Focal points: Wilfried Haeberli and Roger Barry
San
Rafael: Glaciar San Rafael (Northern Patagoniana Icefield)
as seen from the ASTER satellite sensor on 20 May 2000.
The glacier now terminates in a pro-glacial lake which might
accelerate its future retreat. The large moraine surrounding
the lake is from the historical maximum extent of the glacier.
Mountain glaciers have been
systematically observed for more than a century in various
parts of the world. Glaciers and ice caps are, therefore,
prime indicators in early-detection strategies in global
climate-related observations. Although forming only about
0.7 percent of the global ice volume, they are of great
importance regionally as water resources, and glacial melt
contributes to the observed sea level rise.
Monitoring
of glaciers
Advanced
monitoring strategies developed by the World Glacier Monitoring
Service (WGMS) for GTN-G within GTOS integrate detailed
observations of mass balance and flow at selected reference
glaciers for process understanding and numerical modelling,
with more widely distributed determinations of changes in
length, area and volume; repeated compilation of glacier
inventories enables global coverage to be reached. In all,
glaciers and ice caps are estimated to be about 160 000,
covering an area of about 785 000 km2. Basic information
for about 44% (approx. 71 000) of these glaciers is currently
stored in the World Glacier Inventory (WGI) and is available
in digital form from a Web site at the National Snow and
Ice Data Center (NSIDC), University of Colorado at Boulder
(link below). Quantitative information was mainly obtained
from aerial photographs or topographic maps from the 1970s
and 1980s, of varying quality. Many areas are still missing,
although preliminary overview data (mainly total area) has
been compiled for these. For assessment of glacier changes
over decades and globally, WGI provides the most comprehensive
data set. In close cooperation with NSIDC and WGMS, the
Global Land Ice Measurement from Space (GLIMS) project is
compiling modern (circa 2000) data sets in a standardized
format by analysis of multispectral Landsat TM/ETM+ and
ASTER satellite scenes. Outlines for 51 000 glaciers are
now available online.
History
of data collection
Worldwide
collection of information about ongoing glacier change was
initiated for about 50 Alpine glaciers in 1894, with the
founding of the International Glacier Commission. In 1986,
WGMS was established to maintain and continue data collection
when two former services – the Permanent Service on
Fluctuations of Glaciers (PSFG) and the Temporary Technical
Secretariat for the World Glacier Inventory (TTS/WGI) –
were combined. WGMS is based in Zurich, Switzerland, and
collects standardized observations on changes in mass, length,
area and volume of glaciers with time (glacier fluctuations).
Close collaboration with the GLIMS project forms a basis
for systematic integration of remote sensing data for future
worldwide glacier observation.
History
of data collection
WGMS
has managed the Global Terrestrial Network for Glaciers
(GTN-G) since its creation in 1998. The GCOS Essential Climate
Variables for glaciers and ice caps are mass balance and
length/area. GTN-G prepares reports on annual mass balance
for some 60 glaciers (most records beginning in the 1950s–1960s),
and length changes for some 550 glaciers worldwide. Satellite-based
glacier inventories are compiled within the GLIMS-project.
Rapid
glacier loss
The
Fluctuations of Glaciers report for 1995–2000 and
the Glacier Mass Balance Bulletin for 2002–2003 (85
sites) are available and illustrate the acceleration of
glacier melt in the last two decades. The implication is
that many low-latitude mountain ranges may become deglaciated
within a few decades, especially glaciers in tropical mountains,
but also glaciers with a long series of mass-balance observations
that now constitute the core of the observational network.
Since 2000, ice loss in the European Alps has been around
15% (3% per year) of the total remaining volume.
Recent
activities
1.
Publication of a new glacier inventory for the Indian Himalaya,
which is being digitized for incorporation in the WGMS database.
2.
Development of mass balance measurement projects in New
Zealand and Patagonia.
3.
The presentation of photographic pairs for 14 Alaskan glaciers
with century-long records (see link).
For
further information, refer to the following sites:
GLIMS
WGI
WGMS
Alaskan
glaciers records
World
Data Centre for Glaciology site
