The global permafrost has been warming at different rates over the past decades. Based on observations and modeling, significant progress has been made in understanding the impacts of long-term climate change on permafrost variability.

In recent years, the frequency and intensity of extreme events have increased. Several studies have demonstrated that extreme events can significantly impact the permafrost environment by altering the hydrothermal conditions of the active layer, destabilizing slopes, and triggering landslides, etc.

However, the processes and mechanisms by which short-term extreme events affect the active layer and permafrost remain unclear.

Using a long series of meteorological, active layer hydrothermal, and permafrost monitoring data, researchers from the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences (CAS) found that the permafrost region of the central Qinghai-Xizang Plateau experienced a summer heatwave in 2022.

This work was published in npj Climate and Atmospheric Science.

The results show that the average summer temperature of 2022 reached 6.5°C, which is the highest temperature recorded during the 1961-2022 period and 3.2°C higher than the 1961-1990 baseline period.

Four active layer sites experienced maximum active layer thicknesses (ALT) in 2022 (mean: 207.7 cm), which was 20% higher than the mean ALT during 2000–2021 (mean: 175.9 cm). The mean annual ground temperature (MAGT) observed in 2022 was also the highest, exceeding the average of the previous years by 10%.

The contribution of heat wave to the seasonal thaw depth of the active layer was quantified using the Stefan model, ranging from 6.6% to 13.6%, with the maximum contribution occurring in 2022.

These findings are helpful for a better understanding of the impact processes of extreme events on the active layer and permafrost. These results obtained contribute to a deeper understanding of the mechanisms by which extreme events affect the active layer and permafrost.

Fig. 1 Temporal characteristics of active layer thickness (ALT).

Fig. 2 Changes in the mean summer ground temperature of permafrost.