Abstract
Abstract. Past temperature reconstructions from Antarctic ice cores require a good quantification and understanding of the relationship between snow isotopic composition and 2 m air or inversion (condensation) temperature. Here, we focus on the French–Italian Concordia Station, central East Antarctic plateau, where the European Project for Ice Coring in Antarctica (EPICA) Dome C ice cores were drilled. We provide a multi-year record of daily precipitation types identified from crystal morphologies, daily precipitation amounts and isotopic composition. Our sampling period (2008–2010) encompasses a warmer year (2009, +1.2 °C with respect to 2 m air temperature long-term average 1996–2010), with larger total precipitation and snowfall amounts (14 and 76 % above sampling period average, respectively), and a colder and drier year (2010, −1.8 °C, 4 % below long-term and sampling period averages, respectively) with larger diamond dust amounts (49 % above sampling period average). Relationships between local meteorological data and precipitation isotopic composition are investigated at daily, monthly and inter-annual scale, and for the different types of precipitation. Water stable isotopes are more closely related to 2 m air temperature than to inversion temperature at all timescales (e.g. R2 = 0.63 and 0.44, respectively for daily values). The slope of the temporal relationship between daily δ18O and 2 m air temperature is approximately 2 times smaller (0.49 ‰ °C−1) than the average Antarctic spatial (0.8 ‰ °C−1) relationship initially used for the interpretation of EPICA Dome C records. In accordance with results from precipitation monitoring at Vostok and Dome F, deuterium excess is anti-correlated with δ18O at daily and monthly scales, reaching maximum values in winter. Hoar frost precipitation samples have a specific fingerprint with more depleted δ18O (about 5 ‰ below average) and higher deuterium excess (about 8 ‰ above average) values than other precipitation types. These datasets provide a basis for comparison with shallow ice core records, to investigate post-deposition effects. A preliminary comparison between observations and precipitation from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis and the simulated water stable isotopes from the Laboratoire de Météorologie Dynamique Zoom atmospheric general circulation model (LMDZiso) shows that models do correctly capture the amount of precipitation as well as more than 50 % of the variance of the observed δ18O, driven by large-scale weather patterns. Despite a warm bias and an underestimation of the variance in water stable isotopes, LMDZiso correctly captures these relationships between δ18O, 2 m air temperature and deuterium excess. Our dataset is therefore available for further in-depth model evaluation at the synoptic scale.
Highlights
Antarctic ice cores provide exceptional past climate records, thanks to the wealth of climatic and environmental information archived in the water and air of deep ice cores (e.g. Jouzel and Masson-Delmotte, 2010; WAIS Divide Project Members, 2015)
Since the 1950s, observations (Dansgaard, 1964), theoretical distillation models (Jouzel and Merlivat, 1984) and atmospheric general circulation models (Jouzel, 2014) have evidenced a close relationship between the isotopic composition of polar precipitation and condensation temperature. While this has formed the basis for past temperature reconstructions from deep Antarctic ice cores, key sources of uncertainties have been identified in the climatic interpretation of water stable isotope records
The isotope ratio mass spectrometry (IRMS) provides an analytical precision of ±0.05 ‰ for δ18O and ±0.7 ‰ for δD, while the cavity ring-down spectroscope (CRDS) used here warrants a precision of ±0.1 ‰ for δ18O and ±0.5 ‰ for δD, with a final precision on the calculated deuterium excess of ±0.8 and ±0.9 ‰, respectively
Summary
Antarctic ice cores provide exceptional past climate records, thanks to the wealth of climatic and environmental information archived in the water and air of deep ice cores (e.g. Jouzel and Masson-Delmotte, 2010; WAIS Divide Project Members, 2015). Since the 1950s, observations (Dansgaard, 1964), theoretical distillation models (Jouzel and Merlivat, 1984) and atmospheric general circulation models (Jouzel, 2014) have evidenced a close relationship between the isotopic composition of polar precipitation and condensation temperature While this has formed the basis for past temperature reconstructions from deep Antarctic ice cores, key sources of uncertainties have been identified in the climatic interpretation of water stable isotope records. Based on simulations performed with distillation models, it is possible to extract information on both condensation temperature and evaporation conditions from the combined measurements of water stable isotopes This methodology has been applied to several deep Antarctic ice cores (e.g. Stenni et al, 2001; Vimeux et al, 2002; Uemura et al, 2012).
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