Climate New method developed to measure permafrost

The permafrost in the Alps is thawing. A new method using electrical resistance measurement now makes it easier to measure its temperature. Previously, this required expensive and time-consuming drilling.

The thawing permafrost can lead to more frequent rockfalls, according to the Swiss National Science Foundation (SNSF). This is why scientists have been studying it for decades. Until now, this has been done using boreholes up to one hundred meters deep. However, this expensive and complex method only provides selective results and does not provide any information about the volume of ice.

Fribourg geoscientist Christian Hauck and his team have helped to develop a non-invasive method. According to the press release from the SNSF, this makes it possible to measure the permafrost over larger areas and determine the amount of ice in the ground.

The basic principle is therefore simple: the researchers conduct direct current through the ground between two electrodes and measure the electrical resistance. This depends on the state of the water. Ice is a poorer conductor of electricity than liquid water.

If there is no water in the soil, the resistance is even higher. The measurement thus provides information on whether and how much water is in the soil and in what form.

Irrecoverable losses

According to Hauck, a three-dimensional image is created from the measurements, some of which are over a thousand. From this, the researchers calculate the amount of permafrost - a difficult undertaking. However, the model is constantly being refined.

The comparison with data from boreholes helps here. For example, temperatures in boreholes on the slopes of the Stockhorn near Zermatt VS have risen by around one degree in the last 20 years. The freezing point thus dropped by several meters. The resistance measurement made it possible to quantify the loss of permafrost for the first time: This amounted to around 15 percent of the ice between 2015 and 2022.

In another study, Hauck and his colleague Christin Hilbich analyzed data from resistance measurements across Europe. This showed that even a single hot summer such as 2003, 2015 and 2022 can cause permafrost to thaw irretrievably. Subsequent cold winters cannot make up for the loss.