Abstract
Abstract. A single isotope ratio (δD or δ18O) of water is widely used as an air-temperature proxy in Antarctic ice core records. These isotope ratios, however, do not solely depend on air-temperature but also on the extent of distillation of heavy isotopes out of atmospheric water vapor from an oceanic moisture source to a precipitation site. The temperature changes at the oceanic moisture source (Δ Tsource) and at the precipitation site (Δ Tsite) can be retrieved by using deuterium-excess (d) data. A new d record from Dome Fuji, Antarctica spanning the past 360 000 yr is presented and compared with records from Vostok and EPICA Dome C ice cores. In previous studies, to retrieve Δ Tsource and Δ Tsite information, different linear regression equations were proposed using theoretical isotope distillation models. A major source of uncertainty lies in the coefficient of regression, βsite which is related to the sensitivity of d to Δ Tsite. We show that different ranges of temperature and selections of isotopic model outputs may increase the value of βsite by more than a factor of two. To explore the impacts of this coefficient on reconstructed temperatures, we apply for the first time the exact same methodology to the isotope records from the three Antarctica ice cores. We show that uncertainties in the βsite coefficient strongly affect (i) the glacial–interglacial magnitude of Δ Tsource; (ii) the imprint of obliquity in Δ Tsource and in the site-source temperature gradient. By contrast, we highlight the robustness of Δ Tsite reconstruction using water isotopes records.
Highlights
Climate records preserved in Antarctic ice cores provide important clues for the climate history over the several hundred thousand years
To interpret the d and δD records as Tsource and Tsite information, we used an isotopic inversion methodology based on the mixed cloud isotopic model (MCIM) model as previously performed by Vimeux et al (2002); Stenni et al (2001) on the Vostok and EDC ice cores respectively
A major source of uncertainty lies in the coefficient of regression, βsite which is related to the sensitivity of d to Tsite
Summary
Climate records preserved in Antarctic ice cores provide important clues for the climate history over the several hundred thousand years. Source and site climatic information can be extracted from ice core δD and d records, using a linear regression model based on the Rayleigh distillation isotopic model and/or more sophisticated models (Vimeux et al, 2001; Cuffey and Vimeux, 2001; Stenni et al, 2001, 2010) This dual isotope approach allows corrections to site temperature estimates for moisture source effects. Such site and source temperature inversions have been conducted using different methodologies (e.g. different adjustments of the linear regression coefficients) for Vostok (Cuffey and Vimeux, 2001; Vimeux et al, 2002), EDC (Stenni et al, 2001, 2003, 2010), and EPICA Dronning Maud Land (EDML) (Stenni et al, 2010) ice cores.
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