Abstract
Abstract. Stable isotope data from lipid biomarkers and diatom silica recovered from lake sediment cores hold great promise for paleoclimate and paleohydrological reconstructions. However, these records rely on accurate calibration with modern precipitation and hydrologic processes and only limited data exist on the controls on the δD values for n-alkanoic acids from plant leaf waxes. Here we investigate the stable isotopic composition of modern precipitation, streams, lake water and ice cover, and use these data to constrain isotope systematics of the Lake El'gygytgyn Basin hydrology. Compound-specific hydrogen isotope ratios determined from n-alkanoic acids from modern vegetation are compared with modern precipitation and lake core top sediments. Multi-species net (apparent) fractionation values between source water (precipitation) and modern vegetation (e.g., ϵwax/precip mean value is −107 ± 12‰) agree with previous results and suggest a consistent offset between source waters and the δD values of alkanoic acids. We conclude that although there may be some bias towards a winter precipitation signal, overall δD values from leaf wax n-alkanoic acids record annual average precipitation within the El'gygytgyn Basin. A net fractionation calculated for 200-yr-integrated lake sediments yields ϵ30/precip = −96 ± 8‰ and can provide robust net "apparent" fractionation to be used in future paleohydrological reconstructions.
Highlights
SciencesHydrogen isotope ratios of lipid biomarkers are emerging as a new paleoclimatic and paleohydrological proxy (e.g., Sauer et al, 200O1;cHeuaanng Setcaile., n20c0e2; Jacob et al., 2007; Feakins and Sessions, 2010; Castaneda and Schouten, 2011; Sachse et al, 2012 and references therein)
The oxygen and hydrogen isotopic compositions of the water samples were analyzed at the Alfred Wegener Institute for Polar and Marine Research (AWI) Potsdam, Germany, with a Finnigan mean air temperature (MAT) Delta-S mass spectrometer equipped with two equilibration units for online determination following the methods of Meyer et al (2000)
Our data show less negative n-alkanoic acid εwax/w values for woody plants versus grasses (Table 3). These results suggest that vegetation changes, especially during major climatic shifts, have the potential to affect the overall δD of plant leaf waxes (δDwax) signal in catchment sediments
Summary
SciencesHydrogen isotope ratios (δD) of lipid biomarkers are emerging as a new paleoclimatic and paleohydrological proxy (e.g., Sauer et al, 200O1;cHeuaanng Setcaile., n20c0e2; Jacob et al., 2007; Feakins and Sessions, 2010; Castaneda and Schouten, 2011; Sachse et al, 2012 and references therein). Multiple environmental variables affect the δD values of meteoric water such as temperature, elevation and water vapour source (Craig, 1961; Craig and Gordon, 1965; Dansgaard, 1964; Gonfiantini, 1986; Gat, 1996). The isotopic composition of meteoric water is coTnthroelleCd bryycoosntpinhenetarleand “latitudinal effects” (Dansgaard, 1964; Craig, 1961; Gonfiantini, 1986; Gat, 1996; Bowen and Revenaugh, 2003; Kurita et al, 2004), which are reflected in the δD of plant leaf waxes (δDwax) (Sachse et al, 2006; Smith and Freeman, 2006; Hou et al, 2008; Liu and Yang, 2008; Polissar and Freeman, 2010). Changes in sedimentary δDwax have been interpreted as shifts in precipitation δD (δDp) (e.g., Liu and Yang, 2008; Tierney et al, 2008) or in Published by Copernicus Publications on behalf of the European Geosciences Union
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