Climate warming over the past half century has led to thermal degradation of permafrost on the Qinghai–Tibet Plateau

Abstract

Abstract. Air temperature increases thermally degrade permafrost, which has widespread impacts on engineering design, resource development, and environmental protection in cold regions. This study evaluates the potential thermal degradation of permafrost over the Qinghai–Tibet Plateau (QTP) from the 1960s to the 2000s using estimated decadal mean annual air temperatures (MAATs) by integrating remote-sensing-based estimates of mean annual land surface temperatures (MASTs), leaf area index (LAI) and fractional snow cover values, and decadal mean MAAT date from 152 weather stations with a geographically weighted regression (GWR). The results reflect a continuous rise of approximately 0.04 ∘C a−1 in the decadal mean MAAT values over the past half century. A thermal-condition classification matrix is used to convert modelled MAATs to permafrost thermal type. Results show that the climate warming has led to a thermal degradation of permafrost in the past half century. The total area of thermally degraded permafrost is approximately 153.76×104 km2, which corresponds to 88 % of the permafrost area in the 1960s. The thermal condition of 75.2 % of the very cold permafrost, 89.6 % of the cold permafrost, 90.3 % of the cool permafrost, 92.3 % of the warm permafrost, and 32.8 % of the very warm permafrost has been degraded to lower levels of thermal condition. Approximately 49.4 % of the very warm permafrost and 96 % of the likely thawing permafrost has degraded to seasonally frozen ground. The mean elevations of the very cold, cold, cool, warm, very warm, and likely thawing permafrost areas increased by 88, 97, 155, 185, 161, and 250 m, respectively. The degradation mainly occurred from the 1960s to the 1970s and from the 1990s to the 2000s. This degradation may lead to increased risks to infrastructure, reductions in ecosystem resilience, increased flood risks, and positive climate feedback effects. It therefore affects the well-being of millions of people and sustainable development at the Third Pole.

Multisatellite Analyses of Spatiotemporal Variability in Photosynthetic Activity Over the Tibetan Plateau

“…Finally, direct application of the estimated precipitation breakpoints to the forecast of long‐term productivity changes associated with future climate change should be done with caution. In a warming world, the relationship between productivity and precipitation, which is used to estimate the precipitation breakpoints, might be changed by the continuing degradation of the Tibetan permafrost (Ran et al, ), which could affect the moisture available for vegetation productivity.…”

The Role of Winter Warming in Permafrost Change Over the Qinghai‐Tibet Plateau

“…• Winter warming in past decades is over twice than summer warming over the Qinghai-Tibet Plateau (QTP) • The influence of winter warming on permafrost thermal regime exceeded summer warming over the QTP after 2000 • Alpine continuous permafrost on the northern QTP has experienced an obvious regional warming due to rapid winter warming since 2000 especially on the northern QTP (Qian & Lin, 2004;Ran et al, 2018;Zhao et al, 2004). Research on temperature extremes shows that the rate of winter warming is generally higher than the annual basis in China (You et al, 2013;Yue et al, 2013).…”

Elevation‐dependent thermal regime and dynamics of frozen ground in the Bayan Har Mountains, northeastern Qinghai‐Tibet Plateau, southwest China

“…Permafrost on the QTP is generally warm and represents the southernmost occurrence in the northern hemisphere . Overall, permafrost temperatures on the QTP are primarily influenced by elevation, latitude and longitude (aridity), as well as some local environmental variables .…”

“…It is generally recognized that permafrost warming has occurred and will continue to occur both in high latitudes and at high elevations, in the context of climate warming . There is growing evidence that the rate of warming is amplified with elevation, being characterized by more rapid changes of temperatures at high‐mountain environments than at lower elevations . For example, on the basis of climatic records, climate warming at higher elevations on the QTP has been more prominent in the past five decades, especially in winter and spring .…”

“…Nevertheless, elevation‐dependent permafrost warming has not been convincingly evaluated, due to the lack of long‐term and systematic monitoring of permafrost temperatures over elevation gradients. In addition, surface characteristics including vegetation and snow‐cover complicate the thermal regime of the underlying active layer and permafrost . Consequently, it is not straightforward to clarify the relationship between elevation and irreversible variations of relevant cryospheric features, such as the hydrological cycle and ecosystem processes, which further accelerates permafrost degradation.…”