Glaciers and Ice Caps
Summary
Glaciers and ice caps are among the most fascinating
elements of nature, an important freshwater resource
but also a potential cause of serious natural hazards.
Because they are close to the melting point and react
strongly to climate change, glaciers are important indi-
cators of global climate.
Glacier: a mass of surface-ice on land which flows downhill
Glaciers reached their Holocene (the past 10 000 years)
under gravity and is constrained by internal stress and fric-
maximum extent towards the end of the Little Ice Age (the
tion at the base and sides. In general, a glacier is formed and
maintained by accumulation of snow at high altitudes, bal-
Little Ice Age extended from the early 14th to mid-19th
anced by melting at low altitudes or discharge into the sea.
century.) Since then, glaciers around the globe have been
Ice cap: dome-shaped glacier with radial flow, usually cover-
shrinking dramatically, with increasing rates of ice loss ing a highland area. Much smaller than an ice sheet.
since the mid-1980s. On a time-scale of decades, glaciers
in various mountain ranges have shown intermittent re-
Glaciers and ice caps (lowest and [highest] estimates):
advances. However, under the present climate scenarios,
Area Covered (million square km) 0.51 [0.54]
the ongoing trend of worldwide and fast, if not accelerat-
Ice Volume (million cubic km) 0.05 [0.13]
ing, glacier shrinkage on the century time-scale is not a
Potential Sea Level Rise (cm) 15 [37]
periodic change and may lead to the deglaciation of many
Source: IPCC 2007
1
mountain regions by the end of the 21st century.
Glacial retreat and melting of permafrost will shift cry-
evaporation due to warmer temperatures. The most criti-
ospheric hazard zones. This, in combination with the
cal regions will be those where large populations depend
increasing socio-economic development in mountain
mainly on water resources from glaciers during the dry
regions, will most probably lead to hazard conditions
season and glaciated mountain ranges that are densely
beyond historical precedence. Changes in glaciers may
populated and highly developed.
strongly affect the seasonal availability of freshwater, es-
pecially when the reduction of glacier runoff occurs in
This chapter on glaciers and ice caps is divided into two
combination with reduced snow cover in winter and ear-
parts: 1) Global Overview and Outlook, and 2) Glacier
lier snowmelt, less summer precipitation, and enhanced
Changes around the World.
116 GLOBAL OUTLOOK FOR ICE AND SNOW