冰水系统中的砖在融化过程中水分迁移实验研究     

李述训  程国栋 《冰川冻土》1991,13(4):323-329

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Some aspects on the variations in depositional flux of excess Thorium-230 in the Central Indian basin during Late Quaternary     

N. P. Sukumaran 《Journal of Earth System Science》1994,103(4):489-497

Examined in this paper is the tentative history of the depositional flux of²³⁰Th_xs (the unsupported fraction of²³⁰Th scavenged from the overlying water column), for the Late Quaternary period from a sediment core of the Central Indian Basin (CIB). The measured depositional flux of²³⁰Th_xs is found substantially higher than that of the possible theoretical flux from the overlying water column. Historical records, reconstructed from the²³⁰Th_xs chronology suggests that the depositional flux has varied considerably with time, reflecting an enhanced scavenging during the Holocene and the preceding interglacial periods whereas, comparatively lower flux than the predicted one occurred during the Last Glacial Maximum (LGM) period. The average ratio of the measured depositional flux to that of the predicted flux from the overlying water column, indicates that the core site acts as a sink for²³⁰Th_xs and based on the existence of bottom current activity; the²³⁰Th_xs could be the result of focusing of younger sediments. The depositional index (Di) has also been calculated to quantify the extent of lateral supply throughout the core with time. The estimated (Di) suggests that bottom focusing and feeble deposition and/or winnowing processes had occurred and that the former was most prevalent during the Holocene and the preceding interglacials, whereas the latter was observed at the LGM period.  相似文献   

On the stable growth of segregated ice in freezing soil under negligible overburden pressure     

Yoshisuke Nakano 《Advances in water resources》1986,9(4)

The stable growth condition of a segregated ice layer is studied by the use of the principle of mass and heat conservation. This condition evidently depends upon the properties of a thin transitional zone, which is believed to exist between the boundary of an ice layer and a 0[°C] isotherm. All probable models of the transitional zone are classified and the conditions for each model is derived. The effect of the small amount of soil minerals contained in an ice layer is also studied.  相似文献   

近百年长江中游旱涝的变化   总被引：1，自引：0，他引：1  

叶愈源  赵文兰 《热带气象学报》1995,11(2):181-186

利用史料和器测雨量记录重建的近百年长江中游区域平均逐年旱涝等级指数序列研究了旱涝变化特征，发现：（１）２０世纪前涝后旱，（２）２２年、５－６年和２－３年的准周期振动，（３）６个交替出现的旱涝阶段。  相似文献   

末次冰期东亚季风快速波动的模式与成因     

管清玉  潘保田  邬光剑  高红山  李琼  苏怀 《沉积学报》2007,25(3):429-436

通过对位于东亚季风区中东部与西部边缘的两个高分辨率黄土剖面记录的对比研究，发现它们不仅捕捉到了20个Dansgaard Oeschger事件与6个Heinrich事件，而且黄土记录与GRIP冰芯记录的这些快速气候波动基本上是同步的。暗示在整个末次冰期，东亚季风气候同样存在千年—百年尺度上的快速波动。所不同的是，西面的沙沟剖面对这些快速气候波动的反应比东面的王官剖面敏感。结合末次冰期中国黄土记录的先前研究结果，我们发现，自西向东Dansgaard Oeschger旋回的幅度逐渐变小，推测这主要是由西风与东亚夏季风共同作用所造成的。  相似文献   

Morphology and geological setting of Iseo Lake (Lombardy) through multibeam bathymetry and high-resolution seismic profiles     

Alfredo Bini  Daniele Corbari  Paolo Falletti  Mauro Fassina  Cesare R. Perotti  Andrea Piccin 《Swiss Journal of Geoscience》2007,100(1):23-40

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对青藏高原末次冰盛期降温值、平衡线下降值与模拟结果的讨论   总被引：5，自引：2，他引：5       下载免费PDF全文

施雅风 《第四纪研究》2002,22(4):312-322

1999年 5期《第四纪研究》刊登的“青藏高原冰期环境与冰期全球降温”论文 ,内容丰富 ,提出了许多重大问题和新鲜讯息 ,发人深思。本文就部分内容进行讨论 ,认为根据新近若干冰期降温值较大的信息 ,就得出冰期降温幅度为过去认识的两倍的普遍性推断 ,还为时过早。青藏高原新近研究表明夏季降温值是较小的 ;冰川平衡线高度取决于以夏季温度为标志所提供的消融热量与全年降雪积累量的平衡 ,单纯就降温值 ,不能决定平衡线下降值 ;全球各地气候、地形差别很大 ,冰期变化也很悬殊 ,不存在全球均一的 1 0 0 0m左右平衡线下降值 ,干旱区的下降值多低于此数。青藏高原末次冰盛期 (LGM)冰川堆积 (终碛、侧碛 )和侵蚀形态(冰斗、槽谷 )一般保存良好、形态鲜明 ,较易识别 ,近年已获取测年资料 ,证明过去地貌法判别的LGM冰川规模 ,并以此决定的LGM平衡线位置基本恰当 ,当然也有误判者。从 2 0世纪 2 0年代起 ,研究者逐渐认识高原内部主要是中西部LGM平衡线下降值较小 ,经过多次改进的LGM平衡线高度分布图显示约有 1 /3左右地区 ,平衡线下降值不足 30 0m ,实为世所罕见。其原因可能主要在高原西北部是全球惟一高海拔寒旱核心区域 ,为极大陆型或极地型冰川分布区 ,以现代西昆仑山崇测冰川、古里雅冰帽为例 ,平衡线高度  相似文献   

“Greatest lake period” and its palaeo-environment on the Tibetan Plateau     

Li Bing-yuan  Zhu Li-ping 《地理学报(英文版)》2001,11(1):34-42

The “greatest lake period” means that the lakes are in the stage of their maximum areas. As the paleo lake shorelines are widely distributed in the lake basins on the Tibetan Plateau, the lake areas during the “greatest lake period” may be inferred by the last highest lake shorelines. They are several, even tens times larger than that at present. According to the analyses of tens of lakes on the Plateau, most dating data fell into the range of 40-25 ka BP, some lasted to 20 ka BP. It was corresponded to the stage 3 of marine isotope and interstitial of last glaciation. The occurrence of maximum areas of lakes marked the very humid period on the Plateau and was also related to the stronger summer monsoon during that period.  相似文献   

黑北公路冻土路基设计原则及病害特征   总被引：4，自引：1，他引：4  

孟凡松  刘永智等 《冰川冻土》2001,23(3):307-311

依据位于小兴安岭地区的黑北公路沿线退化多年冻土特征，以及地质、水文、气候等工程环境条件，分析了黑北公路路基可能会发生的病害和发展过程，提出了适合于黑经公路的路基设计与病害防治措施，以便比选与优化退化型多年冻土地区的路基稳定性设计原则及结构形式，同时在路基设计形式和病害处理上提出了一些初步设想和建议。  相似文献   

An abrupt cooling event early in the last interglacial in the northern South China Sea     

TU Xia  ZHENG Fan  Wang Jiliang  CAI Huimei  WANG Pinxian  C.Bühring  M.Sarnthein 《中国科学D辑(英文版)》2001,44(10):865-870

The high-resolution quantitative analysis of the planktonic foraminifera and the δ¹⁸O records of the section between 96.49– 137.6 mcd at ODP Site 1144 on the continental slope of northern South China Sea reveals an abrupt cooling event of sea surface temperature (SST) during the last interglacial (MIS 5.5, i.e. 5e). The dropping range of the winter SST may come to 7.5°C corresponding to 1.2‰ of the δ¹⁸O value of sea surface water. This event is comparable with those discovered in the west Europe and the northern Atlantic Ocean, but expressed in a more intensive way. It is inferred that this event may have been induced by middle- to low-latitude processes rather than by polar ice sheet change. Since the Kuroshio-index speciesPulleniatina obliquiloculata displayed the most distinct change at the event, it may also be related to the paleoceanographic change of the low-latitude area in the western Pacific Ocean. This event can be considered as one of “Younger Dryas-style coolings” and is indicative of climate variability of the last interglacial stage.  相似文献