Climate Response of Oxygen Isotopic Compositions in Tree-Ring Cellulose in Java: Evaluation Using a Proxy System Model

Tree-ring cellulose oxygen isotopic composition (δ18O) is controlled by several hydrological factors such as precipitation, relative humidity, and temperature. A proxy system model can reveal how these factors affect tree-ring cellulose δ18O. In this study, to identify a key control on tree-ring cellulose δ18O variations, we performed model calculation of year-to year variation of tree-ring cellulose δ18O of Javanese teak in Indonesia from 1960 to 1998. Our model results reasonably reproduce the observed δ18O values and their temporal variations (r = 0.6; p < 0.001). Moreover, the sensitivity test shows that the cellulose δ18O values are sensitive to the teak growing period. The simulation result with earlier or later shifts of the growing period captured the amplitude of observed δ18O variations over 39 years. These results indicate that the tree-ring cellulose δ18O of Javanese teak might be influenced by a subtle shift of the intra-annual growing period.

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Model evaluation for reconstructing the oxygen isotopic composition in precipitation from tree ring cellulose over the last century

Chemical Geology ◽

10.1016/s0009-2541(01)00285-6 ◽

2002 ◽

Vol 182 (2-4) ◽

pp. 121-137 ◽

Cited By ~ 90

Author(s):

W.T Anderson ◽

S.M Bernasconi ◽

J.A McKenzie ◽

M Saurer ◽

F Schweingruber

Keyword(s):

Isotopic Composition ◽

Tree Ring ◽

Model Evaluation ◽

Oxygen Isotopic Composition ◽

Oxygen Isotopic ◽

Tree Ring Cellulose

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Isotopic equilibrium between precipitation and water vapor in Northern Patagonia and its consequences on δ18Ocellulose estimate

10.5194/egusphere-egu2020-22376 ◽

2020 ◽

Author(s):

Tiphaine Penchenat ◽

Françoise Vimeux ◽

Valérie Daux ◽

Olivier Cattani ◽

Maximiliano Viale ◽

...

Keyword(s):

Water Vapor ◽

Isotopic Composition ◽

Tree Ring ◽

Late Summer ◽

Oxygen Isotopic Composition ◽

Source Water ◽

Isotopic Equilibrium ◽

Perfect Agreement ◽

The Impact ◽

Tree Ring Cellulose

<div> <div> <div> <p>Modelling of the oxygen isotopic composition (&#948;<sup>18</sup>O) of tree-ring cellulose rely on the isotopic equilibrium assumption between the atmospheric water vapor and the tree source water, which is frequently assimilated to integrated precipitation. We explore the veracity of this assumption based on observations collected (&#948;<sup>18</sup>O of rain, rivers, leaves, tree-rings) or monitored (&#948;<sup>18</sup>O of water vapor) during a field campaign in R&#237;o Negro province, Argentina, in late summer 2017 (February-March). We examine, firstly, how the &#948;<sup>18</sup>O of water vapor deviate from the equilibrium with precipitation and, secondly, what is the impact of the isotopic equilibrium assumption on the calculation of the isotopic composition of tree-ring cellulose.</p> <p>For oxygen, the isotopic disequilibrium between rain and vapor range between -2.0 and 4.1&#8240;. Rain drops re-evaporation during their fall, evaporation of soil water and vegetation transpiration (resulting in transpired water accounting for 14 to 29% of ambient water vapor) could produce this disequilibrium. The small value of the disequilibrium at the study site is likely due to the high level of relative humidity (from 70 to 96%) favoring the isotopic diffusive exchanges between the two water phases and thus promoting the isotopic equilibrium.</p> <p>A perfect agreement between observed and calculated isotopic composition of cellulose is obtained if the source water is assumed to be in isotopic equilibrium with the measured water vapor. This hypothetical source water has a significantly higher &#948;<sup>18</sup>O than the expected averaged isotopic composition of precipitation over the growing period or than the groundwater (river value). The veracity of the hypothesis of the isotopic equilibrium between water vapor and source water in tree-ring paleoclimate studies is discussed in light of these results.</p> </div> </div> </div>

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Changes of Ionic and Oxygen Isotopic Composition of the Snowpack at the Glacier Austre Okstindbreen, Norway, 1995

Hydrology Research ◽

10.2166/nh.1998.0001 ◽

1998 ◽

Vol 29 (1) ◽

pp. 1-20 ◽

Cited By ~ 20

Author(s):

Peter Raben ◽

Wilfred H. Theakstone

Keyword(s):

Isotopic Composition ◽

Sea Level ◽

Oxygen Isotopes ◽

Oxygen Isotopic Composition ◽

Isotopic Ratios ◽

Vertical Variations ◽

Oxygen Isotopic ◽

The Difference ◽

Liquid Precipitation ◽

Different Altitudes

Marked vertical variations of ions and oxygen isotopes were present in the snowpack at the glacier Austre Okstindbreen during the pre-melting phase in 1995 at sites between 825 m and 1,470 m above sea level. As the first meltwater percolated from the top of the pack, ions were moved to a greater depth, but the isotopic composition remained relatively unchanged. Ions continued to move downwards through the pack during the melting phase, even when there was little surface melting and no addition of liquid precipitation. The at-a-depth correlation between ionic concentrations and isotopic ratios, strong in the pre-melting phase, weakened during melting. In August, concentrations of Na+ and Mg2+ ions in the residual pack were low and vertical variations were slight; 18O enrichment had occurred. The difference of the time at which melting of the snowpack starts at different altitudes influences the input of ions and isotopes to the underlying glacier.

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δ2Hn-alkane and δ18Osugar biomarker proxies from leaves and topsoils of the Bale Mountains, Ethiopia, and implications for paleoclimate reconstructions

Biogeochemistry ◽

10.1007/s10533-021-00773-z ◽

2021 ◽

Author(s):

Bruk Lemma ◽

Lucas Bittner ◽

Bruno Glaser ◽

Seifu Kebede ◽

Sileshi Nemomissa ◽

...

Keyword(s):

Isotopic Composition ◽

Leaf Growth ◽

Thermal Conversion ◽

Oxygen Isotopic Composition ◽

Leaf Water ◽

Isotope Ratio Mass Spectrometer ◽

Oxygen Isotopic ◽

Calibration Study ◽

Microclimatic Conditions ◽

Paleoclimate Reconstructions

AbstractThe hydrogen isotopic composition of leaf wax–derived n-alkane (δ2Hn-alkane) and oxygen isotopic composition of hemicellulose–derived sugar (δ18Osugar) biomarkers are valuable proxies for paleoclimate reconstructions. Here, we present a calibration study along the Bale Mountains in Ethiopia to evaluate how accurately and precisely the isotopic composition of precipitation is imprinted in these biomarkers. n-Alkanes and sugars were extracted from the leaf and topsoil samples and compound–specific δ2Hn-alkane and δ18Osugar values were measured using a gas chromatograph–thermal conversion–isotope ratio mass spectrometer (GC–TC–IRMS). The weighted mean δ2Hn-alkane and δ18Osugar values range from − 186 to − 89‰ and from + 27 to + 46‰, respectively. Degradation and root inputs did not appear to alter the isotopic composition of the biomarkers in the soil samples analyzed. Yet, the δ2Hn-alkane values show a statistically significant species dependence and δ18Osugar yielded the same species–dependent trends. The reconstructed leaf water of Erica arborea and Erica trimera is 2H– and 18O–enriched by + 55 ± 5 and + 9 ± 1‰, respectively, compared to precipitation. By contrast, Festuca abyssinica reveals the most negative δ2Hn-alkane and least positive δ18Osugar values. This can be attributed to “signal–dampening” caused by basal grass leaf growth. The intermediate values for Alchemilla haumannii and Helichrysum splendidum can be likely explained with plant physiological differences or microclimatic conditions affecting relative humidity (RH) and thus RH–dependent leaf water isotope enrichment. While the actual RH values range from 69 to 82% (x̄ = 80 ± 3.4%), the reconstructed RH values based on a recently suggested coupled δ2Hn-alkane –δ18Osugar (paleo–) hygrometer approach yielded a mean of 78 ± 21%. Our findings corroborate (i) that vegetation changes, particularly in terms of grass versus non–grassy vegetation, need to be considered in paleoclimate studies based on δ2Hn-alkane and δ18Osugar records and (ii) that the coupled δ2Hn-alkane –δ18Osugar (paleo–) hygrometer approach holds great potential for deriving additional paleoclimatic information compared to single isotope approaches.

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