LANZHOU, June 24 (Xinhua) -- A new study by Chinese scientists provides valuable scientific insights for assessing the thermal stability of engineering projects in cold regions and guiding ecological management in areas affected by aeolian desertification, according to the Northwest Institute of Eco-Environment and Resources (NIEER) under the Chinese Academy of Sciences.
The study, conducted by researchers from the NIEER, deepens the understanding of thermal stability changes in frozen ground under aeolian desertification conditions. Its findings have been published in the journal Agricultural and Forest Meteorology, said the institute.
The Qinghai-Tibet Plateau is one of China's regions with the most extensive frozen ground and is particularly sensitive to climate change, according to Jiang Guanli, a researcher at the institute.
Jiang noted that in recent years, climate warming and aeolian desertification processes have been influencing the plateau's frozen ground environment. By altering heat transfer between the surface and the subsurface, aeolian sand cover exerts significant impacts on the thermal state and freeze-thaw processes of frozen ground.
Given this context, the team launched the study to clarify how aeolian sand regulates the thermal regime, maximum seasonal freezing depth (MSFD) and freeze-thaw processes of seasonally frozen ground on the plateau.
Researchers conducted continuous observations of soil thermal regimes under different aeolian sand-layer thicknesses in the Beiluhe River and Honglianghe River basins on the plateau.
The team quantitatively analyzed the relative contributions of climatic factors and surface conditions to changes in seasonal frozen ground on the plateau. It also systematically assessed the effects of aeolian sand cover on the thermal regime and freeze-thaw processes in the region.
The results show that the aeolian sand cover layer significantly altered the thermal regime of seasonally frozen ground and the maximum seasonal freezing depth. As the aeolian sand layer thickened, the duration of the ground's freezing period shortened noticeably.
During the thawing phase of permafrost, the aeolian sand cover layer exhibited distinct regulatory characteristics, with the top-down thawing period shortened significantly, while the bottom-up thawing period lengthened. This indicates that thick aeolian sand layers enhance asymmetry in the freeze-thaw process, manifesting as accelerated freeze-thaw rates in the upper part and decelerated rates in the lower part.
The study further showed that the maximum seasonal freezing depth of frozen ground generally decreases as the aeolian sand layer thickens, according to Wu Qingbai, a researcher at the NIEER.
Temperature is the primary factor influencing the maximum seasonal freezing depth, while precipitation and net solar radiation play comparatively smaller roles. However, under the combined influence of thick aeolian sand layers and low vegetation coverage, the maximum seasonal freezing depth tends to increase, according to the study.
"Through in-situ observation data and quantitative study, our study extends understanding of thermal stability changes on the Qinghai-Tibet Plateau. It adds scientific basis for assessing thermal stability of engineering projects in cold regions, parameterizing permafrost freeze-thaw processes, and enhancing ecological management in aeolian-sand-affected regions," Wu said. ■
