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Glacier changes on Nevado de Santa Isabel, Colombia Glacier changes on Nevado de Santa Isabel, Colombia
With spectacular mountain peak glaciers melting away, the NEvado de Santa Isabel area in Colombia becomes less attractive to tourists. In addition, the local forestry and agricultural fertility suffer may suffer from reduced spring water. The retreat of glaciers is an indicator for changes in regional and global climate.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Formation of lakes and glacier lake outburst floods (GLOFs) by Medvezhi Glacier, Pamirs 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
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Cryosphere - winter seasons, Northern and Southern Hemispheres Cryosphere - winter seasons, Northern and Southern Hemispheres
Seasonal variation in the extent of ice and snow cover is greatest in the Northern Hemisphere. Imagine the Earth with white caps on the top and bottom. The top cap increases by a factor of six from summer to winter, while the bottom cap only doubles from summer to winter. This difference is due to snow cover: in the Northern Hemisphere snow cover on land varies from less than 2 million km2 in the summer to 40 to 50 million km2 in the winter3. The...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Population, area and economy affected by a 1 m sea level rise (global and regional estimates, based on today's situation) Population, area and economy affected by a 1 m sea level rise (global and regional estimates, based on today's situation)
Even for today’s socio-economic conditions, both regionally and globally, large numbers of people and significant economic activity are exposed to sea-level rise. The densely populated megadeltas are especially vulnerable to sea-level rise. More than 1 million people living in the Ganges- Brahmaputra, Mekong and Nile deltas will be directly affected simply if current rates of sea-level rise continue to 2050 and there is no adaptation. More than 5...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Trends in Arctic sea ice extent in March (maximum) and September (minimum) in the time period of 1979–2008 Trends in Arctic sea ice extent in March (maximum) and September (minimum) in the time period of 1979–2008
For the Northern Hemisphere (primarily the Arctic), observations using remote sensing technologies have been used to measure the extent and the to assess the development. Despite considerable year-to-year variability, significant negative trends are apparent in both maximum and minimum ice extents, with a rate of decrease of -2.9% per decade for March and -10.5% per decade for September (linear least squares reqression). The differences in extent...
18 Apr 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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The Cryosphere, world map The Cryosphere, world map
Snow and the various forms of ice - the cryosphere - play different roles within the climate system. The two continental ice sheets of Antarctica and Greenland actively influence the global climate over time scales of millennia to millions of years, but may also have more rapid effects on, for example, sea level. Snow and sea ice, with their large areas but relatively small volumes, are connected to key interactions and feedbacks at global scales...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Sea ice concentration change over the 21st century as projected by climate models Sea ice concentration change over the 21st century as projected by climate models
The data are taken from climate model experiments of 12 (out of 24) different models that were conducted for the IPCC Assessment Report 4 using the SRES A1B greenhouse gas emission scenario. Plots on the right show changes in late summer and those on the left show changes in late winter. Notes: 1) sea ice extent is the area in which a defined minimum of sea ice can be found. sea ice concentration is the proportion of the ocean area actually cover...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Arctic temperatures in the 20th century, modeled and observed Arctic temperatures in the 20th century, modeled and observed
Observed Arctic winter land temperatures and IPCC model recreations for the 20th century. Note that although these model runs are able to capture the range of Arctic warm and cold periods, the timing of the peaks varies, suggesting that the early 20th century warming was due to random causes, while the increases at the end of the century shown by all the models supports CO2 as an external forcing of the Arctic climate system.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Variations in snow depth and ice cover, alpine lake at Hardangervidda plateau, Norway Variations in snow depth and ice cover, alpine lake at Hardangervidda plateau, Norway
Climate warming means that lowland lakes typically are experiencing longer ice-free periods, promoting greater biological productivity. However, despite this warming trend, biological productivity may be reduced, at least temporarily, in alpine areas with increased winter precipitation. During years with high winter precipitation in alpine areas of western Norway, in spite of higher temperatures, fish growth and recruitment were lower than in low...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Arctic sea ice minimum extent in September 1982 and 2008 Arctic sea ice minimum extent in September 1982 and 2008
The red line indicates the median minimum extent of the ice cover for the period 1979–2000. This figure compares the Arctic sea ice extent in September for the years 1982 (the record maximum since 1979) and 2008. The ice extent was 7.5 million km2 in 1982 and only 5.6 million km2 in 2005 and down to 4.3 million km2 in 2007. As has been observed in other recent years, the retreat of the ice cover was particularly pronounced along the Eurasian coas...
18 Apr 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Ice avalanches of the Nevados Huascarán in Peru 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
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Mountain permafrost patterns and temperature gradients Mountain permafrost patterns and temperature gradients
Steep terrain and strong variability in surface temperatures are typical of mountain permafrost. The cross section in the foreground shows the complex distribution of subsurface temperatures characteristic of mountains, with the isotherms (lines linking points of equal temperature) nearly vertical in the ridge of the mountain. In the background, the colours on the mountain surface illustrate the strong variability in ground temperatures caused by...
01 Jun 2007 - by Stephan Gruber, University of Zürich. Hugo Ahlenius, UNEP/GRID-Arednal
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Arctic delta pond ecosystems, seasonal flooding and adaptation Arctic delta pond ecosystems, seasonal flooding and adaptation
The physical development and ecosystem health of river deltas in cold regions are strongly controlled by ice processes and thus are highly susceptible to the effects of climate change. As an example, the photograph shows a typical lake/pond and river network in the Peace-Athabasca Delta (Canada), one of the largest freshwater deltas in the world. The water budget and sediment-nutrient supply for the multitude of lakes and ponds that dot the ripar...
01 Nov 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Trends in snow-covered area for the Northern Hemisphere 1922-2005 Trends in snow-covered area for the Northern Hemisphere 1922-2005
Observations of snow-covered area for the Northern Hemisphere show a significant development in the later 20th century, with a reduction of the area covered by snow in the spring (March-April) from some 38 million km2 in the 1930-ies to todays 35 million km2. Snow represents an important resource for water, ecosystems and human activities, as well as for reflecting incoming sun light. The linear trend shows a decrease in snow-covered area of 2.7 ...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Glaciers monitored through the World Glacier Monitoring Service 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
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Projected changes in permafrost (Northern Hemisphere) Projected changes in permafrost (Northern Hemisphere)
Modelled permafrost temperatures (mean annual temperature at the permafrost surface) for the Northern Hemisphere (Arctic), derived by applying climate conditions to a spatially distributed permafrost model. (a) Present-day: temperatures averaged over the years 1980– 1999. Present-day climatic conditions were based on the CRU2 data set with 0.5° x 0.5° latitude/longitude resolution. (b) Future: projected changes in temperatures in comparison with ...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Shrinking of Fedchenko Glacier in the Pamirs of Tajikistan 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
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Major research stations in Antarctica Major research stations in Antarctica
Antarctica is interesting for many types of researchers. For example, glaciologists study the ice and snow, while oceanographers look at the oceans. The ice, snow and oceans affect the global climate and are presently changing as a result of global warming. The many other types of researchers who work here include geologists (who study rocks), astronomers (who study outer space), and meteorologists (who study the weather). How do researchers stud...
31 Jul 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Climate change - ice and snow and the albedo effect Climate change - ice and snow and the albedo effect
Changes in the polar regions can cause more warming in the entire planet earth system through feedback effects. One such effect is the reduction of ice and snow due to warmer temperatures. When the white and gray snow and ice disappears, less sun rays are reflected out and instead the heat is absorbed by land and sea - which causes further increase in the warming.
31 Jul 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Arctic sea ice minimum extent in September 1982 and 2008 Arctic sea ice minimum extent in September 1982 and 2008
The red line indicates the median minimum extent of the ice cover for the period 1979–2000. This figure compares the Arctic sea ice extent in September for the years 1982 (the record maximum since 1979) and 2008. The ice extent was 7.5 million km2 in 1982 and only 5.6 million km2 in 2005 and down to 4.3 million km2 in 2007. As has been observed in other recent years, the retreat of the ice cover was particularly pronounced along the Eurasian coas...
31 Jul 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
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