Copyright 2018 地球科学进展 编辑部
First author:Sun Zhizhong(1974-), male, Qingyuan County, Liaoning Province, Associate professor. Research areas include environment and engineering in cold regions.E-mail:email@example.com
Supported Project supported by the National Natural Science Foundation of China “Observation and simulation study on water-heat process of thawed interlayer under the embankment in permafrost regions”(No.41571064) and “Thermo-mechanical influences and environmental effects of the Qinghai-Tibet Expressway’s building on the permafrost engineering corridor” (No.41630636).;
Permafrost changes under natural sites along the Qinghai-Tibet Railway were investigated based on the ground temperature monitored from the year of 2006 to 2015. Among these sites, mean permafrost table was 3.54 m, with a range of 0.88 to 9.14 m. Among the sites with decreasing permafrost table, mean decreasing amplitude of permafrost table was 0.51 m, with a range of 0.05 to 2.22 m; mean decreasing rate of permafrost table was 0.07 m/a, with a range of 0.01 to 0.25 m/a. Decreasing amplitude and decreasing rate of permafrost table in high temperature regions were 0.47 m and 0.06 m/a greater than those in low temperature regions, respectively. In general, ground temperatures at permafrost table and 15 m depth presented rising tendency. Mean rising amplitude of ground temperature at permafrost table was 0.16 ℃, with a range of 0.01 to 0.60 ℃; mean rising rate of ground temperature at permafrost table was 0.018 ℃/a, with a range of 0.001 to 0.067 ℃/a. Rising amplitude and rising rate of ground temperature at permafrost table in low temperature regions were 0.12 ℃ and 0.014 ℃/a greater than those in high temperature regions, respectively. Mean rising amplitude of ground temperature at 15 m depth was 0.10 ℃, with a range of 0.01 to 0.48 ℃; mean rising rate of ground temperature at 15 m depth was 0.011 ℃/a, with a range of 0.002 to 0.054 ℃/a. Rising amplitude and rising rate of ground temperature at 15 m depth in low temperature regions were 0.11 ℃ and 0.012 ℃/a greater than those in high temperature regions, respectively. Due to the effect of local factors, increasing of permafrost table and decreasing of ground temperature were observed under several sites.
 Permafrost temperature monitoring through 10 boreholes up to 10.7 m depth has been conducted half-monthly from 1996 through 2006 along the Qinghai-Tibetan Highway. The primary results show that the long-term mean annual permafrost temperatures at 6.0 m depth vary from 0908080.1900°C at the Touerjiu Mountains (TM1) site to 0908083.4300°C at Fenghuo Mountain (FH1) site, with an average of about 0908081.5500°C from all 10 sites over the period of their records, indicating permafrost is relatively warm on the Plateau. Mean annual permafrost temperatures at 6.0 m depth have increased 0.1200°C to 0.6700°C with an average increase of about 0.4300°C during the past decade. Over the same period, mean annual air temperatures from four National Weather Service Stations show an increase of about 0.600°C to 1.600°C, generally sufficient to account for the permafrost warming although other factors, such as changes in snow cover and soil moisture conditions, may also play important roles in permafrost warming. Increase in summer rainfall and decrease in winter snowfall may be cooling factors to the underlying soils, offsetting less degree of permafrost warming compared with the magnitude of air temperature increase. Permafrost temperatures at 6.0 m depth increased year-around with most of the increase happened in spring and summer. Winter air temperature has increased 2.900°C to 4.200°C from 1995 through 2005, which may account for significant spring and summer permafrost warming at 6.0 m depth due to three to six month time lag. However, there were no significant trends of air temperature change in other seasons. Further investigation, especially comprehensive monitoring, is needed to better comprehend the physical processes governing the thermal regime of the active layer and permafrost on the Qinghai-Tibetan Plateau.
Cheng GD, Wu T H. Responses of permafrost to climate change and their environmental significance, Qinghai-Tibet Plateau[J]. , 2007, 112: F02S03.
 In this paper we summarize recent research in geocryological studies carried out on the Qinghai-Tibet Plateau that show responses of permafrost to climate change and their environmental implications. Long-term temperature measurements indicate that the lower altitudinal limit of permafrost has moved up by 25 m in the north during the last 30 years and between 50 and 80 m in the south over the last 20 years. Furthermore, the thickness of the active layer has increased by 0.15 to 0.50 m and ground temperature at a depth of 6 m has risen by about 0.1脗掳 to 0.3脗掳C between 1996 and 2001. Recent studies show that freeze-thaw cycles in the ground intensify the heat exchange between the atmosphere and the ground surface. The greater the moisture content in the soil, the greater is the influence of freeze-thaw cycling on heat exchange. The water and heat exchange between the atmosphere and the ground surface due to soil freezing and thawing has a significant influence on the climate in eastern Asia. A negative correlation exists between soil moisture and heat balance on the plateau and the amount of summer precipitation in most regions of China. A simple frozen soil parameterization scheme was developed to simulate the interaction between permafrost and climate change. This model, combined with the NCAR Community Climate Model 3.6, is suitable for the simulation of permafrost changes on the plateau. In addition, permafrost degradation is one of the main causes responsible for a dropping groundwater table at the source areas of the Yangtze River and Yellow River, which in turn results in lowering lake water levels, drying swamps and shrinking grasslands.
GaoBaolin, SunZhizhong, DongTianchun, et al. Characteristics of thawed interlayer beneath embankment of the Qinghai-Tibet Railway in permafrost regions and its effect on embankment settlement deformation[J]. , 2015,37(1):126-131.
 The active layer over permafrost plays a significant role in surface energy balance, hydrologic cycle, carbon fluxes, ecosystem, and landscape processes and on the human infrastructure in cold regions. Over a period from 1995 to 2007, a systematic soil temperature measurement network of 10 sites was established along the Qinghai-Tibetan Highway. Soil temperatures up to 12 m depth were continuously measured semimonthly. In this study, we investigate spatial variations of active layer thickness (ALT) and its change over the period of record. We found that ALT can be estimated with confidence using semimonthly soil temperature profiles compared to those determined from available daily soil temperature profiles over the Qinghai-Tibetan Plateau. The primary results demonstrate that long-term and spatially averaged ALT is 652.41 m with a range of 1.32–4.57 m along the Qinghai-Tibetan Highway. All monitoring sites show an increase in ALT over the period of their records. The mean increasing rate of ALT is 657.5 cm/yr. ALT shows a closely positive correlation with the thawing index of air temperature on the plateau. We estimated ALT using the thawing index over a period from 1956 to 2005 near the Wudaoliang Meteorological Station in the northern plateau. ALT had no or very limited change from 1956 to 1983 and a sharp increase of 6539 cm from 1983 to 2005. The magnitude of ALT increase is greater in the warm permafrost region than in the cold permafrost region. The primary control of increase in ALT is caused by an increase in summer air temperature, whereas changes in the winter air temperature and snow cover condition play no or a very limited role.
Wu QB, Liu YZ.Ground temperature monitoring and its recent change in Qinghai-Tibet Plateau[J]. , 2004, 38(2/3): 85-92.
The monitoring data is used to analyze the recent change in the thickness of active layer, the subsurface temperature, the near permafrost surface temperature, and the permafrost temperature at the depth of 6 or 8 m. The results show that their changes have a better accordance with air temperature change. The climate change has an impact on the change of the active layer and the thermal regime of the permafrost. The change of the active layer and the thermal regime of the permafrost can indirectly explain some features of climate change.
ZhaoL, Wu QB, Marchenko SS, et al. Thermal state of permafrost and active layer in central Asia during the International Polar Year[J].,2010,21(2):198-207.
Abstract Permafrost in Central Asian is present in the Qinghai–Tibet Plateau in China, the Tien Shan Mountain regions in China, Kazakhstan and Kyrgyzstan, the Pamirs in Tajikistan, and in Mongolia. Monitoring of the ground thermal regime in these regions over the past several decades has shown that the permafrost has been undergoing significant changes caused by climate warming and increasing human activities. During the International Polar Year, measured mean annual ground temperature (MAGT) at a depth of 665m ranged from 613.2°C to 0.2°C on the Qinghai–Tibet Plateau and the active-layer thickness (ALT) varied between 105 and 32265cm at different sites. Ground temperatures at the bottom of the active layer (TTOP) warmed on average by 0.06°C yr 611 over the past decade. In Mongolia, MAGT at 10–1565m depth increased by up to 0.02–0.03°C yr 611 in the Hovsgol Mountain region, but by 0.01–0.02°C yr 611 in the Hangai and Hentei Mountain regions. The increase in permafrost temperatures in the northern Tien Shan from 1974 to 2009 ranged from 0.3°C to 0.6°C. At present measured permafrost temperatures vary from 610.5°C to 610.1°C. The ALT increased from 3.2 to 465m in the 1970s to a maximum of 5.265m between 1995 and 2009. Copyright 08 2010 John Wiley & Sons, Ltd.
In this study, we investigated changes in active layer thickness (ALT) and permafrost temperatures at different depths using data from the permafrost monitoring network along the Qinghai-Xizang (Tibet) Railway (QXR) since 2005. Among these sites, mean ALT is ~3.1 m, with a range of ~1.1 to 5.9 m. From 2006 through 2010, ALT has increased at a rate of ~6.3 cm a 1. The mean rate of permafrost temperature rise at the depth of 6.0 m is ~0.02 °C a 1, estimated by linear regression using 5 yr of data, and the mean rate of mean annual ground temperature (MAGT) rise at a depth of zero amplitude is ~0.012 °C a 1. Changes for colder permafrost (MAGT < 1.0 °C) are greater than changes for relatively warmer permafrost (MAGT > 1.0 °C). This is consistent with results observed in the Arctic and subarctic.
Based on field monitoring datasets, characteristics of embankment deformation were summarized along the Qinghai–Tibet Railway in four permafrost regions with different mean annual ground temperatures (MAGTs). Then, further analyses were carried out at some typical monitoring profiles to discuss mechanisms of these embankment deformations with consideration of detailed information of thermal and subsurface conditions. The results indicated that in regions with MAGT <61021.502°C, embankments only experienced seasonal frost heaves, and of which the magnitudes were not significant. So, the embankments in the regions performed satisfactorily. Whereas in regions with MAGT ≥61021.502°C, both traditional embankment and crushed rock embankment experienced settlements, but characteristics and mechanisms of the settlements were different for the two kinds of embankment. For crushed rock embankment, the magnitudes of settlement and differential settlement between right and left embankment shoulders were not significant and increased slowly. In respect that upwards movements of permafrost tables and better thermal stability of permafrost beneath embankment, mechanism of settlements on the embankment was inferred as creep of warm and ice-rich layer often present near permafrost table. While for traditional embankment, particularly in warm and ice-rich permafrost regions, the magnitudes of settlement and differential settlement between right and left embankment shoulders were significant and still increased quickly. Considering underneath permafrost table movements and permafrost temperature rises, mechanisms of settlements on the embankment included not only creep but also thawing consolidation of underlying permafrost. Therefore, some strengthened measures were needed to ensure long-term stability of these traditional embankments, and special attention should be paid on temperature, ice content and applied load within the layer immediately beneath permafrost table since warming and thawing of the layer could give rise to considerable settlement.
The permafrost monitoring network in the polar regions of the Northern Hemisphere was enhanced during the International Polar Year (IPY), and new information on permafrost thermal state was collected for regions where there was little available. This augmented monitoring network is an important legacy of the IPY, as is the updated baseline of current permafrost conditions against which future changes may be measured. Within the Northern Hemisphere polar region, ground temperatures are currently being measured in about 575 boreholes in North America, the Nordic region and Russia. These show that in the discontinuous permafrost zone, permafrost temperatures fall within a narrow range, with the mean annual ground temperature (MAGT) at most sites being higher than -2掳C. A greater range in MAGT is present within the continuous permafrost zone, from above -1掳C at some locations to as low as -15掳C. The latest results indicate that the permafrost warming which started two to three decades ago has generally continued into the IPY period. Warming rates are much smaller for permafrost already at temperatures close to 0掳C compared with colder permafrost, especially for ice-rich permafrost where latent heat effects dominate the ground thermal regime. Colder permafrost sites are warming more rapidly. This improved knowledge about the permafrost thermal state and its dynamics is important for multidisciplinary polar research, but also for many of the 4 million people living in the Arctic. In particular, this knowledge is required for designing effective adaptation strategies for the local communities under warmer climatic conditions. Copyright 漏 2010 John Wiley & Sons, Ltd.