The Qinghai-Tibet Plateau (QTP) is characterized by its extreme climate and dominated by periglacial processes. Permafrost conditions vary greatly, and the recent changes on the QTP are not well known in the hinterland. Here, we examine the changes in climate and permafrost temperatures in several different regions. Climate data were obtained from three weather stations from 1957 to 2019. Annual mean air temperature (T-a) has gradually increased at .031 degrees C/yr-.039 degrees C/yr. Climate warming has been more rapid in the past two decades, particularly during the cold season (November to February). Precipitation has also been slowly increasing during the instrumental record. However, there is pronounced heterogeneity in the seasonal distribution of precipitation, with very little falling between October and April. Ground temperatures and active-layer thickness (ALT) have been investigated over similar to 20 years at five sites representative of the hinterland of the QTP. These sites are located along the Qinghai-Tibet Highway, which crosses the permafrost zone and traverses the mountainous area and basin areas. Annual mean ground temperatures within the active layer (T-al similar to 1 m depth) indicate recent ground warming at all sites, at rates near .05 degrees C/yr. The ALT at five sites has been increasing steadily by 2-9 cm/yr, with an average of 4.6 cm/yr. The temperature near the permafrost table (T-ps) has been increasing at .01 degrees C/yr and .06 degrees C/yr, with an average of .03 degrees C/yr. Permafrost temperatures at 15 m depth (T-g) have been increasing by about .01 degrees C/yr-.02 degrees C/yr. The southern boundary (AD site) of the permafrost has warmed the least among the five locations. In high mountainous areas where permafrost temperatures are low (e.g., KLS site), the annual mean T-g has increased by nearly .02 degrees C/yr. The rate of permafrost warming at a basin site (BLH), with relatively high ground temperatures, was approximately .01 degrees C/yr. The GIPL2.0 model simulation results indicate that the annual mean permafrost temperature at 1 m depth at these sites will increase by .6 degrees C-1.8 degrees C in the next 100 years (to 2100) and that ALT will increase by similar to 40-100 cm. We also discuss the impacts of permafrost changes on the environment and infrastructure on the QTP. This study provides useful information to understand observed and anticipated permafrost changes in this region, under different shared socioeconomic pathways, which will allow engineers to develop adaptation measures.

Permafrost that exists near the boundary of the permafrost zone is generally more sensitive to climate change. By analyzing ground temperatures observed from two 30-m-deep boreholes, a case study was conducted to present some characteristics of recent permafrost warming in the Xidatan area, near the northern limit of the permafrost zone on the Qinghai-Tibetan Plateau. The rate of permafrost degradation from top to bottom in the area was far less than that from bottom to top. Local conditions produced spatial differences in permafrost characteristics, and thus the site covered by alpine meadow had a thinner active layer and lower rate of change than the site with desert steppe. With permafrost warming, the depths of zero annual amplitude at the two sites showed significant decreasing trends, suggesting that the warming could change the proportion of unfrozen water and ice in permafrost, and then lead to a decrease in the mean thermal diffusivity of formation. Mean annual permafrost temperatures at depth of zero annual amplitude of the two boreholes were respectively 0.4 and -0.7 degrees C, indicating that high-temperature permafrost is widely distributed in the study area. The lower temperature permafrost had a higher warming rate and a higher upward shift rate of the permafrost base. The pattern of permafrost degradation near the limit of permafrost was characterized by nonuniform speed and staged development.

Although the thermal regime and degradation of permafrost on the Qinghai-Tibet Plateau (QTP) have been widely documented, little information exists regarding the island permafrost in the area. Ground temperatures were therefore measured for 8 years (2013-2020) at a permafrost island and at two contrasting sites in the Xidatan region to elucidate the permafrost in this area. Results indicate that the ground temperatures in the island permafrost were markedly higher than those at the same depth in the nearby marginal permafrost and the interior continuous permafrost. In addition, a distinct increasing trend was observed in the ground temperature of the island permafrost over the past 8 years, and warming was signficanty faster in the deep soil than in the topsoil, indicating a bottom-up degradation pattern in the island permafrost. Moreover, due to the persistent increase in the thickness of the active-layer and the decrease in the depth of permafrost table, the permafrost island abruptly disappeared in 2018, which may be attributed to the anomalously high air temperatures that occurred in 2016 and 2017. The results of this study may provide references for understanding of the thermal regime and degradation process of island permafrost on the QTP.

Permafrost that exists near the boundary of the permafrost zone is generally more sensitive to climate change. By analyzing ground temperatures observed from two 30-m-deep boreholes, a case study was conducted to present some characteristics of recent permafrost warming in the Xidatan area, near the northern limit of the permafrost zone on the Qinghai-Tibetan Plateau. The rate of permafrost degradation from top to bottom in the area was far less than that from bottom to top. Local conditions produced spatial differences in permafrost characteristics, and thus the site covered by alpine meadow had a thinner active layer and lower rate of change than the site with desert steppe. With permafrost warming, the depths of zero annual amplitude at the two sites showed significant decreasing trends, suggesting that the warming could change the proportion of unfrozen water and ice in permafrost, and then lead to a decrease in the mean thermal diffusivity of formation. Mean annual permafrost temperatures at depth of zero annual amplitude of the two boreholes were respectively 0.4 and -0.7 degrees C, indicating that high-temperature permafrost is widely distributed in the study area. The lower temperature permafrost had a higher warming rate and a higher upward shift rate of the permafrost base. The pattern of permafrost degradation near the limit of permafrost was characterized by nonuniform speed and staged development.

The geothermal record for 1977-2014 from a 29m deep borehole in permafrost on Mont Jacques-Cartier, in southeastern Canada, shows substantial decadal fluctuations and an overall warming trend. An extremely thin winter snow cover on the wind-blown summit favours the presence of permafrost. As a consequence, the instability of the thermal regime was found to be a direct response to air temperature variations modelled from data produced by the National Center for Environmental Prediction and National Center for Atmospheric Research. At a depth of 14m, an increase of 0.4 degrees C from 1979 to 1984 was followed by a decrease of 0.7 degrees C over the next decade, and then by a marked, but irregular increase of 1 degrees C up to 2013. Since 2008, diurnal data, refined by a one-dimensional, transient heat transfer model, indicate an active layer averaging 8.6m in depth, but whose thickness is sensitive to fluctuations in annual mean ground surface temperatures. For a permafrost body already close to the thawing point, the continuation of the overall warming trend of the last 37years would lead to its rapid degradation, and the permafrost would then become relict, thinning progressively both from the base and the surface. Copyright (c) 2016 John Wiley & Sons, Ltd.