Rheological properties of the upper mantle of Northern Eurasia and nature of regional boundaries according to the data of long-range seismic profiles

Deep seismic investigation carried out in Russia in long-range profiles with peaceful nuclear explosions allowed clarifying in details the structure of the upper mantle and the transition zone down to the depth of 700 km within the huge territory of old and young platforms of Northern Eurasia. Variability of horizontal heterogeneity of the upper mantle depending on the depth serves to qualitative estimation of its rheological properties. The upper part of the mantle to the depth of 80–100 km is characterized by the block structure with significant velocity steps of seismic waves at the blocks often divided by deep faults. This is the most rigid part of lithosphere. Below 100 km horizontal heterogeneity is insignificant, i.e., at these depths the substance is more plastic and not capable to retain block structure. On the lithosphere bottom at the depth of 200–250 km plasticity increase is observed as well but the zone of the lower velocities that might have been bound with the area of partial melting (asthenosphere) has not been found. These three layers with different rheological properties are divided by seismic boundaries presented by thin layering zones with alternating higher and lower velocities. At the specified depths any phase boundaries have been distinguished. These thin layering zones are assumed to form due to higher concentration of deep fluids at some levels of depths where mechanical properties and permeability of substance change. Insignificant number of fluids may result in appearance of streaks with partial or film melting at relatively low temperature—to the rise of the weakened zones where subhorizontal shifts are possible. According to seismic data in many world regions seismic boundaries are also observed at the depth of about 100 and 200 km; they may be globally spread. There are signs that areas of xenoliths formation and earthquake concentration, i.e., zones of high deformations, are confined to these depths.     

Structural Evolution of the Eastern Margin of Eurasia in Late Mesozoic and Cenozoic

This paper features the structural evolution of the eastern margin of Eurasia in Late Mesozoic and Cenozoic.It is characterized by three stages of development: the riftogenic stage (Jurassic-Early Cretaceous), the platform stage (Late Cretaceous) and the neotectonic one (Paleogene-Quarternary). The boundaries between these stages are distinctly fixed by the geological time limits of planetary range. It is demonstrated that the riftogenic and neotectonic stages were characterized by a high degree of geodynamic activity, and the platform one by a decrease in contrast of tectonic movements. The main river net was formed in the Early Cretaceous and in the Neogene. It experienced a serious reconstruction accompanied by the formation of the Amur River valley being similar to the modem one.     

欧亚大陆夏季地表热力异常与同期中国东部夏季降水的可能联系

利用ERA-40再分析资料、CRU TS3.0数据集以及中国站点观测数据,分析了欧亚大陆夏季地表热力异常的变化特征,在此基础上探讨了我国东部夏季降水与同期欧亚大陆地表热力异常之间的可能联系。研究发现,欧亚大陆地表气温与浅层土壤温度的大尺度变化特征基本一致:经验正交函数分解第一模态空间型表现为大陆西南部分区域与欧亚大陆其他区域反相变化,对应的时间系数均在20世纪80年代末出现转折。当夏季欧亚中纬度印度以北地区和我国中东部地区地表气温偏高时,东亚夏季风的强度偏强,西太平洋副热带高压位置偏东,我国东部偏南风偏强,江淮流域水汽偏少,且气流上升运动偏弱,降水偏少;华南和北方地区水汽偏多,且气流上升运动偏强,降水偏多;反之亦然。当欧亚大陆中高纬贝加尔湖以东及以西地区夏季地表气温偏高,而我国东北部地区夏季地表气温偏低时,东亚夏季风的强度偏强,西太平洋副热带高压位置偏西,我国东南部地区偏南风异常偏强,有利于水汽向江淮流域输送,东南沿海及内蒙古中部水汽偏少,且气流上升运动偏弱,降水偏少;而东部其余地区水汽偏多,且气流上升运动偏强,降水偏多;反之亦然。     

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Snow water equivalent over Eurasia in the next 50 years projected by aggregated CMIP3 models

Based on remote sensing snow water equivalent (SWE) data, the simulated SWE in 20C3M experiments from 14 models attending the third phase of the Coupled Models for Inter-comparison Project (CMIP3) was first evaluated by computing the different percentage, spatial correlation coefficient, and standard deviation of biases during 1979–2000. Then, the diagnosed ten models that performed better simulation in Eurasian SWE were aggregated by arithmetic mean to project the changes of Eurasian SWE in 2002–2060. Results show that SWE will decrease significantly for Eurasia as a whole in the next 50 years. Spatially, significant decreasing trends dominate Eurasia except for significant increase in the northeastern part. Seasonally, decreasing proportion will be greatest in summer indicating that snow cover in warmer seasons is more sensitive to climate warming. However, absolute decreasing trends are not the greatest in winter, but in spring. This is caused by the greater magnitude of negative trends, but smaller positive trends in spring than in winter. The changing characteristics of increasing in eastern Eurasia and decreasing in western Eurasia and over the Qinghai-Tibetan Plateau favor the viewpoint that there will be more rainfall in North China and less in the middle and lower reaches of the Yangtze River in summer. Additionally, the decreasing rate and extent with significant decreasing trends under SRES A2 are greater than those under SRES B1, indicating that the emission of greenhouse gases (GHG) will speed up the decreasing rate of snow cover both temporally and spatially. It is crucial to control the discharge of GHG emissions for mitigating the disappearance of snow cover over Eurasia.     

欧亚大陆湖泊记录和两万年来大气环流变化

159个湖泊地质记录提供了欧亚大陆两万年来大气环流变化信息。盛冰期北欧低湖面而地中海地区高湖面,反映冰流反气旋控制和西风带南迁。随着晚冰期冰流高压减弱、西风带回迁,南欧为低湖面而北欧低湖面范围减小。全新世早中期北欧阻塞高压发展,干燥炎热;南欧地区性季风环流加强,气旋雨增加。中国青藏高原至东西伯利亚高湖面,反映东亚季风扩张、季风雨以及高原对流雨增加。晚更新世以来湖泊所反映的西风带和季风环流变化,揭示了辐射异常和北半球冰流消长的动力控制。     

Intraplate mountain building in response to continent–continent collision—the Ancestral Rocky Mountains (North America) and inferences drawn from the Tien Shan (Central Asia)

The intraplate Ancestral Rocky Mountains of western North America extend from British Columbia, Canada, to Chihuahua, Mexico, and formed during Early Carboniferous through Early Permian time in response to continent–continent collision of Laurentia with Gondwana—the conjoined masses of Africa and South America, including Yucatán and Florida. Uplifts and flanking basins also formed within the Laurentian Midcontinent. On the Gondwanan continent, well inboard from the marginal fold belts, a counterpart structural array developed during the same period. Intraplate deformation began when full collisional plate coupling had been achieved along the continental margin; the intervening ocean had been closed and subduction had ceased—that is, the distinction between upper versus lower plates became moot. Ancestral Rockies deformation was not accompanied by volcanism. Basement shear zones that formed during Mesoproterozoic rifting of Laurentia were reactivated and exerted significant control on the locations, orientations, and modes of displacement on late Paleozoic faults.Ancestral Rocky Mountain uplifts extend as far south as Chihuahua and west Texas (28° to 33°N, 102° to 109°W) and include the Florida-Moyotes, Placer de Guadalupe–Carrizalillo, Ojinaga–Tascotal and Hueco Mountain blocks, as well as the Diablo and Central Basin Platforms. All are cored with Laurentian Proterozoic crystalline basement rocks and host correlative Paleozoic stratigraphic successions. Pre-late Paleozoic deformational, thermal, and metamorphic histories are similar as well. Southern Ancestral Rocky Mountain structures terminate along a line that trends approximately N 40°E (present coordinates), a common orientation for Mesoproterozoic extensional structures throughout southern to central North America.Continuing Tien Shan intraplate deformation (Central Asia) has created an analogous array of uplifts and basins in response to the collision of India with Eurasia, beginning in late Miocene time when full coupling of the colliding plates had occurred. As in the Laurentia–Gondwana case, structures of similar magnitude and spacing to those in Eurasia have developed in the Indian plate. Within the present orogen two ancient suture zones have been reactivated—the early Paleozoic Terskey zone and the late Paleozoic Turkestan suture between the Siberian and East Gondwanan cratons. Inverted Proterozoic to early Paleozoic rift structures and passive-margin deposits are exposed north of the Terskey zone. In the Alay and Tarim complexes, Vendian to mid-Carboniferous passive-margin strata and the subjacent Proterozoic crystalline basement have been uplifted. Data on Tien Shan uplifts, basins, structural arrays, and deformation rates guide paleotectonic interpretations of ancient intraplate mountain belts. Similarly, exhumed deep crustal shear zones in the Ancestral Rockies offer insight into partitioning and reorientation of strain during contemporary intraplate deformation.     

Hemispheric-scale climate response to Northern Eurasia land surface characteristics and snow anomalies

This paper presents a synopsis of recently published studies by the co-authors, which show that several land surface characteristics unique to Northern Eurasia are responsible for facilitating a causal relationship between autumn snow anomalies in this region and subsequent hemispheric winter climate patterns. The large size and extratropical location of the contiguous Eurasian land mass results in broad, continental-scale interannual snow cover extent and depth variations throughout autumn and winter, and corresponding diabatic heating anomalies. These surface anomalies occur in the presence of a large region of stationary wave activity, produced in part by the orographic barriers that separate northern/central Eurasia from southern/eastern Eurasia. This co-location of snow-forced anomalies and ambient wave energy is unique to Northern Eurasia, and initiates a teleconnection pathway involving stationary wave–mean flow interaction throughout the troposphere and stratosphere, ultimately resulting in a modulation of the winter Arctic Oscillation (AO). Complementary new results are also presented which show that partial snow cover extent or snow depth only anomalies in Northern Eurasia are insufficient to initiate the teleconnection pathway and produce a winter AO signal. This synopsis provides a useful interpretation of the earlier studies in the specific context of Northern Eurasia regional climate and environmental change.     

ANALYSIS OF LAND BRIDGE TRANSPORTATION

Land bridge transportation means transportation from one seaport to another by railway across continents instead of by ocean ship. At present, there are two common routes for using land bridge transportation in the world. One is Asia-America-Europe land bridge, the other is Europe-Asia land bridge.Eurasia land bridge has obvious advantages over Asia-America-Europe land bridge due to its shorter distance, shorter transportation time and special freight rate. China started Eurasia land bridge transportation business in 1980. It mainly used the mode of railway-railway combined transportation. The comparison between using Eurasia land bridge and using shipping transportation from China to Northern and Western Europe shows that Euraria land bridge transportation can save time and get foreign exchange in time, and commodity turnover will be speeded up. According to the port layout and railway network structure, China's land bridge transportation projects are proposed. They are Suifenhe project, Dalian project