Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)     

《Comptes Rendus Geoscience》2015,347(1):43-51

Past ocean pH and pCO₂ are critical parameters for establishing relationships between Earth's climate and the carbon cycle. Previous pCO₂ estimates are associated with large uncertainties and are debated. In this study, laboratory cultures of the foraminiferan genus Amphistegina were performed in order to examine the possible factors that control the Li isotope composition (δ⁷Li) of their shells. δ⁷Li is insensitive to temperature and pH variations but correlates positively with the Dissolved Inorganic Carbon (DIC) of seawater. Li/Ca ratio in the shells shows negative correlation with δ⁷Li, consistent with published data for planktonic foraminifera from core tops and from short periods during the Cenozoic. We propose that the sensitivity of δ⁷Li and Li/Ca ratio to DIC is a biological phenomenon and is related to biomineralization mechanisms in foraminifera. We used the published foraminiferal δ⁷Li records, and our experimental results, to determine the paleo-ocean DIC and pH for the last glacial–interglacial cycle. The results are consistent with published estimates of pH and pCO₂ based on boron isotopes and ice cores. We suggest Li and its isotopes may serve as a new complementary proxy for the paleo-ocean carbonate chemistry.  相似文献   

Reconstructing High-resolution Deep-sea Environmental Change: Inorganic Geochemical Proxy Methods of Cold-water Bamboo Corals     

Haowen Dang  Xiaolin Ma  Ce Yang  Haiyan Jin  Zhimin Jian 《地球科学进展》2019,34(12):1262-1272

The cold-water bamboo coral, dwelling in the depths of global seas, is characterized by the “bamboo-like” skeletal structure of alternating calcite internodes and gorgonin nodes, and has “tree-ring-like” concentric growth rings transversally. Paleoceanograhic reconstructions using bamboo coals would fill the geographic and temporal gaps of traditional means. In this work, the inorganic geochemical proxy methods for bamboo coral are introduced, including Mg/Ca for ambient temperature, Ba/Ca for seawater nutrient content, and δ¹¹B for seawater pH. Also, the potential influences of vital effect on the proxy reconstructions are briefly discussed. With the recent findings of deep-sea bamboo coral forests in the western Pacific region, a new territory of bamboo coral paleoceanography is opened for the scientists from the nearby countries.  相似文献   

基于日记的历史气候变化研究综述   总被引：2，自引：1，他引：1  

黄媛  李蓓蓓  李忠明 《地理科学进展》2013,32(10):1545-1554

重建历史时期的气候变化可为分析当前气候变化规律和模拟未来气候变化趋势提供历史参考情景。古代私人日记中保存的气候信息,因其直观性强、分辨率高等特点而受到研究者的重视,成为重建历史气候时使用较多的一类代用数据。近年来,国内外学者利用日记资料,已经重建了多个地区历史上的温度、降水及物候变化,并已逐步由定性描述发展到定量研究。本文从代用指标、研究方法、研究成果3 个方面,对基于日记的历史气候重建研究成果进行综述,得到以下结论:① 重建指标选取上,国内外均较常使用天气情况日数和感应记录两类指标;此外,国内常用自然生长植物的物候期,而国外还使用风向、云量等指标;重建指标类型可分为定量、半定量、定性3 类,定量与定性指标使用较多,半定量指标使用相对较少。② 重建方法上,中外研究者多采用定性分析法和定量转换法等;资料校对方法上,西方学者多采用器测资料进行检验,国内则常选用方志与官私文件进行校订。③ 国外研究的重建内容主要涉及区域温度和降水;而国内除了温度和降水重建外,还研究了沙尘和梅雨等中国特有的天气气候现象。利用日记重建历史气候的优势在于,日记中保存的历史气候信息细节丰富、时间分辨率高,因而能够很好地保证重建结果的准确性。未来这一领域的研究还应继续改进代用指标的定量转换和重建结果的校验方法,并加强对不同区域、不同时段的同类研究结果的集成研究。  相似文献   

以Al/Ti比值为地球化学示踪剂反演海洋古生产力的研究进展   总被引：9，自引：0，他引：9  

任景玲  张经  刘素美 《地球科学进展》2005,20(12):1314-1320

地球化学家通常用Al对其它重金属进行归一化以校正沉积物来源、粒度、矿物组成等方面的影响,因此现代海洋沉积物样品中Al、Ti含量的结果主要用于定量描述陆源输送的贡献。近期研究结果发现,在受陆源物质输送影响较小,沉降颗粒主要以生源颗粒物为主的赤道大洋区,沉积物中出现明显的“过剩铝”信号,“过剩铝”约占沉积物中总铝含量的50％。因此,用沉积物中Al的含量来估算陆源碎屑的比例会导致过高的结果,建议用Ti、Sc作为参比元素校正陆源物质的影响。沉积物中的Al/Ti比值可用来示踪水体中颗粒物的沉降通量和初级生产的改变。综述了近期以Al/Ti比值这种新的地球化学示踪剂反演古生产力的最新研究进展,提出了在我国陆架边缘海开展此项工作可能存在的问题与挑战。  相似文献   

Proxy Record of a Firn-Core From an Alpine Glacier and Its Implication to Recent Glacio-Climatic Varia tions on Mt. Yulong, Southeastern Part of Tibetan Plateau     

He Yuanqing  Yang MeixueWT  ”BX 《地学前缘》2000,(Z1)

PROXY RECORD OF A FIRN-CORE FROM AN ALPINE GLACIER AND ITS IMPLICATION TO RECENT GLACIO-CLIMATIC VARIATIONS ON MT. YULONG, SOUTHEASTERN PART OF TIBETAN PLATEAU  相似文献   

南沙群岛永暑礁晚全新世软体动物记录与古环境变化   总被引：1，自引：0，他引：1  

冯伟民  蓝琇  陈木宏 《热带海洋学报》2005,24(4):41-50

对南沙群岛永暑礁南永3井软体动物的丰度、营养结构、化学元素和堆积速率的定量分析表明,晚全新世永暑礁漏湖经历了数次相对开放与封闭、与外海交流时强时弱以及盐度多次显著变化的过程。与氧同位素和北半球晚全新世快速气候事件的进一步对比表明,晚全新世快速变化的气候事件也波及到南海,由此造成的溺湖水动力环境、古盐度和沉积速率的变化深刻地影响着软体动物的发育。基于软体动物的替代指标和氧同位素变化的综合分析,初步划分了晚全新世永暑礁漏湖7个变化阶段。  相似文献   

气候环境变化的湖泊沉积学响应   总被引：24，自引：0，他引：24  

李玉成  王苏民  黄耀生 《地球科学进展》1999,14(4):412-416

湖泊沉积可作为气候和环境变化的信息库,它能提供时间分辨率高达百年至十年的气候变化信息。湖泊沉积能灵敏地反映与地球轨道力变化相关的气候效应,以及在此背景上叠加的非线性气候事件。湖泊沉积与其中的古生物组合、元素同位素组成是古气候环境的重要替代指标,为检验大气动力学气候模型和进一步改进模型,预测未来气候提供了依据。  相似文献   

Measurement of the sortable silt current speed proxy using the Sedigraph 5100 and Coulter Multisizer IIe: precision and accuracy   总被引：2，自引：1，他引：1  

Bianchi  Hall  McCave  & Joseph 《Sedimentology》1999,46(6):1001-1014

The weight percentage and mean size of the 10–63 μm terrigenous silt fraction (termed 'sortable silt') of fine-grained marine sediments have recently been argued to be proxies for near-bottom palaeocurrent intensity. This paper details the accuracy and precision of the Sedigraph 5100 and the Coulter Multisizer IIe in determining the weight percentage and mean size of the sortable silt at abundances characteristic of deep-ocean sediments. Three sortable silt standards and a fine silt/clay diluent were generated from natural deep-sea sediment of the Iceland Basin. These were used to produce silty clays with standard additions of sortable silt ranging from 1% to 20% of the total by weight. Accuracy was measured relative to the size of the pure spike measured by each instrument. At sortable silt abundance >5%, the Sedigraph and the Coulter Multisizer estimate both weight percentage and mean grain size precisely and accurately, while below 5%, instrumental noise degrades their performance. On the basis of the Sedigraph results, a series of percentage errors is defined, which may be applied to sortable silt mean size and weight percentage estimates used in palaeoceanographic near-bottom current reconstruction. It is suggested that, ideally, palaeocurrent reconstructions should be based on Sedigraph determinations of the 0–63 μm grain size distribution, yielding both mean and abundance, or on Coulter Multisizer determinations of the sortable silt grain size mean. The Coulter Multisizer may prove especially useful in regions of very depleted (<5%) sortable silt component.  相似文献   

古湖沼学研究揭示湖泊生态系统服务变化的过程     

徐敏  董旭辉  羊向东 《湖泊科学》2014,26(3):331-339

当今在气候变化和人类活动等多重压力影响下,作为地表过程重要组成部分的湖泊生态系统正遭受着巨大威胁,其服务功能急剧退化.如何客观地评价湖泊生态系统服务的现状,并科学地预测其发展趋势,是当前亟待解决的问题.开展长期生态系统服务变化过程与机理的分析,有助于未来生态系统服务变化趋势的预测.然而,现有的观测数据往往时间较短(通常小于50年).连续的湖泊沉积记录为研究生态系统服务变化的长期过程提供了可能.本文结合前人研究成果,列举了可反映湖泊生态系统服务变化的一些古湖沼学指标,依据这些指标相对明确的生态和环境指示意义,将其与各项服务关联起来.最后,结合巢湖实例分析来说明这些指标在评估湖泊生态系统服务方面的具体应用,研究表明当今巢湖生态系统服务供应能力的持续增加是以调节服务的丧失为代价的.尽管目前的研究尚处于起步阶段,但古湖沼学手段无疑为今后湖泊生态系统服务历史状况的评估提供了途径,为古湖沼学的应用提供了一种新的思路,并为今后生态系统的保护和可持续利用提供重要的决策依据.  相似文献   

Evaluating ice‐rafted debris as a proxy for glacier calving in Upernavik Isfjord,NW Greenland     

Flor Vermassen  David J. Wangner  Laurence M. Dyke  Sabine Schmidt  Amalie E. Cordua  Kurt H. Kjr  Konstanze Haubner  Camilla S. Andresen 《第四纪科学杂志》2019,34(3):258-267

Records of ice‐rafted debris (IRD) in sediments are commonly used as a proxy for iceberg production and to reconstruct past changes of glacier stability. However, the interpretation of IRD is complex as multiple processes modulate its variability. This study investigates the relationship between IRD variability and glaciological change by measuring IRD records from Upernavik Fjord and comparing these to frontal positions of Upernavik Isstrøm during the past century. Results show that the spatial variability of IRD deposition throughout the fjord is high, indicating that randomness inherent to IRD distorts the calving signal. However, we investigate whether IRD records can be combined to improve the reconstruction, as previously suggested, and show the importance of core site selection and number of cores on this approach. The outer‐fjord core compares relatively well to the observed front positions and this is reflected in the composite record: increased IRD deposition in 1937–1946, 1968–1980, and 1996–1999 occurred during periods of faster retreat. Comparison with climatic records shows that the calving episodes in the late ‘30 s/early ‘40 s and late ‘90 s are related to warm ocean and air temperatures, whereas intensified retreat and calving during the ‘70 s reflects partly an internal glacier response to the fjord geometry.  相似文献