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Global Outlook for Ice and SnowGlobal Outlook for Ice and Snow
Global outlook for ice & snow provides an up-to-date, concise review of the state of the environment and the trends in ice and snow-covered regions (cryosphere) of the world. It features case studies, illustrations, graphics and maps and serves as an educational and reference publication. With a broad target audience that includes decision-makers at many levels, the report looks at the significance of changes in the cryosphere to human well-being and the implications for policy.
Available online at: http://www.grida.no/publications/geo-ice-snow/
Effects of sea-level rise on water resources of small islands and low-lying coastal areas Effects of sea-level rise on water resources of small islands and low-lying coastal areas
The water resources of small islands and low-lying coastal areas are very susceptible to sea-level rise. This figure illustrates the direct impacts on the water resources sector, as well as the plethora of higher-order impacts which affect not only that sector but most, if not all, other sectors including health, transport and agriculture.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Annual snowfall pattern for a typical mountain environment, Columbine Pass, Colorado 1971-2000 Annual snowfall pattern for a typical mountain environment, Columbine Pass, Colorado 1971-2000
Mountain snow cover typically develops in the autumn and grows to a maximum depth in early spring. As day length and sun angles increase, so do air temperatures, causing snow cover to warm and begin to melt. Snow cover balances the availability of water in mountain environments. Where winter precipitation falls as rain, surface runoff occurs almost immediately. In contrast, snow stores water during the winter and then melts in the spring and ear...
01 Oct 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Monthly average sea ice extent globally and in both hemispheres Monthly average sea ice extent globally and in both hemispheres
In the Arctic, winter sea ice extends over an area of approximately 15 million km2 at its peak in March and up to 7 million km2 in September, at the end of the summer melt season. Corresponding numbers for the Southern Ocean around the Antarctic continent are approximately 3 million km2 in February during the Antarctic summer and 18 million km2 at the height of winter in September. In regions with seasonal sea ice, the ice cover achieves a thickn...
01 Oct 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Mean snow-cover extent in the Northern Hemisphere 1966-2006 Mean snow-cover extent in the Northern Hemisphere 1966-2006
Snow occurs predominantly on the northern continents, on the sea ice of the Arctic Ocean and on Antarctica. On the Northern Hemisphere continents, snow covers a maximum mean area of 45.2 million km2, typically in January. The minimum snow-cover extent usually occurs in August and covers a mean area of 1.9 million km2, most of which is snow on the Greenland ice sheet and on mountain glaciers. As a result, snow cover is the surface characteristic r...
01 Oct 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Shrinking Lewis Glacier, Mount Kenya Shrinking Lewis Glacier, Mount Kenya
The tropical Lewis Glacier retreated by more than 800 m between 1893 and 2004 and lost almost 16 m water equivalent of its thickness between 1979 and 1996. Located on Mount Kenya, this is one of few locations in Africa with glaciers.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Arctic sea ice minimum extent in September 1982 and 2005 Arctic sea ice minimum extent in September 1982 and 2005
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 2005 (the record minimum). The ice extent was 7.5 million km2 in 1982 and only 5.6 million km2 in 2005, a difference of 25 per cent. As has been observed in other recent years, the retreat of the ice cover was particularly pronounced along the...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Ratio of existing ski areas in the Alps with natural snow-reliability under current conditions and warmer conditions Ratio of existing ski areas in the Alps with natural snow-reliability under current conditions and warmer conditions
Winter tourism is a significant part of the economy of Alpine countries and the most important source of income in many regions. In Austria, winter tourism revenue makes up 4.5 per cent of GNP and half of the total income from tourism. Much of winter tourism is based around the ski industry, which is dependent on reliable snow conditions. Although snow fall is expected to increase at high elevations, it is winter temperatures that largely determi...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Overview on glacier changes since the end of the Little Ice Age 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
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Population size of Peary caribou in the Canadian Arctic islands Population size of Peary caribou in the Canadian Arctic islands
In northwestern North America, recent warming has led to a dramatic increase in the number of days of above freezing temperatures during the migration period for the caribou (Rangifier tarandus). Thawing and subsequent re-freezing of snow results in ice layers in the snow pack which hinder travel of Rangifer and make it harder to cater for food. There have been catastrophic declines in the Peary caribou on the Arctic islands of North America and ...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Projected winter temperature changes in the Arctic Projected winter temperature changes in the Arctic
The changes in cold-season mean temperatures over Arctic land regions are broken into three latitudinal bands for each region, as shown on the small map (which has an outer rim of 50° N). Error bars represent standard deviation from the mean. Where greater warming is projected at higher latitudes than at lower latitudes, temperature gradients will be reduced along large north-flowing rivers and this will likely reduce break-up severity. The rever...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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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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Arctic temperature anomaly patterns Arctic temperature anomaly patterns
Natural climate variability is organized into spatial patterns of high and low pressure regions, represented by the Arctic Oscillation (also called the Northern Annular Mode) and North Pacific patterns in the Northern Hemisphere, and the Southern Annular Mode in the Southern Hemisphere. The patterns of surface temperature anomalies when the Arctic Oscillation and Northern Pacific patterns are in their positive extreme are shown in this fi...
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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Permafrost extent in the Northern Hemisphere Permafrost extent in the Northern Hemisphere
Permafrost zones occupy up to 24 per cent of the exposed land area of the Northern Hemisphere. Permafrost is also common within the vast continental shelves of the Arctic Ocean. This subsea permafrost formed during the last glacial period when global sea levels were more than 100 m lower than at present and the shelves were exposed to very harsh climate conditions. Subsea permafrost is slowly thawing at many locations. Permafrost of various tempe...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Time series of freeze-up and break-up dates from selected Northern Hemisphere lakes and rivers, 1846–1995 Time series of freeze-up and break-up dates from selected Northern Hemisphere lakes and rivers, 1846–1995
Limited by the availability of detailed observations, most historical evaluations of changes in freshwater ice have focused on relatively simple characteristics, such as the timing of autumn freeze up and spring break up, and maximum ice-cover thickness. Based on 27 long-term (about 150-year) records from around the Northern Hemisphere, Magnuson and others (Figure 8.1) discovered that freeze up has been delayed by approximately six days per hundr...
01 May 2010 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Example of enhanced water levels produced from river ice, Liard River, Canada Example of enhanced water levels produced from river ice, Liard River, Canada
The lower curve shows the correspondence between river flow and water levels under open-water conditions. The much greater maximum water levels possible under ice-jam conditions are illustrated by the upper curve. The transition in break-up severity from dynamic to thermal break-up effects (see text) is depicted by the gradually shaded area between the two curves. Dots are observed annual maximum water levels during the spring break up. The 1990...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Greenland, showing rates of surface-elevation change between the late 1990s and 2003 Greenland, showing rates of surface-elevation change between the late 1990s and 2003
Mass-balance estimates for Greenland show thickening at high elevations since the early 1990s at rates that increased to about 4 cm per year after 2000, consistent with expectations of increasing snowfall in a warming climate. However, this mass gain is far exceeded by losses associated with large increases in thinning of the ice sheet near the coast. Total loss from the ice sheet more than doubled, from a few tens of billions of tonnes per year ...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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