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Past temperature and δ~(18)O of surface ocean waters inferred from foraminiferal Mg/Ca ratios

机译:从有孔虫的Mg / Ca比推断过去的温度和地表海水的δ〜(18)O

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摘要

Determining the past record of temperature and salinity of ocean surface waters is essential for understanding past changes in climate, such as those which occur across glacial-interglacial transitions. As a useful proxy, the oxygen isotope composition (δ~(18)O) of calcite from planktonic foraminifera has been shown to reflect both surface temperature and seawater δ~(18)O, itself an indicator of global ice volume and salinity. In addition, magnesium/calcium (Mg/Ca) ratios in foraminiferal calcite show a temperature dependence due to the partitioning of Mg during calcification. Here we demonstrate, in a field-based calibration experiment, that the variation of Mg/Ca ratios with temperature is similar for eight species of planktonic foraminifera (when accounting for Mg dissolution effects). Using a multi-species record from the Last Glacial Maximum in the North Atlantic Ocean we found that past temperatures reconstructed from Mg/Ca ratios followed the two other palaeotemperature proxies: faunal abundance and alkenone saturation. Moreover, combining Mg/Ca and δ~(18)O data from the same faunal assemblage, we show that reconstructed surface water δ~(18)O from all foraminiferal species record the same glacial-interglacial change—representing changing hydrography and global ice volume. This reinforces the potential of this combined technique in probing past ocean-climate interactions.
机译:确定过去的海洋表层水温和盐度记录对于了解过去的气候变化(例如跨冰河间过渡的气候变化)至关重要。作为有用的替代物,浮游有孔虫的方解石的氧同位素组成(δ〜(18)O)已显示出既反映了地表温度又反映了海水δ〜(18)O,这本身就是全球冰量和盐度的指标。另外,有孔虫方解石中的镁/钙(Mg / Ca)比显示出温度依赖性,这是由于钙化过程中镁的分配所致。在这里,我们在一个基于现场的校准实验中证明,八种浮游有孔虫的Mg / Ca比值随温度的变化相似(考虑到Mg的溶出作用时)。利用北大西洋最后一次冰期最高峰的多物种记录,我们发现,根据Mg / Ca比例重建的过去温度紧随其他两个古温度指标:动植物丰度和烯酮饱和度。此外,结合来自相同动物群落的Mg / Ca和δ〜(18)O数据,我们表明,所有有孔虫物种的重建地表水δ〜(18)O记录了相同的冰间变化,代表着水文和全球冰的变化体积。这加强了这种组合技术在探测过去的海洋-气候相互作用中的潜力。

著录项

  • 来源
    《Nature》 |2000年第6785期|p.442-445|共4页
  • 作者

    H. Elderfield; G. Ganssen;

  • 作者单位
  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 自然科学总论;
  • 关键词

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