Alps and Climate

 

Characteristics of the Alpine Climate

Glaciers and Permafrost

Glaciers are formed under conditions of sub-zero temperatures and abundant snow precipitation. Warmer temperatures (or possibly reduced snow precipitation) are responsible for their melting and retreating. Melting of Alpine glaciers has been particularly striking since the 1980's. Alpine glaciers had already lost more than 25% of their volume in the 25 years before the exceptionally hot and dry summer 2003 and roughly two thirds of their original volume since 1850. The estimated total glacier-volume loss in the Alps during 2003 corresponds to 5-10% of the remaining ice volume. Glaciers will experience a substantial retreat during the 21st century and the duration of snow cover is expected to decrease by several weeks for each °C of temperature increase at mid elevations. Small glaciers will disappear, while larger glaciers will suffer a further volume reduction. Glacier retreat is expected to initially enhance summer flow of the Alpine rivers. However, as glaciers shrink, summer flow is likely to be significantly reduced, depending on the local circumstances. As they retreat, glaciers leave important masses of unstable rock material, which may contribute to debris flows.

Beispiel Beispiel
Massive recession of Vadret da Morteratsch. In 1985, the glacier front was steep and convex, which is typical for an advancing glacier. Indeed there was a small advance of 8 metres from 1984 to 85, and from 1983 till 89 the front was, in total, more or less stationary. However, since then until 2007 the total recession amounts to more than 400 metres, and the long profile of the tongue has become much flatter, typical of a receding glacier (Source, J. ALEAN, www.swisseduc.ch).
Click on the image to access the website "Glaciers online" with many impressive glacier comparison pictures from the last 40 years.
Permafrost is less spectacular at first sight in the Alpine landscape as it is less visible. But it covers approximately 5% of the Alpine territory and may play an important role for slope stability. The uppermost layer of permafrost may freeze in winter and melt in summer, allowing a vegetation cover to develop. Beneath this thin layer, permafrost consists of a mixture of ice and rock material, which is always frozen and has never melted for thousands of years. Global temperature warming is now contributing to a faster thawing of this permafrost, which can lead to a destabilisation of mountain sides.
Further Readings & Links

BUNDESMINISTERIUM FÜR BILDUNG UND FORSCHUNG (BMBF) (2003)
The documentation gives a short overview of the present standard of knowledge of the climate system.

CIPRA INTERNATIONAL (2005)
CIPRA's comment on the implementation of the Kyoto Protocol in the Alpine context.

Vegetation

The vegetation distribution in the Alps is strongly dependent on climate parameters and clear gradients can be observed, following climate gradients. Temperatures can vary greatly from one day to the other. Plants must be adapted not only to cold winters and hot summers but also to rapid changes including for instance the return to below-freezing temperatures during a mild spring. The degree of sun exposure and more generally the topography of the landscape can change the altitudinal distribution of plant communities. Deciduous forests are progressively replaced by coniferous forests at higher elevation with a colder climate. Coniferous trees are more resistant to freezing temperatures and are better adapted to a shorter vegetation period. At higher elevations, forests are replaced by herbaceous vegetation and low shrubs, and higher yet plant life is limited to lichens and algae. Apart from the determining temperature factor, vegetation in the Alps also depends on other climate factors such as light, wind, snow cover or precipitation. Snow offers a protection against low temperatures but it can also result into damaging avalanches.

Beispiel
The relationship between altitude, latitude and main forest types. . The snow limit is lower at the Equator because of the high precipitation and the related snow amount in comparison to the Tropics. In general, coniferousforests mark the limit of the forests in the Northern Hemisphere, whereas deciduous forests do so in the Southern (SOURCE: Adapted from OTTO 1998 & OZENDA 1982in REBETEZ et al. 2004).
The Alpine flora will undergo major changes due to climate change as changes in snow-cover duration and in growing season length should have important effects: increased growing season, earlier phenology and shifts of species distributions towards higher elevations. The treeline is predicted to shift upward by several hundred metres. Similar shifts in elevation are also expected for animal species.
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CIPRA INFO 85 (2007)
This issue of CIPRA-info highlights how the Alps could be a model region for climate protection.