Reconstructing precipitation in the tropical South Pacific from dinosterol 2H/1H ratios in lake sediment

Maloney, Ashley E.; Nelson, Daniel B.; Richey, Julie N.; Prebble, Matthew; Sear, David; Hassall, Jonathan; Langdon, Peter G.; Croudace, Ian W.; Zawadzki, Atun; Sachs, Julian P.

doi:10.1016/j.gca.2018.10.028

Cited by 24 publications

(65 citation statements)

References 110 publications

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“…For Lake Emoatul (Vanuatu) and Lake Lanoto'o (Samoa), precipitation (mm/d) was calculated with the δ 2 H dinosterol −GPCP (Global Precipitation Climatology Project) core top calibration detailed in ref. 41 and SI Appendix. Algal lipids obtain all of their lipid hydrogen from lake water, which in turn responds isotopically to increases and decreases in precipitation and evaporation.…”

Section: Methodsmentioning

confidence: 99%

Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought

Sear

Allen

Hassall

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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The timing of human colonization of East Polynesia, a vast area lying between Hawai‘i, Rapa Nui, and New Zealand, is much debated and the underlying causes of this great migration have been enigmatic. Our study generates evidence for human dispersal into eastern Polynesia from islands to the west from around AD 900 and contemporaneous paleoclimate data from the likely source region. Lake cores from Atiu, Southern Cook Islands (SCIs) register evidence of pig and/or human occupation on a virgin landscape at this time, followed by changes in lake carbon around AD 1000 and significant anthropogenic disturbance from c. AD 1100. The broader paleoclimate context of these early voyages of exploration are derived from the Atiu lake core and complemented by additional lake cores from Samoa (directly west) and Vanuatu (southwest) and published hydroclimate proxies from the Society Islands (northeast) and Kiribati (north). Algal lipid and leaf wax biomarkers allow for comparisons of changing hydroclimate conditions across the region before, during, and after human arrival in the SCIs. The evidence indicates a prolonged drought in the likely western source region for these colonists, lasting c. 200 to 400 y, contemporaneous with the phasing of human dispersal into the Pacific. We propose that drying climate, coupled with documented social pressures and societal developments, instigated initial eastward exploration, resulting in SCI landfall(s) and return voyaging, with colonization a century or two later. This incremental settlement process likely involved the accumulation of critical maritime knowledge over several generations.

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Section: Methodsmentioning

confidence: 99%

Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought

Sear

Allen

Hassall

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…The results suggested that the grain size of Lake Ta-Lung-Chi in the Tianshan Mountains sensitively recorded the information of precipitation changes. The proxies that are sensitive to precipitation changes in lake sediments are different in different regions, for example, biomarker compounds [34,71,72], Rb/Sr ratios [73], and magnetic susceptibility [74] are sensitive to changes in precipitation in some regions. In addition, the environmental information reflected by the grain size of lake sediments in different regions is also different, for example, it can reflect wind intensity and dust transport [75,76], riverine input [77] and lake water level changes [78]; however, it can be used as a useful indicator for quantitative reconstruction of long-term paleoprecipitation in the region of Lake Ta-Lung-Chi in Tianshan Mountains.…”

Section: Discussionmentioning

confidence: 99%

“…In recent years, many scholars in Central Asia have integrated tree rings into their studies [23][24][25][26][27][28][29][30] to recover and reconstruct long-term changes in temperature, precipitation, or humidity. Compared with tree rings, lake sediments effectively record information on lake hydrology, regional temperature, precipitation, and vegetation, and extracting climate information from lake records is one of the basic means for studying paleoclimate and paleoenvironment [31][32][33][34]. However, previous studies have not provided effective links between long-term paleoclimate reconstruction and modern investigations regarding climate and environmental parameters.…”

Section: Introductionmentioning

confidence: 99%

Variations in Sediment Grain Size from a Lake in the Tianshan Mountain of Central Asia: Implications for Paleoprecipitation Reconstruction

Abuduwaili

Liu

et al. 2020

Applied Sciences

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The Tianshan Mountain is the largest mountain range in Central Asia, and the source area of many river systems. Changes in precipitation result in significant alterations to regional hydrological processes. Lake sediment from the Tian Shan representative of the last 90 years was chosen as the object of this research study. The grain-size data were used in conjunction with instrumental data to provide a method for determining changes in paleoprecipitation. The results showed the three-point moving average curve of the silty fraction content with a size of 16 to 32 μm to be significantly consistent with the curve of total precipitation from April to September since 1950. The total content of clay and fine-silty fraction (0–16 μm) was clearly consistent with the monthly precipitation in July. The total precipitation from April to September showed a significant downward trend from 1930 to 1975, and then an overall increasing trend beginning in 1975, which may have been influenced by the North Atlantic Oscillation. The change in precipitation reconstructed by the grain size of lake sediments was significantly different from the high-resolution gridded datasets (Climatic Research Unit Time-Series version 4.04) because of the lack of data from meteorological stations in China before 1950. The conclusions of this study are significant for evaluating the validity of climatic research unit (CRU) data in arid areas of Western China. In addition, the results of this study serve as a bridge between modern instrumental records and long time-scale paleoclimate research and provide important reference values for future reconstructions of long time-scale paleoclimate.

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“…Four or five surface sediment samples were collected from each swamp along a transect from the inland edge to the coast. cessed following the protocol of Maloney et al (2019). For all these lake sediments, the acid-containing fraction was eluted with 6 ml 4 % acetic acid in diethyl ether from an aminopropyl gel column and the alkane-containing fraction was eluted with 6 ml hexane from a silica gel column.…”

Section: Site Description and Sample Collectionmentioning

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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Reconstructing precipitation in the tropical South Pacific from dinosterol 2H/1H ratios in lake sediment

Cited by 24 publications

References 110 publications

Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought

Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought

Variations in Sediment Grain Size from a Lake in the Tianshan Mountain of Central Asia: Implications for Paleoprecipitation Reconstruction

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

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