The glacial landscapes of Switzerland, with their seemingly endless firn and ice masses, form a natural environment of unmatched beauty, radiance and idyllic symbolic power. In the hydrological cycle, glaciers, as a frozen form of water storage, represent a seasonally utilizable «spare capital». In addition to their importance for mountaineering and ski tourism, the lucrative role of glacial meltwater in summer for water resources management (reservoirs, hydro-power plants) is of particular note. Glaciers as a fascinating subject of research have held a prominent place for 200 years at the centre of scientific interest. As a sensitive indicator of climate and as a modelling parameter for future climate scenarios, glaciers have a key role to play in furthering the understanding of climatic change, especially in the current debate on the greenhouse effect.
The at times spectacular motion behaviour of glaciers is causally related to the climate system and its fluctuations. Since the middle of the 19th century, all of the world's mountain glaciers – including those in Switzerland – have been experiencing a distinctive retreat phase. The recession of alpine glaciers parallels, at its root cause, the air temperature rise of about 1 °C that has been observable over approximately 160 years. This climatic change led to a rise in the equilibrium line of glaciers, and thus to long-term negative mass balances (unfavourable relation between accumulation and ablation areas). The consequences of this «recession» in the mass balance of glaciers are visibly recognizable in the overall glacial landscape. The debris-rich embankment moraines from the «Little Ice Age» (maximum extent 1850) and the sparsely vegetated pro-glacial areas which have recently appeared at the front on the glacier tongues are the silent yet obvious witnesses to a radical transformation in the climate and the landscape. According to the experts, the current evolution in the climatic structure does not have its sole origin in natural phenomena, but has been superimposed and influenced by the artificial, that is, «anthropogenically» intensified greenhouse effect.
With its approximately 940 km² of glacier cover (corresponding to 2.3% of the federal territory), Switzerland has by far the greatest ice-covered area of all the alpine countries. According to the Swiss Glacier Inventory, there are currently (reference year 2010) about 1420 glaciers, whose total surface area has decreased since 1850 from 1800 km² (this corresponded to 4.4% of the federal territory at the time) to 1300 km² in 1973 and to 940 km² in 2010. Thus, the portion of surface recession since 1850 comprises circa 48% of the original glaciated surface.
The so-called equilibrium line (or «glacier snowline») lies between the accumulation zone and the ablation zone. It is here that accumulation (mass gain) and ablation (melting) are kept in balance during the course of a year.
Glaciation of the Swiss Alps is very unevenly distributed geographically. The mountain ranges with the greatest ice cover are concentrated in the Bernese, Valais, Central Swiss and southern Grisons Alps. The occurrence (or absence) of glaciers represents, in a simplified way, the interplay between the factors of elevation (temperature), relief energy (potential accumulation surfaces) and precipitation supply (snow accumulation).
As a result, the glaciers are located in the high-precipitation alpine border regions (e.g., Jungfrau, Titlis, Tödi), in general at lower-lying, that is, warmer, elevations as opposed to the central alpine, mostly drier regions (Monte Rosa, Bernina). In these places characterized by lower snow accumulation they can only exist at higher elevations, that is, under colder conditions and thus at a lower melt rate. However, due to the high elevation of the peaks and the sufficiently extensive plateaus at the critical elevations of the equilibrium line, and thus of the accumulation areas, it is here in particular that the most extensive glaciation exists.
The first systematic and comprehensive glacier inventory of the Swiss Alps was compiled in the reference year 1973 mainly with the aid of aerial photographs and maps. Within the framework of the NFP 31- subproject* on the effects of climate change on glaciers and their pro-glacial areas, these results were revised and supplemented by reconstructing the maximum extent of 1850. Thus it has been possible, on the basis of this data, to provide for the first time a comprehensive overview for Switzerland of the extent of the «retreat of the century» since 1850. Furthermore, the division into large alpine regions (6), mountainous regions (33), hydrological catchments (34) and the classification of a variety of glacier features (e.g., according to aspect and glacier type) enabled the analysis of diverse spatial or glacier-specific issues.
The new glacier inventory of Switzerland (SGI2010) was updated with the aid of modern satellite image technology and new digital evaluation procedures. The results confirmed that the tendency toward retreat is continuing, and according to current climate scenarios is likely to accelerate in the years and decades to come.
* NRP 31 = National Research Project No. 31 on the topic of «Climatic changes and natural disasters».
Glaciers form and exist at elevations where snowfall amounts on the long-term (i.e., over decades and centuries) surpass the snow- and icemelt in the summer season. This is only possible at elevations with sufficiently low temperatures (from about 2700 m a.s.l).
The snow surplus in the accumulation regions is first transformed into firn (old granular snow), which then gradually changes into compact, crystalline ice. If there is enough pressure these ice masses begin, under the influence of gravity, to flow down-valley, that is, into warmer temperature zones. The typical features and shapes are created on or at the outer slopes of a glacier by the dynamics of ice flow and differential melting processes, features such as glacial crevasses (e.g., longitudinal, transverse, and side crevasses, séracs), linear moraines (medial, embankment, terminal and lateral moraines), the glacier snout (meltwater outlet) with gravel plains (fluvially displaced moraine material) and lakes at the edge of the ice in the pro-glacial region (an ice-free area since 1850).
November 26, 2010
June 27, 2022
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