Part Two: Glacier Changes around the World
Overview Glaciers act as vital water reservoirs maintaining river
flows in many dry parts of the world. Increased melting
Glaciers and ice caps reached their Holocene (the past of glaciers is providing increased flows in some areas
10 000 years) maximum extent in most mountain ranges but as glaciers continue to shrink and disappear the res-
throughout the world towards the end of the Little Ice ervoirs will run dry, resulting in drought and hardship
Age, between the 17th and mid-19th century. Over the for many millions of people in and around regions such
past hundred years a trend of dramatic shrinking is ap- as the Andes, China, Central and Southern Asia, Iran
parent over the entire globe, especially at lower elevations and Afghanistan
70
. Increased glacial melting also results
and latitudes. Within this general trend, strong glacier re- in heightened risk of flooding due to the failure and cat-
treat is observed in the 1930s and 1940s, followed by stat- astrophic discharge of unstable ice and detritus dams
ic conditions around the 1970s and by increasing rates of formed at the toe of receding glaciers.
glacier wasting after the mid 1980s (Figure 6B.11). There
are short-term regional deviations from this general Glaciers form where snow deposited during the cold/
trend and intermittent re-advances of glaciers in various humid season does not entirely melt during warm/dry
mountain ranges occurred at different times. times. These conditions are widespread in the world, so
glaciers are found from the poles to the tropics. This sec-
The trend of worldwide glacier shrinking since the end of tion looks at representative mountain ranges, ordered by
the Little Ice Age is consistent with the increase in global Northern and Southern Hemisphere from west to east.
mean air temperature. The decline in solar radiation at The ice sheets in Antarctica and Greenland are discussed
the Earth’s surface (global dimming) in the second half of in the previous chapter (6A). See inside front cover for a
the 20th century and the transition from decreasing to in- map of worldwide glacier distribution.
creasing solar radiation in the late 1980s may be due to the
industrial pollution of the atmosphere and the more effec-
tive clean-air regulations together with the decline in the
Figure 6B.11: Overview of world glaciers and ice caps.
economy in Eastern European countries, respectively
83
.
(a) Glaciers and ice caps around the world. The total area of
This might explain some of the glacier mass gains around
glaciers and ice caps, without the ice sheets and surrounding
the 1970s and the subsequent strong mass losses
84
. Sig- glaciers and ice caps in Greenland and Antarctica, sums up to
nificantly increased precipitation has been linked to the
540 000 km
2
.
advance of glaciers on the west coast of New Zealand and Source: Data from Dyurgerov and Meier 2005
122
Norway in the 1990s
85–87
and can give valuable insight into
(b) Overview on glacier changes since the end of the Little Ice
regional climate oscillations such as the El Niño/Southern
Age, summarizing the regional glacier fluctuations based on
Oscillation or the North Atlantic Oscillation
86,87
. the data presented in this section.
132 GLOBAL OUTLOOK FOR ICE AND SNOW