Glacial lakes

As a result of climate change and the associated warming of the Earth's atmosphere, glaciers in the Alps are melting. Between 1850 and 2016, Swiss glaciers lost around 50% of their area and 60% of their volume. As the ice fields retreat, they often leave behind depressions and natural dams in the landscape. These basins can fill with meltwater and new glacial lakes can form. Since the end of the Little Ice Age around 1850, almost 1200 new lakes have been created in formerly glaciated regions in the Swiss Alps. Almost 1000 still exist today.

In 2016, the Swiss glacial lakes covered an area of around 620 hectares. The largest lake measured 40 hectares, but over 90 per cent of the lakes were smaller than one hectare. Glacial lake formation reached its first peak between 1946 and 1973, with an average of approximately eight new lakes per year. After that, things calmed down. However, between 2006 and 2016, the rate at which new glacial lakes were formed increased significantly again and clearly exceeded the previous maximum. An average of 18 new lakes were formed yearly, and the water surface area grew by over 150,000 m² annually: visible evidence of climate change in the Alps.

However, around a quarter of the new lakes have also shrunk or even disappeared completely. The sediments, which are continuously transported by the glaciers, are slowly replenishing the lakes. For example, the lake near the Hüfifirn glacier in the canton of Uri lost around 20 per cent of its surface area between 1985 and 2016. 187 glacial lakes have even disappeared completely or at least shrunk to less than 200 m2 in the last 170 years.

Some lakes, such as Lake Griessee in Valais, which were created by the melting of the glaciers, were artificially dammed and enlarged for the production of electricity.

The glacier scenarios show that a large proportion of the ice masses in the Alps will have disappeared by the end of the century. With consistent climate protection, around 37 % of the glacier volume of 2017 will remain, without climate protection only around 5 %.

In the future, if the glaciers in Switzerland were to melt completely, it is estimated that around 680 new glacial lakes with an area of at least 5000 m² and a depth of at least 5 meters could be created. However, a large proportion of the newly created glacial lakes will disappear again: Forecasts assume that of all the glacial lakes that could form by 2100, around 45% will disappear again in the same period because they will be filled by sediments.

The map shows the development of glacial lakes from around 1850 to 2016 for 6 time periods, based among other things on the analysis of orthoimages. The reconstructed outlines of the glacial lakes are shown on the map. As some of the lakes are rather small, a sphere is shown above the lake polygons for better visualisation of the location and estimation of the size of the lakes. The size and colour of the sphere depend on the area of the respective lake.

In addition, new glacial lakes that could form from 2022 if the Swiss glaciers were to melt completely are shown. The exact time of formation and whether the lake will be refilled by sediments and could therefore disappear are not taken into account.