The origin of present-day Antarctic precipitation from surface snow deuterium excess data

Philippe Ciais (1) , J. White , J. Jouzel (1) , J. Petit

1 LMCE - Laboratoire de Modélisation du Climat et de l'Environnement

The deuterium excess (d) is defined as a linear combination of the D/H and •80/•60 ratios in natural waters. We present an interpretation of deuterium excess data in surface Antarctic snow, using an isotopic model to derive information on the origin of present-day Antarctic precipitation. The data come from near the coast (D47, Adelie Land) and from inland (south pole, 1000 km from the sea). The one-dimensional isotopic model belongs to the Rayleigh family but fully accounts for mixed cloud processes between 0øC and-30øC. Modeling d in polar snowfalls meets the problem of a large sensitivity to the saturation conditions prevailing at snow formation. Therefore we decided to tune the saturation in the model in order to yield realistic mean d values, but we use the seasonal phase of d versus/5, which is less sensitive to the saturation conditions, as an independent validation of the model predictions. Both inland and near the coast, our model can simulate the observed phase between d and/5 in snow with moisture of subtropical origin (40ø-20øS). Although we do not treat specifically storm precipitation near the coast, this study indicates that the observed phase between d and/5 brings up a new validation of isotopic models. It supports a distant vapor source for large-scale precipitation delivered to the Antarctic continent.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Philippe Ciais, J. White, J. Jouzel, J. Petit. The origin of present-day Antarctic precipitation from surface snow deuterium excess data. Journal of Geophysical Research, 1995, 100 (D9), pp.18.917-18.927. ⟨10.1029/95JD01169⟩. ⟨hal-02923793⟩