Reconstructing the thermal structure of the upper ocean: Insights from planktic foraminifera shell chemistry and alkenones in modern sediments of the tropical eastern Indian Ocean
Reconstructing the thermal structure of the upper ocean: Insights from planktic foraminifera shell chemistry and alkenones in modern sediments of the tropical eastern Indian Ocean
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DOI：
10.1029/2011pa002132
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发表时间：
2011-09-10
期刊：
影响因子：
--
通讯作者：
Hebbeln, Dierk
中科院分区：
文献类型：
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作者：
Mohtadi, Mahyar;Oppo, Delia W.;Hebbeln, Dierk
本文研究了印度尼西亚西部和南部海域热带东印度洋69个表层沉积物样品中浮游有孔虫的壳化学和烯酮不饱和指数。将结果与现代水文数据进行了比较，以评估现代环境条件如何保存在沉积记录中，并确定最佳的替代物，以重建世界海洋这一部分的季节性、热梯度和上层水柱特征。我们的研究结果表明，烯酮衍生的温度记录在研究区域的年平均温度。然而，这一发现可能是人为的，因为该代理的温度限制在28摄氏度以上。壳稳定氧同位素和Mg/Ca比值的综合研究表明，Globigerinoides ruber sensu stricto（s.s.）G. Ruber Sensu Lato（s.l.），和G. socculifer钙化的混合层之间的20米和50米，而Globigerina bulloides记录混合层条件在类似的50米深度在北方夏季。平均钙化的Pulleniatina pulliciloculata，Neogloboquadrina dutertrei，和Globorotalia膨胀发生在顶部的温跃层在北方夏季，在类似的75米，75-100米，100米，分别。所有物种的壳Mg/Ca比值在其表观钙化深度处与温度显著相关，并验证了先前发表的温度校准的应用，除了G。膨胀，需要区域Mg/Ca温度校准（Mg/Ca = 0.41 exp（0.068*T））。结果表明，混合层物种和温跃层物种的Mg/Ca温度差异，特别是G.鲁伯公司(or（单位：千美元）和P. damiloculata，可以应用于跟踪上层水柱分层的变化。我们的研究结果提供了关键的工具，重建过去的变化，水文的研究区域及其与季风，厄尔尼诺南方涛动，印度洋偶极子模式。
Shell chemistry of planktic foraminifera and the alkenone unsaturation index in 69 surface sediment samples in the tropical eastern Indian Ocean off West and South Indonesia were studied. Results were compared to modern hydrographic data in order to assess how modern environmental conditions are preserved in sedimentary record, and to determine the best possible proxies to reconstruct seasonality, thermal gradient and upper water column characteristics in this part of the world ocean. Our results imply that alkenone-derived temperatures record annual mean temperatures in the study area. However, this finding might be an artifact due to the temperature limitation of this proxy above 28 degrees C. Combined study of shell stable oxygen isotope and Mg/Ca ratio of planktic foraminifera suggests that Globigerinoides ruber sensu stricto (s.s.), G. ruber sensu lato (s.l.), and G. sacculifer calcify within the mixed-layer between 20 m and 50 m, whereas Globigerina bulloides records mixed-layer conditions at similar to 50 m depth during boreal summer. Mean calcifications of Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, and Globorotalia tumida occur at the top of the thermocline during boreal summer, at similar to 75 m, 75-100 m, and 100 m, respectively. Shell Mg/Ca ratios of all species show a significant correlation with temperature at their apparent calcification depths and validate the application of previously published temperature calibrations, except for G. tumida that requires a regional Mg/Ca-temperature calibration (Mg/Ca = 0.41 exp (0.068*T)). We show that the difference in Mg/Ca-temperatures of the mixed-layer species and the thermocline species, particularly between G. ruber s.s. (or s.l.) and P. obliquiloculata, can be applied to track changes in the upper water column stratification. Our results provide critical tools for reconstructing past changes in the hydrography of the study area and their relation to monsoon, El Nino-Southern Oscillation, and the Indian Ocean Dipole Mode.