Refined Simple Model of Stable Water Isotopic Content in Central Antarctic Precipitation with Oxygen-17 Fractionation

Modeling the isotopic composition of atmospheric precipitation is an important tool for climatic, paleoclimatic, and hydrological studies. This paper presents an improved simple model of the isotopic composition of precipitation in central Antarctica. It differs from the previous version published by Salamatin et al. (2004) by (1) the fact that it includes the geochemical cycle of oxygen-17 and (2) the possibility of solving the inverse problem (i.e., finding trajectory parameters that could form the isotopic composition of the precipitation observed at the end of the trajectory). The paper examines in detail the main tuning parameters of the model, among the most important of which are the temperature and humidity in the moisture source; the “circulation parameter,” which takes into account the advection of vapor into the moisture source; the condensation temperature; and the degree of air supersaturation with moisture in ice clouds. Based on the analysis of data on the isotopic composition (including “excess of oxygen-17,” 17O-xs) of water vapor in the surface layer of the atmosphere over the ocean and surface snow sampled along meridional profiles in East Antarctica, the optimal tuning of the model for calculating the isotopic composition of atmospheric precipitation at the Antarctic Vostok station was performed. In particular, it is shown that the temperature and humidity of the air in the moisture source are +17.4°C and 72%, respectively, and the condensation temperature is –41.3°C. The possibilities of using the model to analyze the isotopic composition of liquid precipitation falling on other continents are discussed. The final part of the paper discusses the limitations of the model. In particular, it is noted that the model does not take into account processes such as the evaporation of precipitation when it falls in arid conditions, mixing of trajectories, the influence of local sources of moisture, or the features of isotope fractionation during the evaporation of moisture from the continents.