Calibration of the boron isotope proxy in the planktonic foraminifera Globigerinoides ruber for use in palaeo-CO2 reconstruction
Calibration of the boron isotope proxy in the planktonic foraminifera Globigerinoides ruber for use in palaeo-CO2 reconstruction
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DOI：
10.1016/j.epsl.2012.12.029
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发表时间：
2013-02-15
影响因子：
5.3
通讯作者：
Elliott, Tim
中科院分区：
文献类型：
--
作者：
Henehan, Michael J.;Rae, James W. B.;Elliott, Tim
硼同位素- ph代理，应用于混合层浮游有孔虫，有很大的潜力来估计过去的二氧化碳水平，这反过来又对我们了解这种温室气体如何影响地球气候至关重要。以往的培养实验表明，尽管各种浮游有孔虫的硼同位素组成依赖于pH值，但它们与代理的水相地球化学基础不一致。在这里，我们概述了Globigerinoides橡胶（白色）在pH范围内（类似于7.5-8.2）的培养实验结果，并通过多收集器电感耦合等离子体质谱（MC-ICPMS）进行了分析，并将这些数据与岩芯顶部和沉积物陷阱样品进行了比较，以获得一个强大的新的物种特异性硼同位素-pH校准。与早期的培养研究一致，我们发现与海水中的硼酸盐离子相比，共生浮游有孔虫中硼同位素组成的pH依赖性降低。我们还提出了G. ruber的δ B-11的尺寸分数效应的证据。最后，我们利用我们的新定标在ODP站点999A和站点GeoB1523-1两个赤道站点重建了最后一次冰期的大气CO2浓度。这些数据为硼同位素- ph代用法重建过去大气CO2水平提供了进一步的依据。(C) 2012 Elsevier B.V.版权所有
The boron isotope-pH proxy, applied to mixed-layer planktic foraminifera, has great potential for estimating past CO2 levels, which in turn is crucial to advance our understanding of how this greenhouse gas influences Earth's climate. Previous culture experiments have shown that, although the boron isotopic compositions of various planktic foraminifera are pH dependent, they do not agree with the aqueous geochemical basis of the proxy. Here we outline the results of culture experiments on Globigerinoides ruber (white) across a range of pH (similar to 7.5-8.2) and analysed via multicollector inductively-coupled plasma mass spectrometry (MC-ICPMS), and compare these data to core-top and sediment-trap samples to derive a robust new species-specific boron isotope-pH calibration. Consistent with earlier culture studies, we show a reduced pH dependency of the boron isotopic composition of symbiont-bearing planktonic foraminifera compared to borate ion in seawater. We also present evidence for a size fraction effect in the delta B-11 of G. ruber. Finally, we reconstruct atmospheric CO2 concentrations over the last deglacial using our new calibration at two equatorial sites, ODP Site 999A and Site GeoB1523-1. These data provide further grounding for the application of the boron isotope-pH proxy in reconstructions of past atmospheric CO2 levels. (C) 2012 Elsevier B.V. All rights reserved.