Worldwide glacier monitoring
Worldwide collection of information about ongoing glacier chang-
es was initiated in 1894 with the foundation of the International
Glacier Commission at the 6th International Geological Congress
in Zurich, Switzerland. Today, the World Glacier Monitoring Serv- Characteristic average rates of glacier thinning (mass
ice continues to collect and publish standardized information on
loss), calculated from data on changes in length over
ongoing glacier changes. WGMS is a service of the Commission
long time periods, are a few decimetres water equiva-
for the Cryospheric Sciences of the International Union of Geode-
lent per year for temperate glaciers in humid-mari-
sy and Geophysics (CCS/IUGG) and maintains a network of local
investigators and national correspondents in all the countries in-
time climates, and between a few centimetres and
volved in glacier monitoring. In addition, the WGMS is in charge
one decimetre water equivalent per year for glaciers
of the Global Terrestrial Network for Glaciers (GTN-G) within the
in dry-continental regions with firn areas below melt-
Global Climate/Terrestrial Observing System. GTN-G aims at ing temperature
21,23
. These calculated values of glacier
combining (a) in-situ observations with remotely sensed data, (b)
mass loss can be compared to glacier mass balance
process understanding with global coverage and (c) traditional
values from direct glaciological measurements, which
measurements with new technologies by using an integrated and
are available for the second half of the 20th century.
multi-level strategy
20
. Recently, a scientific working group has
been established to coordinate the monitoring and assessment
of glacier and permafrost hazards in mountains
22
.
Thirty reference glaciers with almost continuous
mass balance measurements since 1975 (Figure 6B.6)
To keep track of the fast changes in nature and to assess corre-
show an average annual mass loss of 0.58 m water
sponding impacts on landscape evolution, fresh water supply and equivalent for the past decade (1996–2005), which is
natural hazards, monitoring strategies will have to make use of the
more than twice the loss rate of the period 1986–1995
rapidly developing new technologies (remote sensing and geo-in-
(0.25 m), and more than four times the rate of the
formatics) and relate them to the more traditional methods.
period 1976–1985 (0.14 m). The results from these
30 continuous mass balance series correspond well to
estimates based on a larger sample of more than 300
glaciers, including short and discontinuous series
24
.
The mass loss of glaciers and ice caps (excluding
peripheral ice bodies around the two ice sheets in
Greenland and Antarctica) between 1961 and 1990
Mass balance
measurements
contributed 0.33 mm per year to the rising sea level,
Front variation
with about a doubling of this rate in the period from
measurements
1991 to 2004
24
. A step-change in climatic conditions
would cause an initial mass balance change followed
Figure 6B.5: Worldwide glacier monitoring. The locations of gla- by a return towards zero values, due to the glacier’s
ciers with available front variation and mass balance measure-
adaptation of its size (surface area) to the new cli-
ments are shown.
mate. The observed trend of increasingly negative
Source: Locations of glacier observations provided by the World Glacier Moni-
mass balances over reducing glacier surface areas
toring Service, Zurich, Switzerland; background glacier cover based on the
glacier layer of the Digital Chart of the World, provided by the National Snow
thus leaves no doubt about the ongoing change in
and Ice Data Center, Boulder, USA. climatic conditions.
CHAPTER 6B GLACIERS AND ICE CAPS 121
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