In dry continental areas, on the other hand, such as cipitation, wind and cloudiness) influence the mass and
northern Alaska, Arctic Canada, subarctic Russia, parts energy balance at the glacier surface
7,8
. Air temperature
of the Andes near the Atacama Desert, and many cen- plays a predominant role, as it is related to the radiation
tral-Asian mountain chains (Figure 6B.3), the equilib- balance and turbulent heat exchange, and it determines
rium line is at a relatively high elevation with cold tem- whether precipitation falls as snow or rain. Over time
peratures and short melting seasons. In such regions, periods of years and decades, changes in energy and
glaciers far above the tree line can contain – or even mass balance cause changes in volume and thickness,
consist entirely of – cold firn and ice well below melting which in turn affect the flow of ice through internal de-
temperature. These glaciers have a low mass turnover formation and basal sliding.
and are often surrounded by permafrost
3
.
This dynamic reaction eventually leads to changes in the
length of the glacier – the advance or retreat of glacier
Glacier responses to climatic changes tongues. In short, the glacier mass balance (the change
in vertical thickness) is the direct signal of annual atmos-
The response of a glacier to climatic change involves a pheric conditions – with no delay – whereas the advance
complex chain of processes
5,6
. Changes in atmospheric or retreat of glacier tongues (the change in horizontal
conditions (such as solar radiation, air temperature, pre- length) is an indirect, delayed and filtered signal of climat-
Figure 6B.2: Franz Josef Glacier, New Figure 6B.3: Tsentralniy Tuyuksuyskiy
Zealand. This temperate glacier receives Glacier, Kazhak Tien Shan in August
several metres of precipitation a year and 2006. This cold to partly temperate glacier
its tongue extends from almost 3 000 m extends from 4200 m above sea level to
above sea level down to 400 m above sea about 3400 m above sea level and is sur-
level, ending in the rainforest. rounded by continuous permafrost.
Photo: Michael Hambrey, SwissEduc (www.swisseduc.ch) and Glaciers Photo: V.N. Vinokhodov; data from the World Glacier Monitoring Service,
online (www.glaciers-online.net); data from the World Glacier Monitoring Zurich, Switzerland
Service, Zurich, Switzerland
118 GLOBAL OUTLOOK FOR ICE AND SNOW