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首页> 外文期刊>Paleoceanography >Calibration and Validation of Environmental Controls on Planktic Foraminifera Mg/Ca Using Global Core-Top Data
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Calibration and Validation of Environmental Controls on Planktic Foraminifera Mg/Ca Using Global Core-Top Data

机译：校准和验证全球核心顶级数据

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摘要

The Mg/Ca of planktic foraminifera is commonly assumed to be a univariate function of ocean temperature, but recent work suggests that nonthermal variables may have a secondary effect, thereby complicating an inverse approach for paleotemperature reconstructions. However, the significance of secondary variables has not been independently validated, and their inclusion may reflect statistical overfitting. Here we evaluate the significance of seven predictive variables on a global compilation (n = 1,124) of core-top planktic foraminifera Mg/Ca spanning five species. An additive approach was used to construct models that included only variables with significant validation skill. Optimal models support the use of Mg/Ca as a paleothermometer but also find evidence for nonthermal variables: (a) Mg/Ca (N. pachy+incompta) = 0.186 ± 0.001 · exp(0.095 ± 0.002 · T) + 2.95E-3 ± 5.4E-6 · size; (b) Mg/Ca (G. ruber) = 0.685 ± 0.005 · exp(0.058 ± 0.001 · T) + 0.928 ± 0.02 · Omega(deep); (c); Mg/Ca (G. inflata) = 1.737 ± 0.007 · exp(0.065 ± 0.001 · T) · Omega(shallow)^-0.734 ± 0.003; and (d) Mg/Ca (G. bulloides) = 0.623 ± 0.007 · exp(0.079 ± 0.001 · T) + 0.548 ± 0.007 · Omega(deep). Results highlight the importance of independent validation and suggest that Ω and size dependences may complicate univariate inversions for paleotemperature in some species. This is particularly true over timescales when secondary terms cannot be considered constant. Forward modeling is an attractive alternative, and improved Mg/Ca models may reduce bias in paleoceanographic data assimilation efforts. Salinity is absent from all relationships, suggesting that it may have a smaller influence than previously thought or may not vary sufficiently to be resolved at core-top sites. The stepwise approach illustrated in this study is widely applicable, and validation exercises should be applied to the calibration of other paleoceanographic proxies.
机译：浮游有孔虫的Mg/Ca通常被认为是海洋温度的单变量函数，但最近的研究表明，非热变量可能具有次要影响，从而使古温度重建的逆方法复杂化。然而，次要变量的显著性尚未得到独立验证，它们的纳入可能反映了统计上的过度拟合。在这里，我们评估了七个预测变量在五个物种的核心顶部浮游有孔虫Mg/Ca全球汇编（n=1124）中的重要性。一种加性方法用于构建只包含具有显著验证技能的变量的模型。优化模型支持使用Mg/Ca作为古温度计，但也发现了非热变量的证据：（a）Mg/Ca（N.pachy+Impuncta）=0.186±0.001·exp（0.095±0.002·T）+2.95E-3±5.4E-6·size；（b） Mg/Ca（G.ruber）=0.685±0.005·exp（0.058±0.001·T）+0.928±0.02·ω（deep）；（c） )；Mg/Ca（G.充气）=1.737±0.007·exp（0.065±0.001·T）·ω（浅）^-0.734±0.003；和（d）Mg/Ca（大泡球绦虫）=0.623±0.007·exp（0.079±0.001·T）+0.548±0.007·ω（深部）。结果强调了独立验证的重要性，并表明Ω和大小依赖性可能会使某些物种的古温度单变量反演复杂化。当次要项不能被视为常数时，在时间尺度上尤其如此。正演模拟是一种有吸引力的替代方法，改进的Mg/Ca模型可以减少古海洋数据同化工作中的偏差。盐度在所有关系中都不存在，这表明它的影响可能比之前认为的小，或者可能变化不足以在岩芯顶部位置解决。本研究中说明的逐步方法具有广泛的适用性，验证工作应适用于其他古海洋学指标的校准。

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