Constraining Holocene 10Be production rates in Greenland     

Jason P. Briner  Nicolás E. Young  Brent M. Goehring  Joerg M. Schaefer 《第四纪科学杂志》2012,27(1):2-6

The absence of a production rate calibration experiment on Greenland has limited the ability to link ¹⁰Be exposure dating chronologies of ice‐margin change to independent records of rapid climate change. We use radiocarbon age control on Holocene glacial features near Jakobshavn Isbræ, western Greenland, to investigate ¹⁰Be production rates. The radiocarbon chronology is inconsistent with the ¹⁰Be age calculations based on the current globally averaged ¹⁰Be production rate calibration data set, but is consistent with the ¹⁰Be production rate calibration data set from north‐eastern North America, which includes a calibration site nearby on north‐eastern Baffin Island. Based on the best‐dated feature available from the Jakobshavn Isbræ forefield, we derive a ¹⁰Be production rate value of 3.98 ± 0.24 atoms g a^?1, using the ‘St’ scaling scheme, which overlaps with recently published reference ¹⁰Be production rates. We suggest that these ¹⁰Be production rate data, or the very similar data from north‐eastern North America, are used on Greenland. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

南极洲乔治王岛柯林斯冰帽小冰穹顶冰芯数学模式初步断代          下载免费PDF全文

张万昌  韩建康 《极地研究》1994,6(3):28-35

冰芯钻取后，样品截取原则和环境记录的初步解释要求对年代－深度剖面有一初步了解，即要求建立冰体随深度变化的时间尺度。根据柯林斯冰帽一年多野外实测资料所揭示的小冰穹运动状况、温度分布、物质平衡和动力学特征，本文采用Ｄａｎｓｇａｒｒｄ－Ｊｏｈｎｓｅｎ模型和等温冰体流动模型（ｎ＝３），分别对一支８０．２ｍ冰芯的时间尺度进行初步估算。结果表明两种模型断代结果非常接近，在距冰床１０ｍ深度处，两模型分别给出１８９７年和１８５４年的冰龄。对比指出两种模型计算出的冰帽各深度冰龄最大误差不大于２％。与冰芯中上部含深褐色火山灰冰层的历史记录年代相比误差小于３％。  相似文献   

固碳作用与地质时代的大冰期     

王自明 《冰川冻土》1991,13(1):61-66

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七月大气环流对南极海冰异常的响应   总被引：2，自引：0，他引：2  

王召民  黄土松 《气象科学》1994,14(4):311-321

本文用一个全球大气九层谱模式，模拟了七月份南极两个不同海区海冰区异常对大气环流的影响。主要讨论了大气环流对南极海冰异常存在的局地性的及全球性的响应。细致分析了二个区域极冰异常导致的南北半球低频波列分布的差异，以及它们对热带区域及亚洲季风区降水、越赤道气流的不同影响。最后则依据我们的模拟结果，讨论了南极海冰异常影响全球大气环流的动力学机制。  相似文献   

Structures caused by repeated freezing and thawing in various loamy sediments: A comparison of active,fossil and experimental data     

Brigitte Van Vliet-Lanoë  Jean-Pierre Coutard  Albert Pissart 《地球表面变化过程与地形》1984,9(6):553-565

In this paper, the authors present the results of both macroscopic and microscopic investigations on structure development created by repeated ice lensing in various loamy experiments. Experimental data are compared with observations performed on active forms in High Arctic and Alpine Mountain environments. Those observations are also compared with phenomena observed in fossil periglacial formations of Western Europe. Platy and short prismatic structure formation is bonded to the hydraulic and thermal conditions during ice segregation. When a long series of alternating freezing and thawing affects platy structures, the fabric evolves, also being influenced by slope and drainage conditions: cryoturbations, frostcreep, and gelifluction can appear. They are characterized by specific microfabrics which are better developed with an increasing number of cycles: this is clear in experiments where hydraulic and thermal parameters are better controlled. Vesicles are also a prominent characteristic of the surface horizon in experiments and arctic soils. The genesis of vesicles is discussed on the basis of new observations and is related to the mechanical collapse of frost-created aggregates under the mechanical work of soil air escape during soil saturation by water at thaw.  相似文献   

14C dating and palaeoenvironment of the historic ‘little ice age’ glacier advance of Nigardsbreen Southwest Norway     

John A. Matthews  John L. Innes  Christopher J. Caseldine 《地球表面变化过程与地形》1986,11(4):369-375

Moss and grass remains associated with a well-developed in situ palaeosol buried beneath a moraine ridge in front of Nigardsbreen (Jostedalsbreen ice cap, southern Norway) have been ¹⁴C-dated. Pollen preserved with the plant remains suggests the existence of an agricultural landscape prior to the deposition of the moraine. The calibrated dates and the pollen spectra are in close accord with historically-documented evidence for the timing and palaeoenvironment of the ‘Little Ice Age’ advance of the glacier. Considerable potential is indicated for estimating the maximum ages of moraine ridges and for palaeoenvironmental reconstruction where such documentary evidence does not exist.  相似文献   

大气气溶胶中NO￣－＿3、SO￣（2－）＿4研究     

李忠勤  姚檀栋  谢自楚 《地球科学进展》1995,(3)

根据对国内外有关文献资料的总结归纳，对气溶胶中　、　的研究现状及其在不同类型样品中的浓度量值分别进行了阐述；对雪冰层中的　和　进行了本底划分，并对这些本底的来源、组成及特征进行了分析。  相似文献   

北极海冰面积变化与大气遥相关型   总被引：4，自引：0，他引：4  

蒋全荣  王春红 《气象科学》1995,15(4):158-165

本文综述了北极海注面积变化与大气遥相关型研究工作中的一些主要结果。诊断分析表明，北极海冰面积变化具有３－４年的振荡周期，大气中的遥相关型不仅与海冰面积变化的区域有关，还与海冰面积的振荡频率有关。海冰面积变化与大气遥相关型是互相维持的，一方的加强有利于另一方的加强，本文最后还对北极海冰和赤道中，东太平洋海温对北半年冬半年中纬度大气环流影响的相似性等问题进行了讨论。  相似文献   

Oceanographic Change and Terrestrial Human Impacts in a Post A.D. 1400 Sediment Record from the Southwest Iceland Shelf     

A.E. Jennings  S. Hagen  J. Harðardóttir  R. Stein  A.E.J. Ogilvie  I. Jónsdóttir 《Climatic change》2001,48(1):83-100

Environmental proxies of soil erosion on Iceland, and oceanographic conditions on the adjacent shelf, were measured on a 50 cm box core taken from the southwest Iceland shelf in 1993 during cruise 93030 of the Canadian ship, CSS Hudson. These data, covering the last several centuries, are compared with the documentary record of sea-ice changes around Iceland since A.D. 1600. The site is under the influence of the Irminger Current, which carries warm, saline, Atlantic water northward along the shelf. Because of the relative warmth of this current, sea ice rarely occurs off southwest Iceland, even during the most severe sea-ice intervals of the historical record. In severe sea-ice years, however, the ice drifts clockwise around Iceland from the northeast and east and, in rare cases, reaches the southern coasts (Ogilvie, 1992). The chronology of the core was established by converting the basal radiocarbon date to calendar years and assuming a linear sedimentation rate from the base of the core to the year of collection, 1993. Organic carbon, stable C and O isotope ratios, planktonic foraminiferal assemblages, and sediment magnetic parameters were measured on samples from the core, plotted against calendar years and compared to the Icelandic sea-ice index. The environmental proxies suggest that increased soil erosion, reduced salinity, and, possibly, decreased marine productivity prevailed during the severe sea-ice interval lasting from the last quarter of the eighteenth century to around 1920. Such a situation could develop with climatic cooling, increased storminess, and loss of vegetation cover to stabilise the soil. Although the core site generally lies outside the sea-ice limits, the evidence clearly shows the influence of sea ice and fresh water, and is sensitive to the overall climatic deterioration manifested by the sea-ice record.  相似文献   

The Initiation of the "Little Ice Age" in Regions Round the North Atlantic   总被引：3，自引：0，他引：3  

J.M. Grove 《Climatic change》2001,48(1):53-82

The "Little Ice Age" was the most recent period during which glaciers extended globally, their fronts oscillating about advanced positions. It is frequently taken as having started in the sixteenth or seventeenth century and ending somewhere between 1850 and 1890, but Porter (1981) pointed out that the "Little Ice Age" may 'have begun at least three centuries earlier in the North Atlantic region than is generally inferred'. The glacial fluctuations of the last millennium have been traced in the greatest detail in the Swiss Alps, where the "Little Ice Age" is now seen as starting with advances in the thirteenth century, and reaching an initial culmination in the fourteenth century. In the discussion here, evidence from Canada, Greenland, Iceland, Spitsbergen and Scandinavia is compared with that from Switzerland. Such comparisons have been facilitated by improved methods of calibrating radiocarbon dates to calendar dates and by increasing availability of evidence revealed during the current retreat phase. It is concluded that the "Little Ice Age" was initiated before the early fourteenth century in regions surrounding the North Atlantic.  相似文献