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Abstract
D and 18O distributions were investigated in Antarctic precipitation (falling snow) and in water vapour to study their dependance on season and sampling site. Long-term sampling at the former German Georg Forster Station during 1978–93 and at the Japanese Syowa Station during 1994–97 allow conclusions about the present seasonal isotopic variations in the water inflow to Antarctica. The δD and δ18O values of precipitation at these East Antarctic coastal stations were compared with corresponding data from the West Antarctic Georg von Neumayer and Halley stations. The monthly means of these long-term data sets show typical hysteresis-like seasonal patterns of isotopic composition. Significant time lags exist regarding station temperatures, while water vapour δD values do not show such hysteresis patterns. Here, half-yearly and even quarter-yearly time components were found by Fourier analysis. Attempts were made to describe the variation in δD and δ18O values of water vapour and precipitation as well as in the resulting deuterium excess by the mixed cloud isotopic model (MCIM) of Ciais and Jouzel.