NOAA/WDS Paleoclimatology - Dome Fuji 360KYr Stable Isotope Data and Temperature Reconstruction

A single isotope ratio (dD or d18O) 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 (Delta Tsource) and at the precipitation site (Delta 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 Delta Tsource and Delta Tsite information, different linear regression equations were proposed using theoretical isotope distillation models. A major source of uncertainty lies in the coefficient of regression, Beta-site which is related to the sensitivity of d to Delta Tsite. We show that different ranges of temperature and selections of isotopic model outputs may increase the value of Beta-site 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 Beta-site coefficient strongly affect (i) the glacial-interglacial magnitude of Delta Tsource; (ii) the imprint of obliquity in Delta Tsource and in the site-source temperature gradient. By contrast, we highlight the robustness of Delta Tsite reconstruction using water isotopes records.