Petrologic Characteristics of Gas Hydrate Reservoir in the Qilian Mountain Permafrost, China     

LIU Hui  LU Zhenquan  CHEN Yongjin 《《地质学报》英文版》2013,87(Z1):999-999

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Changes in the thermal and hydraulic regime within the active layer in the Qinghai-Tibet Plateau   总被引：1，自引：1，他引：0  

Changwei Xie  Lin Zhao  Tonghua Wu  Xicheng Dong 《山地科学学报》2012,9(4):483-491

The change trends of air temperature,precipitation and evaporation from 1999 to 2008 shows that the climate in the Qinghai-Tibet Plateau permafrost region had become warmer.The analysis of the systematic active-layer data monitoring network along the Qinghai-Tibet Highway indicated that the active-layer thickness had been increasing and the soil temperature was rising.The soil temperature was rising in winter but not at the end of spring or during the entire summer.With thickening and warming of the active layer,the liquid water content of the active layer had an obvious downward migration and liquid water content in the top horizons decreased,but in the deeper horizons it increased.  相似文献   

Development and decay of a lithalsa in Northern Québec: A geomorphological history     

Fabrice Calmels  Michel Allard  Georg Delisle 《Geomorphology》2008,97(3-4):287-299

The complete life cycle of a permafrost mound is reconstructed from its growth until its degradation. The study site is a lithalsa, which is the subject of a long-term monitoring that includes geocryological observations, measurements of permafrost properties on cores, ground temperature measurements, and observations of landform changes. The landform likely grew as a palsa under cold climatic conditions in the past. The peat cover was subsequently eroded. Early stages of degradation are witnessed since 2003 as a new thermokarst pond is starting to form though mound collapse. Settlement of the structure has been observed, and a rim ridge has begun to form. Ultimately, the lithalsa shall disappear and be replaced by a circular thermokarst pond surrounded by a rampart, similar to many other ones in the study area. The monitoring of the thermal regime of the lithalsa illustrates the pattern of internal warming and points to the causes of its degradation.  相似文献   

The distribution of silty soils in the Grayling Fingers region of Michigan: Evidence for loess deposition onto frozen ground     

Randall J. Schaetzl   《Geomorphology》2008,102(3-4):287-296

This paper presents textural, geochemical, mineralogical, soils, and geomorphic data on the sediments of the Grayling Fingers region of northern Lower Michigan. The Fingers are mainly comprised of glaciofluvial sediment, capped by sandy till. The focus of this research is a thin silty cap that overlies the till and outwash; data presented here suggest that it is local-source loess, derived from the Port Huron outwash plain and its down-river extension, the Mainstee River valley. The silt is geochemically and texturally unlike the glacial sediments that underlie it and is located only on the flattest parts of the Finger uplands and in the bottoms of upland, dry kettles. On sloping sites, the silty cap is absent. The silt was probably deposited on the Fingers during the Port Huron meltwater event; a loess deposit roughly 90 km down the Manistee River valley has a comparable origin. Data suggest that the loess was only able to persist on upland surfaces that were either closed depressions (currently, dry kettles) or flat because of erosion during and after loess deposition. Deep, low-order tributary gullies (almost ubiquitous on Finger sideslopes) could only have formed by runoff, and soil data from them confirm that the end of gully formation (and hence, the end of runoff) was contemporaneous with the stabilization of the outwash surfaces in the lowlands. Therefore, runoff from the Finger uplands during the loess depositional event is the likely reason for the absence of loess at sites in the Fingers. Because of the sandy nature and high permeability of the Fingers' sediments, runoff on this scale could only have occurred under frozen ground conditions. Frozen ground and windy conditions in the Fingers at the time of the Port Huron advance is likely because the area would have been surrounded by ice on roughly three sides. This research (1) shows that outwash plains and meltwater streams of only medium size can be significant loess sources and (2) is the first to present evidence for frozen ground conditions in this part of the upper Midwest.  相似文献   

The effect of climate warming and permafrost thaw on desertification in the Qinghai–Tibetan Plateau   总被引：1，自引：1，他引：0  

Xian Xue  Jian Guo  Bangshuai Han  Qingwei Sun  Lichao Liu 《Geomorphology》2009,108(3-4):182-190

Four sets of remote sensing images from 1987, 1994, 2000, and 2006, 50 years of meteorological and soil moisture data corresponding to different desertified lands were combined with populations and livestock data to analyze the process and cause of desertification in a portion of the Qinghai–Tibetan Plateau (QTP). It showed that surface soil temperature in the region has increased at an average rate of 0.6 °C per decade between 1980 and 2005, the thawing days on the surface have increased by 60 days from 1983 to 2001, and the depth of the seasonal thawing layer has increased by 54 cm, 102 cm and 77 cm in April, May and June, respectively, from 1983 to 2003. As a result, the upper soil layer has become drier due to the thickening active layer and soil water infiltration. These changes, in turn, have inhibited the growth of alpine meadow vegetation that has shallow root systems. It is concluded that climate warming and permafrost thawing have caused desertification in grazing regions of the Qinghai–Tibetan Plateau (QTP).  相似文献   

Development of tongue-shaped and multilobate rock glaciers in alpine environments – Interpretations from ground penetrating radar surveys     

John J. Degenhardt Jr.   《Geomorphology》2009,109(3-4):94-107

Rock glaciers occur as lobate or tongue-shaped landforms composed of mixtures of poorly sorted, angular to blocky rock debris and ice. These landforms serve as primary sinks for ice and water storage in mountainous areas and represent transitional forms in the debris transport system, accounting for ~ 60% of all mass transport in some alpine regions. Observations of active (flowing) alpine rock glaciers indicate a common association between the debris that originates from cirque headwalls and the depositional lobes that comprise them. The delivery of this debris to the rock glacier is regulated primarily by the rate of headwall erosion and the point of origin of debris along the headwall. These factors control the relative movement of individual depositional lobes as well as the overall rate of propagation of a rock glacier. In recent geophysical studies, a number of alpine rock glaciers on Prins Karls Forland and Nordenskiöldland, Svalbard, Norway, and the San Juan Mountains of southwest Colorado, USA, have been imaged using ground penetrating radar (GPR) to determine if a relationship exists between the internal structure and surface morphology. Results indicate that the overall morphologic expression of alpine rock glaciers is related to lobate deposition during catastrophic episodes of rockfall that originated from associated cirque headwalls. Longitudinal GPR profiles from alpine rock glaciers examined in this study suggests that the difference in gross morphology between the lobate and tongue-shaped rock glaciers can be attributed primarily (but not exclusively) to cirque geometry, frequency and locations of debris discharge within the cirque, and the trend and magnitude of valley gradient in relation to cirque orientation. Collectively, these factors determine the manner in which high magnitude debris discharges, which seem to be the primary mechanism of formation, accumulate to form these rock glaciers.  相似文献   

多年冻土区桥梁桩基础地震响应的模型振动试验研究   总被引：2，自引：0，他引：2       下载免费PDF全文

吴志坚  王平  霍元坤  陈拓 《地震工程学报》2009,31(4):319-326

以青藏铁路高温不稳定多年冻土区"以桥代路"工程——清水河特大桥的桩基础为研究目标,在负温条件下对该桥梁桩基础结构的缩尺模型进行了地震荷载作用的模型振动试验,研究了地震荷载作用下桩-冻土相互作用,分析了结构的地震响应特征,明确了桩体动荷响应对桩周冻土地温和应变的影响规律,最后对地震荷载作用下高温不稳定多年冻土区桥梁桩基础的稳定性作出了评价.  相似文献   

青海高原多年冻土对气候增暖的响应   总被引：15，自引：1，他引：14  

汪青春  李林  李栋梁  秦宁生  王振宇  朱西德  时兴合 《高原气象》2005,24(5):708-713

利用青海高原气象台站的年平均地温资料,建立了年平均地温与海拔和经纬度的关系模型,结合地理信息分析系统和DEM数据模拟出青海高原的冻土分布图,分析了青海高原多年冻土对气候变化的响应。结果表明：气候变暖已引起高原多年冻土面积的减少和冻土下界的升高,特别是在多年冻土边缘不衔接或岛状冻土区发生比较明显的退化。20世纪60年代与90年代相比,高原多年冻土下界分布高度上升约71m,季节性冻土厚度平均减小20cm。年最大冻土深度变化的空间分布特征与青海高原近40年来气温变化的空间特征相一致。  相似文献   

Thermal and settlement analyses under a riverbank over permafrost     

《Computers and Geotechnics》2017

Thermal regime evolution and settlement behavior of a riverbank over ice-rich permafrost in 20 years were estimated by numerical simulation and layerwise summation calculation. The results show that the permafrost under the riverbank will undergo a thawing process at a dramatically rate under the conditions of practical geology and construction structure, which is responsible for a remarkable settlement. The cases on different conditions of concrete hydration, backfilled soil temperature, seepage and mean annual ground temperature were also discussed, suggesting that these factors have the capability in improving the riverbank performance, among them seepage may be of the most importance.  相似文献   

Response of biomass spatial pattern of alpine vegetation to climate change in permafrost region of the Qinghai-Tibet Plateau,China     

Yu Zhang  Genxu Wang  Yibo Wang 《山地科学学报》2010,7(4):301-314

Alpine ecosystems in permafrost region are extremely sensitive to climate changes.To determine spatial pattern variations in alpine meadow and alpine steppe biomass dynamics in the permafrost region of the Qinghai-Tibet Plateau,China,calibrated with historical datasets of above-ground biomass production within the permafrost region's two main ecosystems,an ecosystem-biomass model was developed by employing empirical spatialdistribution models of the study region's precipitation,air temperature and soil temperature.This model was then successfully used to simulate the spatio-temporal variations in annual alpine ecosystem biomass production under climate change.For a 0.44°C decade-1 rise in air temperature,the model predicted that the biomasses of alpine meadow and alpine steppe remained roughly the same if annual precipitation increased by 8 mm per decade-1,but the biomasses were decreased by 2.7% and 2.4%,respectively if precipitation was constant.For a 2.2°C decade-1 rise in air temperature coupled with a 12 mm decade-1 rise in precipitation,the model predicted that the biomass of alpine meadow was unchanged or slightly increased,while that of alpine steppe was increased by 5.2%.However,in the absence of any rise in precipitation,the model predicted 6.8% and 4.6% declines in alpine meadow and alpine steppe biomasses,respectively.The response of alpine steppe biomass to the rising air temperatures and precipitation was significantly lesser and greater,respectively than that of alpine meadow biomass.A better understanding of the difference in alpine ecosystem biomass production under climate change is greatly significant with respect to the influence of climate change on the carbon and water cycles in the permafrost regions of the Qinghai-Tibet Plateau.  相似文献