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1.
北京地区近70年来白皮松树轮纤维素的碳稳定同位素与气候变化 总被引：5，自引：0，他引：5
对采自北京大学校园内的白皮松（Pinus bungeana)树轮α-纤维素的δ^13C进行了分析，结合北京气象台的气象记录，建立树轮δ^13C与气候各要素的回归方程，重建值与观测值吻合较好，表明北京地区树轮α-纤维素的碳稳定同位素与1928-1999年3-9月的平均气温及6-9月的平均降雨量显著相关，重δ^13C对应于3-9月的低温和6-9月的少雨，轻δ^13C对应于3-9月的高温和6-9月的多雨。而3-9月的温度正好是适宜树木生长的光合作用所需要的最佳温度，6-9月正好是一年中降雨最充沛的时期，由此认为；树轮δ^13C值与生长季节的降水和气温密切相关，可以考虑作为季风盛行地区的气候替代性指标。在一定程度上反映了季风盛行区白皮松树轮纤维素碳稳定同位素与气候因子的关系。 相似文献
2.
从树轮δ13C序列中提取大气δ13C信息的可行性研究 总被引：3，自引：0，他引：3
工业革命以来化石燃料的大量使用和森林的过度砍伐，引起大气CO2浓度大幅度增加，但同时由于“Suess”效应，大气δ^13C值却在不断下降，研究大气δ^13C值的变化历史，不仅有助于预测其今后的趋向，而且可以用来了解碳循环的自然变率和校正全球碳预算模型。由于直接的仪器测量从1978年才开始，因此便产生了各种各样的替代方法。利用树轮δ^13C值重建古大气δ^13C值的变化就是其中的一种，但树轮δ^13C值容易受到外界环境因子的影响，从树轮δ^13C值中得到的大气δ^13C值存在很大的差异。本文分析了树木生长季（5-9月）温度和降水对树轮δ^13C值序列变化趋势的影响，结果表明，温度和降水对树轮δ^13C序列的趋势变化没有明显的影响。树轮δ^13C值近几十年来下降的趋势主要反映的是大气CO2浓度的增加引起的“Suess”效应。但自然灾害的发生和树轮δ^13C值的边材效应可以改变这种结果。如新疆昭苏树轮δ^13C值和年轮宽度分别在1969年和1967年突然升高以及青海祁连树轮δ^13C值在1990年后上升。 相似文献
3.
内蒙古准格尔旗树轮年表的建立及其气候意义 总被引：2，自引：0，他引：2
通过在内蒙古准格尔旗建立树轮宽度年表、早材宽度年表和晚材宽度年表，并和邻近呼和浩特气象站的资料进行相关分析，结果表明各年表和2—6月的降水量之和呈正相关关系。在准格尔旗西南方向、相距约500km的贺兰山树木生长主要受到5—7月降水量的支配。从这两个区域气象站资料的对比中发现，月降水量、月平均温度的多年平均值在年内表现出非常好的一致性，对应单月月降水量、月平均温度序列显著相关，反映了其受共同的气候驱动因子支配。从两个区域年表对各自气象站气候因子的响应可以看出，树木的生长都主要受到生长季前期和生长季早期降水量的支配。 相似文献
4.
秦岭树轮记录中的ENSO事件 总被引：8，自引：1，他引：8
通过秦岭树轮宽度年表和1949年以来6次最强El Nino年和7次最强La Nina年进行对比，发现每个El Nino年都对应正的年表指数正距平，而每个La Nina年都对应年表指数的负距平，赤道东太平洋（Nino3、4）海水表层温度（SST）和树轮宽度差值年表显著正相关（r=0.269,N=121,α=0.008),1960年以后，相关系数0.480(N=33,α=0.028)，同时，树轮年表序列和南方涛动指数（SOI）显著负相关（r=-0.484,N=33,α=0.013)，在此基础上对1743年以来的SOI进行了重建，并且重建序列具有显著的2-3a周期。 相似文献
5.
ENSO事件对西北太平洋热带气旋影响的分级研究 总被引：2，自引：0，他引：2
采用1951-2006年联合台风警报中心(JTWC)最佳路径数据集和气候预测中心(CPC) ENSO资料,分析了西北太平洋不同等级热带气旋累积能量(accumulated cyclone energy,ACE)与ENSO指数之间的关系.结果表明;ACE与ENSO指数间存在正相关关系;分级热带气旋中,ENSO事件主要通过超强台风(Super TY)的活动与ACE指数联系起来的,超强台风频数在El Ni(n)o期间多于La Ni(n)a 期间,同时持续时间也更长;ENSO指数和热带气旋活跃季超强台风ACE指数的滞后相关(ENSO指数滞后5个月内)与它们的同时相关大小相当.此外,还研究了分级热带气旋持续时间、强度和频数分别对ACE指数的贡献,结果显示超强台风频数的贡献最大.接下来,利用1951-2006年不同ENSO位相情况下NCEP再分析资料,分析了ENSO影响超强台风发生发展的物理机制.主要结论为:西北太平洋存在一些SuperTY频数与源地分布在ENSO年与平常年相比有明显差异的关键区;ENSO事件改变关键区低层相对涡度以及海表温度是其影响SuperTY源地及频数变化的重要途径. 相似文献
6.
2011年春季利用基于Morlet小波分析的余弦函数叠加法对中东太平洋的ENSO冷事件(La Nina)未来发展进行预测,结果成功地预测出了一次呈现"双谷"型的ENSO冷事件发展过程。此方法拟合的1980年1月—2011年2月的Nino3.4指数序列与原序列的相关系数为0.68;对2000—2011年间7次ENSO事件预测结果检验,发现提前3、6、9和12个月时Nino3.4指数的平均预报相关系数(R)分别为0.79,0.81,0.83和0.64,平均预报技巧得分(SS)分别为0.87,0.80,0.80和0.27。此方法具有计算简便,易于运行,预报时效稳定的特点,特别在提前6—9个月时对ENSO的预测仍有较好效果。 相似文献
7.
从树轮纤维素中氧的来源、植物体内氧的分馏、最近的研究成果等三个方面评述树轮纤维素氧同位素组成的温度计意义。结果表明，树轮纤维素氧同位素组成的变化是温度变化的良好载体，但在定量恢复古温度变化时遇到了不少限制，有待于进一步完善分馏模型。 相似文献
8.
贺兰山过去196年降水的树轮宽度重建及降水变率 总被引：2，自引：0，他引：2
贺兰山属于中国北方的半干旱地区,位于东亚夏季风的西北缘。应用贺兰山南段、中段和北段的3组树轮宽度差值年表合成贺兰山树轮宽度年表,应用邻近采样点的贺兰山东坡、山顶和西坡的气象站资料合成贺兰山气象数据。通过贺兰山树轮宽度年表和贺兰山气象数据的线性回归分析,重建了1802—1997年2—7月降水标准化序列,重建方程的方差解释量是46%。计算重建序列的11年滑动平均标准差后,发现存在着3次标准差的突然变化:1908年标准差由前年的0.38增加到当年的0.56,1942年标准差由两年前的0.57增加到当年的0.70,1956年标准差由前年的0.74降低到当年的0.63。小波分析表明,1908年到1949年之间存在显著的11年准周期,1942年出现2年准周期,该2年准周期到1959年彻底消失。1965—1997年,存在由8年向3年过渡的准周期。11年周期对应着太阳活动周期,2年周期对应“准两年脉动”,8年到3年周期与ENSO周期比较一致。故此认为,当太阳活动、“准两年脉动”或ENSO活动增强时,贺兰山地区降水变率一般比较大,年际间降水变得不稳定。 相似文献
9.
工业革命以来化石燃料的大量使用和森林的过度砍伐,引起大气CO2浓度大幅度增加,但同时由于"Suess"效应,大气δ13C值却在不断下降。研究大气δ13C值的变化历史,不仅有助于预测其今后的趋向,而且可以用来了解碳循环的自然变率和校正全球碳预算模型。由于直接的仪器测量从1978年才开始,因此便产生了各种各样的替代方法。利用树轮δ13C值重建古大气δ13C值的变化就是其中的一种,但树轮δ13C值容易受到外界环境因子的影响,从树轮δ13C值中得到的大气δ13C值存在很大的差异。本文分析了树木生长季(5—9月)温度和降水对树轮δ13C值序列变化趋势的影响。结果表明,温度和降水对树轮δ13C序列的趋势变化没有明显的影响,树轮δ13C值近几十年来下降的趋势主要反映的是大气CO2浓度的增加引起的"Suess"效应。但自然灾害的发生和树轮δ13C值的边材效应可以改变这种结果,如新疆昭苏树轮δ13C值和年轮宽度分别在1969年和1967年突然升高以及青海祁连树轮δ13C值在1990年后上升。 相似文献
10.
贺兰山树轮晚材宽度记录中的降水量变化 总被引：3，自引：0，他引：3
通过贺兰山地区树木年轮晚材宽度的研究，建立了贺兰山地区最近250年来的树轮晚材宽度年表。与气象观测记录的相关分析结果表明，树木生长与生长季当年5—7月降水量呈明显的正响应，在此年表的基础上重建了贺兰山地区过去250年来5—7月降水量，发现其具有明显的干湿变化，相对干旱年占总年数的52％，相对湿润年占总年数的35．5％，平年为14．5％，旱灾是该地区主要旱涝灾害。谱分析结果显示该地区5—7月降水有明显的2．6、3．5、21．3年的3个准周期。同时贺兰山地区降水量的变化历史可以反映东亚夏季风的变迁历史。 相似文献
11.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
12.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
13.
The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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15.
《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
16.
The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
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18.
Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
19.
Vance P. Vicente 《Marine Ecology》1989,10(2):179-191
Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned. 相似文献
20.
The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献