Palaeoclimatic signals recognized by chemometric treatment of molecular stratigraphic data     

S.C. Brassell  R.G. Brereton  G. Eglinton  J. Grimalt  G. Liebezeit'  I.T. Marlowe  U. Pflaumann  M. Sarnthein 《Organic Geochemistry》1986,10(4-6)

The high-resolution stratigraphy of various marker compounds has been studied, using GC, HPLC and GC-MS, in a 13 m gravity core recovered from the Kane Gap region, eastern equatorial Atlantic, which provides a record of the glacial/interglacial episodes over the last million years. Downhole variations in many presumed source-specific components are observed (e.g. in n-alkanes from terrigenous land plants and dinosterol from dinoflagellates), which may be due to perturbations or cyclicities resulting from climatic change. Fluctuations in the unsaturation of alkenones attributable to variations in water temperatures show correlations with the glacial/interglacial cycles recorded in the δ¹⁸O values for planktonic foraminifera, thereby providing a potential organic geochemical measure of past climates. These molecular abundance data can be linked to the palaeotemperature record, following computer treatments using principal component and spectral analyses. Molecular stratigraphy shows promise as a new chemostratigraphical tool where other means of stratigraphy fail, for example, through calcium carbonate dissolution.  相似文献   

应用D、¹⁸O同位素示踪孝感市厚层黏性土中土壤水入渗补给及其生态环境效应          下载免费PDF全文

刘添文  潘越  胡成  王清  陈植华  史婷婷 《中国地质》2021,48(5):1429-1440

黏性土的渗透系数极低，水分及溶质在黏性土中运移速率慢、耗时长，本次研究通过分析大别山区-江汉平原三水转换野外科学试验场（下文简称"试验场"）ZK1、ZK2钻孔剖面土壤水、大气降雨D、¹⁸O同位素测试数据与孝感站（站号57482）多年年降雨量数据，确定了厚层黏性土土壤水入渗补给年份与深度的对应关系。结果表明：试验场区黏性土垂向岩性差异较小，无明显分层现象，土壤水分以"活塞流"的方式向下运移，夏、秋季的大气降雨为土壤水的主要补给来源；ZK1（取样间隔0.5~2.7 m，深度15 m）的土壤水δD、δ¹⁸O值随着埋深的增大出现周期性的波动，ZK2（取样间隔0.1 m，深度6.2 m）的土壤水δD、δ¹⁸O值随着埋深的增大出现分层波动现象；确定了黏性土层0~6.2 m深度对应的降雨入渗补给年份，并通过¹⁸O的峰值位移法计算得出降雨入渗补给在黏性土层的垂向运移速度为10.8~15.0 cm/a，年均入渗补给量为43.1~58.1 mm，占多年年均降雨量的4.01%，推算出降雨入渗补给需要近130年的时间才能穿透试验场厚层黏性土补给至地下水含水层，表明该厚层黏性土的防污性能良好。本研究所揭示大气-土壤界面下黏性土土壤水分入渗迁移历史演化特征及补给年际对应关系，对江汉平原区地下水环境保护、生态环境改善、旱涝灾害防治等具有重要意义。  相似文献   

夏季楚科奇海河水与海冰融化水组分的空间变化特征   总被引：2，自引：1，他引：1  

童金炉  陈敏  潘红  杨伟锋  张润  郑敏芳  邱雨生 《海洋学报》2014,36(10):90-102

通过对2008年夏季楚科奇海水氧同位素组成的分析,运用S、δ18 O的质量平衡关系计算出河水组分和海冰融化水组分的份额,揭示出楚科奇海河水和海冰融化水组分的空间变化规律,并探讨其影响因素。楚科奇海河水组分的份额介于1.9%~18.4%之间,呈现随深度增加而降低的趋势;河水组分积分高度的变化范围为1.3~16.6m,平均为(4.8±4.0)m。河水组分份额与积分高度均呈现东高西低、北强南弱的特征,与太平洋入流东侧为富含河水组分的阿拉斯加沿岸流、西侧为低河水组分的白令海陆架水,以及北部海域受波弗特流涡埃克曼辐聚作用的影响有关。海冰融化水份额呈现随深度增加而降低的趋势,20~30m以深受到冬季海冰形成时所释放盐卤水的明显影响。海冰融化水积分高度的变化范围为-3.2~1.7m,平均值为(-0.3±1.2)m,其空间分布呈现东低西高、南强北弱的特征,与太平洋入流输入通量的时间变化以及输入路径的西偏有关。  相似文献   

夏末秋初南海18°N断面混合层结构特征分析     

王静  赵飞达  齐义泉 《海洋通报》2015,34(1):52-58

基于2004-2012年8-9月份南海北部开放航次期间18°N断面的温盐深仪(Conductance Temperature Depth,CTD)观测资料,分析了夏末秋初沿18°N断面的温度、盐度和混合层结构特征及其影响因素。研究发现:南海18°N断面的温度、盐度和混合层特征具有显著的年际变化,并且混合层的深度和其倾斜程度与风速及风驱动的Ekman平流有关,而所有航次18°N断面东侧均出现等温线、等盐线下凹现象,这与夏末秋初吕宋岛西侧海域存在一个反气旋式涡旋活动有关。  相似文献   

Roles of Wind Stress and Subsurface Cold Water in the Second-Year Cooling of the 2017/18 La Ni?a Event     

Licheng FENG  Rong-Hua ZHANG  Bo YU  Xue HAN 《大气科学进展》2020,37(8):847-860

After the strong 2015/16 El Ni?o event, cold conditions prevailed in the tropical Pacific with the second-year cooling of the 2017/18 La Ni?a event. Many coupled models failed to predict the cold SST anomalies(SSTAs) in 2017. By using the ERA5 and GODAS(Global Ocean Data Assimilation System) products, atmospheric and oceanic factors were examined that could have been responsible for the second-year cooling, including surface wind and the subsurface thermal state. A time sequence is described to demonstrate how the cold SSTAs were produced in the central-eastern equatorial Pacific in late 2017. Since July 2017, easterly anomalies strengthened in the central Pacific; in the meantime, wind stress divergence anomalies emerged in the far eastern region, which strengthened during the following months and propagated westward, contributing to the development of the second-year cooling in 2017. At the subsurface, weak negative temperature anomalies were accompanied by upwelling in the eastern equatorial Pacific, which provided the cold water source for the sea surface. Thereafter, both the cold anomalies and upwelling were enhanced and extended westward in the centraleastern equatorial Pacific. These changes were associated with the seasonally weakened EUC(the Equatorial Undercurrent) and strengthened SEC(the South Equatorial Current), which favored more cold waters being accumulated in the central-equatorial Pacific. Then, the subsurface cold waters stretched upward with the convergence of the horizontal currents and eventually outcropped to the surface. The subsurface-induced SSTAs acted to induce local coupled air–sea interactions, which generated atmospheric–oceanic anomalies developing and evolving into the second-year cooling in the fall of 2017.  相似文献   

Responses of nutrient biogeochemistry and nitrogen cycle to seasonal upwelling in coastal waters of the eastern Hainan Island     

Nan Zhou  Sumei Liu  Guodong Song  Yunyan Zhang  Lingyan Wang  Xiaoyan Ning 《海洋学报(英文版)》2022,41(6):99-113

The coastal upwelling has profound influence on the surrounding ecosystem by supplying the nutrient-replete water to the euphotic zone. Nutrient biogeochemistry was investigated in coastal waters of the eastern Hainan Island in summer 2015 and autumn 2016. From perspectives of nutrient dynamics and physical transport, the nutrient fluxes entered the upper 50 m water depth（between the mixed layer and the euphotic zone） arisen from the upwelling were estimated to be 2.5-5.4 mmol/（m²·d）,...  相似文献   

4个代表站点的珊瑚δ18O数据对热带印度洋气候变率的反演能力分析*     

陈云帆  陈天然  龙上敏  陈泽生  杜岩 《热带海洋学报》2022,41(1):82-93

珊瑚中的δ¹⁸O含量可以高精度地记录热带海洋中的气候变率及气候变化信息, 从而弥补器测观测时间长度有限的缺陷, 为反演过去长期的气候状况提供了可能。热带印度洋的气候模态通过海气相互作用影响周边区域甚至全球的气候, 具有重要的研究意义。本文对比分析了1880—1999年间热带印度洋4个站点(肯尼亚、坦桑尼亚、塞舌尔、明打威)的珊瑚δ¹⁸O数据, 研究了其对热带印度洋气候的反演情况。结果显示, 珊瑚δ¹⁸O对海表温度(sea surface temperature, SST)的长期变化趋势反演良好, 珊瑚δ¹⁸O与局地SST在季节循环中保持一致, 且在低温季节对SST的变化更为敏感。此外, 4个站点的珊瑚δ¹⁸O对印度洋海盆模态(Indian Ocean Basin Mode, IOBM)和印度洋偶极子模态(Indian Ocean Dipple Mode, IODM)有一定的表征能力, 并且δ¹⁸O记录的热带印度洋年际变率受年代际变率调制。本文的研究结果表明, 珊瑚δ¹⁸O数据对于了解古气候时期热带印度洋气候变率具有重要的指示意义, 但同时也需要综合考虑不同站点的信息来完整地反映印度洋在历史时期的气候变化情况。  相似文献   

基于氢氧稳定同位素的武汉北部新城地表水-地下水转换关系研究          下载免费PDF全文

杨艳林  靖晶  赵永波  何军  杜小锋 《中国地质》2022,49(3):706-715

【研究目的】揭示武汉北部新城地表水、地下水的氢氧稳定同位素特征及其相互作用。【研究方法】2019年，采集、测定了降水样7件、河水样6件、水库样14件、民井样98件、泉水样3件和钻孔样11件，并收集到武汉站1986—1998年的监测数据50件，以空间分析和流域分析为基础，氢氧稳定同位素分析为手段。【研究结果】（1）武汉降水氢氧同位素随季节变化，并表现出“降雨效应”明显、“温度效应”不明显的特点；（2）地表水在枯水期受到强烈的蒸散发，表现出一定的“地貌效应”与“干支流效应”的特征；（3）民井、泉和钻孔等地下水均源于大气降水，表现出“含水层埋深效应”与“山区平原效应”的特点；（4）枯水期，界河流域中界河获得了上游水库和地下水的补给，夏家寺水库流域中夏家寺水库得到了地下水补给。【结论】氢氧同位素能显著提高武汉北部新城地表水-地下水相互转换规律的认识。创新点：利用各类水体氢氧同位素组成及空间分布特征，揭示了武汉北部新城降水、地表水和地下水相互转换的规律  相似文献