Leaf Wax Hydrogen Isotopes as a Hydroclimate Proxy in the Tropical Pacific
Leaf Wax Hydrogen Isotopes as a Hydroclimate Proxy in the Tropical Pacific
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DOI：
10.1029/2020jg005891
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发表时间：
2021-03-01
影响因子：
3.7
通讯作者：
Dubois, N.
中科院分区：
文献类型：
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作者：
Ladd, S. N.;Maloney, A. E.;Dubois, N.
沉积叶蜡的氢同位素比率(增量H-2(Wax)值)越来越多地被用于重建过去的水文气候。在这里，我们将来自15个热带太平洋岛屿的19个湖泊和4个沼泽的H-2(Wax)值添加到最新的全球出版的表层沉积物和土壤数据汇编中。在全球范围内，年平均降水量的增量H-2值(增量H-2(P)值)与叶蜡n-C-29-烷烃(R-2=0.74，n=665)和n-C-28-酸(R-2=0.74，n=242)之间存在很强的线性正相关。热带太平洋三角洲H-2(WAX)值落在基于全球校正的预测值范围内，来自全球回归线的最大残差并不大于其他地方观测到的值，尽管一些太平洋站点的增量H-2(P)值存在很大的不确定性。然而，孤立的热带太平洋三角洲H-2(Wax)值与从等电位线或同位素启用的大气环流模式估计的增量H-2(P)值不相关。来自这些太平洋沉积物样品的孢粉学分析表明，任何特定类型的花粉分布与全球校准线的偏差之间没有系统的关系。相反，在热带太平洋观察到的较差的相关性可能是相对于全球校准线附近的典型残差而言，增量H-2(P)值的小范围的函数。我们的结果表明，增量H-2(Wax)值目前最适合用于探测热带太平洋和其他地区降水的大变化，但这一阈值还有很大的提高空间，这既存在于对植物中增量H-2变异性的理解，也存在于对降水中的H-2变异性的理解。
Hydrogen isotope ratios of sedimentary leaf waxes (delta H-2(Wax) values) are increasingly used to reconstruct past hydroclimate. Here, we add delta H-2(Wax) values from 19 lakes and four swamps on 15 tropical Pacific islands to an updated global compilation of published data from surface sediments and soils. Globally, there is a strong positive linear correlation between delta H-2 values of mean annual precipitation (delta H-2(P) values) and the leaf waxes n-C-29-alkane (R-2 = 0.74, n = 665) and n-C-28-acid (R-2 = 0.74, n = 242). Tropical Pacific delta H-2(Wax) values fall within the predicted range of values based on the global calibration, and the largest residuals from the global regression line are no greater than those observed elsewhere, despite large uncertainties in delta H-2(P) values at some Pacific sites. However, tropical Pacific delta H-2(Wax) values in isolation are not correlated with estimated delta H-2(P) values from isoscapes or from isotope-enabled general circulation models. Palynological analyses from these same Pacific sediment samples suggest no systematic relationship between any particular type of pollen distribution and deviations from the global calibration line. Rather, the poor correlations observed in the tropical Pacific are likely a function of the small range of delta H-2(P) values relative to the typical residuals around the global calibration line. Our results suggest that delta H-2(Wax) values are currently most suitable for use in detecting large changes in precipitation in the tropical Pacific and elsewhere, but that ample room for improving this threshold exits in both improved understanding of delta H-2 variability in plants, as well as in precipitation.