1981—2018年内蒙古典型草原季节性冻土对气候变化的响应

以1981—2018年内蒙古典型草原季节性冻土为研究对象,通过气候倾向率、Mann-Kendall法、多元线性回归等方法,分析最大冻土时空分布特征、年际、年代际变化,研究影响最大冻土深度变化的气象因子。结果表明：（1） 内蒙古典型草原季节性冻土冻结初日在9—11月,终日在4—6月,年内最大冻土深度出现在2—3月,深度在100~280 cm之间。（2） 最大冻土深度年际变化分为下开口抛物线型、上开口抛物线型、正弦曲线型,从最大冻土深度气候倾向率看呈现减小趋势的站点有68%。（3） 最大冻土深度年代际变化分为逐年代递减、减-增型和无明显变化规律,50%的站点在1989年以后最大冻土深度发生突变。（4） 多元线性回归表明气温冻结指数、年平均风速、年极端最低气温对最大冻土深度产生显著影响。该研究揭示了最大冻土深度存在退化的事实,为草原应对气候变化提供指导,为陆地土壤和大气碳循环交换的研究给出提示。     

Ground temperature variation and its response to climate change on the northern Tibetan Plateau

Ground temperature plays a significant role in the interaction between the land surface and atmosphere on the Tibetan Plateau(TP). Under the background of temperature warming, the TP has witnessed an accelerated warming trend in frozen ground temperature, an increasing active layer thickness, and the melting of underground ice. Based on high-resolution ground temperature data observed from 1997 to 2012 on the northern TP, the trend of ground temperature at each observation site and its response to climate change were analyzed. The results showed that while the ground temperature at different soil depths showed a strong warming trend over the observation period, the warming in winter is more significant than that in summer. The warming rate of daily minimum ground temperature was greater than that of daily maximum ground temperature at the TTH and MS3608 sites. During the study period, thawing occurred earlier, whereas freezing happened later, resulting in shortened freezing season and a thinner frozen layer at the BJ site. And a zero-curtain effect develops when the soil begins to thaw or freeze in spring and autumn. From 1997 to 2012, the average summer air temperature and precipitation in summer and winter from six meteorological stations along the Qinghai-Tibet highway also demonstrated an increasing trend, with a more significant temperature increase in winter than in summer. The ground temperature showed an obvious response to air temperature warming, but the trend varied significantly with soil depths due to soil heterogeneity.     

青藏高原西部区域多年冻土分布模拟及其下限估算

准确评估青藏高原西部多年冻土的空间分布及多年冻土下限深度情况对该区地下水资源利用、生态环境保护有重要意义.本文依托科技基础性工作专项“青藏高原多年冻土本底调查”在该区及周边取得的冻土调查资料,利用遥感数据和扩展地面冻结数模型模拟了该区多年冻土的空间分布,调查区的模拟验证表明该方法有较高的精度.在此基础上,根据有限的地温实测资料建立了地温与位置、高程、坡向和太阳辐射的关系,并根据地温-下限关系估算了该区多年冻土下限深度的分布情况.研究表明,该区有多年冻土约占36.9%,季节冻土占57.5%,多年冻土主要分布在34°N~36.5°N范围的喀喇昆仑、西昆仑一带,季节冻土主要分布在塔里木盆地和34°N以南地区.阿里高原及以南是岛状多年冻土分布区域,其多年冻土分布面积少于此前出版的冻土图所绘制的.青藏高原西部区域的多年冻土下限深度整体表现为由东南-西北逐渐加深.     

Study on the sunny-shady slope effect on the subgrade of a high-speed railway in a seasonal frozen region

The temperature distributions of different parts of a subgrade were analyzed based on the results of three years of monitoring data from the Harbin-Qiqihaer Passenger Dedicated Line, a high-speed railway, including the slope toes, shoulders, and natural ground. The temperature variation with time and the maximum frozen depths showed that an obvious sunny-shady effect exists in the railway subgrade, which spans a seasonal frozen region. Development of frost heave is affected by the asymmetric temperature distribution. The temperature field and the maximum frozen depths 50 years after the subgrade was built were simulated with a mathematical model of the unsteady phase transition of the geothermal field.     

Assessing the thermal regime of soils in the depressions of the Prebaikalia and Northern Transbaikalia

Long-term data from meteorological stations have been used in assessing the thermal state of the soil layer in large depressions of the Prebaikalia and Northern Transbaikalia. We examine the characteristics of temperature distribution in depth over an annual cycle for seasonally frozen and permafrost soils. For the Baikalian type depressions we carried out a spatial differentiation of the lowest and highest (having regard to the temperature lag) mean monthly soil temperatures. It is concluded that within a single depression the thermal regime of the soil fluctuates over a very broad range. On the other hand, an identical situation with the temperature regime can occur in different depressions.     

Flow velocities of active rock glaciers in the Austrian Alps

High surface flow velocities of up to 3 m a^–1 were measured near the front of three active rock glaciers in the western Stubai Alps (Rei‐chenkar) and Ötztal Alps (Kaiserberg and Ölgrube) in Tyrol (Austria) using differential GPS technology. Flow velocities have increased since about 1990. The highest velocities were recorded in 2003 and 2004, but showed a slight decrease in 2005. At the Reichenkar rock glacier, flow rates are constant throughout the year, indicating that meltwater has no significant influence on the flow mechanism. At Ölgrube rock glacier, flow velocities vary seasonally with considerably higher velocities during the melt season. Meltwater is likely to influence the flow of Ölgrube rock glacier as evident by several springs near the base of the steep front. Because the high surface velocities cannot be explained by internal deformation alone on Reichenkar rock glacier, we assume that horizontal deformation must also occur along a well defined shear zone within a water‐saturated, fine‐grained layer at the base of the frozen body. The increased surface flow velocities since about 1990 are probably caused by slightly increased ice temperature and greater amounts of meltwater discharge during the summer, a product of global warming.     

Laboratory investigation on the mechanical behavior of ice-saturated frozen loess

To investigate the mechanical properties of ice-saturated frozen soil, a series of triaxial tests under various confining pressures（0.5 to 9.0 MPa） on ice-saturated frozen loess with ice content of 23.7% were carried out at a temperature-6 °C, and at 1.25 mm/min of loading rate. The triaxial tests include two loading modes, one with monotonic loading（i.e., triaxial compression）, and another with static cycle loading. The test results under triaxial compression show that the strength and deformation behaviors of ice-saturated frozen loess are affected by confining pressure. According to the test results of triaxial loading-unloading cycle test, the elastic modulus evolution with the number of cycles under different confining pressures are analyzed.     

Evaluation of the permafrost stability degradation from 1980 to 2010 in China

The degradation of permafrost stability in China over the past 30 years is evaluated using a new, high-resolution near-surface air temperature reanalysis dataset. Results show that the permafrost extent clearly decreased by 22% from 1980 to 2010, that is, a loss of 12.68⁴;104 km². The degradation occurred not only in the transition regions between permafrost and seasonally frozen ground, but also and more importantly, in the interior of the permafrost regions. The degradation in the interior of permafrost regions accounted for 87% of the total degraded areas. The degradation occurred mainly during the 1980s to 1990s in the northeast permafrost area and the Qilian Mountains, and during the 1990s to 2000s in most areas of the Qinghai-Tibet Plateau (QTP). This degradation will have systemic impacts on engineered infrastructures in permafrost regions, the water balance, and the global carbon budget. A more robust physical model should be used to evaluate the permafrost thermal stability at finer resolution in the future.     

Investigation of mountain permafrost in the Kozia Dolinka valley,Tatra Mountains,Poland

The Kozia Dolinka valley lies at an altitude above 1900 m a.s.l. on the northern slope of the main ridge of the High Tatra Mountains. Mountain permafrost occurrences were studied with the use of BTS, infrared imaging, water and ground temperature measurements and DC resistivity soundings. The data suggest the existence of isolated patches of permafrost. The lowest observed bottom temperature of winter snow values was in the order of-10C. DC soundings revealed the existence of a high resistivity layer of limited extent. Permafrost seasonal monitoring was conducted with resistivity soundings. Measurements were carried out in spring-autumn 1999, when a distinct change in permafrost thickness was observed.     

Frost-heave properties of saturated compacted silty clay under one-side freezing condition

In seasonally frozen regions, the frost-heave properties of soil play a significant role in its upper-structure performance and durability. To investigate the frost-heave behaviors of saturated, compacted silty clay soil widely used as subgrade material, a series of one-side freezing tests was carried out; and the freezing depth and frozen front effected by the compactness, temperature, overburden pressure, and water-supply condition were analyzed and discussed. The results show that the moving speed of the frozen front and growth rate of the frozen depth are positively correlated. The frost heave is maximum in the frost-heave stability condition. The frost ratio of saturated soil is proportional to the water supply and cooling temperature under a one-side freezing condition. The frost ratio of saturated soil is inversely proportional to the initial compactness of the soil specimen and the overburden pressure.     

黄河源区冻土分布制图及其热稳定性特征模拟

以黄河源区多年冻土分布现状和热力特征为研究目标,通过野外调查及实测数据,分析了黄河源区不同地形地貌、不同地表覆盖条件下的冻土形成、分布特征和以地温为基础的热学特征,探讨了不同尺度因素对多年冻土分布的影响。结果表明,在高程低于4 300 m的平原区,多年冻土多不发育;在高于4 350 m的山区,局地地形对多年冻土的形成与分布作用显著。除阳坡地形外,多年冻土均比较发育;介于4 300~4 350 m的低山丘陵和平原区,局地地形、地表植被、土壤湿度等因素共同决定着多年冻土的形成和分布格局。以年均地温指标为基础,构建了以纬度、经度和高程为自变量的回归模型,并对阳坡地形进行微调和校正。结果表明,以0oC作为划分季节冻土和多年冻土的标准和界限,多年冻土面积2.5×10⁴km²,约占整个源区面积的85.1%;季节冻土面积0.3×10⁴km²,约占整个源区面积的9.7%。进一步以0.5oC或1.0oC为分类间隔绘制了黄河源区多年冻土热稳定性空间分布图。     

近30年来藏北高原湖泊变化对气候波动的响应

According to the analysis of the climate materials including the topographic map in 1975, the TM and CBERS satellite remote sensing materials from the 1980s to 2005 as well as the air temperature, precipitation, evaporation rate, maximum depth of snow and the biggest depth of frozen soil in the past 45 years, the water level area of four lakes at the southeast of Nagqu, Tibet including Bam Co, Pung Co, Dung Co and Nuripung Co show a distinct trend of expansion in the past 30 years. In 2005, the water level area of the above four lakes increased by 48.2 km², 38.2 km², 19.8 km² and 26.0 km² respectively compared to 1975, with the respective increase rate of 25.6%, 28.2%, 16.2% and 37.6%. That is closely related to the warming and humidified climate change in the recent years such as rise of the air temperature, increase of the precipitation, decrease of the evaporation rate and permafrost degradation. Foundation: National Natural Science Foundation of China, No.40761005 Author: Bian Duo (1966–), Professor, specialized in application of remote sensing and GIS on environment.     

Using relict rockglaciers in GIS-based modelling to reconstruct Younger Dryas permafrost distribution patterns in the Err-Julier area,Swiss Alp

Differences in mean annual air temperature between the Younger Dryas period and today were estimated at the fronts of 32 relict rockglaciers in the Err-Julier area, eastern Swiss Alps. The analyses were based on a case-by-case calculation of direct incoming solar radiation and mean annual air temperature using a digital elevation model (DEM) and meteo data of recent years. Our results suggest that mean annual air temperature during the Younger Dryas was lowered by c. 3C to 4C, and that the lower limit of permafrost occurrence was depressed considerably more than glacier equilibrium lines. This indicates strongly reduced precipitation (30% to 40% reduction) and much larger abundance of mountain permafrost at that time. A model simulation of the corresponding spatial permafrost distribution during the Younger Dryas indicates that glaciers in the study area were mostly surrounded by permafrost at that time and probably had a polythermal structure of englacial temperatures.     

砂田退化对土壤温度和蒸发影响的模拟研究

根据砂田不同耕作年份实地取样,并进行粒径分析,结果表明,砂层中混入的土含量随着砂田耕作年限增加而逐步增加;参照实地取样后粒径分析,以砂层混入土的不同重量百分比梯度设置处理T1-5%、T2-10%、T3-20%、T4-25%、T5-30%、T6-40%,并设对照CK1(纯砂砾覆盖)和CK2(无覆盖裸地),进行温度变化和蒸发效应的模拟研究。结果表明,5 cm、10 cm的土壤温度在8:00和20:00均随着退化程度的加重而降低,而在中午则呈横置S状;与对照纯砂砾覆盖CK1相比日高温延时性随退化程度加重而逐步减弱,日积温减小且昼夜温差增大;蒸发强度随着砂田退化程度的加重而逐渐增强,无覆盖处理蒸发量约是纯砂砾覆盖蒸发量的3倍,而严重退化的处理T5 、T6分别是纯砾石覆盖的2倍,即严重退化砂田年蒸发量要比CK1多110 mm。     

Summary of research on frost heave for subgrade in seasonal frozen ground

The building of railways on seasonally frozen ground is inevitable as China pursues economic development and the improvement of its citizens' living standards. However, railway construction in seasonally frozen soil areas is often faced with frost heave, leading to uneven subgrades which seriously threaten traffic safety. This article summarizes extant research results on frost heave mechanism, frost heave factors, and anti-frost measures of railway subgrades in seasonally frozen soil areas.     

Simulated effect of soil freeze-thaw process on surface hydrologic and thermal fluxes in frozen ground region of the Northern Hemisphere

Soil freeze-thaw process is closely related to surface energy budget,hydrological activity,and terrestrial ecosystems.In this study,two numerical experiments(including and excluding soil freeze-thaw process)were designed to examine the effect of soil freeze-thaw process on surface hydrologic and thermal fluxes in frozen ground region in the Northern Hemisphere based on the state-of-the-art Community Earth System Model version 1.0.5.Results show that in response to soil freeze-thaw process,the area averaged soil temperature in the shallow layer(0.0175?0.0451 m)decreases by 0.35℃in the TP(Tibetan Plateau),0.69℃in CES(Central and Eastern Siberia),and 0.6℃in NA(North America)during summer,and increases by 1.93℃in the TP,2.28℃in CES and 1.61℃in NA during winter,respectively.Meanwhile,in response to soil freeze-thaw process,the area averaged soil liquid water content increases in summer and decrease in winter.For surface heat flux components,the ground heat flux is most significantly affected by the freeze-thaw process in both summer and winter,followed by sensible heat flux and latent heat flux in summer.In the TP area,the ground heat flux increases by 2.82 W/m2(28.5%)in summer and decreases by 3.63 W/m2(40%)in winter.Meanwhile,in CES,the ground heat flux increases by 1.89 W/m2(11.3%)in summer and decreases by 1.41 W/m2(18.6%)in winter.The heat fluxes in the Tibetan Plateau are more susceptible to the freeze-thaw process compared with the high-latitude frozen soil regions.Soil freeze-thaw process can induce significant warming in the Tibetan Plateau in winter.Also,this process induces significant cooling in high-latitude regions in summer.The frozen ground can prevent soil liquid water from infiltrating to deep soil layers at the beginning of thawing;however,as the frozen ground thaws continuously,the infiltration of the liquid water increases and the deep soil can store water like a sponge,accompanied by decreasing surface runoff.The influence of the soil freeze-thaw process on surface hydrologic and thermal fluxes varies seasonally and spatially.     

Thermal structure of the lakes of the North-West of Russia during the freeze-up period

On the basis of analyzing long-term field data, we investigated the vertical thermal structure of 66 lakes of the North-West of Russia during the freeze-up period. The largest variability in thermal structure is characteristic for low-drainage shallow water bodies. Detailed data were obtained at self-contained buoy stations located in a small Lake Vendyurskoe (southern Karelia) were used to identify water temperature changes at the depths for a winter season as well as making assessments of het flows at the water–bottom and water–ice interfaces. The interannual water temperature variability at the depths reaches 2°C. The main geographical factors influencing the formation of thermal stratifications in the 66 lakes used in the study during the winter period are their mean depth, area, water residence time and geographical latitude. The largest vertical water temperature gradients are characteristic for the group of the smallest and shallow lakes, in the bottom layers of which the water temperature exceeds the temperature of maximum density, whereas in the deep lakes (more than 15 m) the water temperature is below 4°C. The lowest values of water temperature are observed in large lakes. The water temperature in the upper layer (up to 10 m) of drainage water bodies also decreases to 0–1°C as the result of the removal of heat with the river discharge. According to the thermal stratifications, the lakes are categorized as small (shallow, deep and drainage lakes), medium-sized and large shallow and large deep lakes. The suggested regression model permits a typical water temperature to be assessed at standard depths at the end of a winter season for any water body in the study region using available geographical information. The verification of the model is done from independent data for eight lakes of Finland.     

Teaching and Tragedy: Lessons from a Population and GIS workshop in Cambodia

Abstract

Long-term collection of soil temperature with depth is important when studying climate change. The international program GLOBE® provides an excellent opportunity to collect such data, although currently endorsed temperature collection protocols need to be refined. To enhance data quality, protocol-based methodology and automated data logging, along with other physical data, were used to collect soil temperature to a depth of one meter. Data show that diurnal and shallow variation ceases at around 50 cm depth. Therefore the need to incorporate deeper depths into the current protocols for heat flux calculations is warranted. The manual methodology was also found to give representative data.     

黄河源区水资源变化及其影响因子

Taking the source region of the Yellow River as a study area and based on the data from Madoi Meteorological Station and Huangheyan Hydrological Station covering the period 1955-2005, this paper analyses the changing trends of surface water resources, climate and frozen ground and reveals their causes. Results show that there exist frequent fluctuations from high to low water flow in the 51-year period. In general, the discharge has shown a de- clining trend in the 51 years especially since the 1990s. The annual distribution shows one peak which, year on year is getting smaller. （1） Precipitation has a significant and sustained influence on discharge. （2） A sharp rise of temperature resulted in the increase of evaporation and the decrease of discharge, which has a greater effect than on ice-snow melting. （3） Frozen ground tends to be degraded markedly. There is a significant positive correlation be- tween the permafrost thickness and the discharge. （4） Evaporation rates are significantly increasing, leading to the decrease of discharge. 70% of the discharge reduction resulted from climate change, and the remaining 30% may have been caused by human activities.     

Vertical distribution of Artemisia halodendron root system in relation to soil properties in Horqin Sandy Land, NE China

Root distribution plays an important role in both vegetation establishment and restoration of degraded land through influencing soil property and vegetation growth. Root distribution at 0~60 cm depth of A. halodendron was investigated in Horqin Sandy Land. Soil organic carbon (SOC) and nitrogen (SN) concentration as well as carbon and nitrogen in root biomass and necromass were measured. Root length density (RLD) was estimated. Total root biomass, necromass and the RLD at 0~60 cm depth was 172 g/m², 245 g/m², and 368 m/m², respectively. Both biomass and necromass of A. halodendron roots decreased with soil depth, live roots were mainly at 0~20 cm (76% of biomass and 63% of root length), while 73% of the necromass was within 0~30 cm depth. N concentration of roots (biomass and necromass) was about 1.0% and 1.5%, respectively. There were significant differences in SOC concentration between soil layers, but insignificant for SN. Soil C/N ratio decreased with depth (P<0.05). C and N storage for belowground system at 0~60 cm decreased markedly with depth; 41.4% of C and 31.7% of N were allocated to the 0~10 cm layer. Root bio- and necromass together contained similar amount of C to that of the soil itself in the top layer. N stock was dominated by soil nitrogen at all depths, but more so in deeper layers. It is clear that differentiating between soil layers will aid in interpreting A. halodendron efficiency in soil restoration in sandy land.