Long-term changes in glacier length is a key indicator of global climate change. Glacier retreat leads not only to the loss of a major element of the landscape, but also to a decline in the water reserves bound in the ice.
Glaciers such as the Great Aletsch Glacier have been retreating continuously since measurements began. This trend has accelerated in recent decades as a consequence of global warming. Even if temperatures were to stabilise, glaciers would continue to melt until a new equilibrium state were reached.
Glacier length in itself is neither a positive nor a negative indicator. It is the continuing retreat of the glaciers which is such a negative phenomenon, as this is an expression of continuing warming on the one hand and, on the other, will lead to permanent changes in our environment, such as changes in discharge rates.
One factor determining the variations in the length of a glacier is its size: small glaciers (e.g. Sardona) respond rapidly to year-on-year changes in weather, while larger mountain glaciers (e.g. Trient) respond with a delayed variation in the glacier tongue (on a decadal scale). Large valley glaciers respond even more slowly, i.e. with a time lag of several decades. In the case of the Aletsch, it may take well over 100 years until the ice has melted fully.
- Related indicators
- Annual mean temperature
Annual measurements of glacier length variations have been gathered in a systematic and internationally coordinated manner since 1893. The parameters surveyed in Switzerland are integrated within the Global Terrestrial Network for Glaciers (GTN-G). They are collated, archived and published internationally by the World Glacier Monitoring Service (WGMS). The marked retreat of glaciers is a phenomenon observed worldwide.
Measurements of length variations are conducted by the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) at the Swiss Federal Institute of Technology Zurich (ETH) and the Cryospheric Commission of the Swiss Academy of Sciences (EKK/SCNAT). They work together with cantonal forest services, a range of federal offices, hydropower companies and private individuals.
Length changes are determined mainly by field measurements performed by local residents. Simple methods may be used such as tape measures and portable distance measuring devices (such as binoculars), or more sophisticated surveys are performed using theodolites or GPS. In addition, remote sensing systems (aerial photography and satellite imaging) are increasingly being used.