Browsing by Author "Edwards, RL"

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    Radiometrically dated speleothem records of Terminations IV and V and linkages to the North Atlantic
    (International Union for Quaternary Research (INQUA), 2019-07-28) Pollard, T; Drysdale, RN; Woodhead, JD; Edwards, RL; Hellstrom, JC; Cheng, H; Dux, F; Daëron, M; Li, XL; Wong, HKY; Couchoud, I; Regattieri, E; Zanchetta, G; Isola, I
    Paleoclimate archives tied to accurate and precise chronologies are crucial for developing a dynamical understanding of the causes and nature of Quaternary glacial terminations [1]. While numerous well-dated archives provide good chronological control through Terminations I and II, there is presently a lack of well-dated records spanning earlier terminations. A notable exception to this is a suite of remarkably well-dated Chinese speleothems that have been used to date the commencement of each termination over the past 640 kyr [2,3]. This has been achieved by correlating weak Asian Monsoon anomalies as captured by speleothem oxygen isotope signals with terminal Heinrich events in the North Atlantic. While this approach is well-suited to testing orbital hypothesis by comparing the timing of termination commencement with insolation metrics, it only provides precise age control at the beginning of each termination. This precludes assessment of the progression of climatic changes over the full course of the termination, and the timing at which full interglacial conditions are reached. Here we present a composite speleothem record spanning glacial terminations IV and V from the Antro del Corchia cave system located on the western coast of central Italy. This record is anchored to a uranium-thorium based chronology and contains numerous proxies representing both local and regional climate, including Δ47-based temperature data derived from a pool carbonate formed under very slow degassing conditions. By taking advantage of established links between speleothem proxies from this cave site and marine proxies from the North Atlantic, we fix the marine sediment data to a radiometric age scale. This allows us to constrain the timing of ocean circulation and SST changes occurring in the North Atlantic throughout the duration of Terminations IV and V, and compare these with terrestrial temperatures in central Italy. © The Authors.
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    What drives vegetation changes in South Sulawesi during the MIS 5e transition?
    (Copernicus Publications, 2024-04-17) Kimbrough, A; Gagan, MK; Dunbar, GB; Treble, PC; Hantoro, WS; Zhao, JX; Edwards, RL; Shen, CC; Suwargadi, B; Wong, HKY; Rifai, H
    Sulawesi speleothem carbon isotopes (δ13C) are found to co-vary with deglacial warming and atmospheric CO2 measured from Antarctic ice cores. This co-variation has thus far been attributed to speleothem δ13C recording changes in vegetation productivity and microbial activity in the soils overlaying caves as vegetation and microbes respond to glacial-interglacial changes in temperature and atmospheric CO2 (Kimbrough et al., 2023; Krause & Kimbrough et al., in press). However, the relationship between speleothem δ13C and regional environmental change is complex and deconvolving the effect of different environmental drivers is difficult. To further investigate the ecosystem response in the Indo-Pacific Warm Pool to substantial warming and CO2 rise during the penultimate deglaciation/marine isotope stage 5e (~127 kyrs ago) we use complimentary geochemical proxies extracted from stalagmite CaCO3. These proxies include phosphorus and sulphur which respond to nutrient uptake by forest biomass above the cave (Treble et al., 2016). The relative abundance of metals such as copper, iron, zinc, and lead are assessed as another means to track biomass/soil regeneration via selective element delivery to the stalagmites by organic colloids flushed from the soil zone (Borsato et al., 2007). These vegetation proxies are compared with the speleothem δ13C and δ18O records and corresponding high-resolution fluorescence mapping of organics via confocal laser scanning (fluorescence) microscopy (Sliwinski & Stoll, 2021). The comparison of transition metals to stable isotopes (δ18O, δ13C) in the Sulawesi speleothem records makes it possible to distinguish between periods in the record where vegetation productivity increased in response to a rise in temperature and CO2 verses periods where changing hydroclimate played a more dominant role. Characterising the appropriate drivers and proxy response is critical to accurately interpret tropical paleoclimate records where interpretations rely on assumptions that rainfall is the primary driver of vegetation change. © Author(s) 2024. This work is distributed under the Creative Commons Attribution 4.0 License.