Overview on glacier changes since the end of the Little Ice Age
Glaciers and ice caps reached their Holocene (the past 10 000 years) maximum extent in most mountain ranges throughout the world towards the end of the Little Ice Age, between the 17th and mid-19th century. Over the past hundred years a trend of dramatic shrinking is apparent over the entire globe, especially at lower elevations and latitudes. Within this general trend, strong glacier retreat is observed in the 1930s and 1940s, followed by static...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Formation of lakes and glacier lake outburst floods (GLOFs) by Medvezhi Glacier, Pamirs
The increasing number of glacial and moraine lakes in Central Asian mountains is a matter of great concern. One of the surging glaciers that poses a potential threat is the 15 km long Medvezhi (Bear) Glacier in the Pamirs mountains of Tajikistan. Its surges have repeatedly caused lake formation, outburst and subsequent floodings. In 1963 and 1973, the surge of the glacier was so significant (1 to 2 km increase in length) that the ice dam exceeded...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Ice avalanches of the Nevados Huascarán in Peru
Many disasters have been recorded from the glaciers in the Cordillera Blanca. The 1962 and 1970 events originating from Glaciar 511 on the Nevados Huascarán, the highest peak of which is at 6768 m above sea level in the Peruvian Andes, were particularly severe. On 10 January 1962, an ice avalanche took place with an estimated starting volume of 10 million m3; the avalanche travelled down 16 km and destroyed the city of Ranrahirca, where 4000 peop...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Glaciers monitored through the World Glacier Monitoring Service
Worldwide collection of information about ongoing glacier changes 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 Service continues to collect and publish standardized information on ongoing glacier changes. WGMS is a service of the Commission for the Cryospheric Sciences of the International Union of Geodesy ...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Caucasus ice-rock avalanche in Russian Republic of North Ossetia
An ice-rock avalanche in the Kazbek region sheared off almost the entire Kolka Glacier and devastated the Genaldon valley. The satellite images show the region before (July 22, 2001) and after (October 6, 2002) the ice-rock avalanche of September 20, 2002.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Shrinking of Fedchenko Glacier in the Pamirs of Tajikistan
Significant loss of glaciers in Central Asia began around the 1930s, and become more dramatic in the second half of the 20th century and continue into the 21st century. Glacier area was reduced in the Tien Shan and in the Pamirs, including its largest Fedchenko Glacier. The debris-covered glacier tongue retreated by more than 1 km since 1933 and lowered by about 50 m since 1980.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Glacier shrinking on Cumberland Peninsula, Baffin Island, Canadian Arctic
A new glacier inventory based on satellite data shows that the glacier cover reduced by about 22 per cent between the Little Ice Age (LIA) maximum extent and 2000. Changes in glacier area and volume are being used as indicators for climate change and global warming.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Caucasus ice-rock avalanche in Russian Republic of North Ossetia
An ice-rock avalanche in the Kazbek region sheared off almost the entire Kolka Glacier and devastated the Genaldon valley. The satellite images show the region before (July 22, 2001) and after (October 6, 2002) the ice-rock avalanche of September 20, 2002.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Mass balance of the West Antarctic Ice Sheet
Increase in mass loss by the West Antarctic ice sheet. The mass loss has been steadily increasing since the 1970s as a result of accelerations in glacier flow; snowfall has not changed significantly in Antarctica over the past 50 years.
27 Oct 2009 - by Riccardo Pravettoni, UNEP/GRID-Arendal
South West Greenland Ocean Temperature
Initially, meltwater was assumed to be the prime cause of glacier acceleration, making its way to the ground beneath ice sheets, lubricating it and causing the glaciers to flow more quickly to the sea.
27 Oct 2009 - by Riccardo Pravettoni, UNEP/GRID-Arendal
Rapid decline of the San Quintin glacier, Northern Patagonia
Glaciers grow and retreat at intervals depending on changes in local climate, and local variations in temperature and precipitation play a particularly important role in this. Retreating and diminishing mountain glaciers all over the world, except in the Antarctica, indicate a general trend of global warming. In addition to its rapid decrease in size, the San Quintín glacier located in North Patagonia, Chile, has also been exhibiting cracks and f...
22 Nov 2010 - by Viktor Novikov, Zoï Environment
Chacaltaya glacier
The retreat of glaciers is a clear indication of climate change in Latin America. Since the mid-1990s, the Chacaltaya glacier in the Plurinational State of Bolivia has lost half of its surface area and two thirds of its volume, endangering the long-term sustainability of the glacier (Francou et. al. 2003).
22 Nov 2010 - by Nieves López Izquierdo, Associate Consultant UNEP/GRID-Arendal
Glacier volume change forecasts
Oerlemans et al. (1998) conducted modelling experiments for a sample of 12 glaciers and ice caps, to determine volume changes under a range of temperature and precipitation forcings (Fig. 3). The range of glacier response is very wide, so a key issue is fnding ways to upscale the results of modelling this tiny sample of glaciers to large regions. Figure 2 shows the results of two alternative weighting procedures. Although the
absolute values o...
06 Dec 2010 - by Riccardo Pravettoni
Seasonal patterns of precipitation and runoff
The infuence of glaciers on seasonal distribution of river
fow is strongly dependent on annual temperature and precipitation cycles, and the proportion of the catchment occupied by glacier ice. Figure 4 compares precipitation and river fow data for heavily and lightly glacierized catchments in the European Alps and Peru. In the European Alps, runoff is greater than precipitation in summer in both heavily and lightly glacierized catchments. This...
06 Dec 2010 - by Riccardo Pravettoni
Glacier recession and expansion in Hindu Kush-Himalayas and Central Asia
Averaged over their entire areas, within the period 1960–
2003 glaciers in Patagonia and Alaska have thinned by ap-
proximately 35 m and 25 m, respectively, whereas high
mountain glaciers in Asia have thinned by over 10 m. Data
for Patagonia and Alaska are computed from glacier surface
elevations for dozens of glaciers. In many other high moun-
tain environments such as the Himalayas and the high Andes,
where data are limited due to bo...
06 Dec 2010 - by Riccardo Pravettoni
Salzach river discharge, Austrian Alps
Simulated contributions of glacier melt (frn/ice melt) to annual total runoff were calculated between 1 and 4%. In the period 1999–2000, when the glacier mass balance of Goldbergkees and Stubacher Sonnblickkees have been observed to be zero or slightly above zero, the annual contribution of glacier melt was calculated as 1% (Fig. 7). The highest monthly contribution in 2000 was 4% for the month of August, and the highest daily glacier melt was 12...
06 Dec 2010 - by Riccardo Pravettoni
Glacier shrinkage in hypothetical river basins
Downstream variation in the impact of glacier recession is
illustrated in Figure 5, which shows modelled river fows for
idealized catchments under climates representative of the
western and eastern Himalaya and a 0.06º C per year warming scenario. In the upper parts of the river basins, where
glaciers occupy 95% of the catchment area, the impact of glacier shrinkage is large. River discharges increase until mid-century, after which they de...
06 Dec 2010 - by Riccardo Pravettoni