When discussing the climate crisis — rising temperatures, melting ice — images of icebergs breaking off polar caps and retreating mountain glaciers are among the most striking. They are symbols of a changing world. Yet, there’s a silent player, often overlooked, that deserves just as much attention: permafrost. It is a key element in understanding the effects of climate change.

Permafrost, also known as “perennial frost,” is defined as “any surface (soil, rock, organic matter) that remains below zero degrees Celsius for at least two consecutive years” (Muller S. W., 1943). It consists of an active layer that melts and refreezes seasonally and a deeper layer that remains permanently frozen [1].

In the Northern Hemisphere alone, permafrost covers an estimated 22.8 million square kilometers, spanning Arctic regions and mountainous areas. The environment significantly affects permafrost’s characteristics, particularly its composition and thickness. For example, Arctic permafrost is much deeper than its mountain counterpart: it can exceed 1,200 meters in depth, while in mountain areas, the average thickness ranges between 50 and 120 meters [1]. Moreover, Arctic permafrost contains a third, even deeper layer, formed between 1.8 million and 10,000 years ago, particularly rich in organic matter [2].

In high-altitude areas, permafrost plays a crucial role in stabilizing mountain slopes, acting as a natural adhesive between rocks and debris. Its thawing directly impacts ground stability: as it degrades, the soil loses cohesion, increasing the risk of landslides, rockfalls, and debris flows — phenomena that have become increasingly frequent in the Alps due to rising heatwaves.

These events threaten ecosystems and pose risks to infrastructure and local communities [3]. Structures such as mountain huts and cable cars, built on previously stable ground, may suffer structural damage as the ground gives way. This phenomenon is particularly concerning in the Alps, where permafrost thawing compromises the safety of numerous installations [4].

Research and monitoring are then essential to understanding permafrost evolution and developing effective adaptation strategies. Since 2012, in Trentino, the PermaNET project has been focused on permafrost research and monitoring, particularly on rock glaciers.

A recent Swiss study introduces an innovative approach to monitoring permafrost thawing in alpine environments: “microgravimetry.” This technique measures variations in mass within the ground, comparing frozen and thawed areas. When permafrost ice melts, the ground becomes saturated with water, increasing its weight — a change that instruments can precisely detect. This method provides a new tool for studying permafrost degradation and its implications [3].

Figure 1: The effects of global warming in the Alps: where the Ortles Glacier’s tail reached in the mid-19th century, a forest now stands. Trafoi, South Tyrol, Italy. Author, summer 2018.