A Cold, Dry, and Rapidly Changing Landscape
In the remote Altun Mountains (Altun Shan) on the northern edge of the Tibetan Plateau, a unique type of frozen ground shows the effects of climate change. This is mountain permafrost, defined as ground that remains at or below 0°C for at least two consecutive years, and it exists here at altitudes over 4,500 meters. Unlike the ice-rich permafrost of the Arctic, the ground here is characterized by extremely cold and dry conditions, resulting in a lower overall ice content.
This lower ice content is the main reason for its rapid warming. Ice has a high capacity to absorb heat without changing temperature—a property known as latent heat. In the Arctic, this high ice content means a great deal of energy is required to melt the ice before the ground temperature can rise significantly. In the Altun Mountains, the lack of substantial ground ice means there is less of a thermal buffer. As air temperatures increase, the ground temperature responds much more quickly.
Data from boreholes drilled deep into the ground confirm this accelerated warming. While global permafrost in mountain regions warmed by an average of 0.19°C between 2007 and 2016, specific monitoring sites on the broader Qinghai-Tibet Plateau show more dramatic changes. Some locations have recorded warming rates at a depth of 10 meters as high as 0.78°C per decade. The permafrost here is some of the coldest on the plateau, with mean annual ground temperatures reaching as low as -4°C, yet it is still experiencing significant warming trends.
High Altitude, High Stakes
The Altun Shan National Nature Reserve, where this permafrost is located, is an arid and largely uninhabited area. This 45,000-square-kilometer reserve is a high-altitude desert ecosystem, a landscape that has preserved a unique environment. The thawing of its permafrost has significant consequences for this fragile stability. As the frozen ground warms and degrades, it affects the region's hydrology and the stability of the land itself.
The layer of ground that thaws in summer and freezes in winter is called the active layer. As permafrost warms, the active layer deepens. On the Qinghai-Tibet Plateau, active layer thickness can exceed 3.5 meters in some areas with high ice content. A deepening active layer in the Altun Mountains could alter drainage patterns and affect the sparse vegetation that has adapted to the stable, frozen substrate.
This region is an important habitat for a number of protected species, including the Tibetan wild ass (kiang), wild yaks, and Tibetan antelopes. The total population of these species has grown significantly in recent decades due to conservation efforts. The stability of their habitat is directly linked to the state of the permafrost. Thawing can lead to ground subsidence and changes in the local water cycle, which underpins the entire ecosystem that these animals depend upon. The reserve is often called a "plateau gene bank," and understanding the changes in its frozen foundation is essential for its future.