Testing solar forcing of pervasive Holocene climate cycles     

Chris Turney  Mike Baillie  Steve Clemens  David Brown  Jonathan Palmer  Jonathan Pilcher  Paula Reimer  Hanns Hubert Leuschner 《第四纪科学杂志》2005,20(6):511-518

The temporal and spatial extent of Holocene climate change is an area of considerable uncertainty, with solar forcing recently proposed to be the origin of cycles identified in the North Atlantic region. To address these issues we have developed an annually resolved record of changes in Irish bog tree populations over the last 7468 years which, together with radiocarbon‐dated bog and lake‐edge populations, extend the dataset back to ～9000 yr ago. The Irish trees underpin the internationally accepted radiocarbon calibration curve, used to derive a proxy of solar activity, and allow us to test solar forcing of Holocene climate change. Tree populations and age structures provide unambiguous evidence of major shifts in Holocene surface moisture, with a dominant cyclicity of 800 yr, similar to marine cycles in the North Atlantic, indicating significant changes in the latitude and intensity of zonal atmospheric circulation across the region. The cycles, however, are not coherent with changes in solar activity (both being on the same absolute timescale), indicating that Holocene North Atlantic climate variability at the millennial and centennial scale is not driven by a linear response to changes in solar activity. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Organic carbon and microbial biomass in a raised beach deposit under terrestrial vegetation in the High Arctic, Ny-Ålesund, Svalbard     

Takayuki Nakatsubo  Shinpei Yoshitake  Masaki Uchida  Masao Uchida  Yasuyuki Shibata  & Hiroshi Koizumi 《Polar research》2008,27(1):23-27

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论煤层的加积方式     

赵万福 《中国煤炭地质》2012,(8):5-11,22

煤层成因是煤地质学的核心。煤层是一种沉积地层,它遵循沉积学、地层学、岩石学以及矿床学的基本规律,也有其特殊性,其成因并不同于煤的成因。传统煤地质学的核心观点是煤层由泥炭沼泽演化而成,其本质就是成煤物质的垂向加积。通过对煤层垂向和侧向加积的分析对比以及大面积稳定展布的厚煤层低自然伽马多峰现象、层理与条带结构等沉积特征的研究,认为成煤物质是机械沉积的,煤层像大多数沉积岩层一样是侧向加积形成的。对于厚煤层而言,多期侧向加积产生了次生垂向加积,其形成过程不是一个简单的、连续的、线性的垂向累加过程,而是一个复杂的、不连续的、非线性的侧向叠合过程,成煤物质是不连续的、多期多源的,厚煤层中普遍存在的夹矸便是其不连续的证据,同时厚煤层是穿时的。煤层侧向加积与较深水或海相沉积共生,是一个有机连续的整体,符合瓦尔特相律和古生态学原理,符合煤层厚度、形态多变及下伏地层沉积体系多种多样,也符合成煤物质超巨量工业富集、含煤地层灰色灰黑色、煤矿床质量优良的事实。  相似文献   

大气环境变化的泥炭地质档案   总被引：2，自引：0，他引：2       下载免费PDF全文

鲍锟山  赵红梅  于晓菲  吕宪国  王国平 《地质论评》2011,57(2):234-242

雨养泥炭沼泽是一种重要的泥炭沼泽类型,具有全球广泛分布的特点,其养分补给主要源于大气降水(包括雨、雪和空气尘埃).它是一个记录大气环境变化的积极的信息储备系统,记录有大气输入的海盐气溶胶、沙尘颗粒、酸沉降、重金属和有机污染物等信息.采用地质定年技术将泥炭深度剖面转化到年代坐标上,并结合泥炭生物地球化学指标检测分析,提取...  相似文献   

Initiation of a multiple peat slide on Cuilcagh Mountain,Northern Ireland     

A. P. Dykes  K. J. Kirk 《地球表面变化过程与地形》2001,26(4):395-408

In October 1998 a multiple peat slide occurred on the northern slopes of Cuilcagh Mountain, Co. Fermanagh, in response to a high‐magnitude rainfall event. Few peat slides have been recorded in Ireland, and a detailed field survey and investigation of the failure was undertaken within four weeks of the event. The morphological evidence indicated a distinct sequence of events which appeared to begin with the failure of a small segment of slope above a degraded transverse drainage ditch which was cut less than ten years previously. This segment of slope was no more than 42 m wide and 25 m long, with 0·7 m of peat overlying up to 0·5 m of a pale coloured clay, the latter containing small pipes and resting on the surface of a darker coloured loamy material. The failure surface was located at or near the base of the pale clay layer. Finite element software was used to model hydrological conditions within the upper segment of slope and to calculate factors of safety for different slope configurations including the presence or absence of a drain or a subsurface pipe. Using the peak shear strength of the pale clay, as determined in the laboratory, both the drain and subsurface pipes were required to obtain a factor of safety of 1·0 or less. Allowing for the uncertainties associated with the hydrological modelling of the pipes, it is suggested that the cutting of the drain and the hydrological impacts of its subsequent degradation are ultimately responsible for the failure. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

长白山区泥炭沼泽磁化率特征及其环境意义   总被引：1，自引：0，他引：1  

鲍锟山  贾琳  王国平 《湿地科学》2009,7(4):321-326

以长白山区泥炭沼泽为研究对象,沿不同海拔选择赤池、锦北、大牛沟、金川和哈尔巴岭5个代表性采样点。通过对沼泽垂直剖面的精细采样,利用210Pb和137Cs方法对5个剖面进行高精度定年,综合研究和分析泥炭沉积物质量磁化率沿深度垂直分布特征,进而揭示其环境意义。结果表明,长白山区泥炭沼泽磁化率在表层具有明显的富集规律,富集时间始于20世纪初,并在20世纪后期达到峰值,且其富集含量可达以下层位富集平均值的5～10倍;长白山区泥炭磁化率的表聚性特征反映了在盛行西风等自然因素作用下,大气降尘和城市扩张等多种人类活动对区域环境的影响,很好地指示了区域磁性颗粒物污染扩大和加剧趋势。  相似文献   

Climatic and topographic limits to the abundance of bog pools     

Lisa R. Belyea 《水文研究》2007,21(5):675-687

On patterned peatlands, open water pools develop within a matrix of terrestrial vegetation (‘ridges’). Regional patterns in the distribution of ridge–pool complexes suggest that the relative cover of these two surface types is controlled in part by climate wetness, but landscape topography must also be an important controlling factor. In this paper, a functional model that relates relative cover of ridges and pools to climate and surface gradient was developed and tested. The model was formulated in terms of a water budget, based on the differential effects of ridges and pools on losses by evapotranspiration and subsurface flow. It predicts a positive relationship between surface gradient and ridge proportion, with a linear effect related to water supply and ridge hydraulic conductivity, modified at high ridge proportion by differences in evapotranspiration between ridges and pools. The limit to patterned peatland distribution occurs where the surface is completely covered by ridges. The model may be sensitive or insensitive to climate differences between localities, depending on whether hydraulic characteristics of ridge peat co‐vary with water supply. To distinguish between these alternative hypotheses, surface gradient and ridge proportion were surveyed along 20 transects in each of three localities in Scotland that differ threefold in net precipitation to pools. The results of the field survey served to reject the climate‐sensitive hypothesis, but were consistent with the climate‐insensitive hypothesis. Analysis of the residuals suggested that variation within localities was related more to topographic control of water supply than to ridge hydraulic conductivity or developmental stage. Hence, within this maritime climate region, the distribution of ridge–pool complexes and the relative abundance of pools are controlled mainly by topographic variables. Field surveys across both maritime and continental regions are required to confirm a subtle climatic effect that allows pools to occur on higher gradients in drier climates than in wetter climates. Further development and testing of the functional model will provide a stronger basis for assessing potential feedback between climate change, peatland surface structure and methane emission from pools. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Sources and biodegradability of dissolved organic matter in two headwater peatland catchments at the Marcell Experimental Forest,northern Minnesota,USA     

Stephen D. Sebestyen  Meghan Funke  James B. Cotner 《水文研究》2021,35(2):e14049

Where they are present in catchments, peatlands are a dominant source of dissolved organic matter (DOM) to surrounding waterways due, in part, to high production rates. Despite the preponderance of peatlands in northern latitudes and expected peatland vulnerability to climate change, little is known about peatland DOM degradation relative to a more comprehensive understanding of degradation when DOM is sourced from upland-dominated catchments. We compared DOM biodegradability of various sources of stream water in two catchments having peatlands (22%–33% of the area) surrounded by upland forests (70%–90% of the area, either deciduous or coniferous). We measured total organic carbon (TOC), and biodegradable dissolved organic carbon concentrations; bacterial respiration rates; streamflow; and upland runoff during and after snowmelt (March to June, 2009–2011). We also explored if DOM in upland runoff stimulated biodegradation of peatland-derived DOM (i.e., a priming effect), and if forest cover type affected DOM biodegradability. As expected, the peatlands were the largest sources of both water (72%–80%) and TOC (92%–96%) to the streams although more area in each catchment was in uplands (70%–90%). Several results were unexpected, yet revealing: (1) DOM from peatlands sometimes had the same biodegradability as DOM from uplands, (2) upland sources of DOM had negligible effects on biodegradability in the peatland and downstream, and (3) upland deciduous cover did not yield more degradable DOM than conifer cover. The most pronounced effect of upland runoff was dilution of downstream TOC concentrations when there was upland runoff. Overall, the effects of upland DOM may have been negligible due to the overriding effect of the large amount of biodegradable DOM that originated in bogs. This research highlights that peatland-sourced DOM has important effects on downstream DOM biodegradability even in catchments where upland area is substantially larger than peatland area.  相似文献   

国外大气沉降泥炭沼泽档案研究进展   总被引：3，自引：3，他引：3  

王国平  贾琳  刘景双  王金达 《湿地科学》2006,4(1):69-74

雨养泥炭沼泽养分补给主要源于大气降水。因为沼泽表面水的流动是缓慢并且有限的,所以沉降至其中的物质依然基本保留在原处。因此,大气颗粒物污染历史在泥炭累积时被保存。在最近20a期间,雨养泥炭沼泽被证明是痕量元素大气沉降富有意义的档案。尤其Pb被广泛深入地研究,并且Pb在泥炭芯中的非迁移性被很好地展示,其它元素也被指明保存在泥炭芯中。国外的泥炭沼泽沉积记录研究在某些方面非常深入细致,前期工作成为后续工作的铺垫,长年的积累形成一定的系统性。利用泥炭沼泽档案,人们对历史时期的环境研究取得了一定成果,尤其在大气金属沉降的泥炭沼泽档案与泥炭地古气候反演方面;但稍显不足的是比较重视对“记录”的研究,而对“机制”的研究深度不够。  相似文献   

中国福建省亚热带山地4000年来植被变化的孢粉记录(英文)     

邱宏烈 《福建地理》2006,(3)

根据采自福建省中部戴云山脉亚高山水系源头地带(大致25°40′N,118°11′E)泥炭沉积洼地的孢粉纪录,对该地区亚热带山地植被近4000年来的变化进行了研究.孢粉记录和其他沉积资料显示,3个取样点的泥炭沉积开始于4000年前,很可能是全新世后期气候转冷的结果.在距今4000~1200年前期间,戴云山脉上部(海拔1300~1600m)的植被为亚热带针阔叶混交类型,优势种属包括Cryptomeria(柳杉)、Castanopsis(栲)、Quercus(栎)和Tsuga(铁杉)等.距今1200年前左右,该区域的植被发生了一次大的变化,表现在上述优势属种的孢粉在样品总孢粉数的比例突然下降,而Pinus(松),Gramineae(禾本科)以及Dicranopteris(芒萁)等属种的比例则提高了.这次剧烈的植被变化在其中的一个泥炭钻孔中留下了一层粘土记录,它代表了当时流域内植被受破坏后出现的严重土壤侵蚀.从泥炭沉积提取的孢粉记录还可以看出,研究区内广泛分布的松林是一种次生植被,它是人类不断干扰的结果.  相似文献