Synchronized proxy‐based temperature reconstructions reveal mid‐ to late Holocene climate oscillations in High Arctic Svalbard          下载免费PDF全文

《第四纪科学杂志》2018,33(1):93-99

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Speciation of trace metals in sediments of a tropical estuary     

C. K. Nair  A. N. Balchand 《Environmental Geology》1993,21(1-2):96-102

Axial surveys were performed in the two river tributaries of the Cochin estuary, SW India during November 1988. Surficial sediments were subjected to sequential chemical extractions to delineate five metal fractions, namely, exchangeable, carbonate bound, easily reducible, organic/sulfide bound, and residual. The results indicated selective accumulation of Mn and Ni in carbonate bound and organic/sulfide forms, along with marginal amounts of Co in the exchangeable fraction. Large portions of Fe and Cr occurred in the residual fraction, whereas composite fractionation of Zn species was noticed. The exchangeable fractions of Fe and Cr as well as of easily reducible cobalt were below detection limits. The levels of Cr and Zn indicate anthropogenic inputs in this estuary, whereas Co and Ni show regional contamination exceeding natural levels. The analytical speciation procedure helps to deduce the sedimental diagenetic processes in the estuarine environment.  相似文献   

Infiltration at the Tai rain forest (Ivory Coast): Measurements and modelling     

A. Wierda  A. W. L. Veen  R. W. A. Hutjes 《水文研究》1989,3(4):371-382

Infiltration experiments have been performed at three sites along a well-known catena under virgin tropical rain forest using a portable sprinkling infiltrometer. Experimentally determined infiltration curves are presented. Infiltration curves are also simulated on the basis of the Mein-Larson equation. The parameters for this model have been obtained from the infiltration curves (saturated conductivity) and simple soil moisture determinations (fillable porosity). The agreement between experimentally determined and modelled infiltration is reasonable, provided (a) saturated conductivity as derived from the experimental data is corrected, (b) a storage parameter, also derived from the experimental data, is added to the Mein-Larson model, and (c) the decline in soil porosity with depth is either small or occurs abruptly at shallow depth. Comparison of observed infiltration rates with rainfall intensity shows that Horton Overland Flow has to occur naturally at least on the middle and lower section of the catena. Despite the fact that most parameters can be estimated in principle from basic soil data, it remains advisable to obtain sprinkling infiltrometer field measurements, because of soil variability due to dynamic surface conditions, macroporosity, air entrapment, and irregularity of the wetting front.  相似文献   

165°E赤道太平洋溶解氧垂直分布异常分析     

王明彪  李杰 《海洋与湖沼》1994,25(1):48-53

根据1986—1990中美热带西太平洋海气相互作用8个航次合作综合调查资料，分析了1987年10月赤道中西太平洋165°E（10°N－6°S）次表层水形成溶解氧最大值的原因。1986－1987年E1Nino衰退时期，该海域赤道附近在E1Nino强盛时期下沉的次表层水开始回升，短时期内形成了类似于中、高纬度海域的理化环境，使浮游生物在混合层内聚集生长，最终导致溶解氧含量在次表层出现最大值和过饱和含量。  相似文献   

近2600年神农架大九湖泥炭的气候变化记录   总被引：24，自引：2，他引：24  

何报寅  张穗  蔡述明 《海洋地质与第四纪地质》2003,23(2):109-115

神农架大九湖沼泽泥炭柱状样提供了分辨率为25a的约2600a来的气候变化记录。对样品进行了环境磁学参数测量、X射线荧光分析(XRF)、孢粉鉴定和统计建模，结果表明，大九湖气温的变化曲线与竺可桢中国东部的物候温度曲线以及格陵兰氧同位素变化曲线大体一致，与青藏高原东部希门错湖泊沉积物温度代用指标的变化曲线也十分相似。特别是550—1300AD间的相对温暖期，与竺可桢首次提出来的中国东部隋唐温暖期(约600-1000AD)和欧洲的中世纪暖期(930-1240AD)在时间跨度上大致对应。可划分为4个阶段：(1)600BC—550AD，气候相对冷湿；(2)550—1300AD，气候相对凉干；(3)1300—1900AD，气候又转变为冷湿，其中最冷期1400—1900AD可与欧洲的小冰期对应；(4)1900AD至今，气候又开始转向相对凉干。同时发现低频磁化率χlf与铁元素含量之比(χlf／Fe)的变化曲线与利用孢粉分析数据恢复的大九湖气候变化曲线对应得很好，特别是二者都清晰地显示了500—1300AD为一相对暖期。这预示着χlf／Fe可能是泥炭剖面的一个更好的气候记录代用指标。  相似文献   

Atmospheric forcing of the eastern tropical Pacific: A review   总被引：1，自引：8，他引：1  

Jorge A. Amador  Eric J. Alfaro  Omar G. Lizano  Victor O. Magaa 《Progress in Oceanography》2006,69(2-4):101

The increase in marine, land surface, atmospheric and satellite data during recent decades has led to an improved understanding of the air–sea interaction processes in the eastern tropical Pacific. This is also thanks to extensive diagnoses from conceptual and coupled ocean–atmosphere numerical models. In this paper, mean fields of atmospheric variables, such as incoming solar radiation, sea level pressure, winds, wind stress curl, precipitation, evaporation, and surface energy fluxes, are derived from global atmospheric data sets in order to examine the dominant features of the low level atmospheric circulations of the region. The seasonal march of the atmospheric circulations is presented to depict the role of radiative forcing on atmospheric perturbations, especially those dominating the atmosphere at low levels.In the tropics, the trade winds constitute an important north–south energy and moisture exchange mechanism (as part of the low level branch of the Hadley circulation), that determines to a large extent the precipitation distribution in the region, i.e., that associated with the Inter-Tropical Convergence Zone (ITCZ). Monsoonal circulations also play an important role in determining the warm season precipitation distribution over the eastern tropical Pacific through a large variety of air–sea–land interaction mechanisms. Westward traveling waves, tropical cyclones, low latitude cold air intrusions, and other synoptic and mesoscale perturbations associated with the ITCZ are also important elements that modulate the annual rainfall cycle. The low-level jets of the Gulf of California, the Intra-Americas Sea (Gulf of Mexico and Caribbean Sea) and Chocó, Colombia are prominent features of the eastern tropical Pacific low-level circulations related to sub-regional and regional scale precipitation patterns. Observations show that the Intra-Americas Low-Level Jet intensity varies with El Niño/Southern Oscillation (ENSO) phases, however its origin and role in the westward propagation and development of disturbances that may hit the eastern tropical Pacific, such as easterly waves and tropical cyclones, are still unclear. Changes in the intensity of the trade winds in the Caribbean Sea and the Gulf of Mexico (associated with eastern tropical Pacific wind jets) exert an important control on precipitation by means of wind–topography interactions. Gaps in the mountains of southern Mexico and Central America allow strong wind jets to pass over the continent imprinting a unique signal in sea surface temperatures and ocean dynamics of the eastern tropical Pacific.The warm pools of the Americas constitute an important source of moisture for the North American Monsoon System. The northeastern tropical Pacific is a region of intense cyclogenetic activity, just west of the coast of Mesoamerica. Over the oceanic regions, large-scale properties of key variables such as precipitation, moisture, surface energy fluxes and wind stress curl are still uncertain, which inhibits a more comprehensive view of the region and stresses the importance of regional field experiments. Progress has been substantial in the understanding of the ocean and atmospheric dynamics of the eastern tropical Pacific, however, recent observational evidence such as that of a shallow meridional circulation cell in that region, in contrast to the classic concept of the Hadley-type deep meridional circulation, suggests that more in situ observations to validate theories are still necessary.This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific Ocean.  相似文献   

热带气旋活动对中国夏季雨带类型与ENSO的响应关系   总被引：2，自引：0，他引：2  

陈文玉  陈菊英 《海洋预报》1997,14(1):25-36

本文分析研究了热带气旋１）活动与中国夏季２）３组（包括８种）主要多雨带类型的响应关系。同时对热带气旋活动与夏季大陆气温和ＥＮＳＯ事件的始终时间的响应关系，也进行了探讨。分析表明，夏季中国的雨带分布特征对热带气旋活动有着十分重要的指示意义。热带气旋活动与中国大陆气温有着正相关关系，与ＥＮＳＯ事件的发生有着反相关关系  相似文献   

银川盆地中更新世以来的孢粉记录及古气候研究   总被引：8，自引：1，他引：8  

杨振京  刘志明  张俊牌  童国榜  阳小兰 《海洋地质与第四纪地质》2001,21(3):43-49

银川盆地中更新世以来的孢粉记录及据此所重建的古气候参数，揭示了该区中更新世以来的古气候演变特征，其演变经过了温湿→凉湿→温和→冷湿→温干→凉较湿→冷湿→温干→凉润→温较干→温干的变化，并与新疆地区，黄土高原以及深海δ^18O曲线进行了对比，结果表明，各地的古环境变化大致同步，该区由于位置靠西，邻近沙漠，最近地质历史时期的区域性干旱特色明显。  相似文献   

日本海古海洋环境的演化     

余煦明 《海洋地质前沿》2005,21(8):6-9

基于近年来有关日本海的古海洋古环境研究成果，总结概述了日本海中新世以来的古气候和古海洋环境演化特征。日本海作为西北太平洋一个主要的边缘海，在全球气候变化过程中起着重要的作用。它的古气候古环境演化，与全球其他地区一样受控于地球轨道参数的变化，同时也发育一些由气候的不稳定性、海峡的开合与其他一些地球气候系统的非线性活动所驱动的突发性快速气候变化事件。日本海的古海平面、古海水温度、古洋流等因子的变化还受到冰盖扩张和退缩、构造运动、冰川性地壳均衡补偿、东亚季风等因素的影响，具有鲜明的区域特点。总体说来，目前对日本海的研究程度还不高，对它在全球气候变化中的作用过程、驱动和响应机制的了解还很有限，需要进一步深入研究。  相似文献   

东南亚10°—25°N,105°—130°E海区热带风暴异常路径的分析     

谢玲娟 《台湾海峡》1994,13(4):346-352

本文４１ａ（１９４９－１９８９年）的资料，对东南亚１０°－２５°Ｎ，１０５°－１３０°Ｅ范围７－９月出现的热带风暴异常路长进行了普查统计和气候分析。结果表明：产生异常路径热风暴的机率约占区域内热带风暴总数的２０％；异常路径的产生与热带风暴所处的地理位置，季节，环下等因素有关。正确地考虑气候规律和具体的天气条件相结合是预报带式风暴异常路径成败的关键。  相似文献