Validation and calibration of soil δ2H and brGDGTs along (E-W) and strike (N-S) of the Himalayan climatic gradient

Veen, I. van der; Peterse, Francien; Davenport, Jesse; Meese, Bernd; Bookhagen, Bodo; France‐Lanord, Christian; Kahmen, Ansgar; Hassenruck‐Gudipati, Hima J.; Gajurel, Ananta P.; Strecker, Manfred R.; Sachse, Dirk

doi:10.1016/j.gca.2020.09.014

Cited by 8 publications

(2 citation statements)

References 92 publications

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“…Tropical Pacific n-C29-alkane δ 2 H values ranged from −177 to −139‰, while those of n-C28-acid ranged from −175 to −119‰ (Table 1; Figure 3). Adding these new measurements to an updated global compilation of δ 2 HWax values from all available surface sediment and soil data sets in non-marine settings (compilations from McFarlin et al, 2019, as well as data from Nelson, 2013;Bakkelund et al, 2018;Feng et al, 2019;Goldsmith et al, 2019;Li et al, 2019;Wu et al, 2019;Daniels et al, 2020;Lu et al, 2020;Struck et al, 2020;van der Veen et al, 2020) has minimal impact on the slope, y-intercept, or correlation coefficients for the global linear regression (Figure 3).…”

Section: Tropical Pacific δ 2 H Values In the Global Contextmentioning

confidence: 99%

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

Ladd

Maloney

Nelson

et al. 2020

Preprint

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Leaf wax 2 H/ 1 H ratios are correlated with mean annual precipitation 2 H/ 1 H ratios globally, but not in the tropical Pacific• Deviations from the global relationship between precipitation leaf wax 2 H/ 1 H ratios cannot be predicted from palynological assemblages• Small range and large uncertainties in estimates of tropical Pacific precipitation 2 H/ 1 H ratios likely account for poor correlations

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Section: Tropical Pacific δ 2 H Values In the Global Contextmentioning

confidence: 99%

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

Ladd

Maloney

Nelson

et al. 2020

Preprint

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“…Tropical Pacific n ‐C 29 ‐alkane δ 2 H values ranged from −177 ‰ to −139 ‰, while those of n ‐C 28 ‐acid ranged from −175 ‰ to −119 ‰ (Table 1; Figure 3). Adding these new measurements to an updated global compilation of δ 2 H Wax values from all available surface sediment and soil data sets in non‐marine settings (compilations from Liu & An, 2019 and McFarlin et al., 2019, as well as data from Bakkelund et al., 2018; Daniels et al., 2020; Feng et al., 2019; Goldsmith et al., 2019; Y. Li et al., 2019; Lu et al., 2020; Nelson, 2013; Struck et al., 2020; Wu et al., 2019; van der Veen et al., 2020) has minimal impact on the slope, y ‐intercept, or correlation coefficients for the global linear regression (Figure 3).…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2021

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Hydrogen isotope ratios of sedimentary leaf waxes (δ 2 H Wax values) are increasingly used to reconstruct past hydroclimate. Here, we add δ 2 H 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 δ 2 H values of mean annual precipitation (δ 2 H 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 δ 2 H 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 δ 2 H P values at some Pacific sites. However, tropical Pacific δ 2 H Wax values in isolation are not correlated with estimated δ 2 H 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 δ 2 H P values relative to the typical residuals around the global calibration line. Our results suggest that δ 2 H 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 δ 2 H variability in plants, as well as in precipitation. Plain Language Summary Past precipitation patterns are difficult to reconstruct, limiting our ability to understand Earth's climate system. Geochemists reconstruct past precipitation by measuring the amount of heavy hydrogen naturally incorporated into the waxy coating of leaves, which is preserved in mud that accumulates in lakes, soils, and oceans. Heavy hydrogen in leaf waxes is strongly correlated with local precipitation, allowing us to learn about rainfall intensity, temperature, and cloud movement. However, no existing calibration studies include sites from the tropical Pacific, home to the most intense rainfall on the planet and populations that rely on rain for drinking water and farming. We measured heavy hydrogen in leaf waxes from tropical Pacific islands and show that although values are within the global calibration error, no precipitation relationship exists within the region. Plant type distributions do not explain the lack of correlation, which is best attributed to poorly constrained estimates of heavy hydrogen in local rain and the relatively small range of variability within the region. At present, heavy hydrogen from ancient leaf waxes can show large changes in past precipitation, but improved processlevel understanding is needed to use this tool to understand smaller changes in the tropical Pacific and elsewhere. LADD ET AL.

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