Seasonal variation in deuterium and oxygen-18 concentrations of water vapor and precipitation over the Antarctic

D and O-18 distributions were investigated in Antarctic precipitation (fall ing snow) and in water vapour to study their dependance on season and sampl ing site. Long-term sampling at the former German Georg Forster Station dur ing 1978-93 and at the Japanese Syowa Station during 1994-97 allow conclusi ons about the present seasonal isotopic variations in the water inflow to A ntarctica. The delta D and delta(18)O 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 o f isotopic composition. Significant lime lags exist regarding station tempe ratures, while water vapour delta D Values do not show such hysteresis patt erns. Here, half-yearly and even quarter-yearly time components were found by Fourier analysis. Attempts were made to describe the Variation in delta D and delta(18)O values of water vapour and precipitation as well as in the resulting deuterium excess by the mixed cloud isotopic model (MCIM) of Cia is and Jouzel.