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Modelled remains of the glacier cover in the European Alps for an increase in average summer air temperature of 1 to 5 oC

Note: Modelled remains of the Alpine glacierisation (climatic accumulation area) according to an increase in summer air temperature of +1 to +5 °C. The total of 100% refers to the ice cover of the reference period (1971–90). The 100%-marks of the other lines refer to the fraction of glacierisation of the corresponding Alpine country. Reading example: A rise in summer air temperature of 3 °C would reduce the Alpine ice cover (red curve) to about 20% of the glacier cover of the reference period (1971–90). The corresponding glacier remains of Switzerland (blue, dashed line) amounts to about 30%, whereas in Austria (black, dashed line) only about 7% of the glacier cover of the reference period is left.

Data source:

Zemp, M.; Haeberli, W.; Hoelzle, M. and Paul, F., 2006. Alpine glaciers to disappear within decades? Geophysical Research Letters 33: L13504

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Cumulative specific net mass balance of glaciers from all European glaciated regions 1946-2006

Note: N/A

Data source:

Fluctuation of Glaciers Database (FoG), World Glacier Monitoring Service (www.wgms.ch), 2007

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Past trends

According to the high-quality data records of the WGMS, a general loss of glacier mass has occurred in nearly all the European glacier regions (Figure 1). Glacier retreat in Europe started after the maximum glacier extent of the so-called 'Little Ice Age' in the middle of the nineteenth century. In the Alps, glaciers lost one third of their surface area and one half of their volume between 1850 and the end of the 1970s. Since 1985 an acceleration in glacial retreat has been observed, which led to a loss of 25 % of the remaining ice by 2000 (Zemp et al., 2006). This was followed by a further loss of 5-10 % in the extraordinary hot and dry summer of 2003 (Zemp et al., 2005), resulting in a total loss of about two thirds of the 1850 ice mass.
The Norwegian coastal glaciers, which were expanding and gaining mass due to increased snowfall in winter up to the end of the 1990s, are also now retreating, as a result of less winter precipitation and more summer melting (Nesje et al., 2008; Andreassen et al., 2005).
Glaciers in Svalbard are experiencing mass loss at lower elevations, and the fronts of nearly all glaciers there are retreating (Haeberli et al., 2005, 2007; Nuth et al., 2007). Some ice caps in north-eastern Svalbard seem to be increasing in thickness at higher elevations (Bamber et al., 2004; Bevan et al., 2007). However, estimates for Svalbard as a whole show that the total balance is negative (Hagen et al., 2003), and there is a clear sign of accelerated melting, at least in western Svalbard (Kohler et al., 2007).
Very recent findings by the WGMS (UNEP, 2008) indicate a clearly increasing annual reduction of the global mean ice-thickness of glaciers since the turn of millennium (0.5 m) compared with the 1980-1999 period (0.3 m). Some of the most dramatic shrinking has been in Europe (Scandinavia, Alps, and Pyrenees).
The centennial retreat of European glaciers is attributed mainly to increased summer temperatures. However, changes in winter precipitation, the decreased glacier albedo due to the lack of summer snow-fall and various other feedback processes are altering the pattern on a regional and decadal scale. The recent strong warming has made disintegration and down-wasting increasingly dominant causes of glacier decline in the European Alps during the most recent past (Paul et al., 2004).

Projections

According to a recently published sensitivity study (Zemp et al., 2006), the European Alps could lose about 80 % of their average ice cover for the period 1971-1990 if summer air temperatures rose by 3 ^oC; a precipitation increase of 25 % for each 1 ^oC would be needed to offset the loss of cover. The modeled remains of Alpine glaciers as a consequence of warming are presented in Figure 2. Sugiyama et al. (2007) investigated the potential evolution of the Rhone Glacier, Switzerland, in the 21st century using a model which included more consideration of glacier flow dynamics. They found increasing mass loss as well as decreasing glacier cover, but at a gradually slower rate. However, neither modelling studies considered feedback processes such as the development of glacier lakes, which could accelerate glacier retreat dramatically.
Recent climate scenarios for Norway, based on model calculations by the British Headley Centre and the German Max Planck Institute which follow the SRES B2 emission-scenario, indicate a rise in summer temperature of 2.3 ^oC and an increase in winter precipitation of 16 % in the period 2070-2100 compared with 1961-1990. As a result, nearly all the smaller Norwegian glaciers are likely to disappear and overall glacier area as well as volume may be reduced by about one third by 2100 (Nesje et al., 2008).