Leaf Wax Hydrogen Isotopes as a Hydroclimate Proxy in the Tropical Pacific

作者：S. Nemiah Ladd, Ashley E. Maloney, Daniel B. Nelson, Matthew Prebble, Giorgia Camperio, David Sear, Jonathan Hassall, Peter G. Langdon, Julian P. Sachs, Nathalie Dubois · 年份：2020 · DOI：10.1002/essoar.10503377.1 · 被引用次数：7 · 研究领域：Isotope Analysis in Ecology、Geology and Paleoclimatology Research、Coastal wetland ecosystem dynamics

The hydrogen isotope composition (H/H ratios) of leaf waxes preserved in sediments is increasingly used to reconstruct past hydroclimate. Here, we extend the global calibration of leaf wax H/H ratios to include surface sediments from 23 lakes and swamps on 15 tropical Pacific islands. Leaf wax H/H ratios from this new data set are not correlated with regional estimates of mean annual precipitation H/H ratios derived from isoscapes or from isotope-enabled general circulation models. Nevertheless, the new data fall within the predicted range of values based on a global calibration compiled from published surface sediments. In our global compilation, we find a strong positive linear correlation between H/H ratios of mean annual precipitation and the common leaf waxes -C-alkane (R = 0.73, n = 581) and -C-acid (R = 0.74, n = 242). In the tropical Pacific, the largest residuals are no greater than those observed elsewhere, and are likely due to (1) uncertainty in the H/H ratios of local precipitation and (2) variability in net fractionation for different plant types. Palynological analyses from the same samples suggest that there is no systematic relationship between any particular type of pollen distribution and deviations from the global calibration line. Overall, our results support the use of leaf wax H/H ratios in tropical Pacific lake sediments as proxies for large hydrological changes, especially when paired with H/H ratios of source-specific biomarkers. However, the interpr...