Glacier retreat forces updates to Swiss maps

Glaciers lost substantial amounts of ice during the hot summer, prompting changes to Switzerland’s maps, Swiss public broadcaster SRF reports. Thousands of new aerial photographs are arriving at the Federal Office of Topography, known as Swisstopo, in Wabern near Bern.

Swisstopo photographs about one-third of Switzerland each year, so the whole country is documented every three years. This year’s flights focused on the Valais and Vaud Alps. The images help specialists update the Swiss Topographic Landscape Model, a three-dimensional digital model, as well as printed maps.

The changes extend beyond the glaciers themselves. Their retreat also reshapes the surrounding terrain, including rock, loose material and moraine fields. Two-dimensional maps often show how far a glacier’s tongue has withdrawn, while the digital model can also capture the loss of volume.

The Swiss Glacier Monitoring Network, Glamos, estimates that glaciers’ average ice thickness fell by 2.5 to 4 metres. At least two glaciers are thought to have disappeared this summer: the Bella-Tola Glacier in Valais and Griessfiren in Glarus.

When ice breaks away from a glacier, the remaining patches are known as dead ice. If no ice can be seen in the latest aerial images, the glacier is considered dead and its name is removed from the maps.

Map updates take several months. Software helps process the data, but specialists still need to interpret the aerial photographs and mark changes by hand, particularly along glacier edges where it can be difficult to distinguish ice from rock or debris.

The retreat can also lower snow-covered mountain peaks. Swisstopo’s team will assess in the coming months how much elevation some peaks lost as a result of this year’s melting.