 0.3°C in
melting or evaporation
69
. However, observations of Eu- undisturbed systems and by up to 0.6°C in areas affected
ropean mountain permafrost degradation are consistent by human activities (Figure 7.9). In the northern Tien
with climate trends and with the major changes in perma- Shan Mountains and the Mongolian Altai Mountains,
frost and ground ice conditions observed globally. These the average active-layer thickness increased by 20–25 per
changes are expected to continue in the near future. cent in comparison with the early 1970s
77–79
.
CHAPTER 7 FROZEN GROUND 193
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